Final Report Summary - CITYHUSH (Acoustically Green Road Vehicles and City Areas)
Executive Summary:
The European-funded CityHush project starts from a vision: the quiet city! Implementing quiet zones with the help of quiet electric (or hybrid) vehicles resulting in noise levels 10-15 dB(A) lower than before, quiet tyres and road surfaces, as well as design solutions for buildings and noise barriers to mitigate low-frequency noise are the project’s key instruments to achieve that.
Road traffic noise is the major noise problem in European cities. Changing to electric vehicles can bring about a significant noise reduction. In order to make the possible benefits tangible as early as possible – with only a small share of the vehicle fleet being electric in the beginning – CityHush is proposing quiet zones, so called Q-Zones. In Q-Zones only electric vehicles will be allowed, defined via a certain maximum noise level. Compared to the situation before, noise levels are expected to be reduced by about 15 dB(A) in the inner part of the zone. This concept has been supported by innovative designs for low-noise tyres and road surfaces. To further improve the situation at hot spots, CityHush suggests innovative noise barriers to absorb or mitigate the propagation of low-frequency noise. Below a list of measures and successful results from the CityHush project is shown:
- Evaluation of the concept of Q-zones to reduce traffic noise in urban areas.
A noise reduction exceeding 12 dB within the Q-zone has been achieved.
- Evaluation of the concept of embedded parks inside the Q-zone.
- A refined noise rating model for the outdoor has been described and implemented in public noise calculation software.
- A refined noise rating model for the indoor has been described and implemented in public noise calculation software.
- A smooth dense road surface with optimized road texture has been developed. Measurements show a noise reduction of 2 dB(A)-units compared to a new road surface with the same maximum stone size (8 mm).
- A new low noise tyre from Goodyear has been developed for electrical vehicles. Measurements show a noise reduction of up to 5 dB(A)-units compared to a reference prototype tyre.
- Measures for reducing airborne and structure borne low frequency noise has been described. The concepts focus on already exploited areas where ordinary measures cannot be used. The concepts include barriers in the ground and low frequency absorbing facades.
- Development of a measurement system allowing for the detection, separation and quantification of the various noise sources contributing to the overall noise of road traffic.
- Development of an objective and psychoacoustic evaluation tool for low noise low emission vehicles
- Proposal of a modified test method for type approval electric vehicles regarding noise.
Recommended criteria´s for purchasing green low noise vehicles have been described. Recommended criteria´s for vehicles to enter a Q-zone (in this project) free of charge have been described.
- Active and passive noise attenuation measures within the concept of tyre hoods.
- Definition of criteria for use of low noise motorcycles within a city environment using a holistic approach taking into account benefits in terms of congestion reduction and other.
Project Context and Objectives:
As a general target for the environment as formulated in the SST-2008.-RTD-1 is stated that:
- Noise reduction within urban areas by 10 - 20 dB(A) units should be achieved;
- New passenger car CO2 emission should be reduced by 40 - 50% and for heavy duty vehicles by 10 - 30%;
- Total of other emissions should be near zero.
The CITYHUSH project is a response to the Call SST.2008.1.1.3 Greening of surface transport. Greening of Products & Operations Holistic noise and vibration abatement
The CITYHUSH project has as objectives:
- to reduce the overall noise levels in the treated city zones by 10-20 dB(A);
- to substantially reduce the CO2 emissions;
- to reduce other emissions to near zero at least in certain cases.
The large and medium sized European cities (> 100 000 inhabitants) will, according to the EC Noise Directive 2002/49, have to produce and deliver noise maps and noise action plans at year 2012 and 2013 respectively. At these dates, the cities with > 250 000 inhabitants shall also supply to the Commission their revised noise maps and Actions Plans.
The CITYHUSH project will support city administrations in the production and implementation of these noise action plans as well as of the noise reduction technology that will be the framework in these Noise Action Plans.
The identified hot spots and noise action plans made with the existing technology suffer from major shortcomings:
1. the correlation between hot spots with annoyance and complaints is very poor;
2. proposed mitigation measures in general result in increased emissions;
3. only indoor noise comfort is addressed whilst a silent outdoor environment is also very important especially in cities where people live, work and recreate outdoors during many hours per day.
Step change solutions (such as Q-Zones) are proposed within the CITYHUSH project in order to meet the challenging combined noise and CO2 reduction criteria.
The noise score models for dwellings will be improved to increase correlation between hot spots and annoyance (e.g. by including effects of low frequency noise) and to increase correlation between hot spots and complaints (e.g. by including maximum levels to account for specific sources such as motorcycles).
A noise score model for outdoor noise will be developed to be able to evaluate the beneficial aspects of the creation of parks and other calm areas.
The project mainly aims at reducing noise in the city environment, it deals with developing suitable problem identification and evaluation tools (noise score models) and with designing and developing solutions, to be integrated in city action plans, for problems which are identified as hot spots but which show also high correlation with annoyance and complaints. The developed solutions will be validated in a city environment. All solutions will target a combined reduction of all emissions (noise, CO2 and fine particles).
Following innovative solutions and tools will be developed:
1. Concept of Q-Zones (zones in inner city where only quiet low emission vehicles are tolerated) and where the noise levels will be reduced by more than 10 dB in comparison with the existing situation, figure 1.
2. Concept of parks embedded in Q-Zones where the noise levels will be reduced by 10-15 dB in comparison with the existing situation, figure 2.
3. Indoor noise score rating models, which correlate better with annoyance and noise complaints by integrating low frequency noise and the occurrence of high noise single event (e.g. passing motorcycles) into the analysis.
4. Noise score rating models for the outdoors in order to be able to assess the complete living and working environment, figure 3, 4 & 5.
5. Objective and psychoacoustic evaluation tool for low-noise/low-emission vehicles.
6. Mathematical synthesis tool for noise from low-noise/low-emission vehicles to be used in simulation studies.
7. General performance noise specifications for purchasing low-noise/low-emission vehicles and noise criteria for acceptance of vehicles within the Q-Zones, figure 6.
8. Novel concepts for low noise roads based upon dense elastic road surfaces.
9. Novel concepts for low noise roads based upon grinding of asphalt top layers.
10. Novel concepts for tyres for low noise vehicles, including heavy vehicles, figure 7.
11. Criteria for use of low noise motorcycles within a city environment using a holistic approach taking into account benefits in terms of congestion reduction and other, figure 8.
12. Active and passive noise attenuation measures within the tyre hood.
13. Solutions for noise mitigation based upon high low frequency absorption at facades of buildings.
14. Solutions for noise mitigation based upon efficient low frequency isolation in the propagation path to reduce ground borne noise, figure 9.
All the above solutions and tools will be designed, prototyped and validated. They will result in obtaining the anticipated noise impacts.
Conclusion
CITYHUSH covers not only one subject of the call but it deals with all the subjects highlighted in the call and offers a holistic approach by considering all elements: the vehicle, the infrastructure, the emission, the propagation and the immission at the receiver. An innovative approach is included to better correlate noise hot spots as determined according to the EC Directive with annoyance and complaints. This is done by integrating low frequency noise and high noise impact levels into the noise score models. Emphasis is placed on solutions, which do not only minimise noise but also CO2 emission and fine dust emission. Not only residents inside buildings are considered but also the effect of quiet outdoor city zones (parks) will be quantified. This is an important factor in a global assessment of the noise performance of a city.
Project Results:
3.1 ACOUSTICALLY GREEN CITY AREAS - Q-ZONES
3.1.1 Tools for creating Q-Zones
Five different European cities have been chosen (see deliverable D 1.1.1) to evaluate the effects of establishing prospective Q-Zones during P1. Evaluation of the different cities, based on geographical data, traffic data, population data and assumptions on population behaviour, has been performed during period 2. Traffic models have been created and these have then been used to simulate noise distributions for various hypothetical Q-Zone scenarios. The difference in the noise situation of these scenarios with the current situation has been compared and are presented in deliverable D1.1.2.
For the five test sites, a varying number of scenarios have been simulated. The results have been discussed above in their specific site context. Although the results are specific to the chosen sites, we will try to generalise the results at least to some extent, building on similarities as well as differences. We may start by recognising that introducing a Q-Zone implies a reduction of the road network capacity. The impact of such a capacity loss will be more or less severe, depending on the initial use of the network, i.e. the congestion level. The higher the congestion level, the higher the price in terms of increased travel total times in the network. Likewise, the larger the zone, the larger the congestion effect of the implementation. Sufficient network capacity will obviously be a major condition for introducing a Q-Zone. If there is little traffic zoning in the city, a main effect of the Q-Zone will be to push through traffic away to the remaining network. For congested networks, this may imply increase travel times for a large part of the network. It may however appear a bit unfair to contribute the cost of mitigating through traffic just to the noise effects of the Q-Zone introduction. In many cities, zoning systems have been introduced for improving the environment in a number of aspects, including all kind of emissions, safety and other living conditions. It has not been possible to make an evaluation of all these aspects in this project, but they should also be considered by decision makers. It should also be noted that traffic zoning is also likely to reduce ambient noise, which may otherwise constrain the potential of the Q-Zone. Therefore, a traffic-zoning scheme may also imply a favourable condition for a Q-Zone introduction. It goes without saying that traffic zoning in itself will reduce noise levels, but then a Q-Zone concept is required to utilise the potential of new vehicle technology for further noise reductions. The traffic zone (or environmental zone) concept could also be extended to include the Q-Zone dimension. Other favourable conditions like tunnels for through traffic may also exist. In such cases, ambient noise levels are likely to be much lower which increases the potential of a Q-Zone introduction.
- Q-Zone size considerations
Because of the potentially strong effect of Q-Zone introduction on congestion, the initial size of a Q-Zone cannot be very large. A minimum size will be defined by the impact of ambient noise, which depends on local factors such as distances to major surrounding roads and local topology. A question may then be if the zone size can be expanded as the level of low noise vehicles increases. Then it can be expected that fewer drivers will have to change route because fewer drivers will have (banned or charged) standard vehicles, and consequently the effect on congestion would be lower. However, the rate of transformation of the vehicle fleet is very slow, and in the recent national Swedish transport plan reaching a level of only 5 percent was forecast for the year 2020. This view is supported also by a market outlook to the EU Climate Change Commission (AEA 2009). It is obvious that a reduction of the redistributed traffic of about 5 percent will be very small, and that an expected increase of low noise vehicles will not be a driver for Q-Zone size enlargement for the next 10 – 15 years. A level of 20 percent is of course even further away, although the speed of transformation can be expected to increase as the technology matures.
- Low Noise Vehicle Ownership considerations
The level of low noise vehicle ownership inside the Q-Zone may be more easily affected than the outside level. Depending on the Q-Zone policy, incentives to acquire low noise vehicles may be much stronger for Q-Zone residential households than for other households. Exempting Q-Zone households from a ban/charge may be necessary at the time of Q-Zone introduction, but will provide less incentive to change vehicle at least for a transition period. After this period, a ban or fee will provide some incentive, and additional incentives may be provided like free street parking for low noise vehicles. If the Q-Zone is introduced already at the exploitation of a new area, the transition period can even be skipped – standard vehicles might not be allowed in the new area. Assumptions of higher levels of low noise vehicle ownership are therefore motivated. Our simulations show that high levels of low noise vehicle ownership are necessary to bring about more significant noise reductions, especially in cases where traffic zoning has already taken place.
- Noise fee level considerations
The noise fees that have been studied are to be paid on Q-Zone entry or exit. The fee levels that have been simulated (0.5 - 2 Euros per entry or exit) give almost the same results as the ban does. This is more outspoken in those cases where the traffic simulation allows for route choice only. This effect is because the extra delay for changing route is for most drivers too small to match the fee. As there is a cost of fee collection, and as the size of the zone is small which implies a low number of paying vehicles, it has not been motivated to simulate even smaller fees. The choice between a ban and a fee is more a choice between ease of monitoring and giving some flexibility to drivers. In this project, we have however not tried to calculate monitoring or fee collection costs.
3.1.2 Parks embedded in Q-Zones
For identification of boundary conditions and maximum noise gains for parks embedded in Q-Zones, different sizes of embedded parks within each test site were defined during P1. For the test sites Essen and Bratislava an interface between the traffic model (build-up by partner KTH) and the updated noise model were created. For each test site, numerous traffic scenarios were worked out and evaluated using the criteria “number of people affected”, Noise Score, area affected, monetary benefit based on HEATCO Study, figure 10.
Numerous site inspections have been carried out in each of the cities that are addressed in this work. Contact has also been made with the relevant city administrations/authorities in order to identify potential sites to be considered for a Q-Zone and to discuss possible local issues.
The following results and conclusions have been seen from the study:
- Simulation/forecast of the maximum noise gains expected from embedment of chosen parks in the appropriate Q-Zones.
- Improvements of the noise situation in the Q-Zone and the corresponding park were achieved in many cases.
- Capacity increases were achieved in many cases.
- Negative impacts on areas outside the Q-Zone were identified.
- Approach for individual adaption of standard Q-Zone configurations has been suggested, to reduce negative effects in the areas outside the Q-Zone.
- Noise situation in parks can be improved by embedding the park in a Q-Zone
- Possible negative effects outside the Q-Zone need to be mitigated by measures that need to be assessed and defined for each individual case
- An approach is shown that gives reason to believe that negative effects can be minimized by individual modification of the standard Q-Zone configurations
3.2 NOISE SCORE RATING MODELS AND ANNOYANCE
3.2.1 Noise score rating method for the outdoors
As a starting point for the noise-rating model for the outdoors, an overview is made of information on the effects of noise in the outdoor environment. Based on this information and an analysis of the effects to be expected in urban (street, park) areas, a tentative noise score rating model for pedestrians and visitors of parks is designed. In this rating model, indicators for outdoor noise are combined with information about the function of the area and the number of people making use of the area at a given time to predict the overall annoyance response, i.e. the percentage and number of visitors that will be expected to be annoyed by noise in a given area. The state of the art regarding effects of noise on the outdoor environment as well as the preliminary noise-rating model for the outdoors are described in Deliverable 2.1.1 submitted December 21, 2011.
Furthermore, preparations have been made for a field study intended to gain more information on the effect of noise in the outdoor environment. In order to develop a noise score rating model that enables an evaluation of the outdoor environment as perceived by pedestrians on the streets and visitors to parks, more information is needed on the impact of noise in different urban and recreational areas.
Within the project, the noise rating model for the outdoors was further tested by investigating the effect of noise in the outdoor urban environment in subjects residing and walking in a realistic situation, both in an urban non-natural environment (streets) and in an urban natural environment (parks). For each type of location, both noisy and relatively quiet locations were included in the study. Measures involve self-report measures such as annoyance, mood state and perceived restoration, as well as accompanying physiological measures such as heart rate and autonomic nervous system activity. Also noise exposure is individually assessed to enable the establishment of both instantaneous and aggregated relationships between exposure and human (annoyance) response. Based on these relationships, the above-mentioned tentative environmental noise rating model for pedestrians and visitors of parks was evaluated and improved.
The state of the art regarding effects of noise on the outdoor environment as well as the preliminary noise-rating model for the outdoors are described in Deliverable 2.1.1 submitted December 21, 2010. In the literature, several noise indicators were used to predict annoyance or the perceived sound scope quality as primary indicators. However, since the LAeq level was the indicator that most consistently correlated with annoyance, and because of the consistency with environmental noise policy and the exposure-response relationships for annoyance at the dwelling, LAeq (during daytime) is chosen as the primary noise indicator in the noise score rating model for the outdoors. In addition, an indicator of the low frequency components of the noise (LCeq-LAeq) is proposed, as well as an additional indicator of the difference between peak and background noise levels (LA5-LA95). The influence of these more specific noise characteristics will have to be based primarily on extrapolation of their observed influence on indoor annoyance or on the evaluation of noise in laboratory listening tests. Furthermore, based on the limited studies available, a tentative exposure-response relationship between outdoor noise and annoyance is proposed. This resembles the EU exposure-response relationship for residents at the dwelling for the sources of aircraft noise and road traffic noise, except for a -5 dB shift in the LAeq levels corresponding to specific annoyance percentages.
3.2.2 Development of the noise score rating method for residents inside
The objective was to refine and evaluate the noise score-rating model for residents previously developed within the QCITY project based on current knowledge. So far, the model contained methods for incorporating the effect of ambient noise in the immediate vicinity of the dwelling (quiet façades) and outdoor noise in the neighbourhood, described by the proportion of the area with equivalent sound levels above 50dB(A), as well as the effect of insulation of the dwelling. However, indicators for these effects were not yet adequately based on scientific literature or research. An inventory of the literature was made addressing the empirical basis for the influence of outdoor noise in the vicinity of the dwelling, in order to evaluate the outdoor environment component in the noise score rating model for residents. In addition, an overview was made of the information regarding effects of additional characteristics of the noise other than the equivalent noise level, such as the influence of spectrum characteristics and the influence of the rate of occurrence of individual events. As far as possible, a method to incorporate the influence of these characteristics has been proposed. The refined rating model for residents is described in Deliverable 2.2.1. The improved noise score model for indoors has been integrated into the CadnaA noise mapping software of Datakustik. The refined model can also be implemented in other software’s for traffic noise.
The refined rating model for residents is described in Deliverable 2.2.1. In the model, indicators for equivalent noise level at the façade of the dwelling are combined with information about outdoor noise levels in the vicinity of the dwelling, spectrum characteristics (in conjunction with insulation characteristics) and temporal variations in noise levels. This model may be used to predict the overall annoyance response, i.e. the percentage and number of residents that will be expected to be annoyed by noise in a given area. In the context of the EU Environmental Noise Directive, it is important to adequately assess the impact of environmental noise on residents. So far, the assessment of the impact of noise on residents is based solely on façade levels of dwellings as obtained from the noise maps. Therefore, measures directed towards a quieter outdoor situation, as far as they are not reflected in façade levels, will not show up in health assessment indicators, nor will measures that influence the frequency spectrum, the indoor levels or the rate of occurrence of individual noise events. Using the refined noise score-rating model for residents, the expected effect of environmental noise on residents may be better quantified.
Typical constructional designs for walls, windows and ventilation from different time periods have been identified and compiled in a table for the case of Stockholm. The SRI was estimated for each component, as well as a resulting sound insulation index for typical exterior walls of the period, based on a window/wall ratio typical for the time period.
From the estimated SRI two curves were produced based on the most typical constructional designs of exterior walls as a function of the year of construction. One graph is for open passive ventilation slots and the other for closed passive ventilation slots. Trend lines were added, producing two polynomial equations.
The values shown in Figure 11 can only be used for Stockholm but the procedure can be used in other cities in order to estimate the SRI as a function of construction year, figure 11.
3.2.3 Cost/benefit analysis of Q-Zones
An extensive literature search and review of cost benefit analysis methods and noise (primarily, transportation noise) has been carried out in order to determine an appropriate methodology for the costs and benefits related to specific intervention measures.
Ultimately, the HEATCO methodology (Developing Harmonised European Approaches for Transport Costing and Project Assessment, December 2006) was chosen as the preferred method for cost benefit analysis of noise impacts, because it had been tested and agreed as appropriate for other European studies.
The methodology has been initially tested for Bratislava and later Stockholm and Gothenburg. This has proven the overall utility of the method. Initial results implemented for Bratislava have shown that the methodology chosen for cost benefit analysis of noise intervention is robust and most importantly is readily integrated with the results of the noise modeling for Q-zones.
The HEATCO CBA methodology has provided the ability to compare different scenarios. Below as an example results for an initial test site in Stockholm can be seen, figure 12.
3.3 NOISE AND VIBRATION CONTROL AT SOURCE – ACOUSTICALLY GREEN VEHICLES
3.3.1 External noise from hybrid and electric vehicles
Modification of the head visor microphone array for the automated evaluation of moving sources
A measurement system has been developed based on existing hardware and software (HEADVisor technology) allowing for the detection, separation and quantification of the various noise sources contributing to the overall noise of road traffic. The traffic consists of many single vehicles. Each vehicle contains a number of noise sources (e.g. tire/road interaction, engine etc.).
The system is capable to distinguish and track a single vehicle using optical information by means of calibrated video cameras. The position of the dominant noise sources is determined using the microphone array technology. The combination of optical and acoustical information allows for the identification of the noise sources at each passing vehicle.
The spatial resolution of a microphone array depends strongly on the array size. To resolve the complex traffic noise a modular system consisting of square grids (1.5 m x 1.5 m) has already been developed. The grids can be combined arbitrarily to build e.g. an array of 6 m x 3 m with up to 192 microphones and 3 video cameras to cover the entire street, figures 13 & 14.
The algorithms for vehicle detection, classification (e.g. passenger car, motorcycles, trucks) and tracking have been tested for synthesized traffic noise scenarios first. To distinguish between the various vehicles in real traffic flow the calibrated wide-angle panorama camera was developed. Using image analysis techniques, the single vehicles in the traffic flow can be detected and traced. The noise emission of the main sources can be calculated and exported as time signals, figure 15.
The system developed within the scope of CityHush has been successfully tested within two major measurement campaigns for the evaluation of traffic flows and analysis of tire/road combinations.
Using the microphone array data, time signals can be calculated for each source at the vehicles. Based on the measurements of a large number of different pass-by events leading to a set of data points consisting in physical descriptors (vehicle, position, speed, acceleration, source type) and a calculated time signal representing the source emission, an Acoustical Fingerprint technique can be applied. The Acoustical Fingerprint allows for the synthesized and interpolated evaluation of heterogeneous data points using standard acoustic or psychoacoustic descriptors. The Acoustical Fingerprint can be used to characterize the emission of single vehicles (comparing, e.g. different sets of tires) or road locations, Figure 16.
For the validation of the system performance, measurement campaigns on a test track and on the GOOD proving ground have been conducted. In the first campaign, four different vehicles including an electric car have been measured under traffic like running conditions. In the second campaign, an electric vehicle has been tested with two sets of tires (normal and low noise) on two different road surfaces (smooth and rough road). A total of 53 pass-by measurements are synthesized for the acoustical fingerprint using the standard A-weighted sound pressure level, time-invariant loudness, and sharpness. The data allows detailed analyses as well as quintessential statements.
Measurement and evaluation of single pass-by noise and free flow noise with head visor
Acoustical measurements of different vehicles were performed on a test track and public roads. Diverse measurements of single pass-by noise of vehicles under various running conditions for a hybrid vehicle on the market and electric vehicles were realized, figure 17.
Different receiver positions were considered to investigate the change of noise due to a source-receiver distance increase. Moreover, measurements near the most important sources were performed to separate the different source contributions and to be able to estimate the improvement due to potential mitigation measures (reduction of tire-road noise).
The acoustical measurements were analyzed with respect to several (psycho-) acoustic quantities. In addition to it, listening tests were performed to collect data about subjective reactions to new road traffic noise caused by electric and/or hybrid vehicles.
Traffic flow measurements on a variety of different vehicles have been analyzed using the Acoustical Fingerprint technology. The traffic flow consisted of a large number of single pass-by events that were partially overlapping in time. Each single event was analyzed regarding the type (size) of the vehicle and the current speed and acceleration. For the dominant noise sources time signals were calculated. These time signals can be evaluated using standard and psychoacoustic analyses. It was confirmed that free traffic flow noise can be analysed by the developed head visor technology (modified microphone array).
Moreover, it was found that the psychoacoustic evaluation of the measurement and simulation signals produces comparable results.
Extension of the traffic noise synthesizer for the simulation of hybrid vehicles
HAC has developed an extended synthesis tool to auralize exterior noise of vehicles and whole road traffic scenarios for hybrid and electric vehicles. The syntheses of the source signals can be based on different data; spectra and time signal based synthesis can be performed as described in the QCity report.
The synthesis is controlled by the measured position and the velocity information during the tests. The simulation of the vehicle noise uses first the measured near-field signals. Each source (tire and driveline) corresponds to a microphone signal. These signals are loaded into the simulation software and processed.
To model the radiation characteristics from the near field to the far field, the near-field microphone signals are modified using radiation filters. For each source, specific characteristics must be considered.
The resulting filtered source signals were used to calculate the propagation to the receiver position. The propagation calculation consists of the following steps:
1. Damping of the source signals due to the distance between source and receiver.
2. Damping of the signals due to the air absorption.
3. Frequency shift of the signals due to the relative speed between source and receiver (Doppler Effect).
4. Binaural filtering of the signals depending on the angle of the source in relation to the receiver.
These steps have been performed for different hybrid and electric vehicles taking also into account the appropriate driving conditions.
Integration of the psychoacoustic evaluation metric in existing noise maps and noise score models
Activities have been performed using the Traffic Noise Synthesizer in order to calculate sound pressure time signals at various points related to a simple traffic noise scenario (studying e.g. the influence of barriers, influence of additional sound sources at vehicles). These time signals have been used to calculate different psychoacoustic quantities like loudness, sharpness, roughness at the points of interest leading to first psychoacoustic noise maps.
To check the possibility to combine existing noise mapping information with psychoacoustic evaluation methods a case study was performed, where simulations were prepared for the Essener Park. Different ratios of electric vehicles to passenger cars powered by internal combustion engines were considered and auralized. In addition to it, psychoacoustic analyses of the simulated road traffic noises were performed.
The case studies of the example scene Essener Park have shown the applicability and usefulness of the developed universal noise synthesizer in the context of quiet zones. It is a tool providing additional information beyond conventional noise maps. Planned mitigation measures can be validated not only with respect to the sound pressure level reduction but also regarding the impact on other perception-relevant acoustic parameters.
Based on the current software tools, it is possible to simulate the noise immission of a given traffic scenario at various locations in a scene for later visualization on a noise map. As each vehicle is modelled by multiple distinct noise sources, like engine noise and tire-road noise, the impact of the modification of each source can be analysed individually.
3.3.2 Noise specifications for vehicle purchase and noise criteria for vehicle free access to Q-Zones
Until now, the definition of environmentally friendly vehicles only included chemical and particulate emissions, not noise. The objective of this study is therefore to develop a universal functional noise specification to be included in green car purchase specifications in Europe.
The main goal of the CityHush project is to present solutions that reduce the overall traffic noise levels in urban areas by 10 to 20 dB(A) units. One possible way to achieve this is to allow only free access to certain Quiet zones (Q-zones) in the city only to quiet hybrid/electric vehicles. The objective of this task is therefore to develop suitable noise criteria for vehicles that are allowed free access in the Q-zones.
The following has been performed within this work package:
- Studies regarding proper test methods for type approval of passenger cars in urban areas with a focus on electric and hybrid cars;
- Sound measurements on new hybrid and electric passenger cars;
- Collection of noise emission data from normal passenger cars [1];
- Development of noise classifications covering the whole range in exterior noise from passenger cars based on the measured and collected noise data;
- Proposal on suitable noise limit in order for a passenger car to be considered environmentally friendly with respect to noise;
- Proposal on suitable noise limit in order for a passenger car to be allowed free access in Q-zones.
The following conclusions for passenger cars has been given:
- Type approval according to ECE R51 method B (ISO 362 :2007);
- Full acceleration test from 30 km/h instead of 50 km/h for electric passenger cars with weak engines (e.g. PMR < 40). More studies should be made in this area;
- A passenger car that are considered environmentally friendly has to fulfil
Lurban < 68 dB(A) (i.e. noise class A or B);
- A passenger car that is granted free access in Q-zones has to fulfil
Lurban < 64 dB(A) (i.e. noise class A). This is about 8-10 lower noise levels compared to normal passenger cars during normal urban driving on urban main streets with speed limit 50 km/h. This noise limit is likely to imply that only pure electric vehicles are granted free access.
- Similar noise limits should be developed for other vehicle categories as well in order to consider all types of vehicles.
3.3.3 Creating a low noise road surface for inner city use
Development of a smooth elastic dense road surface
The performed studies show that it is possible to create a low noise road surface for inner city use by optimizing the road texture. The noise reduction might not be as high as for porous road surfaces but the effect hopefully last for a longer time period. For standard vehicles at lower speeds, the effect from reducing the tyre/road noise is small due to the higher driveline noise. For hybrid and electrical vehicles, the tyre/road noise is dominating which means that the reduced tyre/road noise results in a reduced total noise level for the whole vehicle.
The result from the final measurements show that the developed smooth road surface with optimized thread pattern can reduce the tyre/road noise with 2 dB(A)-units compared to a new reference pavement with a maximum stone size of 8 mm.
Comments on the results and relation between road texture and noise are discussed in deliverable D.3.3.1 figure 18.
Cost/benefit analysis of low noise road surface
In almost all regions in Europe, the use of low noise road pavements is selected as an action plan within the requirements of the European Directive of Strategic Noise Mapping and Action Planning.
However, the real realisation on the field is sometimes limited by financial implications: the cost is thought to be too high.
In this study, it is sought to develop a Cost Benefit Analysis (CBA) procedure to better estimate the real cost, but also to better valuate the benefits of low noise road pavements. By this approach, it is hoped to find additional arguments to implement more and/or faster additional low noise road pavements.
Different approaches for both the estimation of costs, and of benefits will be proposed. Further, they will be evaluated for application in both, a larger region and an agglomeration.
In addition to this, automated calculation and visualisation methods of hot spot identification of noise problems are evaluated as a method for optimisation of the application of low noise pavements: prioritising of road segments for renovation or refurbishing based on the number of people annoyed. Those methods will be applied to the same examples as used for the cost benefit analysis above.
Cost/Benefit analysis
Cost-benefit analysis (CBA) provides a means for systematically comparing the value of outcomes with the value of resources achieving the outcomes required. It measures the economic efficiency of the proposed approach. When all else is equal more efficient approaches should be chosen over less efficient ones. When there are many options to consider during a decision-making task, it is useful to evaluate the options with a common metric. Cost-benefit analysis refers to any type of structured method for evaluating decision options.
CBA has become widely accepted among business and governmental organisations. Although CBA has definite limitations, especially in the non-standard way that the payoff function is derived and calculated, its potential for making decisions more rational is comforting to those who must make the decisions. The presentation of a cost-benefit analysis is the preferred way to demonstrate the reasoning behind investments. The CBA of measures against noise pollution comprise consequently, figure 19:
- the costs of the measures;
- the reduction of the costs for public health;
- the willingness to pay: how much are people prepared to pay for a less noisier environment?
For the evaluation of road pavements, this general approach can be applied,with omission of effects such as time savings and productivity reduction and costs at the transmission paths and at the receiver.
Conclusions
For benefit analysis, a monetarisation method based on noise dose effect relations (as proposed by Heatco) has been retained as very valuable. It has been indicated that for larger regions, simple low noise road pavements such as standard porous asphalt give very positive results. More sophisticated low noise road pavements give a higher noise reduction, but are much more difficult to recommend based on cost benefit analysis. For agglomerations, low noise road pavements alone are not sufficient to reduce the noise annoyance sufficient.
The methods set forward can be used by noise action planners to evaluate in more detail the effect of low noise pavements as action plans. It is illustrated that at least simple low noise road pavements should be applied: the cost benefit analysis showed that the return on investment is very high. The “Willingness to Pay” for such measures exceeds the additional costs for implementation. The use of hot spot identification methods has been demonstrated and shown to give additional information on the prioritising of refurbishment of road pavements.
3.3.4 Developing quiet tyre designs for quiet road surfaces
The concept that GOOD developed is based on the fact that the tyre tread pattern plays a dominant role for noise reduction on smooth road surfaces and less of a role on coarse or rough road surfaces. By selecting only the most quiet tread patterns to be run on smooth road surfaces with maximum stone size of 5-8 mm, it is believed that up to 6 dB(A) units in noise reduction could be achieved.
GOOD developed ten different designs in CATIA CAD software. Tread pattern geometry of the designs has been optimized to provide reduced noise (interior & exterior) generation for smooth low noise roads and quite electrical or hybrid cars. The designs have been laser carved on smooth (slick) tires and tested in the anechoic chamber. Interior and exterior noise indicators have been assessed against the control (reference) tires. Based on the results of the assessment, three low noise concepts were selected, modified and laser carved (five tires per concept) for further road testing (handling, braking, rolling resistance). A low noise tire structure with transitional closed cellular rubber layer has been investigated to achieve the additional noise reduction: Twenty tires were built and the acoustical performance has been evaluated.
Three low noise tire concepts have been developed and manufactured (laser carved on slick tires in size 175/55R15) developed for further road testing on low noise smooth roads and quiet electrical or hybrid cars. The concepts give reduced structure-borne and air-borne noise. The noise reduction is around 5 - 6 dB(A) on the smooth low noise road replica (lab assessment) in comparison to a typical/standard treaded tire.
The concepts were manufactured (five tires per design) for further road testing. Tire structure/carcass modification (additional subtread elastic porous layer) gives an additional noise reduction of 2 dB(A).
When testing the developed concepts on electrically driven vehicles running on smooth road (surface according to 2001/43/EC TIRE/ROADNOISE DIRECTIVE), a traffic noise reduction of approximately 6 dB(A) at 70-90 km/h is expected (relative to current production standard tires driving on a standard asphalt pavement).
ACL made calculations to estimate the total traffic noise reduction when combining DualQ tyres and electrically driven road vehicles. A DualQ tyre consists of two tyres only 90 mm wide that are mounted on a common rim in such a way that an air slot of at least 60 mm is provided between the two tyres. Based on work done in the previous research project QCity, it is concluded that road traffic noise is dominated by tyre/road noise for velocities above approximately 30 km/h. Therefore, it is essential that electric vehicles with lower driveline noise are equipped with low noise tyres. If not, the low emissions of the driveline are masked by excessive tyre/road noise. It has been shown that the total traffic noise reduction achieved by a combination of DualQ tyre design and electrically driven vehicles is approximately 10 dB(A) units at 40 km/h even on rough roads.
The feasibility of manufacturing the prototype tyres and to perform tests on an electrically driven car is secured by testing the DualQ concept on a Volvo C30 electric car at Volvo proving grounds. Both external as well as internal sound levels will be measured. The manufacturing of the special rims are currently under way. Testing will take place in the autumn of 2011 for the deliverable to be finished on time at M24.
When testing the DualQ tyre prototypes on electrically driven cars running on smooth asphalt, a traffic noise reduction of approximately 10 dB(A) units at 40 km/h is expected (relative to standard car with standard tyres driving on a standard asphalt pavement).
UCAM worked on the tyres for heavy vehicles:
- Tread pattern to contact-patch force mapping. An existing model for the dynamical response of a single tread block transiting the contact patch of a tyre on a smooth road has been developed to provide a complete, time-dependent set of contact-patch forces, for a given tread-pattern input.
- Integration of contact-patch forcing into tyre-response model. An in-house model for the tyre vibration response to forcing by a single, concentrated force was available. This has been extended in order to allow driving by the full, contact-patch force distribution.
- Boundary Element Method (BEM) calculations for the noise radiated by the vibrating tyre. Candidate BEM programs have been evaluated, and an open-source code has been selected. Import of vibration results into the BEM is in progress.
3.3.5 Definition of a noise & annoyance standard for motorcycles in the urban environment
The scope of the work to be performed in the WP3.5 can be summarised in two steps.
- A first step is to describe the specific noise signature of 2/3-wheelers (e.g.: spectra, pitch, pass-by duration, L1), not only LAmax (EU Directive 97/24/EC), perform a psychoacoustic evaluation of PTW in listening tests, derive a noise criteria linked to the annoyance for the classification of PTW, establish of the relevance of single events (motorbikes, mopeds, scooters, …) for long-term overall evaluations.
- A second step is the examination and modelling of road traffic noise and resulting annoyance as a function of different percentages of PTW, of the effect of general ban of PTW and the effect of the shift to low noise PTW on noise annoyance.
- TTE conducted an extensive literature and field study that can be summarizes as follows:
- Literature review (annoyance of PTW in other studies, noise levels and noise signatures of PTW in other studies, statistical data to understand where, how and when the PTW are driven).
- Evaluation of annoyance from PTW by means of about 200 interviews on the street (questionnaires based on a set of 10 questions on the environment and other questions on age, gender, nationality, language), with simultaneous recording of the noise and analysis of LAeq, Lmax, L5, roughness, sharpness, loudness and traffic type.
- Derivation of the specific annoying characteristics of PTW (under real, representative conditions!) by means of a three days continuous measurement in a major road in Athens, where PTW were recorded following the requirements of a statistical pass by and each single event was afterwards analysed into a database.
- Traffic counting to derive typical traffic patterns (number and time pattern of pass by per vehicle type) for use in assessing the effect of single events.
Based on this real and new data, annoyance curve as function of the traffic type and distribution was derived (Paviotti-Vogiatzis curve), and a comparison was made towards the annoyance curve proposed by WG 2 (Anderson et al. (1993)). Agreement was found with the upper curve proposed for annoyance outdoors.
A literature research was performed to get relationships to relate health effects of noise and values for energy consumption, energy cost, CO2 and NOx emissions, so as to compare (roughly) the following parameters:
- Sleep disturbance;
- Social impact;
- CO2 emissions;
- Safety;
- NOx emissions;
- Economic implications.
Simulations and analyses of the possible scenarios was performed and a chart to visualise results was prepared.
HAC took a more analytical approach to obtain acceptable noise characteristics for quiet motorcycles. In addition, the effect of motorcycle specific noise signatures (especially in relation with Lmax and L1 indices during “sensitive” periods of night) on noise score rating values were evaluated. Finally, the effect of forbidding high environmental noise motorcycles in specified periods of day and the use of low noise motorcycles in combination with circulation time restrictions patterns was evaluated.
Acoustical measurements were performed on a test track and on public roads with different powered two wheelers (PTW). For comparison, purposes powered two wheelers with combustion engine and fully electrified powered two wheelers were investigated. In addition to the ISO 9645 conditions, further conditions were considered. The diverse acoustical measurements are used in listening tests and they are needed for the implementation of PTW into the Traffic Noise Synthesizer technology.
Listening tests in the laboratory were carried out to collect data about subjective reactions to different PTWs and to investigate the relation between psychoacoustic parameters and annoyance ratings. It is expected that the noise of PTWs causes stronger annoyance reactions than passenger cars.
Measurement and analysis data was exchanged with TTE.
HAC has accomplished within this work package:
First, measurements of different powered two wheelers (electric scooters, scooter powered with combustion engines, motorbikes) on a test track were performed for all relevant driving conditions.
Second, the measurements (near-field and far-field measurements) were post-processed to enable the inclusion of powered two wheelers in the traffic noise synthesizer technology. New vehicle models were created in addition to the existing vehicle models.
Third, the measurements and simulations, which were generated by the traffic noise synthesizer technology, were subject to extensive listening tests in laboratory. The results were analyzed with respect to the noise annoyance potential of different scooter types also taking into account varying boundary conditions.
Based on this work, two major conclusions were drawn.
First, road traffic with a certain share of scooters powered by combustion engines is always perceived as more annoying than road traffic scenarios, where the scooters are powered by electric engines. This trend is even more significant, when the surrounding traffic consists of electric vehicles, figure 20.
Second, the surrounding road traffic consisting mainly of passenger cars (in the context of temporarily occurring scooters) influences noise annoyance only for road traffic scenarios, where only E-scooters are present. Scooters powered by combustion engines dominate the perception and evaluation to such an extent that the surrounding road traffic is almost insignificant for the overall noise annoyance (see figure 20).
This outcome makes clear that a restrictive policy against powered two wheelers equipped with combustion engines has to be applied for Q-Zones.
3.4 PROPAGATION ATTENUATION OF ROAD TRAFFIC NOISE
3.4.1 Wave propagation analysis for heavy quiet vehicle tyres
A reciprocal-configuration Boundary Element Method calculation of acoustic radiation characteristics has been implemented for a generic tyre geometry. The influence of the geometric parameters on the radiation characteristics has been studied. Based on the results, recommendations for acoustically optimal truck tyre dimensions have been formulated.
The degree of amplification of noise sources on the tyre belt is strongly affected by the overall tyre width. In contrast, the tyre radius predominantly influences the pattern of the varying amplification around the belt, rather than its absolute level. Radiusing the tyre’s ‘shoulder’ region is potentially beneficial in terms of lowering amplification levels, for a tyre of fixed overall width. However, it is less effective than maintaining sharp shoulders and reducing the overall width.
3.5 VALIDATION OF PROJECT RESULTS
3.5.1 Q-Zones in Stockholm
The results presented in WP1 and WP2 have been verified in regards to percentage highly annoyed people (%HA) using extended tools for analysis indoors. Results showing the change of percentage highly annoyed due to creation of Q-zone are presented in Deliverable 1.2.1.
Improved analysis tools
The noise evaluation tools for residences stated in the Environmental Noise Directive 2002/49/EC only consider the sound level on the most exposed façade. The sound level on the most exposed façade is used for example to plan the type of windows on a building, that sound level is not necessary corresponding to percentage highly annoyed people. Improvements to the existing evaluation tools have been made within the project CityHush. The Deliverable 2.2.1 introduces a method, which treats several characteristics of noise other than the noise level on the most exposed façade.
The refined method that has been validated considers the following additional acoustic factors:
- Quiet façade;
- Quiet areas in the neighbourhood;
- Façade insulation;
- Noise frequency characteristics .
The actual façade insulation of the building used in the refined method is a fixed value. The calculated correction due to the façade insulation is constant even though a city holds a large variation of buildings with various façade insulations. A Survey of façade insulation for a large variety of buildings was carried out. The methodology on how to include the façade insulation was composed in Deliverable 2.2.3 using the construction year as a basis for information of the construction elements.
The evaluated methods for calculating noise levels and annoyance for residents are:
- Sound level at most exposed façade;
- Refined Method for annoyance at home;
- Refined Method for annoyance at home using insulation data corresponding year of construction.
The added characteristics in the refined methods could indicate whether the sound pressure level on the façade is overestimated or underestimated. Depending on the cityscape, and type of buildings the refined method would indicate worse or better scenarios corresponding to highly annoyed people. Using noise mapping software’s the redistribution could be noticed, since a noise map only show sound pressure level and take no account to example quite façade or façade insulation. A calculated noise map showing overestimated and underestimated sound pressure level is shown below. The noise map shows buildings in red and green colour. The green buildings indicate that the sound pressure level on the most exposed façade is larger than the recalculated noise level including additional aspects like sound insulation i.e. calculated sound level are overestimated for %HA considerations. The red buildings indicate that the sound pressure level on the most exposed façade is smaller than the recalculated noise level i.e. calculated sound level is underestimated, figure 21.
3.5.2 Embedded parks in Gothenburg
Evaluation methods for outdoor recreation areas such as parks have been developed in previous stages of the CityHush project. Evaluation of parks could be made using a straightforward approach using only the average sound level inside the park. Methods for a more detailed evaluation of parks have also been developed, where the number of park visitors and their distribution inside the park are included. Previously developed relationship for outdoor road traffic annoyance enables quantification of the annoyance in the park.
Previous work also shows the benefits of Q-zones and gives a view of the potential improvements by introducing zoning in urban areas.
The developed methods for evaluating outdoor noise in parks and recreation areas have been evaluated for six different parks. Two parks are located in Gothenburg and four parks are located in Stockholm. The processed evaluation methodology results in some deviations in comparison with a more straightforward evaluation. This deviation is a result of improvements made with the proposed evaluation method, which have made it possible to include additional information. The results show no consistent exaggeration or understatement of the resulting annoyance in urban parks. Consequently all parks are specific and resulting annoyance inside that park may deviate either way depending on several factors such as size, visitor distribution inside the park, topography and number of nearby residents.
As well as getting a better idea of the annoyance or/and perceived soundscape quality in urban recreation areas and urban parks, the potential benefits of Q-zone implementation could be evaluated.
Conclusion
It is important to include noise levels outdoor to get an overview of the level of noise that affects the population of a city. In the current situation, the focus is only on the noise levels in residential buildings. Used response curve for traffic noise annoyance makes it possible to calculate the number of annoyed visitors in a given outdoor area.
Analyses of outdoor environments such as recreation areas and parks according to developed methods will help the assessment of environmental noise in the outdoor situation on residents, figure 22.
Comparisons made in this project show that the quality of the noise evaluation could be more precise including factors like distribution of people inside the park. Comparing the amount of annoyance using the average noise inside the park and distribution based method could differ up to 8 %, which could be of great importance. Deviations in results point out the importance of including the use and purpose of the area and the number of people making use of the area at a given time i.e. the distribution of the people to predict the overall annoyance response.
Evaluation based on the arithmetic average noise level inside the park is acceptable if the noise level is evenly distributed in the park. It is important to include aspects of visitor distribution and number of visitors when evaluation parks and recreation areas in order to quantify the number of people annoyed. If the park holds both noisy and quiet areas, points of interest like cafés or for example, a playground the importance of the visitor distribution increases, figure 23.
Even though both embedded parks, Mariatorget in Stockholm and Trädgårdsföreningen in Gothenburg, are located in the Q-zone boundary the annoyance drops with the introduction of the Q-Zone. The calculated reduced annoyance corresponds in both Gothenburg and Stockholm to 1000 less annoyed park visitors. The concept of embedded parks, evaluation tools comparable to the response curve and distribution based noise score evaluation are important tools for designing and preserving existing and future green areas.
3.5.3 Noise score rating models for Q-zones in Athens
The noise score rating models have been validated in a case study in Athens, including for Q-Zones and embedded parks. Noise score models for indoor and outdoor noise were used. A detailed analysis with different noise score rating models have identified the actual and perceived benefits of the noise effects and impact of Q-Zones and embedded parks. Also situations were analyzed with high noise levels from motorcycles as well as situations with low frequency noise annoyance, figure 24.
Conclusion
With the respective Athens Q-Zone scenario configurations it has been shown that the average noise levels in the Q-Zone and the park can slightly be reduced and the park capacity can be increased. Measures with a special focus on the reduction of conventionally powered motorbikes and scooters (PTWs) were included. The emission values of various PTWs were derived - from the known values of car emissions and from past measurements - in the form of a correction function as a function of speed. These derived values were then used to perform the simulation analysis on the effects of the overall noise levels by shifting the proportion of conventionally and electrically driven PTWs. In result, the noise difference maps show slight noise reductions, while it is more marked if other measures are included, like speed limits. Further measures, such as increasing the proportion of low noise cars and reducing the noise level of the railway by 5dB, enhances this positive effect.
The effects these noise reductions have on both noise rating models, the amount of HAP and on the number of annoyed park visitors was predicted. As expected, the amount of HAP and the number of park visitors are correlated with the reduction of overall noise level. This means that the falling trend of noise level reduction seen throughout the different scenarios is also reflected in the amount of HAP and the number of annoyed park visitors.
Finally the noise costs were estimated, which appear to decrease with the falling average noise levels. Thus scenario S7 contains the least noise costs whereas scenario S1 (base case) shows the highest noise costs. However costs of introducing the new measures were not considered.
3.5.4 Reduction of low frequency air borne noise in Antwerp
In the later part of the project, on site measurements were performed on double façades. The results of these measurements are presented in the present deliverable 5.5.1. Six different setups have been installed and measured, table 1.
Detalied results can be found in the public deliverable on the CityHush website. Following conclusions can be drawn from the measurement results:
- Adding the glass pane at the first distance (300 mm) gives an increase in the insulation value in the 1/3 octave bands of 50 Hz, 63 Hz and > 250 Hz. At 50 and 63 Hz, the value of the increase is 2 to 4 dB. In narrowbands, the increase in insulation value can be detected for frequencies up to 65 Hz;
- Increasing the cavity depth give increasing insulation values for the low frequencies (1/3 octave bands of 40 and 50 Hz) up to 5 or 6 dB;
- The insulation values in the 1/3 octave band of 63 Hz does not improve by increasing the cavity depth;
- Increasing the cavity depth also does not influence the insulation values for the higher frequencies (> 250 Hz);
- Adding absorption in the cavity hardly improves the insulation values for frequencies < 100 Hz and > 800 Hz;
- For frequencies between 100 and 800 Hz, there is an improvement of up to 4 dB by adding absorption in the cavity.
3.5.5 Reduction of low frequency structureborne noise in Brussels
A solution for low frequency structure borne noise has been designed and modelled for a real site in the city.
- A site was selected and traffic-induced vibrations due to passage of a bus over a speed table and a road joint has been measured.
- The numerical tool proposed in the WP4 has been used for modelling and design of the isolating system. The numerical model can account for the road-soil interaction, the wave transmission through the ground, and the structure of the isolating barrier.
- The efficiency of the designed system has been validated by means of an experimental measurement in a scaled test bench.
In a selected site in the City of Leuven, real traffic-induced vibrations due to passage of a bus over a speed table as well as over a road joint have been measured. Based on the real measured vibration, two types of isolating barrier have been designed and the efficiency of each system has been investigated by both numerical and experimental simulation.
Two types of isolating solution (1) a concrete barrier and (2) a concrete-EPS-concrete barrier have been designed. Results of experimental measurements in the scaled test bench show that a three-layer barrier would be more efficient than a one-layer barrier. This confirms results of the numerical modelling presented in WP4.
To have an estimation on the noise reduction, the level of the insertion loss at a point close to the building (at around 10 m from the road) should be considered. Then, the level of noise reduction can be determined using the equation (2). The following table shows a resume of the noise reduction inside the building using different barrier configurations, table 2.
To obtain higher efficiency, deeper barriers with higher depth ratio H b /λ must be used. For instance, using a concrete-EPS-concrete barrier of 8 m (with H b /λ = 1.4) or a concrete barrier of 13 m (H b /λ = 2.3) can guarantee an efficiency of at least 10 dB.
Potential Impact:
4.1 POTENTIAL IMPACT
The main concept of CityHush-project is the Quiet zone. Within the Q-zone concept lots of products and tools have been developed. The developed products (low noise tyres, low noise road surface etc.) are available on the market as soon as the market request the products. All the refined/developed methods, in order to evaluate the concept of Q-zones, has described in public reports and the implemented in the commercial software CadnaA. Local authorities and stakeholders now have the possibility to order investigations in cities, referring to the methods described within the CityHush project. The results from the CityHush project will of course also be useful for all other investigations regarding traffic noise in cities and urban areas.
4.2 DISSEMINATION ACTIVITIES
4.2.1 PROJECT WEBSITE
A website on CityHush was developed in May 2010 (see Figure 28) and is available at www.cityhush.org and www.cityhush.eu. All public results and reports of the CityHush project have been made available on the website. The presentations given at the various dissemination events are accessible online (see Figure 29). Links to related projects and networks are provided (see Figure 30).
4.2.2 PROJECT NEWSLETTER
The CityHush electronic newsletter informed the expert target groups about the project objectives, its progress and outputs as well as of CityHush tools and CityHush dissemination events. The newsletter ensured a regular flow of information on the project to interested stakeholders in order to maintain awareness of the project throughout its lifetime.
4.2.3 NETWORKING AND EXTERNAL EVENTS
To raise interest of various target groups in CityHush, results have been presented in general and scientific articles, as well as at relevant conferences. In accordance with the project’s respective target groups, both general and more scientific media are targeted, but with the main emphasis on publications for specialist audiences and expert conferences.
Publications
Interesting and relevant journals and conferences were identified by the consortium. A list of relevant publications to disseminate CityHush results was developed at an early stage and has, since then, continuously been updated. Realized publications are based on that list (see table 3).
Between January 2010 and December 2012 18 articles were published (while 2 are awaiting publication in conference proceedings) (see ANNEX). Out of these articles, 12 were scientific publications focusing on research findings.
Conferences
Relevant conferences to present CityHush results have been identified by topic experts among the consortium. Throughout the project, CityHush results were presented at 20 conferences on noise across Europe (see detailed outline in ANNEX). Half of these presentations took place in the final year of the CityHush project which ensured the dissemination of final research findings.
4.2.4 SEMINARS AND TRAINING SESSIONS
To pass on research results from CityHush two types of CityHush dissemination events have been organised:
- 3 dissemination seminars,
- 2 training workshops for local authorities
Dissemination Seminars
The dissemination seminars targeted a wide range of urban transport stakeholders and noise experts. The objective of the seminars was to disseminate the project results to a broad audience. Each event aimed at about 50-100 participants. To reach these stakeholders across Europe, the seminars are geographically well distributed.
Training Workshops
The training sessions targeted transport experts from local authorities. The aim of the trainings was to highlight the research findings’ implications for cities and to teach the participants how to make use of the CityHush concepts within their local noise abatement strategies. The targeted number of participants in each training was about 20.
List of Websites:
http://www.cityhush.eu
The European-funded CityHush project starts from a vision: the quiet city! Implementing quiet zones with the help of quiet electric (or hybrid) vehicles resulting in noise levels 10-15 dB(A) lower than before, quiet tyres and road surfaces, as well as design solutions for buildings and noise barriers to mitigate low-frequency noise are the project’s key instruments to achieve that.
Road traffic noise is the major noise problem in European cities. Changing to electric vehicles can bring about a significant noise reduction. In order to make the possible benefits tangible as early as possible – with only a small share of the vehicle fleet being electric in the beginning – CityHush is proposing quiet zones, so called Q-Zones. In Q-Zones only electric vehicles will be allowed, defined via a certain maximum noise level. Compared to the situation before, noise levels are expected to be reduced by about 15 dB(A) in the inner part of the zone. This concept has been supported by innovative designs for low-noise tyres and road surfaces. To further improve the situation at hot spots, CityHush suggests innovative noise barriers to absorb or mitigate the propagation of low-frequency noise. Below a list of measures and successful results from the CityHush project is shown:
- Evaluation of the concept of Q-zones to reduce traffic noise in urban areas.
A noise reduction exceeding 12 dB within the Q-zone has been achieved.
- Evaluation of the concept of embedded parks inside the Q-zone.
- A refined noise rating model for the outdoor has been described and implemented in public noise calculation software.
- A refined noise rating model for the indoor has been described and implemented in public noise calculation software.
- A smooth dense road surface with optimized road texture has been developed. Measurements show a noise reduction of 2 dB(A)-units compared to a new road surface with the same maximum stone size (8 mm).
- A new low noise tyre from Goodyear has been developed for electrical vehicles. Measurements show a noise reduction of up to 5 dB(A)-units compared to a reference prototype tyre.
- Measures for reducing airborne and structure borne low frequency noise has been described. The concepts focus on already exploited areas where ordinary measures cannot be used. The concepts include barriers in the ground and low frequency absorbing facades.
- Development of a measurement system allowing for the detection, separation and quantification of the various noise sources contributing to the overall noise of road traffic.
- Development of an objective and psychoacoustic evaluation tool for low noise low emission vehicles
- Proposal of a modified test method for type approval electric vehicles regarding noise.
Recommended criteria´s for purchasing green low noise vehicles have been described. Recommended criteria´s for vehicles to enter a Q-zone (in this project) free of charge have been described.
- Active and passive noise attenuation measures within the concept of tyre hoods.
- Definition of criteria for use of low noise motorcycles within a city environment using a holistic approach taking into account benefits in terms of congestion reduction and other.
Project Context and Objectives:
As a general target for the environment as formulated in the SST-2008.-RTD-1 is stated that:
- Noise reduction within urban areas by 10 - 20 dB(A) units should be achieved;
- New passenger car CO2 emission should be reduced by 40 - 50% and for heavy duty vehicles by 10 - 30%;
- Total of other emissions should be near zero.
The CITYHUSH project is a response to the Call SST.2008.1.1.3 Greening of surface transport. Greening of Products & Operations Holistic noise and vibration abatement
The CITYHUSH project has as objectives:
- to reduce the overall noise levels in the treated city zones by 10-20 dB(A);
- to substantially reduce the CO2 emissions;
- to reduce other emissions to near zero at least in certain cases.
The large and medium sized European cities (> 100 000 inhabitants) will, according to the EC Noise Directive 2002/49, have to produce and deliver noise maps and noise action plans at year 2012 and 2013 respectively. At these dates, the cities with > 250 000 inhabitants shall also supply to the Commission their revised noise maps and Actions Plans.
The CITYHUSH project will support city administrations in the production and implementation of these noise action plans as well as of the noise reduction technology that will be the framework in these Noise Action Plans.
The identified hot spots and noise action plans made with the existing technology suffer from major shortcomings:
1. the correlation between hot spots with annoyance and complaints is very poor;
2. proposed mitigation measures in general result in increased emissions;
3. only indoor noise comfort is addressed whilst a silent outdoor environment is also very important especially in cities where people live, work and recreate outdoors during many hours per day.
Step change solutions (such as Q-Zones) are proposed within the CITYHUSH project in order to meet the challenging combined noise and CO2 reduction criteria.
The noise score models for dwellings will be improved to increase correlation between hot spots and annoyance (e.g. by including effects of low frequency noise) and to increase correlation between hot spots and complaints (e.g. by including maximum levels to account for specific sources such as motorcycles).
A noise score model for outdoor noise will be developed to be able to evaluate the beneficial aspects of the creation of parks and other calm areas.
The project mainly aims at reducing noise in the city environment, it deals with developing suitable problem identification and evaluation tools (noise score models) and with designing and developing solutions, to be integrated in city action plans, for problems which are identified as hot spots but which show also high correlation with annoyance and complaints. The developed solutions will be validated in a city environment. All solutions will target a combined reduction of all emissions (noise, CO2 and fine particles).
Following innovative solutions and tools will be developed:
1. Concept of Q-Zones (zones in inner city where only quiet low emission vehicles are tolerated) and where the noise levels will be reduced by more than 10 dB in comparison with the existing situation, figure 1.
2. Concept of parks embedded in Q-Zones where the noise levels will be reduced by 10-15 dB in comparison with the existing situation, figure 2.
3. Indoor noise score rating models, which correlate better with annoyance and noise complaints by integrating low frequency noise and the occurrence of high noise single event (e.g. passing motorcycles) into the analysis.
4. Noise score rating models for the outdoors in order to be able to assess the complete living and working environment, figure 3, 4 & 5.
5. Objective and psychoacoustic evaluation tool for low-noise/low-emission vehicles.
6. Mathematical synthesis tool for noise from low-noise/low-emission vehicles to be used in simulation studies.
7. General performance noise specifications for purchasing low-noise/low-emission vehicles and noise criteria for acceptance of vehicles within the Q-Zones, figure 6.
8. Novel concepts for low noise roads based upon dense elastic road surfaces.
9. Novel concepts for low noise roads based upon grinding of asphalt top layers.
10. Novel concepts for tyres for low noise vehicles, including heavy vehicles, figure 7.
11. Criteria for use of low noise motorcycles within a city environment using a holistic approach taking into account benefits in terms of congestion reduction and other, figure 8.
12. Active and passive noise attenuation measures within the tyre hood.
13. Solutions for noise mitigation based upon high low frequency absorption at facades of buildings.
14. Solutions for noise mitigation based upon efficient low frequency isolation in the propagation path to reduce ground borne noise, figure 9.
All the above solutions and tools will be designed, prototyped and validated. They will result in obtaining the anticipated noise impacts.
Conclusion
CITYHUSH covers not only one subject of the call but it deals with all the subjects highlighted in the call and offers a holistic approach by considering all elements: the vehicle, the infrastructure, the emission, the propagation and the immission at the receiver. An innovative approach is included to better correlate noise hot spots as determined according to the EC Directive with annoyance and complaints. This is done by integrating low frequency noise and high noise impact levels into the noise score models. Emphasis is placed on solutions, which do not only minimise noise but also CO2 emission and fine dust emission. Not only residents inside buildings are considered but also the effect of quiet outdoor city zones (parks) will be quantified. This is an important factor in a global assessment of the noise performance of a city.
Project Results:
3.1 ACOUSTICALLY GREEN CITY AREAS - Q-ZONES
3.1.1 Tools for creating Q-Zones
Five different European cities have been chosen (see deliverable D 1.1.1) to evaluate the effects of establishing prospective Q-Zones during P1. Evaluation of the different cities, based on geographical data, traffic data, population data and assumptions on population behaviour, has been performed during period 2. Traffic models have been created and these have then been used to simulate noise distributions for various hypothetical Q-Zone scenarios. The difference in the noise situation of these scenarios with the current situation has been compared and are presented in deliverable D1.1.2.
For the five test sites, a varying number of scenarios have been simulated. The results have been discussed above in their specific site context. Although the results are specific to the chosen sites, we will try to generalise the results at least to some extent, building on similarities as well as differences. We may start by recognising that introducing a Q-Zone implies a reduction of the road network capacity. The impact of such a capacity loss will be more or less severe, depending on the initial use of the network, i.e. the congestion level. The higher the congestion level, the higher the price in terms of increased travel total times in the network. Likewise, the larger the zone, the larger the congestion effect of the implementation. Sufficient network capacity will obviously be a major condition for introducing a Q-Zone. If there is little traffic zoning in the city, a main effect of the Q-Zone will be to push through traffic away to the remaining network. For congested networks, this may imply increase travel times for a large part of the network. It may however appear a bit unfair to contribute the cost of mitigating through traffic just to the noise effects of the Q-Zone introduction. In many cities, zoning systems have been introduced for improving the environment in a number of aspects, including all kind of emissions, safety and other living conditions. It has not been possible to make an evaluation of all these aspects in this project, but they should also be considered by decision makers. It should also be noted that traffic zoning is also likely to reduce ambient noise, which may otherwise constrain the potential of the Q-Zone. Therefore, a traffic-zoning scheme may also imply a favourable condition for a Q-Zone introduction. It goes without saying that traffic zoning in itself will reduce noise levels, but then a Q-Zone concept is required to utilise the potential of new vehicle technology for further noise reductions. The traffic zone (or environmental zone) concept could also be extended to include the Q-Zone dimension. Other favourable conditions like tunnels for through traffic may also exist. In such cases, ambient noise levels are likely to be much lower which increases the potential of a Q-Zone introduction.
- Q-Zone size considerations
Because of the potentially strong effect of Q-Zone introduction on congestion, the initial size of a Q-Zone cannot be very large. A minimum size will be defined by the impact of ambient noise, which depends on local factors such as distances to major surrounding roads and local topology. A question may then be if the zone size can be expanded as the level of low noise vehicles increases. Then it can be expected that fewer drivers will have to change route because fewer drivers will have (banned or charged) standard vehicles, and consequently the effect on congestion would be lower. However, the rate of transformation of the vehicle fleet is very slow, and in the recent national Swedish transport plan reaching a level of only 5 percent was forecast for the year 2020. This view is supported also by a market outlook to the EU Climate Change Commission (AEA 2009). It is obvious that a reduction of the redistributed traffic of about 5 percent will be very small, and that an expected increase of low noise vehicles will not be a driver for Q-Zone size enlargement for the next 10 – 15 years. A level of 20 percent is of course even further away, although the speed of transformation can be expected to increase as the technology matures.
- Low Noise Vehicle Ownership considerations
The level of low noise vehicle ownership inside the Q-Zone may be more easily affected than the outside level. Depending on the Q-Zone policy, incentives to acquire low noise vehicles may be much stronger for Q-Zone residential households than for other households. Exempting Q-Zone households from a ban/charge may be necessary at the time of Q-Zone introduction, but will provide less incentive to change vehicle at least for a transition period. After this period, a ban or fee will provide some incentive, and additional incentives may be provided like free street parking for low noise vehicles. If the Q-Zone is introduced already at the exploitation of a new area, the transition period can even be skipped – standard vehicles might not be allowed in the new area. Assumptions of higher levels of low noise vehicle ownership are therefore motivated. Our simulations show that high levels of low noise vehicle ownership are necessary to bring about more significant noise reductions, especially in cases where traffic zoning has already taken place.
- Noise fee level considerations
The noise fees that have been studied are to be paid on Q-Zone entry or exit. The fee levels that have been simulated (0.5 - 2 Euros per entry or exit) give almost the same results as the ban does. This is more outspoken in those cases where the traffic simulation allows for route choice only. This effect is because the extra delay for changing route is for most drivers too small to match the fee. As there is a cost of fee collection, and as the size of the zone is small which implies a low number of paying vehicles, it has not been motivated to simulate even smaller fees. The choice between a ban and a fee is more a choice between ease of monitoring and giving some flexibility to drivers. In this project, we have however not tried to calculate monitoring or fee collection costs.
3.1.2 Parks embedded in Q-Zones
For identification of boundary conditions and maximum noise gains for parks embedded in Q-Zones, different sizes of embedded parks within each test site were defined during P1. For the test sites Essen and Bratislava an interface between the traffic model (build-up by partner KTH) and the updated noise model were created. For each test site, numerous traffic scenarios were worked out and evaluated using the criteria “number of people affected”, Noise Score, area affected, monetary benefit based on HEATCO Study, figure 10.
Numerous site inspections have been carried out in each of the cities that are addressed in this work. Contact has also been made with the relevant city administrations/authorities in order to identify potential sites to be considered for a Q-Zone and to discuss possible local issues.
The following results and conclusions have been seen from the study:
- Simulation/forecast of the maximum noise gains expected from embedment of chosen parks in the appropriate Q-Zones.
- Improvements of the noise situation in the Q-Zone and the corresponding park were achieved in many cases.
- Capacity increases were achieved in many cases.
- Negative impacts on areas outside the Q-Zone were identified.
- Approach for individual adaption of standard Q-Zone configurations has been suggested, to reduce negative effects in the areas outside the Q-Zone.
- Noise situation in parks can be improved by embedding the park in a Q-Zone
- Possible negative effects outside the Q-Zone need to be mitigated by measures that need to be assessed and defined for each individual case
- An approach is shown that gives reason to believe that negative effects can be minimized by individual modification of the standard Q-Zone configurations
3.2 NOISE SCORE RATING MODELS AND ANNOYANCE
3.2.1 Noise score rating method for the outdoors
As a starting point for the noise-rating model for the outdoors, an overview is made of information on the effects of noise in the outdoor environment. Based on this information and an analysis of the effects to be expected in urban (street, park) areas, a tentative noise score rating model for pedestrians and visitors of parks is designed. In this rating model, indicators for outdoor noise are combined with information about the function of the area and the number of people making use of the area at a given time to predict the overall annoyance response, i.e. the percentage and number of visitors that will be expected to be annoyed by noise in a given area. The state of the art regarding effects of noise on the outdoor environment as well as the preliminary noise-rating model for the outdoors are described in Deliverable 2.1.1 submitted December 21, 2011.
Furthermore, preparations have been made for a field study intended to gain more information on the effect of noise in the outdoor environment. In order to develop a noise score rating model that enables an evaluation of the outdoor environment as perceived by pedestrians on the streets and visitors to parks, more information is needed on the impact of noise in different urban and recreational areas.
Within the project, the noise rating model for the outdoors was further tested by investigating the effect of noise in the outdoor urban environment in subjects residing and walking in a realistic situation, both in an urban non-natural environment (streets) and in an urban natural environment (parks). For each type of location, both noisy and relatively quiet locations were included in the study. Measures involve self-report measures such as annoyance, mood state and perceived restoration, as well as accompanying physiological measures such as heart rate and autonomic nervous system activity. Also noise exposure is individually assessed to enable the establishment of both instantaneous and aggregated relationships between exposure and human (annoyance) response. Based on these relationships, the above-mentioned tentative environmental noise rating model for pedestrians and visitors of parks was evaluated and improved.
The state of the art regarding effects of noise on the outdoor environment as well as the preliminary noise-rating model for the outdoors are described in Deliverable 2.1.1 submitted December 21, 2010. In the literature, several noise indicators were used to predict annoyance or the perceived sound scope quality as primary indicators. However, since the LAeq level was the indicator that most consistently correlated with annoyance, and because of the consistency with environmental noise policy and the exposure-response relationships for annoyance at the dwelling, LAeq (during daytime) is chosen as the primary noise indicator in the noise score rating model for the outdoors. In addition, an indicator of the low frequency components of the noise (LCeq-LAeq) is proposed, as well as an additional indicator of the difference between peak and background noise levels (LA5-LA95). The influence of these more specific noise characteristics will have to be based primarily on extrapolation of their observed influence on indoor annoyance or on the evaluation of noise in laboratory listening tests. Furthermore, based on the limited studies available, a tentative exposure-response relationship between outdoor noise and annoyance is proposed. This resembles the EU exposure-response relationship for residents at the dwelling for the sources of aircraft noise and road traffic noise, except for a -5 dB shift in the LAeq levels corresponding to specific annoyance percentages.
3.2.2 Development of the noise score rating method for residents inside
The objective was to refine and evaluate the noise score-rating model for residents previously developed within the QCITY project based on current knowledge. So far, the model contained methods for incorporating the effect of ambient noise in the immediate vicinity of the dwelling (quiet façades) and outdoor noise in the neighbourhood, described by the proportion of the area with equivalent sound levels above 50dB(A), as well as the effect of insulation of the dwelling. However, indicators for these effects were not yet adequately based on scientific literature or research. An inventory of the literature was made addressing the empirical basis for the influence of outdoor noise in the vicinity of the dwelling, in order to evaluate the outdoor environment component in the noise score rating model for residents. In addition, an overview was made of the information regarding effects of additional characteristics of the noise other than the equivalent noise level, such as the influence of spectrum characteristics and the influence of the rate of occurrence of individual events. As far as possible, a method to incorporate the influence of these characteristics has been proposed. The refined rating model for residents is described in Deliverable 2.2.1. The improved noise score model for indoors has been integrated into the CadnaA noise mapping software of Datakustik. The refined model can also be implemented in other software’s for traffic noise.
The refined rating model for residents is described in Deliverable 2.2.1. In the model, indicators for equivalent noise level at the façade of the dwelling are combined with information about outdoor noise levels in the vicinity of the dwelling, spectrum characteristics (in conjunction with insulation characteristics) and temporal variations in noise levels. This model may be used to predict the overall annoyance response, i.e. the percentage and number of residents that will be expected to be annoyed by noise in a given area. In the context of the EU Environmental Noise Directive, it is important to adequately assess the impact of environmental noise on residents. So far, the assessment of the impact of noise on residents is based solely on façade levels of dwellings as obtained from the noise maps. Therefore, measures directed towards a quieter outdoor situation, as far as they are not reflected in façade levels, will not show up in health assessment indicators, nor will measures that influence the frequency spectrum, the indoor levels or the rate of occurrence of individual noise events. Using the refined noise score-rating model for residents, the expected effect of environmental noise on residents may be better quantified.
Typical constructional designs for walls, windows and ventilation from different time periods have been identified and compiled in a table for the case of Stockholm. The SRI was estimated for each component, as well as a resulting sound insulation index for typical exterior walls of the period, based on a window/wall ratio typical for the time period.
From the estimated SRI two curves were produced based on the most typical constructional designs of exterior walls as a function of the year of construction. One graph is for open passive ventilation slots and the other for closed passive ventilation slots. Trend lines were added, producing two polynomial equations.
The values shown in Figure 11 can only be used for Stockholm but the procedure can be used in other cities in order to estimate the SRI as a function of construction year, figure 11.
3.2.3 Cost/benefit analysis of Q-Zones
An extensive literature search and review of cost benefit analysis methods and noise (primarily, transportation noise) has been carried out in order to determine an appropriate methodology for the costs and benefits related to specific intervention measures.
Ultimately, the HEATCO methodology (Developing Harmonised European Approaches for Transport Costing and Project Assessment, December 2006) was chosen as the preferred method for cost benefit analysis of noise impacts, because it had been tested and agreed as appropriate for other European studies.
The methodology has been initially tested for Bratislava and later Stockholm and Gothenburg. This has proven the overall utility of the method. Initial results implemented for Bratislava have shown that the methodology chosen for cost benefit analysis of noise intervention is robust and most importantly is readily integrated with the results of the noise modeling for Q-zones.
The HEATCO CBA methodology has provided the ability to compare different scenarios. Below as an example results for an initial test site in Stockholm can be seen, figure 12.
3.3 NOISE AND VIBRATION CONTROL AT SOURCE – ACOUSTICALLY GREEN VEHICLES
3.3.1 External noise from hybrid and electric vehicles
Modification of the head visor microphone array for the automated evaluation of moving sources
A measurement system has been developed based on existing hardware and software (HEADVisor technology) allowing for the detection, separation and quantification of the various noise sources contributing to the overall noise of road traffic. The traffic consists of many single vehicles. Each vehicle contains a number of noise sources (e.g. tire/road interaction, engine etc.).
The system is capable to distinguish and track a single vehicle using optical information by means of calibrated video cameras. The position of the dominant noise sources is determined using the microphone array technology. The combination of optical and acoustical information allows for the identification of the noise sources at each passing vehicle.
The spatial resolution of a microphone array depends strongly on the array size. To resolve the complex traffic noise a modular system consisting of square grids (1.5 m x 1.5 m) has already been developed. The grids can be combined arbitrarily to build e.g. an array of 6 m x 3 m with up to 192 microphones and 3 video cameras to cover the entire street, figures 13 & 14.
The algorithms for vehicle detection, classification (e.g. passenger car, motorcycles, trucks) and tracking have been tested for synthesized traffic noise scenarios first. To distinguish between the various vehicles in real traffic flow the calibrated wide-angle panorama camera was developed. Using image analysis techniques, the single vehicles in the traffic flow can be detected and traced. The noise emission of the main sources can be calculated and exported as time signals, figure 15.
The system developed within the scope of CityHush has been successfully tested within two major measurement campaigns for the evaluation of traffic flows and analysis of tire/road combinations.
Using the microphone array data, time signals can be calculated for each source at the vehicles. Based on the measurements of a large number of different pass-by events leading to a set of data points consisting in physical descriptors (vehicle, position, speed, acceleration, source type) and a calculated time signal representing the source emission, an Acoustical Fingerprint technique can be applied. The Acoustical Fingerprint allows for the synthesized and interpolated evaluation of heterogeneous data points using standard acoustic or psychoacoustic descriptors. The Acoustical Fingerprint can be used to characterize the emission of single vehicles (comparing, e.g. different sets of tires) or road locations, Figure 16.
For the validation of the system performance, measurement campaigns on a test track and on the GOOD proving ground have been conducted. In the first campaign, four different vehicles including an electric car have been measured under traffic like running conditions. In the second campaign, an electric vehicle has been tested with two sets of tires (normal and low noise) on two different road surfaces (smooth and rough road). A total of 53 pass-by measurements are synthesized for the acoustical fingerprint using the standard A-weighted sound pressure level, time-invariant loudness, and sharpness. The data allows detailed analyses as well as quintessential statements.
Measurement and evaluation of single pass-by noise and free flow noise with head visor
Acoustical measurements of different vehicles were performed on a test track and public roads. Diverse measurements of single pass-by noise of vehicles under various running conditions for a hybrid vehicle on the market and electric vehicles were realized, figure 17.
Different receiver positions were considered to investigate the change of noise due to a source-receiver distance increase. Moreover, measurements near the most important sources were performed to separate the different source contributions and to be able to estimate the improvement due to potential mitigation measures (reduction of tire-road noise).
The acoustical measurements were analyzed with respect to several (psycho-) acoustic quantities. In addition to it, listening tests were performed to collect data about subjective reactions to new road traffic noise caused by electric and/or hybrid vehicles.
Traffic flow measurements on a variety of different vehicles have been analyzed using the Acoustical Fingerprint technology. The traffic flow consisted of a large number of single pass-by events that were partially overlapping in time. Each single event was analyzed regarding the type (size) of the vehicle and the current speed and acceleration. For the dominant noise sources time signals were calculated. These time signals can be evaluated using standard and psychoacoustic analyses. It was confirmed that free traffic flow noise can be analysed by the developed head visor technology (modified microphone array).
Moreover, it was found that the psychoacoustic evaluation of the measurement and simulation signals produces comparable results.
Extension of the traffic noise synthesizer for the simulation of hybrid vehicles
HAC has developed an extended synthesis tool to auralize exterior noise of vehicles and whole road traffic scenarios for hybrid and electric vehicles. The syntheses of the source signals can be based on different data; spectra and time signal based synthesis can be performed as described in the QCity report.
The synthesis is controlled by the measured position and the velocity information during the tests. The simulation of the vehicle noise uses first the measured near-field signals. Each source (tire and driveline) corresponds to a microphone signal. These signals are loaded into the simulation software and processed.
To model the radiation characteristics from the near field to the far field, the near-field microphone signals are modified using radiation filters. For each source, specific characteristics must be considered.
The resulting filtered source signals were used to calculate the propagation to the receiver position. The propagation calculation consists of the following steps:
1. Damping of the source signals due to the distance between source and receiver.
2. Damping of the signals due to the air absorption.
3. Frequency shift of the signals due to the relative speed between source and receiver (Doppler Effect).
4. Binaural filtering of the signals depending on the angle of the source in relation to the receiver.
These steps have been performed for different hybrid and electric vehicles taking also into account the appropriate driving conditions.
Integration of the psychoacoustic evaluation metric in existing noise maps and noise score models
Activities have been performed using the Traffic Noise Synthesizer in order to calculate sound pressure time signals at various points related to a simple traffic noise scenario (studying e.g. the influence of barriers, influence of additional sound sources at vehicles). These time signals have been used to calculate different psychoacoustic quantities like loudness, sharpness, roughness at the points of interest leading to first psychoacoustic noise maps.
To check the possibility to combine existing noise mapping information with psychoacoustic evaluation methods a case study was performed, where simulations were prepared for the Essener Park. Different ratios of electric vehicles to passenger cars powered by internal combustion engines were considered and auralized. In addition to it, psychoacoustic analyses of the simulated road traffic noises were performed.
The case studies of the example scene Essener Park have shown the applicability and usefulness of the developed universal noise synthesizer in the context of quiet zones. It is a tool providing additional information beyond conventional noise maps. Planned mitigation measures can be validated not only with respect to the sound pressure level reduction but also regarding the impact on other perception-relevant acoustic parameters.
Based on the current software tools, it is possible to simulate the noise immission of a given traffic scenario at various locations in a scene for later visualization on a noise map. As each vehicle is modelled by multiple distinct noise sources, like engine noise and tire-road noise, the impact of the modification of each source can be analysed individually.
3.3.2 Noise specifications for vehicle purchase and noise criteria for vehicle free access to Q-Zones
Until now, the definition of environmentally friendly vehicles only included chemical and particulate emissions, not noise. The objective of this study is therefore to develop a universal functional noise specification to be included in green car purchase specifications in Europe.
The main goal of the CityHush project is to present solutions that reduce the overall traffic noise levels in urban areas by 10 to 20 dB(A) units. One possible way to achieve this is to allow only free access to certain Quiet zones (Q-zones) in the city only to quiet hybrid/electric vehicles. The objective of this task is therefore to develop suitable noise criteria for vehicles that are allowed free access in the Q-zones.
The following has been performed within this work package:
- Studies regarding proper test methods for type approval of passenger cars in urban areas with a focus on electric and hybrid cars;
- Sound measurements on new hybrid and electric passenger cars;
- Collection of noise emission data from normal passenger cars [1];
- Development of noise classifications covering the whole range in exterior noise from passenger cars based on the measured and collected noise data;
- Proposal on suitable noise limit in order for a passenger car to be considered environmentally friendly with respect to noise;
- Proposal on suitable noise limit in order for a passenger car to be allowed free access in Q-zones.
The following conclusions for passenger cars has been given:
- Type approval according to ECE R51 method B (ISO 362 :2007);
- Full acceleration test from 30 km/h instead of 50 km/h for electric passenger cars with weak engines (e.g. PMR < 40). More studies should be made in this area;
- A passenger car that are considered environmentally friendly has to fulfil
Lurban < 68 dB(A) (i.e. noise class A or B);
- A passenger car that is granted free access in Q-zones has to fulfil
Lurban < 64 dB(A) (i.e. noise class A). This is about 8-10 lower noise levels compared to normal passenger cars during normal urban driving on urban main streets with speed limit 50 km/h. This noise limit is likely to imply that only pure electric vehicles are granted free access.
- Similar noise limits should be developed for other vehicle categories as well in order to consider all types of vehicles.
3.3.3 Creating a low noise road surface for inner city use
Development of a smooth elastic dense road surface
The performed studies show that it is possible to create a low noise road surface for inner city use by optimizing the road texture. The noise reduction might not be as high as for porous road surfaces but the effect hopefully last for a longer time period. For standard vehicles at lower speeds, the effect from reducing the tyre/road noise is small due to the higher driveline noise. For hybrid and electrical vehicles, the tyre/road noise is dominating which means that the reduced tyre/road noise results in a reduced total noise level for the whole vehicle.
The result from the final measurements show that the developed smooth road surface with optimized thread pattern can reduce the tyre/road noise with 2 dB(A)-units compared to a new reference pavement with a maximum stone size of 8 mm.
Comments on the results and relation between road texture and noise are discussed in deliverable D.3.3.1 figure 18.
Cost/benefit analysis of low noise road surface
In almost all regions in Europe, the use of low noise road pavements is selected as an action plan within the requirements of the European Directive of Strategic Noise Mapping and Action Planning.
However, the real realisation on the field is sometimes limited by financial implications: the cost is thought to be too high.
In this study, it is sought to develop a Cost Benefit Analysis (CBA) procedure to better estimate the real cost, but also to better valuate the benefits of low noise road pavements. By this approach, it is hoped to find additional arguments to implement more and/or faster additional low noise road pavements.
Different approaches for both the estimation of costs, and of benefits will be proposed. Further, they will be evaluated for application in both, a larger region and an agglomeration.
In addition to this, automated calculation and visualisation methods of hot spot identification of noise problems are evaluated as a method for optimisation of the application of low noise pavements: prioritising of road segments for renovation or refurbishing based on the number of people annoyed. Those methods will be applied to the same examples as used for the cost benefit analysis above.
Cost/Benefit analysis
Cost-benefit analysis (CBA) provides a means for systematically comparing the value of outcomes with the value of resources achieving the outcomes required. It measures the economic efficiency of the proposed approach. When all else is equal more efficient approaches should be chosen over less efficient ones. When there are many options to consider during a decision-making task, it is useful to evaluate the options with a common metric. Cost-benefit analysis refers to any type of structured method for evaluating decision options.
CBA has become widely accepted among business and governmental organisations. Although CBA has definite limitations, especially in the non-standard way that the payoff function is derived and calculated, its potential for making decisions more rational is comforting to those who must make the decisions. The presentation of a cost-benefit analysis is the preferred way to demonstrate the reasoning behind investments. The CBA of measures against noise pollution comprise consequently, figure 19:
- the costs of the measures;
- the reduction of the costs for public health;
- the willingness to pay: how much are people prepared to pay for a less noisier environment?
For the evaluation of road pavements, this general approach can be applied,with omission of effects such as time savings and productivity reduction and costs at the transmission paths and at the receiver.
Conclusions
For benefit analysis, a monetarisation method based on noise dose effect relations (as proposed by Heatco) has been retained as very valuable. It has been indicated that for larger regions, simple low noise road pavements such as standard porous asphalt give very positive results. More sophisticated low noise road pavements give a higher noise reduction, but are much more difficult to recommend based on cost benefit analysis. For agglomerations, low noise road pavements alone are not sufficient to reduce the noise annoyance sufficient.
The methods set forward can be used by noise action planners to evaluate in more detail the effect of low noise pavements as action plans. It is illustrated that at least simple low noise road pavements should be applied: the cost benefit analysis showed that the return on investment is very high. The “Willingness to Pay” for such measures exceeds the additional costs for implementation. The use of hot spot identification methods has been demonstrated and shown to give additional information on the prioritising of refurbishment of road pavements.
3.3.4 Developing quiet tyre designs for quiet road surfaces
The concept that GOOD developed is based on the fact that the tyre tread pattern plays a dominant role for noise reduction on smooth road surfaces and less of a role on coarse or rough road surfaces. By selecting only the most quiet tread patterns to be run on smooth road surfaces with maximum stone size of 5-8 mm, it is believed that up to 6 dB(A) units in noise reduction could be achieved.
GOOD developed ten different designs in CATIA CAD software. Tread pattern geometry of the designs has been optimized to provide reduced noise (interior & exterior) generation for smooth low noise roads and quite electrical or hybrid cars. The designs have been laser carved on smooth (slick) tires and tested in the anechoic chamber. Interior and exterior noise indicators have been assessed against the control (reference) tires. Based on the results of the assessment, three low noise concepts were selected, modified and laser carved (five tires per concept) for further road testing (handling, braking, rolling resistance). A low noise tire structure with transitional closed cellular rubber layer has been investigated to achieve the additional noise reduction: Twenty tires were built and the acoustical performance has been evaluated.
Three low noise tire concepts have been developed and manufactured (laser carved on slick tires in size 175/55R15) developed for further road testing on low noise smooth roads and quiet electrical or hybrid cars. The concepts give reduced structure-borne and air-borne noise. The noise reduction is around 5 - 6 dB(A) on the smooth low noise road replica (lab assessment) in comparison to a typical/standard treaded tire.
The concepts were manufactured (five tires per design) for further road testing. Tire structure/carcass modification (additional subtread elastic porous layer) gives an additional noise reduction of 2 dB(A).
When testing the developed concepts on electrically driven vehicles running on smooth road (surface according to 2001/43/EC TIRE/ROADNOISE DIRECTIVE), a traffic noise reduction of approximately 6 dB(A) at 70-90 km/h is expected (relative to current production standard tires driving on a standard asphalt pavement).
ACL made calculations to estimate the total traffic noise reduction when combining DualQ tyres and electrically driven road vehicles. A DualQ tyre consists of two tyres only 90 mm wide that are mounted on a common rim in such a way that an air slot of at least 60 mm is provided between the two tyres. Based on work done in the previous research project QCity, it is concluded that road traffic noise is dominated by tyre/road noise for velocities above approximately 30 km/h. Therefore, it is essential that electric vehicles with lower driveline noise are equipped with low noise tyres. If not, the low emissions of the driveline are masked by excessive tyre/road noise. It has been shown that the total traffic noise reduction achieved by a combination of DualQ tyre design and electrically driven vehicles is approximately 10 dB(A) units at 40 km/h even on rough roads.
The feasibility of manufacturing the prototype tyres and to perform tests on an electrically driven car is secured by testing the DualQ concept on a Volvo C30 electric car at Volvo proving grounds. Both external as well as internal sound levels will be measured. The manufacturing of the special rims are currently under way. Testing will take place in the autumn of 2011 for the deliverable to be finished on time at M24.
When testing the DualQ tyre prototypes on electrically driven cars running on smooth asphalt, a traffic noise reduction of approximately 10 dB(A) units at 40 km/h is expected (relative to standard car with standard tyres driving on a standard asphalt pavement).
UCAM worked on the tyres for heavy vehicles:
- Tread pattern to contact-patch force mapping. An existing model for the dynamical response of a single tread block transiting the contact patch of a tyre on a smooth road has been developed to provide a complete, time-dependent set of contact-patch forces, for a given tread-pattern input.
- Integration of contact-patch forcing into tyre-response model. An in-house model for the tyre vibration response to forcing by a single, concentrated force was available. This has been extended in order to allow driving by the full, contact-patch force distribution.
- Boundary Element Method (BEM) calculations for the noise radiated by the vibrating tyre. Candidate BEM programs have been evaluated, and an open-source code has been selected. Import of vibration results into the BEM is in progress.
3.3.5 Definition of a noise & annoyance standard for motorcycles in the urban environment
The scope of the work to be performed in the WP3.5 can be summarised in two steps.
- A first step is to describe the specific noise signature of 2/3-wheelers (e.g.: spectra, pitch, pass-by duration, L1), not only LAmax (EU Directive 97/24/EC), perform a psychoacoustic evaluation of PTW in listening tests, derive a noise criteria linked to the annoyance for the classification of PTW, establish of the relevance of single events (motorbikes, mopeds, scooters, …) for long-term overall evaluations.
- A second step is the examination and modelling of road traffic noise and resulting annoyance as a function of different percentages of PTW, of the effect of general ban of PTW and the effect of the shift to low noise PTW on noise annoyance.
- TTE conducted an extensive literature and field study that can be summarizes as follows:
- Literature review (annoyance of PTW in other studies, noise levels and noise signatures of PTW in other studies, statistical data to understand where, how and when the PTW are driven).
- Evaluation of annoyance from PTW by means of about 200 interviews on the street (questionnaires based on a set of 10 questions on the environment and other questions on age, gender, nationality, language), with simultaneous recording of the noise and analysis of LAeq, Lmax, L5, roughness, sharpness, loudness and traffic type.
- Derivation of the specific annoying characteristics of PTW (under real, representative conditions!) by means of a three days continuous measurement in a major road in Athens, where PTW were recorded following the requirements of a statistical pass by and each single event was afterwards analysed into a database.
- Traffic counting to derive typical traffic patterns (number and time pattern of pass by per vehicle type) for use in assessing the effect of single events.
Based on this real and new data, annoyance curve as function of the traffic type and distribution was derived (Paviotti-Vogiatzis curve), and a comparison was made towards the annoyance curve proposed by WG 2 (Anderson et al. (1993)). Agreement was found with the upper curve proposed for annoyance outdoors.
A literature research was performed to get relationships to relate health effects of noise and values for energy consumption, energy cost, CO2 and NOx emissions, so as to compare (roughly) the following parameters:
- Sleep disturbance;
- Social impact;
- CO2 emissions;
- Safety;
- NOx emissions;
- Economic implications.
Simulations and analyses of the possible scenarios was performed and a chart to visualise results was prepared.
HAC took a more analytical approach to obtain acceptable noise characteristics for quiet motorcycles. In addition, the effect of motorcycle specific noise signatures (especially in relation with Lmax and L1 indices during “sensitive” periods of night) on noise score rating values were evaluated. Finally, the effect of forbidding high environmental noise motorcycles in specified periods of day and the use of low noise motorcycles in combination with circulation time restrictions patterns was evaluated.
Acoustical measurements were performed on a test track and on public roads with different powered two wheelers (PTW). For comparison, purposes powered two wheelers with combustion engine and fully electrified powered two wheelers were investigated. In addition to the ISO 9645 conditions, further conditions were considered. The diverse acoustical measurements are used in listening tests and they are needed for the implementation of PTW into the Traffic Noise Synthesizer technology.
Listening tests in the laboratory were carried out to collect data about subjective reactions to different PTWs and to investigate the relation between psychoacoustic parameters and annoyance ratings. It is expected that the noise of PTWs causes stronger annoyance reactions than passenger cars.
Measurement and analysis data was exchanged with TTE.
HAC has accomplished within this work package:
First, measurements of different powered two wheelers (electric scooters, scooter powered with combustion engines, motorbikes) on a test track were performed for all relevant driving conditions.
Second, the measurements (near-field and far-field measurements) were post-processed to enable the inclusion of powered two wheelers in the traffic noise synthesizer technology. New vehicle models were created in addition to the existing vehicle models.
Third, the measurements and simulations, which were generated by the traffic noise synthesizer technology, were subject to extensive listening tests in laboratory. The results were analyzed with respect to the noise annoyance potential of different scooter types also taking into account varying boundary conditions.
Based on this work, two major conclusions were drawn.
First, road traffic with a certain share of scooters powered by combustion engines is always perceived as more annoying than road traffic scenarios, where the scooters are powered by electric engines. This trend is even more significant, when the surrounding traffic consists of electric vehicles, figure 20.
Second, the surrounding road traffic consisting mainly of passenger cars (in the context of temporarily occurring scooters) influences noise annoyance only for road traffic scenarios, where only E-scooters are present. Scooters powered by combustion engines dominate the perception and evaluation to such an extent that the surrounding road traffic is almost insignificant for the overall noise annoyance (see figure 20).
This outcome makes clear that a restrictive policy against powered two wheelers equipped with combustion engines has to be applied for Q-Zones.
3.4 PROPAGATION ATTENUATION OF ROAD TRAFFIC NOISE
3.4.1 Wave propagation analysis for heavy quiet vehicle tyres
A reciprocal-configuration Boundary Element Method calculation of acoustic radiation characteristics has been implemented for a generic tyre geometry. The influence of the geometric parameters on the radiation characteristics has been studied. Based on the results, recommendations for acoustically optimal truck tyre dimensions have been formulated.
The degree of amplification of noise sources on the tyre belt is strongly affected by the overall tyre width. In contrast, the tyre radius predominantly influences the pattern of the varying amplification around the belt, rather than its absolute level. Radiusing the tyre’s ‘shoulder’ region is potentially beneficial in terms of lowering amplification levels, for a tyre of fixed overall width. However, it is less effective than maintaining sharp shoulders and reducing the overall width.
3.5 VALIDATION OF PROJECT RESULTS
3.5.1 Q-Zones in Stockholm
The results presented in WP1 and WP2 have been verified in regards to percentage highly annoyed people (%HA) using extended tools for analysis indoors. Results showing the change of percentage highly annoyed due to creation of Q-zone are presented in Deliverable 1.2.1.
Improved analysis tools
The noise evaluation tools for residences stated in the Environmental Noise Directive 2002/49/EC only consider the sound level on the most exposed façade. The sound level on the most exposed façade is used for example to plan the type of windows on a building, that sound level is not necessary corresponding to percentage highly annoyed people. Improvements to the existing evaluation tools have been made within the project CityHush. The Deliverable 2.2.1 introduces a method, which treats several characteristics of noise other than the noise level on the most exposed façade.
The refined method that has been validated considers the following additional acoustic factors:
- Quiet façade;
- Quiet areas in the neighbourhood;
- Façade insulation;
- Noise frequency characteristics .
The actual façade insulation of the building used in the refined method is a fixed value. The calculated correction due to the façade insulation is constant even though a city holds a large variation of buildings with various façade insulations. A Survey of façade insulation for a large variety of buildings was carried out. The methodology on how to include the façade insulation was composed in Deliverable 2.2.3 using the construction year as a basis for information of the construction elements.
The evaluated methods for calculating noise levels and annoyance for residents are:
- Sound level at most exposed façade;
- Refined Method for annoyance at home;
- Refined Method for annoyance at home using insulation data corresponding year of construction.
The added characteristics in the refined methods could indicate whether the sound pressure level on the façade is overestimated or underestimated. Depending on the cityscape, and type of buildings the refined method would indicate worse or better scenarios corresponding to highly annoyed people. Using noise mapping software’s the redistribution could be noticed, since a noise map only show sound pressure level and take no account to example quite façade or façade insulation. A calculated noise map showing overestimated and underestimated sound pressure level is shown below. The noise map shows buildings in red and green colour. The green buildings indicate that the sound pressure level on the most exposed façade is larger than the recalculated noise level including additional aspects like sound insulation i.e. calculated sound level are overestimated for %HA considerations. The red buildings indicate that the sound pressure level on the most exposed façade is smaller than the recalculated noise level i.e. calculated sound level is underestimated, figure 21.
3.5.2 Embedded parks in Gothenburg
Evaluation methods for outdoor recreation areas such as parks have been developed in previous stages of the CityHush project. Evaluation of parks could be made using a straightforward approach using only the average sound level inside the park. Methods for a more detailed evaluation of parks have also been developed, where the number of park visitors and their distribution inside the park are included. Previously developed relationship for outdoor road traffic annoyance enables quantification of the annoyance in the park.
Previous work also shows the benefits of Q-zones and gives a view of the potential improvements by introducing zoning in urban areas.
The developed methods for evaluating outdoor noise in parks and recreation areas have been evaluated for six different parks. Two parks are located in Gothenburg and four parks are located in Stockholm. The processed evaluation methodology results in some deviations in comparison with a more straightforward evaluation. This deviation is a result of improvements made with the proposed evaluation method, which have made it possible to include additional information. The results show no consistent exaggeration or understatement of the resulting annoyance in urban parks. Consequently all parks are specific and resulting annoyance inside that park may deviate either way depending on several factors such as size, visitor distribution inside the park, topography and number of nearby residents.
As well as getting a better idea of the annoyance or/and perceived soundscape quality in urban recreation areas and urban parks, the potential benefits of Q-zone implementation could be evaluated.
Conclusion
It is important to include noise levels outdoor to get an overview of the level of noise that affects the population of a city. In the current situation, the focus is only on the noise levels in residential buildings. Used response curve for traffic noise annoyance makes it possible to calculate the number of annoyed visitors in a given outdoor area.
Analyses of outdoor environments such as recreation areas and parks according to developed methods will help the assessment of environmental noise in the outdoor situation on residents, figure 22.
Comparisons made in this project show that the quality of the noise evaluation could be more precise including factors like distribution of people inside the park. Comparing the amount of annoyance using the average noise inside the park and distribution based method could differ up to 8 %, which could be of great importance. Deviations in results point out the importance of including the use and purpose of the area and the number of people making use of the area at a given time i.e. the distribution of the people to predict the overall annoyance response.
Evaluation based on the arithmetic average noise level inside the park is acceptable if the noise level is evenly distributed in the park. It is important to include aspects of visitor distribution and number of visitors when evaluation parks and recreation areas in order to quantify the number of people annoyed. If the park holds both noisy and quiet areas, points of interest like cafés or for example, a playground the importance of the visitor distribution increases, figure 23.
Even though both embedded parks, Mariatorget in Stockholm and Trädgårdsföreningen in Gothenburg, are located in the Q-zone boundary the annoyance drops with the introduction of the Q-Zone. The calculated reduced annoyance corresponds in both Gothenburg and Stockholm to 1000 less annoyed park visitors. The concept of embedded parks, evaluation tools comparable to the response curve and distribution based noise score evaluation are important tools for designing and preserving existing and future green areas.
3.5.3 Noise score rating models for Q-zones in Athens
The noise score rating models have been validated in a case study in Athens, including for Q-Zones and embedded parks. Noise score models for indoor and outdoor noise were used. A detailed analysis with different noise score rating models have identified the actual and perceived benefits of the noise effects and impact of Q-Zones and embedded parks. Also situations were analyzed with high noise levels from motorcycles as well as situations with low frequency noise annoyance, figure 24.
Conclusion
With the respective Athens Q-Zone scenario configurations it has been shown that the average noise levels in the Q-Zone and the park can slightly be reduced and the park capacity can be increased. Measures with a special focus on the reduction of conventionally powered motorbikes and scooters (PTWs) were included. The emission values of various PTWs were derived - from the known values of car emissions and from past measurements - in the form of a correction function as a function of speed. These derived values were then used to perform the simulation analysis on the effects of the overall noise levels by shifting the proportion of conventionally and electrically driven PTWs. In result, the noise difference maps show slight noise reductions, while it is more marked if other measures are included, like speed limits. Further measures, such as increasing the proportion of low noise cars and reducing the noise level of the railway by 5dB, enhances this positive effect.
The effects these noise reductions have on both noise rating models, the amount of HAP and on the number of annoyed park visitors was predicted. As expected, the amount of HAP and the number of park visitors are correlated with the reduction of overall noise level. This means that the falling trend of noise level reduction seen throughout the different scenarios is also reflected in the amount of HAP and the number of annoyed park visitors.
Finally the noise costs were estimated, which appear to decrease with the falling average noise levels. Thus scenario S7 contains the least noise costs whereas scenario S1 (base case) shows the highest noise costs. However costs of introducing the new measures were not considered.
3.5.4 Reduction of low frequency air borne noise in Antwerp
In the later part of the project, on site measurements were performed on double façades. The results of these measurements are presented in the present deliverable 5.5.1. Six different setups have been installed and measured, table 1.
Detalied results can be found in the public deliverable on the CityHush website. Following conclusions can be drawn from the measurement results:
- Adding the glass pane at the first distance (300 mm) gives an increase in the insulation value in the 1/3 octave bands of 50 Hz, 63 Hz and > 250 Hz. At 50 and 63 Hz, the value of the increase is 2 to 4 dB. In narrowbands, the increase in insulation value can be detected for frequencies up to 65 Hz;
- Increasing the cavity depth give increasing insulation values for the low frequencies (1/3 octave bands of 40 and 50 Hz) up to 5 or 6 dB;
- The insulation values in the 1/3 octave band of 63 Hz does not improve by increasing the cavity depth;
- Increasing the cavity depth also does not influence the insulation values for the higher frequencies (> 250 Hz);
- Adding absorption in the cavity hardly improves the insulation values for frequencies < 100 Hz and > 800 Hz;
- For frequencies between 100 and 800 Hz, there is an improvement of up to 4 dB by adding absorption in the cavity.
3.5.5 Reduction of low frequency structureborne noise in Brussels
A solution for low frequency structure borne noise has been designed and modelled for a real site in the city.
- A site was selected and traffic-induced vibrations due to passage of a bus over a speed table and a road joint has been measured.
- The numerical tool proposed in the WP4 has been used for modelling and design of the isolating system. The numerical model can account for the road-soil interaction, the wave transmission through the ground, and the structure of the isolating barrier.
- The efficiency of the designed system has been validated by means of an experimental measurement in a scaled test bench.
In a selected site in the City of Leuven, real traffic-induced vibrations due to passage of a bus over a speed table as well as over a road joint have been measured. Based on the real measured vibration, two types of isolating barrier have been designed and the efficiency of each system has been investigated by both numerical and experimental simulation.
Two types of isolating solution (1) a concrete barrier and (2) a concrete-EPS-concrete barrier have been designed. Results of experimental measurements in the scaled test bench show that a three-layer barrier would be more efficient than a one-layer barrier. This confirms results of the numerical modelling presented in WP4.
To have an estimation on the noise reduction, the level of the insertion loss at a point close to the building (at around 10 m from the road) should be considered. Then, the level of noise reduction can be determined using the equation (2). The following table shows a resume of the noise reduction inside the building using different barrier configurations, table 2.
To obtain higher efficiency, deeper barriers with higher depth ratio H b /λ must be used. For instance, using a concrete-EPS-concrete barrier of 8 m (with H b /λ = 1.4) or a concrete barrier of 13 m (H b /λ = 2.3) can guarantee an efficiency of at least 10 dB.
Potential Impact:
4.1 POTENTIAL IMPACT
The main concept of CityHush-project is the Quiet zone. Within the Q-zone concept lots of products and tools have been developed. The developed products (low noise tyres, low noise road surface etc.) are available on the market as soon as the market request the products. All the refined/developed methods, in order to evaluate the concept of Q-zones, has described in public reports and the implemented in the commercial software CadnaA. Local authorities and stakeholders now have the possibility to order investigations in cities, referring to the methods described within the CityHush project. The results from the CityHush project will of course also be useful for all other investigations regarding traffic noise in cities and urban areas.
4.2 DISSEMINATION ACTIVITIES
4.2.1 PROJECT WEBSITE
A website on CityHush was developed in May 2010 (see Figure 28) and is available at www.cityhush.org and www.cityhush.eu. All public results and reports of the CityHush project have been made available on the website. The presentations given at the various dissemination events are accessible online (see Figure 29). Links to related projects and networks are provided (see Figure 30).
4.2.2 PROJECT NEWSLETTER
The CityHush electronic newsletter informed the expert target groups about the project objectives, its progress and outputs as well as of CityHush tools and CityHush dissemination events. The newsletter ensured a regular flow of information on the project to interested stakeholders in order to maintain awareness of the project throughout its lifetime.
4.2.3 NETWORKING AND EXTERNAL EVENTS
To raise interest of various target groups in CityHush, results have been presented in general and scientific articles, as well as at relevant conferences. In accordance with the project’s respective target groups, both general and more scientific media are targeted, but with the main emphasis on publications for specialist audiences and expert conferences.
Publications
Interesting and relevant journals and conferences were identified by the consortium. A list of relevant publications to disseminate CityHush results was developed at an early stage and has, since then, continuously been updated. Realized publications are based on that list (see table 3).
Between January 2010 and December 2012 18 articles were published (while 2 are awaiting publication in conference proceedings) (see ANNEX). Out of these articles, 12 were scientific publications focusing on research findings.
Conferences
Relevant conferences to present CityHush results have been identified by topic experts among the consortium. Throughout the project, CityHush results were presented at 20 conferences on noise across Europe (see detailed outline in ANNEX). Half of these presentations took place in the final year of the CityHush project which ensured the dissemination of final research findings.
4.2.4 SEMINARS AND TRAINING SESSIONS
To pass on research results from CityHush two types of CityHush dissemination events have been organised:
- 3 dissemination seminars,
- 2 training workshops for local authorities
Dissemination Seminars
The dissemination seminars targeted a wide range of urban transport stakeholders and noise experts. The objective of the seminars was to disseminate the project results to a broad audience. Each event aimed at about 50-100 participants. To reach these stakeholders across Europe, the seminars are geographically well distributed.
Training Workshops
The training sessions targeted transport experts from local authorities. The aim of the trainings was to highlight the research findings’ implications for cities and to teach the participants how to make use of the CityHush concepts within their local noise abatement strategies. The targeted number of participants in each training was about 20.
List of Websites:
http://www.cityhush.eu
