Network for noise Cutting down noise inside vehicles requires a new understanding of the relationship between acoustics and design. The ENHANCED network has trained a new generation of engineers and developed the tools they need to enable quieter cars. Transport and Mobility © pathdoc, Shutterstock Trying to listen to the radio or have a conversation in a car is often made more difficult by exterior noise and vibrations. Engineers try and design vehicle interiors with reduced noise levels but the mechanisms involved in doing this are not fully understood. The EU funded Initial Training Network ENHANCED was created in 2013 to train the next generation of noise reduction researchers to solve this problem. ‘The aim has been to network PhD-level researchers within a group of expert institutes,’ explains the network co-ordinator Professor Paolo Castellini of the University Politecnica delle Marche (UNIVPM), Ancona, Italy. The project’s academic partner was joined by global engineering and technology company, Siemens – a world leader in software for simulations and experimental testing of vibro-acoustic phenomena. A third partner, non-profit association AIVELA, assisted with project events and dissemination activities. ‘Nowadays, the automotive industry is asked to fulfil ever more demanding requirements for noise reduction and passenger comfort,’ explains Castellini. ‘International legal restrictions on noise, air pollution and increasing customer demand for acoustic comfort means that automotive companies have been driving more and more resources into acoustic treatment and isolation.’ Design engineers are asked to solve this big challenge at low cost and therefore a great deal of effort has gone into the modelling of noise numerically. These models can then help to fine-tune vehicle design, diagnose potential noise sources and predict the effects of proposed design modifications such as changing the types of materials used. Understanding how different materials can affect acoustics is not always straightforward. Materials usually have a solid and fluid component, for example the air in materials’ pores. The interaction between the two phases is responsible for how a material absorbs or magnifies acoustic effects. Finding the right types of absorbing materials could drastically improve interior noise levels. To do this, experimentally-validated models are needed. According to Castellini, in the past, ‘the deviations between experimental measurement and predictions indicated that we needed to improve the numerical models.’ The network has provided a forum to do this. ‘Another big challenge lies in accurately measuring experimental data to describe the acoustics inside a vehicle cabin and characterize the contribution of exterior noise sources,’ he adds. The network has developed specialised acoustic imaging techniques to identify noise sources and how noise is distributed, so as to be able to evaluate the contribution of individual sources such as road noise, wind noise or engine noise. The network also focused on recreating or ‘auralizing’ the sound within a vehicle. Analogous to visualization, auralization involves generating a simulation of the sound environment. The data collected during the project allowed the creation of a Virtual Car Sound (VCS) simulator. The ENHANCED project, which ended in July 2017, has helped strengthen European industry’s ability to tackle the technical challenges of vehicle acoustics. The UNIVPM and Siemens are hoping to cooperate on a future training network, together with additional industrial and academic partners. They are also collaborating on other acoustics projects including the use of microphone arrays to measure and quantify sound as well as measuring the acoustics of rotating machinery. Keywords Noise design, auralization, vehicle cabin noise, vibro-acoustic phenomena
