Sound wave-bending innovation cuts noise pollution
Road traffic in Europe has worsened over the years, contributing to air pollution, an increased risk of accidents and higher levels of noise. In fact, road traffic is the most widespread source of environmental noise in the EU. “More than 100 million people across Europe are affected by harmful levels,” notes WHISSPER project coordinator Bart Willems from 4Silence in the Netherlands. “Long-term exposure is known to increase stress and disrupt sleep.” Studies have even shown that excessive traffic noise can contribute towards cardiovascular disease and learning problems for children. Authorities are aware of the need to tackle this problem, and around EUR 5.43 billion is spent each year on mitigation measures. Typically, this is achieved by either blocking noise with a noise barrier or screen, or absorbing it with porous asphalt. “These solutions have seen only incremental improvements over the years,” says Willems. “And they tend to be insufficient or unattractive.”
Novel sound reduction
The WHISSPER project focused on bringing to market a novel approach to addressing this challenge. Instead of seeking to absorb or block noise from traffic, the goal is to instead diffract noise in an upward direction. To achieve this, 4Silence has developed walls and sections of concrete at ground level that feature a series of grooves of varying size. “This innovation is based on the principle that sound waves deflect when they interact with other sound waves,” explains Willems. “What happens is sound waves from passing cars shoot into the grooves, where they start to resonate.” This resonance leads to resistance in the air, hindering horizontal sound waves. Sound moves like water: it looks for the path of least resistance. So troublesome sound waves look to ‘dodge’ the resonance being created in the grooves by deflecting upward, resulting in a quieter area alongside the road. These innovations can also be placed alongside railway lines.
Diffracting sound waves
Two prototype products based on this concept have since been developed: WHISstone, a concrete diffractor that is placed directly next to the road at ground level; and WHISwall, a 1 m high noise barrier that achieves the same results as a regular 3 m high noise barrier. Pilot demonstrations – critical to ensuring commercial viability and product acceptance – were carried out in Belgium, Denmark, Germany and the Netherlands. Noise levels were measured by certified organisations. Tests revealed significant noise reductions of up to 40 %.
Demonstrating operational viability
Despite some delay due to the COVID pandemic, the WHISSPER project was successful in achieving its goals. “The prototypes have been shown to be highly efficient and easy to implement and maintain,” adds Willems. “With the WHISSPER project, we wanted to focus on optimising these solutions, and then test them in various operational environments.” To this end, production methods for both WHISstone and WHISwall have been scaled up, enabling the firm to meet predicted demand. Commercial campaigns were also carried out in Belgium, Denmark, France, Germany, the Netherlands and the United Kingdom to increase awareness of the technology and to assess the potential for market uptake. “The WHISSPER project has already enabled us to change the world of noise reduction significantly,” says Willems.
Keywords
WHISSPER, traffic, health, noise, pollution, resonance, road, railway
