Improving the acoustic performance of low noise road surfaces using resonators

Road surfaces made of porous asphalt are widely used to reduce the tire-road-noise generated during the rolling process of passenger cars and trucks. As the engine noise was reduced significantly in the last decades the tire-road-noise is the main sound source for driving speeds of 40 kmph (25 mph) and higher for passenger cars. This means that low noise road surfaces may not only be used on highways but also on inner-city main roads to generate a significant reduction on traffic noise. However, the acoustic performance of road surfaces made of porous asphalt is limited as a result of the trade-off between acoustic properties and road surface durability. By including resonators e.g. of Helmholtz type in the porous road surface it is possible to improve its absorbing performance without loss in durability. The paper describes recent research activities on such resonators in porous road surfaces made in the European project HOS ANN A. The acoustic properties in terms of insertion loss have been calculated for different arrays of resonators. Measurements on realized porous road surfaces including resonators were carried out. The results show that resonators can improve the acoustic performance of porous road surfaces substantially. \ua9 2013 Acoustical Society of America