Novel compound material and metamaterial wheelhouse liners for tire noise reduction

Traffic noise has increased in recent years and hence the European Union has regulated the noise emission norm more strictly. New technologies have to be developed to reach the future regulations. Automotive lightweight construction deteriorate the noise, vibrations and harshness performance, though. The airborne and structure-borne noise emitted by tires contribute significantly to the entire noise spectrum of the vehicle. Our goal is to develop a new wheelhouse liner that improves the acoustic attenuation properties in the frequency range of 800 Hz to 4000 Hz. We pursue the strategy of adapting two different approaches. First, we design a compound material consisting of porous layers and a microperforated panel. This approach combines the effect of a porous absorber and local resonators. Thus, broadband noise attenuation is achieved. The starting frequency of the absorbing band is shifted towards lower frequencies than conventional porous absorbers due to the effect of local resonances. Second, we construct an acoustic metamaterial based on resonant cavities. In comparison to the first approach, the material does not produce broadband absorption but targets a particular frequency of interest. Both approaches are first simulated and then experimentally evaluated by impedance tube, Alpha Cabin and full vehicle measurements. The chosen design concepts are developed for mass production and hence a trade-off between being cost-efficient and manufacturable while improving the acoustic attenuation.