The sound level of vehicles, that was initially dominated by engine and flow noise, has been continuously reduced and optimized. Consequently, other previously inconspicuous noise components have emerged. In external noise, this is primarily the tire noise occurring even at low velocities between about 40 to 50 km/h.
In addition to the wheel housing liner, the tire-rim-system can be used for integrating absorbers. Many approaches for this solution can be found in literature. Here, however, the use of fibrous materials fails primarily due to the handling during tire change, which these materials cannot endure permanently. Moreover, the absorber must not influence the driving behavior and driving safety. The solution presented here follows the approach to integrate a robust, purely metallic resonator with micro-perforation in the rim.
The focus is on the standing wave generated in the circular air cavity of the tire, known as torus mode. For conventional tire sizes, it leads to a measurable level increase in the passenger compartment at a frequency of about 200 Hz. To damp the torus mode, the micro-perforated surface is integrated directly into the structure of the rim. A complete set of tires was produced as a prototype for the measurements inside the vehicle. The measurements were carried out on the road and in the acoustic roller test bench at the Fraunhofer IBP. The sound levels were recorded with an artificial head on the front passenger seat. In a comparison with the standard wheel, a sound level reduction of the torus mode of 5 dB could be achieved both on the road and on the roller test bench.
Fraunhofer Institute for Building Physics IBP