In recent years, a silent sound is nominated for a ride comfort improvement method in the high speed vehicle. In the inside of car, the noise of 100-2500 [Hz] is the problem. This study's theme is noise reduction in such a high speed vehicle by using micro-size granular materials, and determination of dumping effect of the granular material. The experimental device is made of an excitation machine, and rubber coupling, and iron container. There are two accelerometers in the input and output side of the excitation machine to indicate frequency response. The dumping gain are measured by taking peak gain difference between "no material" and "granular material" . In this experiment, the max dumping gain is 6[dB].
