モータ放射音の低減を目的とした音響メタマテリアルの試作評価

抄録

Recently, in motor-driven products, the need for noise reduction has been increasing from the viewpoint of improving comfort. In particular, the high-frequency pure tone component generated by the motor, such as electromagnetic noise, is sometimes considered as harsh sound, and noise reduction is required from the viewpoint of improving sound quality. Therefore, in this study, to reduce the pure tone component from the motor, we made a prototype of an acoustic metamaterial in which 1/4 wavelength acoustic tubes were periodically arranged inside and evaluated noise reduction effect. In this paper, firstly, we describe the structure of the acoustic metamaterial prototype which can reduce 2600Hz peak frequency. Secondly, we evaluated the noise reduction effect of the acoustic metamaterial using an acoustic analysis software ACTRAN. As a result, the significant noise reduction effect was obtained at 2600Hz. Thirdly, we evaluated the noise reduction effect using a speaker test. As a result, the significant noise reduction effect was obtained at 2700Hz. finally, we compared the frequency characteristic of noise reduction effect between the acoustic analysis and the speaker test. As a result, the peak frequency of the noise reduction effect was a little different but the shape of the frequency characteristic around the peak frequency was almost the same. It means that it will be possible to estimate the noise reduction effect using the acoustic analysis by improving the analysis accuracy.