2022 年 88 巻 911 号 p. 21-00395
Electric vehicles (EVs) generate different cabin noise from internal combustion engine vehicles (ICE) during low-speed driving. In order to identify the cause of the interior noise of EVs at low-speed (30km/h) and to reduce the noise, a Helmholtz resonator made of pulp molds was fabricated and its noise reduction effect was evaluated. First, a Helmholtz resonator to reduce the cavity resonance of the tire is investigated by numerical calculation. Through numerical calculations, it was demonstrated that a stable noise reduction effect could be achieved by installing multiple Helmholtz resonators. Next, we fabricated a Helmholtz resonator using pulp molds as the material and installed multiple resonators in the tire. In the experiment, the resonators were able to reduce the tire cavity resonance by 13.8 dB to 9.7 dB. When driving tests were conducted with these tires installed, the noise at the ear position of the front seats in the cabin was reduced by 11.3 dB. From these results, we were able to identify that tire cavity resonance is the cause of the cabin noise when the EV is running at low-speeds. In addition, a driving test in which the same number of Helmholtz resonators as installed in the tires were installed on the cabin ceiling resulted in an 8.1 dB reduction in cabin noise. This demonstrated that it is possible to reduce the noise caused by tire cavity resonance even with parts inside the vehicle.
