Optimization of Sound absorption Item and Mounting Position for Interior Noise Reduction of Motorized Car Alert Sound Generator

The National Highway Traffic Safety Administration (NHTSA) regulates all motorized vehicles to be recognized by pedestrians by generating a alert sound when travelling at speeds below 30 kph by September 2020. because there is a collision risk of a pedestrian due to the characteristic that the motorized vehicles have low noise when traveling at a lower speed than the internal combustion engine vehicles. However, the alert sound is transmitted not only to the outside of the vehicle but also to the inside of the vehicle while traveling at low speed. and continuous alert sound occurs and the driver can recognizes it as a noise. Therefore, in this study, we analyze the transmission path for the noise reduction of the electric car alert sound generator system and optimization its the mounting position. For this purpose, pink noises were generated through a alert sound generator and the sound transmission path was analyzed through acoustic transfer function (ATF) measurement. The results show that the dash panel and the floor panel are the most important contributors to the noise transfer. Therefore, noise reduction is improved by optimizing the specifications of the sound - absorbing items attached to the two panels in order to reduce interior noise. In addition, ATF was measured to optimize the mounting position of the alert sound generator, and the alert sound generator was installed at a position that satisfies the exterior noise control regulations based on the evaluation result.