A study on masking system using 1/f fluctuation to improve comfort in ultra-compact EVs

In recent years, ultra-compact electric vehicles have gained increasing interest. These vehicles can easily make turns owing to their compactness, and they have a low impact on the environment. However, exterior road and wind noises have a large impact on occupant comfort in the interior space because an electric motor is used instead of an internal combustion engine. Therefore, an active noise control system using control sound or masking for ultra-compact electric vehicles was studied. To select the sound used for masking, a sound containing 1/f fluctuation, which has a relaxing effect on humans, was investigated. In the study of 1/f fluctuations, various analysis methods for comfort evaluation are used. However, a method of detecting sounds including 1/f fluctuations has not been established and clarified. Thus, a basic study of 1/f fluctuations was performed to select the sound to be used for the masker. Furthermore, brain waves of participants were measured in cases in which participants heard sounds including or not 1/f fluctuation. The results revealed that sounds including 1/f fluctuation of amplitude and frequency helped participants to relax.