The number of quiet vehicles, such as electric and electric-hybrid vehicles, has been increasing. The operation of these quiet vehicles results in a reduction of noise emissions, consequently, there is an elevated risk of collisions with pedestrians. To address this issue, the guidelines requiring the installation of Acoustic Vehicle Alerting Systems (AVAS) for quiet vehicles in 2016. Nevertheless, the awareness of approach informing sound represents from AVAS remains low, with many pedestrians failing to notice approaching vehicles using approach informing sound alone. To design more noticeable approach informing sound, we focused on frequency characteristics of sound, such as harmonic structure, harmonic amplitude, and amplitude modulation. A subjective evaluation was conducted using samples of approach informing sound, focusing on frequency characteristics under laboratory conditions and in real vehicle experiments. In both experiments, the background noise condition being considered. As a result, the approach informing sound with a high robustness against background noise exhibited characteristics such as increased sound pressure levels of low-frequency and a significant proportion of low-frequency components within the sound. From the results of experiment using a real vehicle, sample of approach informing sound made from pink noise based on the onomatopoeia “ga-” was evaluated as most suitable.
Suzuki et al. (Wed,) studied this question.