Impression evaluation of alert sound for electric vehicle based on fluctuation strength for amplitude fluctuation

The motor sound on electric vehicle is quiet at low speeds. Thus, pedestrians have difficulty detecting those vehicles approaching them. Although the vehicle was designed to play an alert sound to solve this problem, it has not been solved yet. When the sound is designed, it should be concerned not only detectability of approaching quiet vehicles but also impression of the sound. For pedestrians, it's important to make it easier to recognize quiet vehicle. Also, alert sounds shouldn't contribute to traffic noise annoyance. Previous studies found that acoustic characteristics of amplitude fluctuation are effective to make them detect approaching vehicles. Here, this study evaluates impressions of those fluctuated sound, investigates relationship between the impression and those characteristics. The impressions of synthesized alert sounds that have periodic and non-periodic amplitude fluctuations were measured by semantic differential method. The obtained data were analyzed by factor analysis. The results revealed that characteristic of amplitude fluctuation influences the factors of "familiarity".