Fluctuation strength on real sound: Motorbike exhaust and marimba tremolo

Abstract

Psychoacoustics research has been contributed on evaluating the timbre of acoustic signals. The fluctuation strength (FS) has been respected as the important index which describes the sensory fluctuation of the acoustic signal based on its amplitude, frequency and the combination of them as well. Although FS has been calculated by tremor components on acoustic signals, here points out not only the inappropriateness of the calculation when simply based on literatures but also a method which focuses on the shape of the waveform in order to extract parameters from it, so that the FS is newly calculated by our original method with estimation results of the subjective scores of sensory fluctuation. Signals dealt with are motorbike exhaust sounds and tremolo played by marimba. The developed method is then applied to the design of an electric vehicle approaching sound for pedestrians in order to let pedestrians notice the approaching car without rising up the sensory loudness, on which designed sounds have a fluctuation with irregular pulses proven to give us the sensory fluctuation so that it is expected to be noticeable for pedestrians. This paper discusses the possibility to apply the prestigious psychoacoustic indexes to industrial and artistic sounds.