耳には聞こえない高周波成分を含む音を発生させる楽器 <資料>

Many kinds of audio-visual information from daily life have been digitized. Digitization accuracy is important to perceptions or evaluations of audio naturalness, and to listener comfort during the listening experience. High-resolution digital sound sources with inaudible high-frequency components (>20 kHz) have become available, owing to recent advances in information and communications technology. However, the effects of sounds that feature such components on human psychophysiological processes have not been sufficiently discussed. One of the reasons for this dearth of research could be that it remains unclear what musical instruments produce sounds with such components. In this technical note, we introduce some percussion instruments that produce sounds with inaudible high-frequency components, and present sound spectra and spectrograms of those sounds. High-frequency components in excess of 20 kHz appeared, in abundance, in the rising phase—but not in the falling phase—of a sound wave. In a sound wave of a tambourine, high-frequency components appeared not only in the rising phase but also in the falling phase. The tambourine sound could be a feasible study subject, given how it features abundant inaudible high-frequency components; it could be used to examine the effects of sounds that feature them on human psychophysiological processes.