Basic frequency analysis on period fluctuations of rhythms produced by humans for their enjoyment

It is necessary to examine comfortable vibrations and swinging motions used in the development of a human-machine interface. Although the present study was limited to the rocking motion of a rocking chair, it was confirmed that the waveform of a swinging motion used as a type of stimulation, the period of which is constant and the power spectrum of the amplitude envelope has the property of 1/f, makes human users comfortable. Next, the features of a swinging motion produced by a person for their enjoyment were examined. As a result, the power spectrum of the envelope of the measured acceleration waveform had the property of nearly 1/f, that is, it had a similar waveform feature that was evaluated as comfortable. In this study, the author focused on the period fluctuations of rhythms produced by humans for their own enjoyment. The rhythms occurring when walking comfortably, hopping on a pogo stick, bouncing on an exercise ball, swinging on a swing, and dribbling a basketball were measured using a portable acceleration measurement system or a sound recording system. Then, the periods of the rhythms were obtained, and the power spectra were examined. As a result, the power spectra showed a downward slope within a low-frequency range; that is, they were similar to the property of 1/f. Further, it was clarified that these power spectra have about the same magnitude, the periods are about the same, and the period fluctuations are not very large.