A study on measures of timbre of electric guitar sounds in terms of power
spectrum and auto correlation function
Shogo Kaieda, Keiji Kawai, Takashi Yano and Yoichi Ando
In order to make appropriate acoustic space for music performance, the relationships between the property of sound fields and the music sound should be considered. However, the study of music sound and acoustic space for modern music like popular and rock music was not done. In this study, timbre of electric guitar sounds was investigated with the final goal of creating acoustic space suitable for popular music or rock music. The electric guitar sound signals with and without vibrato effect were analyzed in terms of power spectrum and autocorrelation function (ACF). Power spectra of non-effected sound signals showed that the signals contained harmonic overtones up to nearly 20th order, and the profile of overtone components were affected by picking point, string and pick-up setting. Then the spectral centroid and flux were calculated and the time trend of them were compared to those of ACF-based factor Wƒ³(0). Wƒ³(0) increased quickly at the beginning of the sounds and gradually increased or stayed almost constant after that. It was found a high correlation between Wƒ³(0) and spectral centroid. Also in Wƒ³(0) it was found similar time trend with that of spectral flux at the beginning of the signal. ƒÓ1 , another measure of ACF, was calculated for sounds signals with vibrato, the value of ƒÓ1 decreased as vibrato extent increased and gradually approached to 1 in process of time. Also, the greater the power in high order overtones was, the smaller the values of ƒÓ1 of vibrato became. Accordingly, Wƒ³(0) was considered to be affected by the high order overtones, and ƒÓ1 by fluctuation of sound signals such as vibrato.
Key words: Timbre, Autocorrelation function, Vibrato, Subjective preference