The effect of harmonic overtones in relation to “sharpness” for perceived brightness of distorted guitar timbre

Abstract

Perceived timbral brightness is often predicted by “sharpness,” which is the conventional predictor described by von Bismarck. Perceived brightness and the predicted “sharpness” value increases when the energy of harmonic overtones in high-frequency range increases. Studies regarding the relationship between “sharpness” and harmonic overtones are relatively rare. “Sharpness” and harmonic overtones may have the synergistic effect or the canceling effect over perceived brightness. The electric guitar is one of the representative musical instruments which controls its timbre by adjusting the harmonic overtones. Under the assumption that there is a specific canceling effect, the stimuli generated by non-linear distortion processor for the electric guitar were compared for the first experiment. The values of the “sharpness” were adjusted by shelving filters. The onset of the each stimulus was deleted for the second experiment, since any variables other than “sharpness” and the harmonic overtones needed to be eliminated. The result indicated that “sharpness” and the amount of harmonic overtones had a canceling effect. A high amount of harmonic overtones decreased the perceived brightness. This result provokes the question of “why did the harmonic overtones cancel the perceived brightness predicted by sharpness?” This canceling effect was discussed by observing acoustic features.