Abstract
After finishing the course of our quality study of speech sounds, we propose here the quality problem of synthesized sounds having formant-like spectra. The immediate aim of our present experiment, is devided into two: one is to determine the discriminatory bounds in quality response in regards to the changes in formant position and formant band width; the other is to illuminate the mechanism of the formation of so-called mental map by which the identification of several sounds which differ in both position and width of formant is established. In order to synthesize a formant-like complex sounds, damped sinusoids with repetition rate of 200 waves per second are made in use by introducing a narrow pulse-train through a single resonant circuit. The following points can be safely concluded as basic properties in timbre judgement. (1) The ratio of the insensitivity σ__<f_0 > to the half-power band width B regarding the formant frequency, defined by the standard deviation of distribution of equal judgement in AB listening test, is approximately constant regardless the resonant frequency f_0. (2) The ratio of the insensitivity σ_B to the formant band width B is generally constant. (3) When considering the confusion matrix rather from the discriminatory view-point, than from the view-point of identification, the insensitivities can be obtained from the confusion data in two directions, i. e. , in outgoing and incoming one. These are far greater than that observed in the discrimination test of pair-comparison type. A member of sound group does not necessarily have same values of insensitivities in two directions. (4) Definiteness of qualities of formant-like sounds, which are correctly identified, cannot be reflected directly on the magnitude of insensitivity defined from the discriminatory view-point.
