A METHODOLOGICAL STUDY OF PERTURBATION AND ADDIT IVE NOISE IN SYNTHET ICALLY GENERATED VOICE

There is a relatively large body of research that is aimed at finding a set of acoustic measures of voice signals that can be used to: (a) aid in the detection, diagnosis, and evaluation f voice-quality disorders; (b) identify individual speakers by their voice characteristics; or(c) improve methods of voice synthesis. Three acoustic parameters that have received arelatively large share of attention, especially in the voice-disorders literature, are pitch perturbation, amplitude perturbation, and additive noise. The present stndy consisted of a series of simulations using a general-purpose formant sy thesizer that were designed primarily to determine whether these three parameters could be measured independent ofone another. Results suggested that changes in any single dhnension can affect measured values of all three parameters. For example, adding noise to a voice signal resulted not only in a change in measured signal-to-noise ratio, butalso in measured values ofpftch and amplitude perturbation, These interactions were quite large in some cases, especially in view of the fact that the perturbatio n phenomena that are being measured are generally quite small. For the most part, the interactions appear to be readily explainable when the measurement techniques are viewed in relation to what is known about he acoustics of voice production. Deve lopments in signal-processing technology have made numerous techniques available to the voice scien-tist for analyzing the acoustic characteristics Of human voices. Measurements of vocal characteristics have bee