Psychoacoustic evaluation of acoustic features distortion in fricative consonant of speech

Abstract

© 2020 Elsevier Ltd The present study investigated the perceptual discrimination between typical (normal) acoustic features duration and intensity in word-initial fricative consonant /ʃ/ and atypical duration (shortened or lengthened) and intensity (weak or strong). Perceptual task distortion contrast was performed in each dimension, duration and intensity, as well as in two-dimensional interaction. Stimulus was the word /ʃuma/ with fricative /ʃ/ in the initial position. Duration and intensity of /ʃ/ were synthesized from typicaly pronounced stimuli in 16-step continuum from 135 ms to 300 ms and from −18 dB to +4.5 dB, respectively. Eight speech-language pathologies (SLPs) performed perceptual task distortion contrast in these two dimensions. Results are presented in the form of identification functions. First experiment tested two-choice decision and three-choice decision tasks in identification of distortion in time domain (shortened/normal/lengthened frictive), second experiment analyzed distortion in intensity domain (weak/normal/strong frictive), third experiment examined mutual interaction of distortion in duration and intensity, and forth experiment analyzed two-dimensional perception of simultaneous distortion in both domains, time and intensity. The results indicate regions of typical and atypical values for duration and intensity of fricative /ʃ/, in Serbian language, and also indicate that distortion in intensity domain does not influence perception of distortion in time domain, except in the case of weak friction. In two-dimensional perception of normal fricative /ʃ/, the dimension duration has higher perceptual significance over dimension intensity, whereas in perception of distorted fricative the dimension intensity has higher perceptual significance over dimension duration. In two-dimensional perception SLPs reported that they selectively recognize at first the dominant distortion and then another distortion.