Fricatives are obstruent sound contrasts made by airflow constrictions in the vocal tract that produce turbulence across the constriction or at a site downstream from the constriction. Fricatives exhibit significant intra/intersubject and contextual variability. Yet, fricatives are perceived with high accuracy. The current study investigated modeled neural responses to fricatives in the auditory nerve (AN) and inferior colliculus (IC) with the hypothesis that response profiles across populations of neurons provide robust correlates to consonant perception. Stimuli were 270 intervocalic fricatives (10 speakers × 9 fricatives × 3 utterances). Computational model response profiles had characteristic frequencies that were log-spaced from 125 Hz to 8 or 20 kHz to explore the impact of high-frequency responses. Confusion matrices generated by k-nearest-neighbor subspace classifiers were based on the profiles of average rates across characteristic frequencies as feature vectors. Model confusion matrices were compared with published behavioral data. The modeled AN and IC neural responses provided better predictions of behavioral accuracy than the stimulus spectra, and IC showed better accuracy than AN. Behavioral fricative accuracy was explained by modeled neural response profiles, whereas confusions were only partially explained. Extended frequencies improved accuracy based on the model IC, corroborating the importance of extended high frequencies in speech perception.
Representations of fricatives in subcortical model responses: Comparisons with human consonant perception
This paper is part of a special issue on Perception and Production of Sounds in the High-Frequency Range of Human Speech. Portions of this work were presented in “Can auditory-nerve and inferior colliculus models explain perceptual confusions for fricatives?,” 43rd Midwinter meeting of the Association for Research in Otolaryngology, San Jose, CA, USA, January 2020.
Current address: Florida State University, School of Communication Science and Disorders, College of Communication and Information, Tallahassee, FL 32306, USA. The work was continued while affiliated at the University of California Irvine (2019–2022) and Florida State University (2022–2023). Electronic mail: [email protected]
Yasmeen Hamza, Afagh Farhadi, Douglas M. Schwarz, Joyce M. McDonough, Laurel H. Carney; Representations of fricatives in subcortical model responses: Comparisons with human consonant perception. J. Acoust. Soc. Am. 1 August 2023; 154 (2): 602–618. https://doi.org/10.1121/10.0020536
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