Encoding of sinusoidal and natural speech tokens in the auditory nerve

Abstract

Sinewave speech is a synthetic variation of natural speech that replaces natural formants with time varying sinusoidal waves. This synthesis preserves the general formant motion of the natural utterance while removing many spectral details; yet sinewave speech tokens can convey a linguistic message [Remez et al., Science 212, 947–950 (1981)]. This study examined the extent that phonetic information in sinusoidal speech is preserved at the level of the auditory periphery. We compared the responses of individual auditory nerve fibers in ketamine anesthetized chinchillas to the natural and sinusoidal tokens of the word /bal/. Comparisons of the first 100 milliseconds of the responses revealed high correlations over the first 20 milliseconds of the responses representing the initial consonant (r=0.82) despite low correlations between the stimuli themselves (r=0.18). Correlation coefficients decreased in the vowel portion of the responses (r=0.30). Spectral reduction in the sinusoidal token may produce the low...