The Role of Word Content, Sentence Information, and Vocoding for Voice Cue Perception

Abstract

Purpose: For voice perception, two voice cues, the fundamental frequency ( f o ) and/or vocal tract length (VTL), seem to largely contribute to identification of voices and speaker characteristics. Acoustic content related to these voice cues is altered in cochlear implant transmitted speech, rendering voice perception difficult for the implant user. In everyday listening, there could be some facilitation from top–down compensatory mechanisms such as from use of linguistic content. Recently, we have shown a lexical content benefit on just-noticeable differences (JNDs) in VTL perception, which was not affected by vocoding. Whether this observed benefit relates to lexicality or phonemic content and whether additional sentence information can affect voice cue perception as well were investigated in this study. Method: This study examined lexical benefit on VTL perception, by comparing words, time-reversed words, and nonwords, to investigate the contribution of lexical (words vs. nonwords) or phonetic (nonwords vs. reversed words) information. In addition, we investigated the effect of amount of speech (auditory) information on f o and VTL voice cue perception, by comparing words to sentences. In both experiments, nonvocoded and vocoded auditory stimuli were presented. Results: The outcomes showed a replication of the detrimental effect reversed words have on VTL perception. Smaller JNDs were shown for stimuli containing lexical and/or phonemic information. Experiment 2 showed a benefit in processing full sentences compared to single words in both f o and VTL perception. In both experiments, there was an effect of vocoding, which only interacted with sentence information for f o . Conclusions: In addition to previous findings suggesting a lexical benefit, the current results show, more specifically, that lexical and phonemic information improves VTL perception. f o and VTL perception benefits from more sentence information compared to words. These results indicate that cochlear implant users may be able to partially compensate for voice cue perception difficulties by relying on the linguistic content and rich acoustic cues of everyday speech. Supplemental Material: https://doi.org/10.23641/asha.23796405