Fusion of dichotic vowels with level differences across ears in normal-hearing listeners

Abstract

Fundamental frequency (voice pitch) is an important cue for sound segregation. Previous studies show that normal-hearing (NH) listeners fuse pure tones with similar pitches. When two different vowels with the same fundamental frequencies are presented dichotically to the two ears, NH listeners often fuse the two vowels and perceive one vowel. Sometimes the perceived vowel is not one of the two vowels presented. Interaural level difference is an important cue for sound localization, which also helps with sound segregation. The current study introduced level differences into the dichotic vowel pair to examine how level differences affect vowel fusion. Dichotic vowel pairs were selected from synthetic vowels /i/, /ae/, /ɔ/, and /ʊ/ with the fundamental frequency of 109.9Hz. The level difference varied between -8 and 8 dB. The results showed that there was no significant effect of level difference on fusion in NH listeners. However, for some vowel pairs, the single fused vowel perceived changed significantly with level difference, indicating that internal representations of fused vowels can shift with level differences. This research was funded by NIH-NIDCD-R01-DC013307.