Effects of masking noise on vowel and sibilant contrasts in normal-hearing speakers and postlingually deafened cochlear implant users.
The role of auditory feedback in speech production was investigated by examining speakers' phonemic contrasts produced under increases in the noise to signal ratio (N/S). Seven cochlear implant users and seven normal-hearing controls pronounced utterances containing the vowels /i/, /u/, /e/ and /ae/ and the sibilants /s/ and /I/ while hearing their speech mixed with noise at seven equally spaced levels between their thresholds of detection and discomfort. Speakers' average vowel duration and SPL generally rose with increasing N/S. Average vowel contrast was initially flat or rising; at higher N/S levels, it fell. A contrast increase is interpreted as reflecting speakers' attempts to maintain clarity under degraded acoustic transmission conditions. As N/S increased, speakers could detect the extent of their phonemic contrasts less effectively, and the competing influence of economy of effort led to contrast decrements. The sibilant contrast was more vulnerable to noise; it decreased over the entire range of increasing N/S for controls and was variable for implant users. The results are interpreted as reflecting the combined influences of a clarity constraint, economy of effort and the effect of masking on achieving auditory phonemic goals-with implant users less able to increase contrasts in noise than controls.
Perkell
Joseph S
JS
Speech Communication Group, Research Laboratory of Electronics, and Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA. perkell@speech.mit.edu
Denny
Margaret
M
Lane
Harlan
H
Guenther
Frank
F
Matthies
Melanie L
ML
Tiede
Mark
M
Vick
Jennell
J
Zandipour
Majid
M
Burton
Ellen
E
D000161:Acoustic Stimulation; D000328:Adult; D001309:Auditory Threshold; D003054:Cochlear Implants; D003638:Deafness / Q000628:therapy*; D005246:Feedback; D005260:Female; D006309:Hearing; D006801:Humans; D008297:Male; D008875:Middle Aged; D009622:Noise; D010470:Perceptual Masking; D010700:Phonetics; D013061:Speech Acoustics; D013067:Speech Perception