Effects of expansion on consonant recognition and consonant audibility.
BACKGROUND
Hearing aid expansion is intended to reduce the gain for low-level noise. However, expansion can also degrade low-intensity speech. Although it has been suggested that the poorer performance with expansion is due to reduced audibility, this has not been measured directly. Furthermore, previous studies used relatively high expansion kneepoints.


OBJECTIVE
This study compared the effect of a 30 dB SPL and 50 dB SPL expansion kneepoint on consonant audibility and recognition.


METHODS
Eight consonant-vowel syllables were presented at 50, 60, and 71 dB SPL. Recordings near the tympanic membrane were made of each speech token and used to calculate the Aided Audibility Index (AAI).


METHODS
Thirteen subjects with mild to moderate sensorineural hearing loss.


RESULTS
Expansion with a high kneepoint resulted in reduced consonant recognition. The AAI correlated significantly with consonant recognition across all conditions and subjects.


CONCLUSIONS
If consonant recognition is the priority, audibility calculations could be used to determine an optimal expansion kneepoint for a given individual.
Brennan
Marc
M
Speech and Hearing Sciences, University of Washington, 1417 NE 42nd St., Seattle, WA 98105, USA. mabrenn1@u.washington.edu
Souza
Pamela
P
D000328:Adult; D000369:Aged, 80 and over; D006310:Hearing Aids; D006319:Hearing Loss, Sensorineural / Q000503:physiopathology* / Q000534:rehabilitation; D006801:Humans; D008144:Loudness Perception; D008875:Middle Aged; D010700:Phonetics; D013067:Speech Perception