Masters Theses

Date of Award

5-2003

Degree Type

Thesis

Degree Name

Master of Arts

Major

Audiology

Major Professor

Samuel Burchfield

Abstract

Directional benefit in hearing aids was quantified physically with ear canal signalto- noise ratio (SNR), perceptually with masked speech recognition threshold (SRT) testing, and subjectively with formal questionnaires. An additional, behavioral method for quantifying the beneficial effects of directional microphones in hearing aids was evaluated in this investigation. This method is the acceptable noise level ( ANL ), which was developed by Nabelek et al. ( 1991 ). ANL was established by selecting the maximum acceptable background noise (multi-talker speech babble) while listening to speech (male running speech) presented at the most comfortable listening level (MCL ). The speech and background noise were presented at o0 and 180° azimuth, respectively. Monaural and binaural measurements were obtained. The ANL was calculated by subtracting the maximum background noise level (BNL) from the MCL for speech (ANL = MCL- BNL). Results of this investigation showed that the mean directional benefit assessed with ANL (mean improvement = 3.53 dB), masked SRT (mean improvement = 3.23 dB), and ear canal SNR (mean improvement = 3.04 dB) are not significantly different. This suggests that directional benefit can be assessed using either of the assessment paradigms (ANL, masked SRT, and ear canal SNR). Abbreviated Profile of Hearing Aid Benefit (APHAB) results also showed a significant percentage increase in directional benefit for the background noise subtest. Directional hearing aid benefit was not different for measures of benefit between hearing aids with analog and digital circuits or hearing aids with different directional polar plots.

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