Doctoral Dissertations

Date of Award

5-2009

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Speech and Hearing Science

Major Professor

Patrick N. Plyler

Abstract

The effect of noise reduction technologies in hearing aids on a listener's acceptable noise level (ANL) was investigated. Technology designed to reduce noise within hearing aids; directional microphones (D-Mic), digital noise reduction algorithms (DNR) and the combination of the two technologies (Combo) were employed in the presence of three distinctly different background noises (single talker speech, speech shaped noise, and multi-talker babble). The same pair of twelve channel wide dynamic range compression behind-the-ear hearing instruments was fit on each of thirty participants. The hearing aids were set with four memories: no noise reduction technology activated (baseline), only D-Mic activated, only DNR activated, and the Combo of technologies activated. All other hearing aid settings and features remained the same across memories. Acceptable noise levels were investigated in each memory in the presence of each noise.In addition, subjective preference rankings of the noise reduction technology were obtained within each background noise (1= best, 3=worst). Listeners yielded significantly lower (better) ANL scores with Combo relative to D-Mic and DNR; and scores obtained with D-Mic were significantly better than those obtained with DNR. A technology x noise interaction was observed only for speech shaped noise in DNR, with listeners accepting significantly more noise in the presence of speech shaped noise than background noise containing speech. Listeners preferred D-Mic and Combo programs significantly more than DNR in the presence of single talker and multi-talker babble, and preferred Combo significantly more in the presence of speech shaped noise. Overall, listeners preferred the D-Mic and Combo programs equally as much and significantly more than DNR.In reviewing the preference data along with the ANL data, it is evident that improving an ANL with hearing aid technology is noticeable to listeners, at least when examined in this laboratory setting. These results indicate that listeners prefer noise technologies that improve their ability to accept noise.

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