Date of Award

Spring 2011

Document Type


Degree Name

Doctor of Audiology (AuD)


School of Communication

First Advisor

Melinda F. Bryan


The present study investigated the effects of hearing aid circuitry and speech presentation level on ANL and hearing in noise in 19 adult, bilateral hearing aid users. The acceptable noise level (ANL) procedure was used to assess acceptance of background noise. Conventional ANLs (i.e., measured at the participant's most comfortable listening level (MCL)) and ANLs at eight fixed speech presentation levels were obtained. Then global ANLs (i.e., ANLs averaged over eight fixed speech presentation levels) and ANL growth (i.e., the slope of the ANL function) were calculated Each measure was obtained in three conditions: unaided, aided with wide dynamic range (WDRC) circuitry, and aided with output limiting compression (dSC) circuitry. Results revealed that conventional ANLs are not significantly different when obtained using any of the three levels of hearing aid circuitry. However, results demonstrated that global ANLs may be affected by hearing aid circuitry in that listeners are able to accept more background noise when in the unaided or dSC circuitry condition compared to using WDRC. Finally, results showed that ANL growth for each type of hearing aid circuit was not significantly different, indicating that ANL growth is stable for all three types of circuitry.