The Influence of Speech Rate on Acceptable Noise Levels.

Abstract

Older adults often struggle with accurate perception of rate-altered speech and have difficulty understanding speech in noise. The acceptable noise level (ANL) quantifies a listener's willingness to listen to speech in background noise and has been found to accurately predict hearing aid success. Based on the difficulty older adults experience with rapid speech, we were interested in how older adults may change the amount of background noise they willingly accept in a variety of speech rate conditions. To determine the effects of age and speech rate on the ANL. A quasi-experimental mixed design was employed. Fifteen young adults (19-27 yr) and fifteen older adults (55-73 yr) with audiometrically normal hearing or hearing loss within age-normed limits served as participants. Most comfortable listening levels (MCLs) and background noise levels (BNLs) were measured using three different speech rates (slow, normal, and fast). The ANL was calculated by subtracting BNL from MCL. Repeated measures analysis of variances were used to analyze the effects of age and speech rate on ANL. A significant main effect of speech rate was observed; however, a significant main effect of age was not found. Results indicated that as speech rate increased the ANLs increased. This suggests that participants became less accepting of background noise as speech rates increased. The findings of the present study provide support for communication strategies that recommend slowing an individual's speaking rate and/or reducing background noise, if possible. Participants in the present study were better able to cope with background noise when the primary stimulus was presented at slow and normal speaking rates.