Effect of Speech Presentation Level on Acceptance of Noise in Listeners with Normal and Impaired Hearing

Experiment I investigated the effects of speech presentation level on acceptance of background noise in listeners with normal (N = 30) and impaired hearing (n = 69); Experiment II investigated the potential for the effects of speech presentation level on acceptance of noise to differentiate full-time (N = 25), part-time (N = 21), and non-users (N = 23) of hearing aids; and Experiment III investigated the predictive probability of acceptance of noise measured at multiple speech presentation levels. Conventional ANL (i.e., ANL at MCL), global ANL (i.e., ANL averaged across speech presentation levels), and ANL growth (i.e., the slope of the ANL function) were measured for all listeners. Results from Experiment I demonstrated that neither global ANLs nor ANL growth were related to hearing sensitivity when listeners were matched for conventional ANL. Additionally, none of the ANL measures were related to pure tone average for listeners with impaired hearing. These results indicate that the effects of presentation level on acceptance of noise may not be related to hearing sensitivity. Results from Experiment II demonstrated that global ANLs differentiated the three hearing aid groups in the same manner as conventional ANL; however, ANL growth differentiated full-time hearing aid users from non-users only. Individual data analysis further demonstrated that both global ANL and ANL growth may be able to better differentiate part-time hearing aid users from the other two groups better than conventional ANL. These results indicate that the effects of presentation level on acceptance of noise show potential in differentiating the three hearing aid groups. Results of Experiment III demonstrated that conventional ANL predicted hearing aid use for successful (i.e., full-time hearing aid users) and unsuccessful (i.e., part-time or non-users of hearing aids) hearing aid users with 68% accuracy. Furthermore, the accuracy of the prediction decreased for global ANL but was maintained or slightly increased for ANL growth or ANL at presentation levels of 65, 70, 75 dB HL. These results indicated that the predictive probability of acceptance of noise measured at multiple speech presentation levels was comparable to the prediction obtained for conventional ANL.