Objectives: The purpose of the study was to explore the effect of intensity on speech perception in individuals with late-onset auditory neuropathy spectrum disorder (ANSD) by obtaining their performance-intensity (PI) function. Additionally, the study investigated the effect of PI function on aided speech perception. It was hypothesized that speech perception abilities of individuals with ANSD vary with intensity and may provide information regarding their aided performance.
Design: A factorial research design was used to obtain the PI function and aided performance. Thirty individuals with late-onset ANSD in the age range of 14 to 42 years were evaluated. All the participants had bilateral mild to moderately-severe symmetrical hearing loss and were naive hearing aid users. A PI function was obtained for each participant for phonemically-balanced words. Further, aided performance was evaluated for binaural digital hearing aids fitted using the National Acoustic Laboratories-Non-linear 1 method.
Results: It was found that the sensation level at which maximum word recognition scores were obtained varied across the participants. However, the majority of the participants had maximum scores below 30 dB SL. A large number of participants had a rollover PI function where the word recognition scores deteriorated with increase in presentation level. However, a few individuals demonstrated improvement in word recognition scores with increase in presentation level. Rollover index calculated from the PI function clearly demarcated those who had improved speech perception with hearing aids from those who did not. It was found that those with a rising pattern had aided speech identification scores that were significantly higher than their unaided scores. No such difference was found in those with a rollover. Further, aided benefit calculated by obtaining the difference between the aided and unaided scores was significantly higher in those with a rising PI function than those with a rollover function.
Conclusions: The word recognition scores of individuals with ANSD varied with sensation level. This implies that obtaining the word recognition scores at a single presentation level may not accurately represent the speech perception abilities of those with ANSD. Further, a PI function helps differentiate those individuals with ANSD who benefit from hearing aids from those who do not.
All India Institute of Speech and Hearing, Manasagangothri, Mysuru, Karnataka, India.
J.P.M. designed and performed the experiment, analyzed the data, and wrote the article. A.Y. designed the experiment, analyzed the data, and performed the critical revision of the manuscript.
The authors have no conflicts of interest to disclose.
Received March 11, 2016; accepted July 19, 2016.
Address for correspondence: Jijo Pottackal Mathai, All India Institute of Speech and Hearing, Manasagangothri, Mysuru, Karnataka, India. E-mail: firstname.lastname@example.org