Encoding of speech sounds at auditory brainstem level in good and poor hearing aid performers

Publication date: Available online 14 July 2016
Source:Brazilian Journal of Otorhinolaryngology
Author(s): Hemanth Narayan Shetty, Manjula Puttabasappa
IntroductionHearing aids are prescribed to alleviate loss of audibility. It has been reported that about 31% of hearing aid users reject their own hearing aid because of annoyance towards background noise. The reason for dissatisfaction can be located anywhere from the hearing aid microphone till the integrity of neurons along the auditory pathway.ObjectivesTo measure spectra from the output of hearing aid at the ear canal level and frequency following response (FFR) recorded at the auditory brainstem from individuals with hearing impairment.MethodsA total of sixty participants having moderate sensorineural hearing impairment with age range from 15 to 65 years were involved. Each participant was classified as either Good or Poor Hearing aid Performers (GHP or PHP) based on acceptable noise level (ANL) measure. Stimuli /da/ and /si/ were presented through loudspeaker at 65dB SPL. At the ear canal, the spectra were measured in the unaided and aided conditions. At auditory brainstem, FFR were recorded to the same stimuli from the participants.Results and conclusionSpectrum measured in each condition at ear canal was same in GHP and PHP. At brainstem level, better F0 encoding; F0 and F1 energies were significantly higher in GHP than in PHP. Though the hearing aid spectra were almost same between GHP and PHP, subtle physiological variations exist at the auditory brainstem. The result of the present study suggests that neural encoding of speech sound at the brainstem level might be mediated distinctly in GHP from that of PHP. Thus, it can be inferred that subtle physiological changes are evident at the auditory brainstem in a person who is willing to accept noise from those who are not willing to accept noise.



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