Effects of nonlinear amplification on differential sensitivity measures in individuals with cochlear hearing impairment

N Devi, G Amritha, Kishore Tanniru

Indian Journal of Otology 2017 23(3):162-167

Objective: The current study focused on exploring the influence of multichannel amplification with wide dynamic range compression (WDRC) on frequency, intensity, and duration discrimination measures at two frequencies in different channels of amplification. Methods: Discrimination measures were performed on twenty ears with moderate flat sensorineural hearing loss using 2-down and 1-up adaptive procedure to achieve 70.7% response on the psychometric function. All stimuli were generated through AUX script and presented using Psycon version 2.18 experimental software and delivered through the speakers oriented at an angle of 0° azimuth. Discrimination measures were performed in both aided and unaided conditions for two pure tone frequencies of 750 and 1500 Hz with 500 ms duration (on/off ramp duration of 80 ms to avoid spectral splatter) presented at a level of 20 dBSL (with reference to the threshold separately in each condition). The responses were recorded through three interval alternative forced choice paradigm with visual feedback. An average of final four reversals out of eight was considered for discrimination threshold estimation. Results and Conclusions: Results revealed a statistically significant deterioration in intensity discrimination and a significant improvement in difference limen for frequency and duration with nonlinear amplification. The deteriorated intensity discrimination scores were explained in perspectives of WDRC acting in amplification device.

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