Encoding of speech in noise in adults using hearing aids: effect of noise reduction algorithm

Introduction: Subjects using hearing aids complains of difficulty in speech understanding in noise. Speech auditory brainstem response (S-ABR) provides cues for temporal and spectral encoding of speech in the brainstem. Objective: This work was designed to evaluate speech processing in patients fitted with hearing aid using S-ABR and to study the effect of noise reduction algorithm on speech processing in patients fitted with hearing aids. Materials and method: This study included 20 adults with mild to severe SNHL fitted with HA at least 3 months with aided threshold in all frequencies better than or equal to 30 dB. Hearing aid was used with all the subjects and was programed for each subject according to his audiogram followed by aided evaluation using S-ABR. Through sound field in four different test conditions with NR algorithm on in quiet and in the presence of noise then with the NR off in quiet and in the presence of noise were performed. Results: There was a statistically significant delay in the S-ABR onset and offset in noise compared to quiet. The effect of noise on S-ABR while the NR was on showed statistically significant difference in the onset response in both quiet and noise. When the NR was off, there was marked effect of noise on both the onset response and offset response. Conclusions: It was found that hearing aid users are vulnerable to noise regarding the speech encoding at the level of the brainstem. Noise reduction algorithm maintains the neural activity in response to speech and improves speech perception in noise.