Impact of Noise on Sound Processing at Lower Auditory System: An Electrophysiological Study.

Abstract

The importance of signal-to-noise ratio (SNR) is well documented in behavioral speech perception experiments and psychophysical measurements. Studies on ABR related to the encoding of signals in ipsilateral noise are very limited. The present study aimed to systematically investigate the effect of various SNRs on the latency and amplitude of ABR to a range of stimuli & to compare the latency and amplitude of ABR recorded in various ipsilateral SNRs in children and adults. We recorded auditory brain stem responses (ABR) in children and young adults for clicks,a speech token /da/ of 40ms duration, and for a 1000Hz tone burst in the presence of a broad band noise and quiet. There were four SNR conditions (+ 10dB SNR, 0dB SNR and -10dB SNR), and the level of noise was varied, while the stimulus level was fixed at 60dB HL. The results showed that SNR affects the latency and amplitude of the wave V peak differentially for the different stimuli. A difference in the performance of children and adults was also observed. SNR measurements using ABR provide an objective index of brainstem ability to process sound in the presence of background noise. This measure is important and can be used to assess the sound-in-noise processing ability in the difficult-to-test population such as infants and children where measures of signal-to-noise tests cannot be administered.