Comparision of the effect of noise on cortical responses evoked by sound onset and acoustic changes

It has been shown in previous studies that cortical potentials obtained in noise have different amplitude and latency values compared to the quiet environment. This effect was observed for both the sound onset and acoustic change responses, and the effect of noise was different based on the stimulus. This study was conducted to examine how the sound onset and acoustic change responses evoked by different stimuli are affected by different noise types. Sound onset and acoustic change N1 responses were recorded from 20 adults (10 females, 10 males) with normal hearing in the age range of 24-33, in quiet, in white noise and speech shaped noise at a signal to noise ratio of +10 dB with stimuli /ui/ and /iu/. In the analysis sound onset amplitudes for / ui / were lower in white noise than in the quiet, and latencies were prolonged in both noise conditions. Acoustic change amplitudes were lower only in speech shaped noise, latencies were not affected by noise. For / iu /, only sound onset latencies were prolonged in both noises. When the responses for two stimuli under the same condition were compared; sound onset latencies were prolonged for / ui / than / iu / only in quiet environment, in other conditions latencies and amplitudes for / ui / and / iu / were not different. The acoustic change responses for / ui / and / iu / were similar only in terms of latencies under noise conditions. When the sound onset and acoustic change responses in the same condition were compared, the acoustic change amplitudes were lower latencies were higher for both stimuli in all conditions. In conclusion, the effect of noise varies according to the stimuli evoking sound onset and acoustic change responses and to the type of noise utilized. In future studies, examining the effects of noise on sound onset and acoustic change responses obtained with stimuli containing different formant transitions in different noise types among individuals with speech discrimination problems may be suggested. Key Words: Auditory cortical N1, noise, sound onset response, acoustic change response