The effect of speech noise on cortical n1 response evoked by different consonant-vowel syllables

The effect of noise on cortical evoked auditory potentials has been demonstrated in previous studies by comparing the amplitude and latency values of speech evoked cortical responses in quiet and noisy conditions. This effect has often been evaluated using a small number of different stimuli in studies. This study aims to compare the effects of noise on cortical responses evoked by four voiced and unvoiced consonant-vowel syllables based on their voicing properties. The stimuli /bi/,/pi/,/di/ and /ti/ were randomly presented to 20 participants (10 Females, 10 Males) aged 18-23 with normal hearing, in quiet and in noise. Cortical N1 response was recorded by presenting stimuli at 65 dB SPL in quiet and in noise at 60 dB SPL at +5 dB signal-to-noise ratio (SNR). In the analysis the N1 latencies for all stimuli showed a prolongation in the noise, and no noise effect was observed in the amplitudes. Regarding the varying effect of noise on different syllables, the latency prolongation of the /pi/ in noise was found to be significantly higher than the /bi/. In addition, while the amplitudes of the /di/ and /ti/ were not different in quiet , the amplitude of the /di/ was higher than /ti/ in noise. The response amplitudes of /ti/ in noise may have been more affected by the noise compared to the /di/ stimulus, and this effect might have resulted in a lower amplitude of /ti/ in noise than /di/. In this respect, it can be assumed that the voicing feature of the syllables has an effect on the effect of noise on the cortical responses evoked by these syllables. Further research may explore the effects of different acoustic properties on the noise effect on cortical responses and investigate processing of which acoustic feature can be hampered by noise in difficult to test populations. Key Words: Auditory cortical N1, noise, speech stimulus, consonant-vowel syllables