Investigation of the effect of changing noise type and signal-to-noise ratio on cortical auditory evoked potentials

Difficulty of understanding speech in the presence of back-ground noise is a commonly reported problem. Understanding how the brain processes speech in noise helps clinicians develop therapies and outcome measures to assist individuals who struggle understanding speech in noise. The aim of this study is to investigate the effect of different noise types at different signal to noise ratios (SNR) on sound onset evoked N1 responses among normal hearing individuals. 14 participants aged between 18-30 are included in the study. In electrophysiological measurements the stimulus /sa/ was presented in quiet, and in white noise and multi talker noise under two SNRs. Sound onset evoked N1 latencies and amplitudes were compared between conditions. All amplitude were significantly reduced for the multi talker condition compared with white noise. Mean latencies for all onset N1 peaks were delayed for noise condition compared with quiet. However, in contrast to the amplitude, differences in latency between white noise and the multi talker noise did not reach statistical significance. These results support the idea that while background noise maskers generally reduce amplitude and increase latency of speech sound evoked cortical responses, the type of masking has a significant influence. Multi talker maskers (six talkers) have a larger effect on the obligatory cortical response to speech sound onset N1 compared with purely energetic white noise maskers, which may be attributed to informational masking effects.