J Audiol Otol.  2020 Jul;24(3):119-126. 10.7874/jao.2019.00514.

Effect of Speech Degradation and Listening Effort in Reverberating and Noisy Environments Given N400 Responses

Affiliations
  • 1Department of Otolaryngology-Head and Neck Surgery, Seoul National University Hospital, Seoul, Korea
  • 2Audiology Institute, Hallym University of Graduate Studies, Seoul, Korea
  • 3Medical Research Institute, College of Medicine, Seoul National University, Seoul, Korea
  • 4Laboratory of Hearing and Technology, Research Institute of Audiology and Speech Pathology, College of Natural Sciences, Hallym University, Chuncheon, Korea
  • 5Division of Speech Pathology and Audiology, College of Natural Sciences, Hallym University, Chuncheon, Korea

Abstract

Background and Objectives
In distracting listening conditions, individuals need to pay extra attention to selectively listen to the target sounds. To investigate the amount of listening effort required in reverberating and noisy backgrounds, a semantic mismatch was examined.
Subjects and Methods
Electroencephalography was performed in 18 voluntary healthy participants using a 64-channel system to obtain N400 latencies. They were asked to listen to sounds and see letters in 2 reverberated×2 noisy paradigms (i.e., Q-0 ms, Q-2000 ms, 3 dB-0 ms, and 3 dB-2000 ms). With auditory-visual pairings, the participants were required to answer whether the auditory primes and letter targets did or did not match.
Results
Q-0 ms revealed the shortest N400 latency, whereas the latency was significantly increased at 3 dB-2000 ms. Further, Q-2000 ms showed approximately a 47 ms delayed latency compared to 3 dB-0 ms. Interestingly, the presence of reverberation significantly increased N400 latencies. Under the distracting conditions, both noise and reverberation involved stronger frontal activation.
Conclusions
The current distracting listening conditions could interrupt the semantic mismatch processing in the brain. The presence of reverberation, specifically a 2000 ms delay, necessitates additional mental effort, as evidenced in the delayed N400 latency and the involvement of the frontal sources in this study.

Keyword

Listening effort; Auditory-visual mismatch; N400; Source localization
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