Central Representation of Speech-in-Noise Perception: A Narrative Review

Abstract

Background and Aim: Speech-in-Noise (SIN) perception is one of the most important issues processed by human listeners. The purpose of speech tests is to determine the perceptual abilities of people in real life conditions; therefore, can speech tests in quiet be a valuable measure of this ability? Is the central representation of speech-in-quiet and SIN perception the same? This review study aimed to investigate the central representation of SIN perception in healthy individuals aged 14 to 60 years.

Recent Findings: Central representation of SIN perception is influenced by various peripheral factors and includes several neural processes. All auditory nerve fibers are stimulated by speech and noise. Low-frequency sounds play a much more important role than high-frequencies. The auditory nerve fibers that are stimulated by speech, respond only to fundamental frequencies (F0). The degree of neural synchronization that increases by noise and causes the simultaneous activity of these fibers, develops auditory processing. Large areas of the auditory cortex and its external parts (parietal, premotor, and mirror neurons) are stimulated. Larger groups of cortical nerve fibers are used for speech signals of the same family with significant ecological importance.

Conclusion: Central representation of SIN perception is not the same as in quiet. Speech perception tests in quiet cannot assess real-life perceptual abilities of people. SIN tests should be used routinely as a practical confirmatory test in audiology clinics. It is very necessary  that the list of words and sentences required for SIN perception tests be prepared for different languages.

Keywords: Speech; noise; perception; auditory cortex; brainstem