Deciphering real-world listening : auditory cognition in complex acoustic scenes

Abstract

Speech-in-noise (SIN) difficulty can be explained by a variety of auditory cognitive factors, and has been linked to general cognitive performance. This work summarises the mechanisms of the auditory system supporting speech perception in noise and reviews the commonly used hearing tests that predict SIN ability. The first two chapters identify the outstanding questions in the field which led to the two main objectives of this thesis: exploring the inter-relations of the auditory cognitive predictors of SIN, and developing new measures of SIN perception that can better assess reallife listening and facilitate research into the link between listening and cognition. Experiments were carried out exploring the interactions of the auditory cognitive predictors of SIN perception using multivariate analyses, including auditory peripheral sensitivity, age, central hearing, auditory short-term memory, phonological working memory, and general intelligence. New listening tests were developed to better predict SIN processing. I designed a dynamic auditory figure-ground paradigm to measure an important aspect of central sound processing: the ability to segregate an auditory figure consisting of roving pure-tone segments following the pitch trajectory of natural speech from a random-frequency tone cloud. Neural responses to the dynamic figure-ground and SIN were investigated to reveal the underlying neural mechanisms of sound segregation and sustained tracking of the target stream. I present evidence showing that central sound segregation, auditory-specific short-term memory, pure-tone audiogram, and age can explain 47% of the variance in SIN perception. Dynamic auditory figure-ground can predict both sentence- and wordlevel SIN better than fixed-frequency figure-ground and can be used to elicit neural entrainment generated by high-level cortical regions and the medial temporal lobe, consistent with previous literature. The peak amplitude of the entrainment response to the dynamic figure-ground correlated with SIN performance, suggesting that the neural entrainment to the dynamic figure-ground can be a biomarker for SIN ability. This work reveals important interactions between the auditory cognitive mechanisms contributing to SIN perception. It suggests new measures to predict real-life listening in both hearing disorders and brain disorders.