Understanding speech-in-noise perception in adults: exploring the relative contributions of noise exposure, musical training and cognition

Background. Current estimates are that between 5-15% of adults who present to medical or audiology clinics for hearing assessment, with concerns about difficulty understanding speech in background noise, are found to have normal pure-tone audiometric thresholds. Al though there is consensus amongst researchers that the audiogram inadequately reflects functional everyday listening, it remains unclear why, within the population of normal - hearing listeners, some people experience greater than expected perceptual difficulties. One suggestion is that excessive noise exposure may cause cochlear synaptopathy in humans, and subsequently lead to suprathreshold auditory processing and speech-in-noise difficulties prior to a clinical diagnosis of hearing loss. It has also been suggested that musical training may ameliorate any deficits arising from noise exposure, by enhancing speech perception in challenging listening environments, but there is debate as to whether such a 'musician advantage' is related to superior neural encoding of sound and/or higher order cognitive processes. Aims and objectives. The overarching goal of this thesis was to understand why some adults in their mid - years, despite having normal or 'near - normal' hearing thresholds, experience greater than expected difficulty understanding speech in noisy environments. Three studies were undertaken. Study 1 aimed to: (i) investigate whether noise exposure was associated with diminished auditory processing skills, including speech - in - noise perception ; and (ii) explore whether musical training is associated with improvements in aspects of auditory processing and counteracted any negative impacts of noise exposure. Study 2 aimed to : (i) identify the main factors that differentiated listeners with regard to their speech-in-noise perception; (ii) develop a model that predicted speech-in-noise difficulties; and (iii) evaluate the model's effectiveness as a 'diagnostic criterion'. Study 3 aimed to determine behavioural and physiological evidence of the 'musician advantage' ...