The Contribution of Auditory Temporal Processing to Speech Perception in Noise: Speech Comprehension Deficits in the Elderly
A common and frustrating difficulty for the elderly is understanding speech in everyday conversation, especially where the background is noisy. People commonly report that different sound sources are “Jumbled” (e.g. voices, background sounds). We propose that the brain relies on high fidelity transmission of sound codes and compares their timing in order to sort out different sound sources: When auditory neurons are activated in synchrony, their activity is perceived as representing a single sound source. Conversely, asynchronous activation conveys the presence of multiple sources. We hypothesize that age-related changes in auditory neurons introduce timing errors to the sound code, thereby compromising the use of synchrony to separate multiple sounds during perception. We will simulate this age-related hearing disorder by altering the temporal structure of speech to disrupt neural synchrony and speech perception in noise so that younger listeners experience elderly-like difficulties understanding speech in noise. In parallel, we will simulate the disorder in established computer models of auditory neurons to delineate the influence of reduced signal fidelity on sound codes and synchrony binding in the brain. The long-term goal of this research is the development of a novel hearing test battery designed to address speech-in-noise problem. We also hope to contribute to the development of novel hearing aid technology, where the device employs the temporal structure of sound to separate a single voice from the noisy environment. Currently, hearing aid technology entails the indiscriminant amplification of all sounds in the listener's environment.