Factors that facilitate perception of degraded speech and speech in noise

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In everyday life, speech is often heard against a background of interfering talkers or other noise. If the background sound is sufficiently intense, target speech is effectively degraded and becomes hard to understand, to the point that even the most sophisticated automatic speech recognition systems will largely fail. Nevertheless, normally hearing human listeners presented with similar levels of background noise understand speech with apparent (deceptive) ease. Humans are adept at using their knowledge and experience to help them interpret an ambiguous speech signal. In particular, meaningful semantic context facilitates comprehension of spoken sentences by young and older adults, especially in difficult listening conditions. Although this research has a long history, our understanding of contextual effects -- when they arise and the mechanisms by which they influence comprehension -- are limited. The work proposed here will explore how constraining information (i.e., meaningful context) facilitates comprehension when speech is difficult to understand, either because it is degraded in some way (e.g., because the interlocutor has a strong accent or the speech is transduced through a cochlear implant) or because it is partially masked by background sounds. This work will contribute fundamentally to a theoretical account of contextual effects in speech perception. This is important because understanding speech in noise is one of the most common complaints of older individuals, and research to date has focused on explanations of the problem (age-related changes in hearing and cognition) that, by their nature, are not easily remediable. Research in my lab is unconventional in its focus on factors that facilitate successful perception of speech and which may act to mitigate the effects of hearing loss. One of the most important of these is the effective use of meaningful context. As people age and the fidelity with which acoustic input is processed deteriorates, such knowledge-based cues to speech comprehension become increasingly important. A more complete understanding of the factors that can facilitate speech comprehension is instrumental to optimizing them and promoting their use.