Auditory processing and speech understanding

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My past research has shown that even when sound is loud enough, micro distortions in its temporal properties affect how well listeners uptake information, especially when they must integrate information to comprehend or remember it. However, linguistic context can mitigate the deleterious effects of signal distortions; i.e., interactions between bottom-up (ear to brain) and top-down (brain to ear) aspects of listening modulate performance. The temporal properties of sound include fast changes in the fine structure (pitch) and slow changes in the sound envelope (rhythm). Older adults with clinically normal hearing have been studied because their problems using temporal cues may explain their difficulties listening in noise and younger adults perform similarly when tested using temporal distortions of fine structure cues to simulate the temporal processing problems of older listeners. Much is known about how the amount of speech energy in different frequencies relates to speech intelligibility, but little is known about the role of temporal cues. In addition, temporal cues are important for the communication of non-linguistic information such as talker identity and emotion. The proposed research will discover how temporal cues contribute to the extraction of linguistic and non-linguistic (e.g., emotion, talker identity) information and how these co-existing types of information interact. A striking preliminary finding is that, after controlling for intensity, words are understood better when spoken in a fearful voice than in a sad voice. One hypothesis is that emotional information alters how the listener attends to linguistic information. Another hypothesis is that because emotional and linguistic cues are expressed simultaneously, the motor acts performed by a talker give rise to interactions. The proposed research aims to discover how the simultaneous communication of linguistic (what is said) and non-linguistic (how it is said) information influences the production and comprehension of spoken language. This research is of great interest to engineers designing communication devices (e.g., hearing aids), as well as being of interest to psychologists, linguists and others who wish to understand how humans use sensory information during communication.