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Second Biennial Hearing Aid Research and Development Conference

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September 22-24, 1997
National Institutes of Health
Bethesda, Maryland

Speech Intelligibility and Localization in a Complex Environment: Relationship to Binaural Hearing

Monica L. Hawley and H. Steven Colburn; Hearing Research Center and Department of Biomedical Engineering, Boston University

Listeners with hearing impairments often complain of the difficulty they encounter when trying to communicate in a complex environment such as a cocktail party. There are many aspects of a cocktail party type situation that can be studied, and we choose to vary the number of speech sources that are played simultaneously and their spatial position in the frontal horizontal plane. Specifically, we are interested to learn whether the intelligibility and localizability of speech changes as a function of the spatial positions of the target and other sources played simultaneously. The total number of speech sources played at any one time varied between one and four. Listeners with normal and impaired hearing were tested. The listeners with hearing impairments were tested with and without their own hearing aids whenever possible. Harvard IEEE sentences (1969) were used with a female talker for the target and male talkers for the distracters.

For listeners with normal hearing, the intelligibility of the target speech is improved when the distracter sources are moved away from the target. Listeners with hearing impairments vary in the benefit obtained by the spatial separation of sources.

Localization of sentences appear to be independent of spatial position of the distracters. For the listeners with hearing impairments, there is a wide range of localization accuracy, with some listeners performing comparably to the listeners with normal hearing and others performing much worse.

We are interested to determine whether these inter-subject differences for the listeners with hearing impairments are due to differences in each listener's binaural processing abilities. Therefore, we are measuring performance in several binaural psychoacoustical experiments (interaural intensity discrimination, interaural time discrimination and binaural detection thresholds under headphones and the minimum audible angle in the sound field using loudspeakers) in the same listeners to see if there is correlation between the functional tasks (benefit of spatial separation on speech intelligibility and localization accuracy experiments) and the psychoacoustical measurements.

[Work supported by the NIDCD]

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