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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



Evaluation of NU 6 Lists 3 and 4 in Multitalker Babble for Subjects with Normal Hearing and Hearing Impairment Tested at 2.5 and 5 dB Steps

Colleen M. Noe and Richard H. Wilson, James H. Quillen VA Medical Center, Mountain Home, Tennessee, Department of Communicative Disorders and Department of Surgery, East Tennessee State University, Johnson City, Tennessee

During a VA sponsored research mentoring workshop, the sensitivity of 5 dB step sizes during word recognition testing was questioned (Dirks, Levitt, and Lilly, 1996). A pilot study was conducted to determine if differences were present when presenting the Speech in Babble (Wilson et al., 1996) materials at 2.5 vs. 5-dB step sizes for subject with normal hearing and hearing loss. The materials used are lists 3 and 4 of NU No. 6 (female speaker) interleaved into a list of 100 words. The tests words were divided into groups of 10 words each mixed digitally with the words at a level that produced signal-to-noise ratios from -2.5 to 25 dB. The mean data were fit with thrid-degree polynomials from which the following 50% points and slopes (20-70% range) were calculated:

Condition Normal Hearing (n=20 Hearing Impaired (n=20) 
2.5 dB steps 1.1 dB S/N 5.4%/dB 11.8 dB S/N 4.0%/dB
5 dB even steps  1.1 dB S/N 5.3%/dB 11.8 dB S/N 3.4%/dB
5 dB odd steps 1.1 dB S/N 5.3%/dB 11.8 dB S/N 4.0%/dB

The competing babble was more detrimental (by 10 dB) to the performance by the subjects with hearing impairment than to the performance by the subjects with normal hearing. The data indicate that 2.5- and 5.0-dB step sizes in word-recognition testing produce equivalent results. Psychometric functions for the individual subjects and words will be presented.

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