The Effects of White Noise on PB Score of Normal and Hearing-Impaired Listeners

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Abstract
There is increasing awareness among clinical audiologists of the inability of current speech discrimination tests to provide diagnostically significant data. In fact the most commonly used test of speech discrimination, the CID auditory test W–22 does not, according to Carhart [1965], separate persons with normal hearing from those with various types and degrees of hearing impairments. Although there has been discussion in the literature of mixing speech with noise to increase the diagnostic value of PB tests, very little data has been reported to date. In the present study 10 persons with normal hearing, 10 persons with high-frequency hearing loss, and 10 persons with relatively flat hearing loss were used as experimental listeners. All listeners yielded PB score in quiet of 92% or better, i.e. a hearing impairment was not reflected in the PB score obtained in quiet. CID auditory test W–22 words lists 1 and 2 were presented to these listeners at 40 dB SL or the sensation level necessary for PB Max. The words were presented in quiet and also in the presence of white noise. Three signal-to-noise (S/N) ratios were used; +8, 0, and –8 dB S/N. As the noise interference level increased the PB scores of all listeners deteriorated. The PB score of normal hearing listeners deteriorated approximately 52% from the quiet to the –8 dB S/N ratio, listeners with high-frequency hearing loss deteriorated approximately 57%, and listeners with flat hearing loss approximately 67%. The PB scores of groups at the –8 dB S/N condition were significantly different at the 1.0% level of confidence. The data indicate certain directions for further research in order to arrive at a more useful speech discrimination test.