The speech intelligibility index (SII) (ANSI S3.5-1997) provides a means for estimating speech intelligibility under conditions of additive stationary noise or bandwidth reduction. The SII concept for estimating intelligibility is extended in this paper to include broadband peak-clipping and center-clipping distortion, with the coherence between the input and output signals used to estimate the noise and distortion effects. The speech intelligibility predictions using the new procedure are compared with intelligibility scores obtained from normal-hearing and hearing-impaired subjects for conditions of additive noise and peak-clipping and center-clipping distortion. The most effective procedure divides the speech signal into low-, mid-, and high-level regions, computes the coherence SII separately for the signal segments in each region, and then estimates intelligibility from a weighted combination of the three coherence SII values.

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The prevalence of spontaneous otoacoustic emissions (SOAEs) was measured in a group of 100 neonates and in a group of 50 normal-hearing young adults. The prevalence of SOAEs in the adult group (0.62) is at the high end of the range of prevalences reported in other surveys of adult SOAEs based on measurements using similar microphones. The prevalence of SOAEs in neonates (0.64) is not significantly different from that in adults. The various tendencies that have been found to be significant in the pooled results of other surveys are also evident in our adult group: more SOAEs in right ears, a higher prevalence of SOAEs in females, and a dependence between ears for the occurrence of SOAEs. The above-mentioned tendencies are also significant in the infant data. The major differences between the infant and adult results are the predominant SOAE frequency range and the average levels of SOAEs. The majority of adult SOAEs are between 1.0 and 2.0 kHz, whereas the majority of neonatal SOAEs are between 2.5 and 5.0 kHz. The average SOAE level is -2.6 dB SPL for adults and 8.5 dB SPL for infants.

The output levels of PLDs are capable of reaching levels that could increase the risk for MIHL, and 14% of teenagers in this study reported behavior that puts them at increased risk for hearing loss. However, measured listening levels in the laboratory settings did not correlate well with self-reported typical listening levels. Further, the Listening Habits Questionnaire described in this study may provide a useful research tool for examining the relationship between attitudes and beliefs and listening behavior.