Critical bandwidth and sensitivity prediction in the acoustic stapedial reflex.

Critical bandwidth measurements and sensitivity prediction from the acoustic reflex (SPAR) test results were obtained on 20 normal-hearing and two groups of 10 hearing-impaired subjects each representing mild-to-moderate and severe hearing loss. Results of critical bandwidth measurements indicated that for center frequencies of 1000 and 2000 Hz the critical bandwidth was significantly greater for the hearing-impaired subjects. A statistical analysis of the differences in critical bandwidth between those predicted by the SPAR test to have a mild-to-moderate hearing loss and those subjects for whom the test predicted severe hearing loss indicated no differences in critical bandwidth at 2000 Hz. A significant difference was found at 1000 Hz but in the wrong direction. Analysis of the relationship between predicted slope of hearing loss and critical bandwidth also failed to show significance. Although the data for hearing-impaired subjects fail to support the rationale for the SPAR test, the results for the entire research sample offer substantial support. Further, the ability of the test to predict categorically degree of hearing loss was also strongly supported.