Slope characteristics of CID W-22 word functions in elderly hearing-impaired listeners

Some variables affecting the slope of monosyllabic word functions were investigated among subjects having mild-to-moderate sensorineural hearing loss. Slope is an important variable because it determines the intensity range and the step size that is likely to accurately and efficiently describe the function. Eighty-one ears from 60 elderly subjects were tested with the Auditec recordings of the CID W-22 words. Slopes were computed between the 20 and 80% intelligibility points from the individual functions. The results indicated that the magnitude of hearing loss did not affect the slope of the intelligibility function. That is, slopes remained at approximately 3% per dB even though spondaic thresholds varied over a 45-dB range (15-60 dB HTL). The audiometric configuration was found to affect slope, although this relationship was weak (r = .30). As the audiogram progressed from flat to steeply falling, the slope decreased from about 3.5% per dB to 2.5% per dB. With subjects having flat and falling audiograms, slope was steeper for the 20-50% intelligibility segment (4.3% per dB) than for the 50-80% interval (2.9% per dB). These subjects also exhibited substantial differences in mean slope, depending on the procedure selected for computations. The mean of individual slopes was steepest (3.3% pr dB), whereas the mean slope was only 2.4% per dB when computed from the function derived in the conventional manner by averaging intelligibility scores at fixed intensities.