Two descriptive experiments were performed on a version of the Northwestern University Auditory Test No. 6 (NU No. 6) recorded by a female speaker that is included on an audio compact disc recently produced by the Department of Veterans Affairs. In Experiment 1, normative psychometric functions for the female speaker version of the NU No. 6 materials were established on 24 young adults for three monaural listening conditions (in quiet, in 60-dB SPL broadband noise, and in 60-dB SPL competing message). The 60-dB SPL broadband noise shifted the psychometric function for the NU No. 6 words 33 dB, whereas the 60-dB SPL competing message shifted the function only 18-22 dB. In contrast to the slopes of the quiet and noise conditions (4.5%/dB), the slope of the competing message function was more gradual (3.5%/dB). In Experiment 2, comparisons between the psychometric functions for the female and the original male speaker versions of NU No. 6 in quiet and in broadband noise were made on 8 young adults. In comparison to the psychometric functions for the male speaker version of NU No. 6, the functions for the female speaker version of NU No. 6 were displaced between the 10-90% correct points to higher sound-pressure levels by 10-13 dB in quiet and by 12-16 dB in noise. The difference in performance on the two versions of NU No. 6 is attributed to spectral differences between the two sets of materials that produced a calibration anomaly.

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This report describes the effects of unilateral peripheral vestibular lesions on the binocular and monocular optokinetic nystagmus (OKN). Six subjects who had undergone surgical removal of an acoustic neuroma were compared to 14 normal subjects. Stimuli consisted of 15° vertical stripes projected onto a flat screen 1 m from the subject. Stimulus velocities were 15, 30, 45, and 60°/sec. Before surgery, contralateral gain of the slow phase velocity was low, approximately 0.6, compared to 0.9 for ipsilateral gain at 60°/sec. In the acute postoperative period (<30 days), the gains of horizontal OKN were low and symmetrical for both stimulus directions. In the intermediate period (30-60 days postoperative), the OKN was asymmetrical (contralateral gain lower than ipsilateral gain), with the greatest discrepancy at 60°/sec. During the chronic phase (>2 months) the OKN was still asymmetrical in 3 of the 6 subjects. These data suggest that monocular and binocular optokinetic testing can be used to monitor the vestibular compensation of subjects following vestibular nerve section.