Word recognition functions for Auditec recordings of the CID W-22 stimuli in multitalker noise were obtained using subjects with normal hearing and with mild-to-moderate sensorineural hearing loss. In the first experiment, word recognition functions were generated by varying the signal-to-noise ratio (S/N); whereas in the second experiment, a constant S/N was used and stimulus intensity was varied. The split-half reliability of word recognition scores for the normal-hearing and hearing-impaired groups revealed variability that agreed closely with predictions based on the simple binomial distribution. Therefore, the binomial model appears appropriate for estimating the variability of word recognition scores whether they are obtained in quiet or in a competing background noise. The reliability for threshold (50% point) revealed good stability. The slope of the recognition function was steeper for normal listeners than for the hearing-impaired subjects. Word recognition testing in noise can provide insight into the problems imposed by hearing loss, particularly when evaluating patients with mild hearing loss who exhibit no difficulties with conventional tests. Clinicians should employ a sufficient number of stimuli so that the test is adequately sensitive to differences among listening conditions.

Articulation functions were generated on a normal-hearing population with the Auditec of St. Louis cassette recordings of the NU-6 and CID W-22 speech discrimination tests. Both tests were similar and yielded slopes of about 4.4%/dB. Each gave a speech discrimination score of approximately 95% at 32 dB SL. Speech reception thresholds were obtained with monitored live voice and yielded good test-retest consistency. Speech thresholds were about 9 dB better than the ANSI (1969) specifications.

The present study investigated the interaction of click polarity (compression, rarefaction, alternating), repetition rate (2.3 and 9.2 clicks per second), and stimulus level (60, 75, and 90 dB nHL) on auditory brainstem responses. Two tracings (trials) were obtained for each condition using 45 normally hearing subjects. Although no systematic Wave I, III, or V latency or amplitude differences were observed among polarities or repetition rates at the three intensities, statistically significant differences were observed for the following conditions: (1) Wave III latency at 90 dB nHL was longer for the 9.2 repetition rate than for the 2.3 rate, and latencies for compression clicks were shorter than rarefaction clicks; (2) Wave V latencies at 75 dB nHL were longer with compression clicks than with rarefaction clicks; (3) mean Wave V latencies at 60 and 75 dB nHL were slightly longer for the 2.3 click rate than for the 9.2 rate; and (4) Wave V amplitudes at 90 dB nHL were larger for rarefaction clicks than for compression clicks. Because latency and amplitude differences were small and only found in a few conditions, the results indicate that polarity is not a significant variable in normally hearing subjects when using slow repetition rates (less than or equal to 10 clicks per second) at moderate to high intensities (60 to 90 dB nHL). Because repetition rates of less than 10 clicks per second increases examination time but does not improve wave morphology, rates of 10 per second or faster are recommended for gathering normative data. Absolute amplitudes showed considerable intersubject variability, especially for Waves I and III. Intrasubject variability (test-retest) also was substantial. These findings suggest that absolute amplitudes may be of little use for distinguishing normal from pathologic populations.

This study assessed the test-retest reliability of distortion-product otoacoustic emissions (DPOAEs) at four frequencies (550, 1000, 2000 and 4000 Hz) over three time intervals. The time intervals were: (1) immediate test-retest reliability, in which the retest followed the test without any delay or repositioning of the probe tip; (2) very short-term test-retest reliability, in which the retest followed a 10-20-min break and involved removal and re-insertion of the probe tip; and (3) short-term test-retest reliability, in which the retest was conducted 5-10 days after the test. Fifty normal-hearing women were tested with a commercially available system for measuring DPOAEs (Grason-Stadler, GSI-60), which generated primary tones at 65 dB SPL (L1=L2). Standard errors of measurement at 550 Hz (approximately 4.6 dB) were nearly twice as large as those found for 1000 Hz, 2000 Hz, and 4000 Hz (approximately 2.5 dB). The short-term test-retest data suggest that there is a 95% probability that an individual's true DPOAE will fall within 5 dB of the obtained distortion product at 1000-4000 Hz and within 10 dB at 550 Hz. The standard error of measurement of the difference was calculated to assess whether two or more DPOAE measurements are significantly different (e.g. before versus after administration of an ototoxic drug or noise exposure). The data revealed that short-term differences (probe removed and subject retested on the same day or on different days) between two DPOAEs must exceed approximately 14 dB at 550 Hz and 7 dB at 1000-4000 Hz to be statistically significant at the 0.05 level of confidence.

The effects of noise on word recognition scores were assessed with normal-hearing and hearing-impaired subjects. Fifty-one normal-hearing subjects were tested at 50 dB HL using signal-to-noise ratios (S/Ns) of 5, 10, and 15 dB. Thirty subjects with mild-to-moderate sensorineural hearing losses were tested in quiet and in noise at S/Ns of 10 dB and 15 dB. Monosyllabic words in a Multitalker Noise were selected for testing. Mean scores for the normal-hearing subjects were 45% at the 5 dB S/N, 74% at the 10 dB S/N, and 87% at the 15 dB S/N. For the hearing-impaired subjects, scores were 85% in quiet, 60% at the 15 dB S/N, and 40% at the 10 dB S/N. These results suggest that background noise which is mildly disruptive for normal hearing subjects can be highly disruptive to hearing-impaired subjects. Moreover, these findings indicate that subjects with mild-to-moderate sensorineural hearing loss require a more favourable S/N than normal listeners to achieve comparable word recognition scores. Test-retest differences for word recognition scores revealed variability that agreed closely with predictions based on the binomial distribution for both groups of subjects. Speech-in-noise abilities must be measured directly because regression equations revealed that speech-in-noise scores cannot be predicted accurately from either puretone thresholds or speech-in-quiet scores. Word recognition functions are presented from several hearing-impaired subjects and demonstrate the value of testing in noise.