Word-recognition performance in interrupted noise by young listeners with normal hearing and older listeners with hearing loss.

BACKGROUND: The most common complaint of adults with hearing loss is understanding speech in noise. One class of masker that may be particularly useful in the assessment of speech-in-noise abilities is interrupted noise. Interrupted noise usually is a continuous noise that has been multiplied by a square wave that produces alternating intervals of noise and silence. Wilson and Carhart found that spondaic word thresholds for listeners with normal hearing were 28 dB lower in an interrupted noise than in a continuous noise, whereas listeners with hearing loss experienced only an 11 dB difference. PURPOSE: The purpose of this series of experiments was to determine if a speech-in-interrupted-noise paradigm differentiates better (1) between listeners with normal hearing and listeners with hearing loss and (2) among listeners with hearing loss than do traditional speech-in-continuous-noise tasks. RESEARCH DESIGN: Four descriptive/quasi-experimental studies were conducted. STUDY SAMPLE: Sixty young adults with normal hearing and 144 older adults with pure-tone hearing losses participated. DATA COLLECTION AND ANALYSIS: A 4.3 sec sample of speech-spectrum noise was constructed digitally to form the 0 interruptions per second (ips; continuous) noise and the 5, 10, and 20 ips noises with 50% duty cycles. The noise samples were mixed digitally with the Northwestern University Auditory Test No. 6 words at selected signal-to-noise ratios and recorded on CD. The materials were presented through an earphone, and the responses were recorded and analyzed at the word level. Similar techniques were used for the stimuli in the remaining experiments. RESULTS: In Experiment 1, using 0 ips as the reference condition, the listeners with normal hearing achieved 34.0, 30.2, and 28.4 dB escape from masking for 5, 10, and 20 ips, respectively. In contrast, the listeners with hearing loss only achieved 2.1 to 2.4 dB escape from masking. Experiment 2 studied the 0 and 5 ips conditions on 72 older listeners with hearing loss, who were on average 13 yr younger and more varied in their hearing loss than the listeners in Experiment 1. The mean escape from masking in Experiment 2 was 7dB, which is 20-25 dB less than the escape achieved by listeners with normal hearing. Experiment 3 examined the effects that duty cycle (0-100% in 10% steps) had on recognition performance in the 5 and 10 ips conditions. On the 12 young listeners with normal hearing, (1) the 50% correct point increased almost linearly between the 0 and 60% duty cycles (slope = 4.2 dB per 10% increase in duty cycle), (2) the slope of the function was steeper between 60 and 80% duty cycles, and (3) about the same masking was achieved for the 80-100% duty cycles. The data from the listeners with hearing loss were inconclusive. Experiment 4 varied the interburst ratios (0, -6, -12, -24, -48, and -infinity dB) of 5 ips noise and evaluated recognition performance by 24 young adults. The 50% points were described by a linear regression (R2 = 0.98) with a slope of 0.55 dB/dB. CONCLUSION: The current data indicate that interrupted noise does provide a better differentiation both between listeners with normal hearing and listeners with hearing loss and among listeners with hearing loss than is provided by continuous noise.

Voice onset time in women as a function of oral contraceptive use.

Previous studies of the effect of hormonal changes across phases of the menstrual cycle on voice onset time (VOT) have not considered the variable of oral contraceptive use. The purpose of this study was to examine both the effects of menstrual cycle phase and that of oral contraceptive use on VOT. It was hypothesized that women taking oral contraceptives would exhibit smaller VOT differences across the phases of their menstrual cycles. The study was a prospective matched-group experimental design. Participants were 10 women who were on oral contraceptives and 10 who were not. The participants were recorded over two menstrual cycles, on the 10th and 20th day to evaluate their speech during the preovulation and premenstrual phases of their menstrual cycle. Participants produced 10 repetitions of the phrase "Speak ___ to me" containing the target syllables /bae/ and /pae/. Repeated measure ANOVAs revealed no significant differences in VOT between the two groups. Statistical results showed significant interactions between the menstrual cycle phase and the 2 recording months. It is possible that month-to-month differences in hormonal levels and other factors that can affect speech may have a greater effect on VOT than either the taking of oral contraceptives or the phase differences within a menstrual cycle.