Use of custom-moulded earmoulds to improve repeatability of DPOAE map measurements.

OBJECTIVE: Distortion product otoacoustic emission (DPOAE) mapping characterises cochlear function, can include both the 2f1-2f2 and 2f2-2f1 DPOAEs, and shows promise for tracking cochlear changes. DPOAE amplitude measurements are not as repeatable longitudinally as pure-tone audiometry, likely due in part to probe placement sensitivity. We hypothesised that DPOAE level map variation over multiple testing sessions could be minimised by replacing traditional rubber tips with custom-moulded probe tips. DESIGN: Traditional rubber tips (TRT) and custom-moulded probes tips (CMPT) were used to measure DPOAE level maps repeatedly over five sessions. Probe placement was assessed using a frequency sweep in the ear canal. Repeatability of the DPOAE level maps was assessed using a Bland-Altman analysis. Overall map repeatability was assessed by measuring differences in distortion product amplitude over sessions. STUDY SAMPLE: Crossover study with a convenience sample size of six adults. RESULTS: The CMPT frequency sweeps showed reduced variability in probe placement. The repeatability coefficient for individual DPOAEs measurements improved from 6.9 dB SPL with the TRT to 5.1 dB SPL with the CMPT. Map repeatability improved for most subjects with the CMPT.

Going wireless and booth-less for hearing testing in industry.

OBJECTIVE: To assess the test-retest variability of hearing thresholds obtained with an innovative, mobile wireless automated hearing-test system (WAHTS) with enhanced sound attenuation to test industrial workers at a worksite as compared to standardised automated hearing thresholds obtained in a mobile trailer sound booth. DESIGN: A within-subject repeated-measures design was used to compare air-conducted threshold tests (500-8000 Hz) measured with the WAHTS in six workplace locations, and a third test using computer-controlled audiometry obtained in a mobile trailer sound booth. Ambient noise levels were measured in all test environments. STUDY SAMPLE: Twenty workers served as listeners and 20 workers served as operators. RESULTS: On average, the WAHTS resulted in equivalent thresholds as the mobile trailer audiometry at 1000, 2000, 3000 and 8000 Hz and thresholds were within ±5 dB at 500, 4000 and 6000 Hz. CONCLUSIONS: Comparable performance may be obtained with the WAHTS in occupational audiometry and valid thresholds may be obtained in diverse test locations without the use of sound-attenuating enclosures.

DPOAE level mapping for detecting noise-induced cochlear damage from short-duration music exposures.

Distortion product otoacoustic emission (DPOAE) level mapping provides a comprehensive picture of cochlear responses over a range of DP frequencies and f2/f1ratios. We hypothesized that individuals exposed to high-level sound would show changes detectable by DPOAE mapping, but not apparent on a standard DP-gram. Thirteen normal hearing subjects were studied before and after attending music concerts. Pure-tone audiometry (500-8,000 Hz), DP-grams (0.3-10 kHz) at 1.22 ratio, and DPOAE level maps were collected prior to, as soon as possible after, and the day after the concerts. All maps covered the range of 2,000-6,000 Hz in DP frequency and from 1.3 to -1.3 in ratio using equi-level primary tone stimuli. Changes in the pure-tone audiogram were significant (P ≤ 0.01) immediately after the concert at 1,000 Hz, 4,000 Hz, and 6,000 Hz. The DP-gram showed significant differences only at f2= 4,066 (P = 0.01) and f2= 4,348 (P = 0.04). The postconcert changes were readily apparent both visually and statistically (P ≤ 0.01) on the mean DP level maps, and remained statistically significantly different from baseline the day after noise exposure although no significant changes from baseline were seen on the DP-gram or audiogram the day after exposure. Although both the DP-gram and audiogram showed recovery by the next day, the average DPOAE level maps remained significantly different from baseline. The mapping data showed changes in the cochlea that were not detected from the DP-gram obtained at a single ratio. DPOAE level mapping provides comprehensive information on subtle cochlear responses, which may offer advantages for studying and tracking noise-induced hearing loss (NIHL).