Auditory Differences in Occupationally Noise-Exposed Workers With Normal Conventional Audiograms: A Multi-Measure Surveillance Approach.
Wulan Zhao, Alexis Pinsonnault-Skvarenina, Meibian Zhang and 8 others
Workers with normal hearing tests showed measurable differences in extended high-frequency hearing, cochlear function, and speech-in-noise performance versus low-noise controls.
These are group-level surveillance findings, not a diagnosis for any individual worker.
Key findings
1Noise-exposed workers with normal conventional audiograms had significantly poorer extended high-frequency thresholds (9–16 kHz), lower DPOAE amplitudes (4–10 kHz), and higher acoustic reflex thresholds at all three elicitor frequencies (0.5, 1, 2 kHz) compared with low-noise controls.
2Speech-in-noise performance (BKB SNR-50) was significantly poorer in the noise-exposed group after adjusting for conventional and extended high-frequency audibility (adjusted difference 0.95 dB, 95% CI 0.28–1.61, p = 0.005).
3Standard click-evoked ABR wave-I and wave-V amplitudes and the V/I ratio showed no significant between-group differences at either 50 or 90 dBnHL.
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What it does not show
Cross-sectional design: the study cannot show that noise caused the observed differences, only that they co-occur with exposure. Exposure estimates are approximate: hearing-protection attenuation was assigned from categories (0, 5, 7, or 15 dB) rather than individually fit-tested, and non-occupational noise was not captured. The speech-in-noise protocol held speech level constant while varying the masker, so less favourable SNRs came with higher overall presentation levels; the group difference cannot be attributed to SNR alone. Acoustic reflex thresholds were measured in 5-dB steps and some participants had no measurable reflex at the maximum output (coded as 105 dB HL); continuous middle-ear admittance was not included as a covariate. The classification model was exploratory, internally validated only, and its operating threshold depends on the 280-to-100 exposed-to-control ratio; it should not be applied as a diagnostic rule in other populations. Single site in one province of China; generalisability to other populations, languages, or industrial settings is untested. No longitudinal follow-up: it is unknown whether these early differences predict later conventional threshold shifts.
Declared interests
Funded by the US National Institute on Deafness and Other Communication Disorders (1R01DC015990) and the Innovation Guidance Special Program for New-type Research and Development Institutions in Jiaxing, China (2025YDZX027). The authors declared no conflicts of interest.
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