Low-sound-level auditory processing in noise-exposed adults

• Published in: Hearing research 2021-09, Vol.409, p.108309-108309, Article 108309
• Main Authors: Perugia, Emanuele, Plack, Christopher J., Stone, Michael A.
• Format: Article
• Language: English
• Subjects: Amplitude modulation depth discrimination; Auditory Perception; Auditory Threshold; Frequency difference limens; Hearing; Hearing Loss, Noise-Induced - diagnosis; Hearing Loss, Noise-Induced - etiology; Humans; Noise - adverse effects; Noise exposure; Noise-induced hearing loss; Sub-clinical hearing damage
• ISSN: 0378-5955; 1878-5891
• DOI: 10.1016/j.heares.2021.108309

•Frequency difference limens and amplitude modulation depth discrimination thresholds improved with music experience.•Amplitude modulation depth discrimination thresholds at 25 dB SL improved with noise exposure.•Improved performance on amplitude modulation depth discrimination may reflect outer hair cell dysfunction.•Results provide no evidence of low sensation level hearing deficits due to noise exposure. Early signs of noise-induced hearing damage are difficult to identify, as they are often confounded by factors such as age, audiometric thresholds, or even music experience. Much previous research has focused on deficits observed at high intensity levels. In contrast, the present study was designed to test the hypothesis that noise exposure causes a degradation in low-sound-level auditory processing in humans, as a consequence of dysfunction of the inner hair cell pathway. Frequency difference limens (FDLs) and amplitude modulation depth discrimination (MDD) were measured for five center frequencies (0.75, 1, 3, 4 and 6 kHz) at 15 and 25 dB sensation level (SL), as a function of noise exposure, age, audiometric hearing loss, and music experience. Forty participants, aged 33-75 years, with normal hearing up to 1 kHz and mild-to-moderate hearing loss above 2 kHz, were tested. Participants had varying degrees of self-reported noise exposure, and varied in music experience. FDL worsened as a function of age. Participants with music experience outperformed the non-experienced in both the FDL and MDD tasks. MDD thresholds were significantly better for high-noise-exposed, than for low-noise-exposed, participants at 25 dB SL, particularly at 6 kHz. No effects of age or hearing loss were observed in the MDD. It is possible that the association between MDD thresholds and noise exposure was not causal, but instead was mediated by other factors that were not measured in the study. The association is consistent, qualitatively, with a hypothesized loss of compression due to outer hair cell dysfunction.