The effect of brief subway station noise exposure on commuter hearing

Objective: To demonstrate that brief exposure to subway noise causes temporary threshold shift and is preventable with noise protection.

Methods: The study was conducted as a randomized crossover trial. Twenty subjects were randomly assigned to two groups, one with hearing protection and one without. Subjects were exposed to subway platform noise for 15 minutes. Pre- and post-exposure pure tone audiometry (PTA) and otoacoustic emissions were compared. After a washout period, subjects switched hearing protection groups and repeated the process.

Results: A statistically significant reduction in PTA thresholds after subway noise exposure was identified, for subjects with and without hearing protection (P < .001). For exposure without hearing protection, the mean threshold was 5.19 dB pre-exposure and 3.91 dB post-exposure (decrease of 1.28 dB; 95% confidence interval, 0.82-1.74). For exposure with hearing protection, the mean threshold was 4.81 dB pre-exposure and 3.47 dB post-exposure (decrease of 1.34 dB; 95% confidence interval, 0.89-1.79).

Conclusion: Brief exposure to subway noise did not cause hearing loss with or without noise protection. Though clinically insignificant, the unexpected finding of reduction in PTA suggests that there are complex heterogeneous short- and long-term cochlear responses to noise exposure that should be further explored.

Level of evidence: 1b.