Is Noise Exposure Associated With Impaired Extended High Frequency Hearing Despite a Normal Audiogram? A Systematic Review and Meta-Analysis.

All included studies were observational (case-control, cross-sectional, or one longitudinal); none were randomised, so the association cannot be read as proof of cause. Heterogeneity was high (I-squared above 75% at most frequencies), meaning the studies disagreed substantially about the size of the effect. Only 7 of the 30 studies used objective noise dosimetry; the rest relied on self-reported questionnaires, which are subject to recall bias. Most studies did not report a power analysis, so some null findings may reflect small samples rather than a true absence of effect. Age-related decline in EHF sensitivity can begin in the late teens, and although participants were capped at 35, the age and noise effects could not be fully separated. No subgroup analyses by sex or ethnicity were possible because the included studies did not report these data.

The authors declared no funding and no conflicts of interest.

Do not read the recreational noise findings as equivalent to the occupational findings. Six of the 13 recreational studies found no significant EHF threshold shift, and the meta-analysis showed significant effects at only three of seven frequencies, compared with six of seven for occupational noise. The overall conclusion that noise is associated with EHF elevation rests heavily on the occupational data.