A standard threshold shift (STS) is a change in hearing threshold of an average of 10 dB or more at 2,000, 3,000, and 4,000 Hz in either ear, relative to the baseline audiogram (29 CFR 1910.95(g)(10)(i)). When an STS is identified, the employer must notify the affected employee in writing within 21 days.
A standard threshold shift (STS) is a change in hearing threshold, relative to the baseline audiogram, of an average of 10 dB or more at 2,000, 3,000, and 4,000 Hz in either ear (29 CFR 1910.95(g)(10)(i)). Three common content errors: (1) stating “10 dB at any frequency” — the STS is the average across those three frequencies, not a single-frequency threshold; (2) stating that all STSs must be logged on the OSHA 300 Log — logging is required only when the STS is work-related AND the employee’s total hearing level in the affected ear is 25 dB or more above audiometric zero; (3) implying OSHA mandates age correction — age correction using Appendix F tables is permitted but not required, and is not allowed in Oregon or Washington for OSHA compliance purposes. When an STS is identified, employer obligations include: written notification to the employee within 21 days; HPD refitting and retraining if the employee is already using protection; HPD fitting and training if not currently using protection; and clinical referral if a problem audiogram is identified alongside the STS. SHOEBOX: SHOEBOX PureTest automatically calculates OSHA STS against the established baseline — online or offline — and flags shifts immediately upon test completion, eliminating the manual comparison delay that can compress the 21-day notification window.
