Standard threshold shift (STS)
A hearing change of 10 dB or more on average at 2,000, 3,000 and 4,000 Hz in either ear, compared with the baseline audiogram.
Definition, in the source's words
29 CFR 1910.95(g)(10)(i)(opens ecfr.gov in a new tab)“As used in this section, a standard threshold shift is a change in hearing threshold relative to the baseline audiogram of an average of 10 dB or more at 2000, 3000, and 4000 Hz in either ear.”
What it means
The employer may allow for age-related hearing loss (presbycusis) when deciding whether an STS has occurred (1910.95(g)(10)(ii)). After an STS, hearing protectors must bring the employee's exposure to 85 dBA or below (1910.95(j)(3)).
An STS is recordable on the OSHA 300 Log only if the employee's hearing level in that ear is also 25 dB or more above audiometric zero, averaged at the same frequencies (1904.10).
Example
Baseline at 2,000, 3,000 and 4,000 Hz: 10, 15 and 20 dB. This year: 20, 25 and 30 dB. The changes are 10, 10 and 10 dB, an average of 10 dB, so it's an STS before any age correction.
Where it appears on the exam
ASP: ASP11 Domain 6, Industrial Hygiene and Occupational Health
CSP: CSP11 Domain 6, Occupational Health and Applied Science
Practice: Occupational Noise
CHST: CHST5 Domain 1, Hazard and Risk Identification and Control
Questions
- Is every standard threshold shift recordable?
- No. Under 1904.10 it's recordable when the hearing level in the same ear is also 25 dB or more above audiometric zero, averaged at 2,000, 3,000 and 4,000 Hz.
Related
Checked 2026-10-16. Spot a problem? Email hello@passcited.com.