Question: If an employee suffers a Standard Threshold Shift (STS) in only one ear, may the employer revise the baselines for both ears?

Answer: No. A Standard Threshold Shift, or STS, is defined in the occupational noise exposure standard at 29 CFR 1910.95(g)(10)(i) as a change in hearing threshold, relative to the baseline audiogram for that employee, of an average of 10 decibels (dB) or more at 2000, 3000, and 4000 hertz (Hz) in one or both ears. The employer is permitted only to revise the baseline in the ear where the employee suffered an STS change in hearing threshold.

Standard Number: 1904.10, 1904 - Table of Contents