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.

What is threshold shift in hearing?

Definition of temporary threshold shift

A temporary threshold shift is a temporary shift in the auditory threshold. It may occur suddenly after exposure to a high level of noise, a situation in which most people experience reduced hearing. A temporary threshold shift results in temporary hearing loss.

What causes permanent threshold shift?

A permanent threshold shift can be caused by exposure to noise. Another common cause is age. We all lose our hearing as we age and hearing loss is a natural consequence of getting older. A permanent threshold shift may also occur as a result of disease, infection or drugs.