Occupational Noise Exposure

29 CFR 1910.95

“As used in this section, 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 2000, 3000, and 4000 Hz in either ear.”

“In determining whether a STS has occurred, allowance may be made for the contribution of aginq (presbycusis) to the change in hearing level by correcting the annual audiogram...”

“If the annual audiogram shows that an employee has suffered a STS, the employer may obtain a retest within 30 days and consider the results of the retest as the annual audiogram.”

“If a comparison of the annual audiogram to the baseline audiogram indicates a STS ... has occurred, the employee shall be informed of this fact in writing, within 21 days of the determination.”

“Unless a physician determines that the STS is not work related or aggravated by occupational noise exposure, the employer shall ensure that the following steps are taken when a STS occurs:

A.     Employees not using hearing protectors shall be fitted with hearing protectors, trained in their use and care, and required to use them.

B.     Employees already using hearing protectors shall be re­fitted and retrained in the use of hearing protectors offering greater attenuation if necessary.

C.     The employee shall be referred for a clinical audiological evaluation or an otological examination, as appropriate, if additional testing is necessary or if the employer suspects that a medical pathology of the ear is caused or aggravated by the wearing of hearing protectors.

D.     The employee is informed of the need for an otological examination if a medical pathology of the ear that is unrelated to the use of hearing protectors is suspected.

“If subsequent audiometric testing of an employee whose exposure to noise is less than an 8-hour TWA of 90 dB indicates that a STS is not persistent, the employer:

A.     Shall inform the employee of the new audiometric inter­pretations; and

B.     May discontinue the required use of hearing protectors for that employee”.

“Revised Baseline. An annual audiogram may be substituted for the baseline audiogram when, in the judgment of the audiologist, otolaryngologist or physician who is evaluating the audiogram:

(i)     The STS revealed by the audiogram is persistent; or

(ii)     The hearing threshold shown in the annual audiogram indicates significant improvement over the baseline audiogram.”

(NOTE: This does not mean the original baseline can be discarded. It does mean an annual can be substituted, to avoid constant referrals due to a persistent STS).