Revising baseline hearing tests one ear at a time

NOTICE: This is an OSHA Archive Document, and may no longer represent OSHA Policy. It is presented here as historical content, for research and review purposes only.

February 23, 1996

Dean A. Harris, Ph.D.
Industrial Audiologist
Dean H. Harris Associates, Inc.
[Recipient address omitted]
Dear Dr. Harris:

This is in response to your letter of October 10, 1995, concerning baseline audiograms.

You said that another audiologist recommended to one of your client companies that they use a separate baseline for each ear and that they revise each of the baselines independently as each ear shows a Standard Threshold Shift (STS). The company asked you to obtain from the Occupational Safety and Health Administration (OSHA) an opinion on this procedure for revising baseline audiograms.

In OSHA's view, this procedure is acceptable and more protective because it provides a clearer indication of how each ear is affected by noise and could provide for the reporting of more STSs. The procedure in OSHA's Noise Standard, 29 CFR 1910.95, permits the baselines for both ears to be revised together even when only one ear shows an STS.

You also said that the audiologist recommended revising the baseline if the hearing showed a 5 dB average improvement at 2000, 3000, and 4000 Hz. You stated that in clinical audiology, a 5 dB change is considered normal day to day variation of the human hearing threshold. You contend that a 10 dB average hearing improvement should be used for revising a baseline. The company asked you to obtain OSHA's opinion on this matter.

Rule 29 CFR 1910.95(g)(9)(ii) states that the audiogram may be revised when, in the judgement of the audiologist, otolaryngologist, or physician who is evaluating the audiogram, the hearing threshold shown in the annual audiogram indicates significant improvement over the baseline audiogram. Thus, there is no specific amount of improvement in hearing threshold that an annual audiogram must indicate before it can be substituted for the current baseline audiogram. OSHA relies on the professional reviewing the annual audiogram to judge when the substitution may be made. If the professional reviewing the annual audiogram judges that the audiogram indicates a significant improvement in hearing threshold over that indicated by the baseline audiogram, then the annual audiogram may be substituted for the baseline audiogram.

We appreciate the opportunity to clarify this matter. If you have further questions please contact Gail Brinkerhoff at (202) 219-8036.

Sincerely,
Ruth McCully, Director
Office of Health Compliance Assistance

[Requester letter reproduced on OSHA page; omitted here.]