OSHA requirements are set by statute, standards and regulations. Our interpretation letters explain these requirements and how they apply to particular circumstances, but they cannot create additional employer obligations. This letter constitutes OSHA's interpretation of the requirements discussed. Note that our enforcement guidance may be affected by changes to OSHA rules. Also, from time to time we update our guidance in response to new information. To keep apprised of such developments, you can consult OSHA's website at https://www.osha.gov.

March 18, 1987

Ms. Mari Franqui, M.A.
Advantage Health Systems, Inc.
Suite 350
14062 Denver West Parkway
Golden, Colorado 80401

Dear Ms. Franqui:

This is in response to your letter of December 17,1986, regarding the calculating of hearing threshold shift.

In a telephone conversation with a member of my staff you indicated that on occasion you test individuals who cannot hear the maximum 4,000 Hertz signal that your audiometers produce, which is 99 dBA, yet these individuals can hear the 2,000 and 3,000 Hertz signals. You inquire in your letter about the appropriate method for calculating the hearing threshold shifts they incur.

The Occupational Safety and Health Administration (OSHA) agrees with your opinion that the correct method of calculating the shifts is to take the average of just the measurable changes in bearing threshold occurring at 2,000 and 3,000 Hertz. The numerical value obtained by the calculation indicates a greater hearing loss than the same numerical value obtained for a normally calculated hearing shift that includes the change in hearing threshold occurring at 4,000 Hertz, however. This is so because, as you may be aware, the amount of hearing loss at 4,000 Hertz is typically greater than the amount of loss at the 2,000 and 3,000 Hertz frequencies.

Therefore, the followup procedures presented at 29 CFR 1910.95(g)(8) should be triggered by a calculated change in hearing threshold of less than 10 dB the calculated change must be, because this issue was not addressed during rulemaking proceedings. Accordingly, at the present time, the amount of calculated change in hearing threshold that triggers followup procedures is left to the professional judgment of the audiologist, otolaryngologist, or physician responsible for the audiometric testing program.

Thank you for contacting OSHA on this matter.


Leo Carey, Director
Directorate of Field Operations

December 17, 1986

Mr. John Miles
Directorate of Field Operations
U.S. Department of Labor
200 Constitution Avenue, N.W.
Washington, D.C. 20210

Dear Mr. Miles:

I am an industrial audiologist in need of an interpretation of the Federal Register: Hearing Conservation Amendment.

I would like to know OSHA's opinion in the handling of those employees that have no measurable hearing at one or more frequencies. Specifically, if an employee has no response at the limits of the audiometer for 4,000 Hz, do we still need to average that frequency (2k + 3k + 4k divided by 3) or can we just average those frequencies in which thresholds were obtained (2k + 3k divided by 2)? It seems to me that if we only average those frequencies in which thresholds have been obtained, our high frequency average becomes more sensitive; thus of greater accuracy when determining the presence of a Standard Threshold Shift.

I would appreciate your assistance in this matter.


Mari Franqui, M.A.