September 2, 2014

Mr. Lawrence W. Grauvogel
Grauvogel & Associates
17660 Fall Creek Drive
Granger, Indiana 46530

Dear Mr. Grauvogel:

Thank you for your October 18, 2013, letter to the Occupational Safety and Health Administration (OSHA). Your letter was referred to the Directorate of Enforcement Programs for a reply. We apologize for the delay of this response. You requested a clarification of OSHA's Occupational Noise Exposure standard, 29 CFR 1910.95. This letter follows a phone conversation you had with a member of our staff; it constitutes OSHA's interpretation only of the requirements discussed and may not be applicable to any question not delineated within your original correspondence. For clarification, your specific question is paraphrased below, followed by OSHA's response.

Background: You describe a situation where an employee with a congenital hearing loss works in an environment with noise levels measured between 85 and 93 decibels A-weighted (dBA). The employee in question utilizes a full insertion, programmable hearing aid that limits noise passing through the device at or below 85 dBA. You report that in the ten years employed, the individual has had no discernable standard threshold shift (STS).

Question: If the hearing aid manufacturer can produce documentation of a noise reduction rating (NRR) for a programmable hearing aid, would OSHA consider that device as an adequate hearing protector under 29 CFR 1910.95?

Response: Yes, an assigned NRR is a manufacturer's rating of the device's effectiveness to attenuate noise. As you are likely aware, the adequacy of hearing protection is determined by the effectiveness in attenuating or reducing noise that reaches the inner ear. This measure of effectiveness is called the NRR. The NRR is a laboratory-derived numerical estimate of attenuation that is provided by the hearing protector. The U.S. Environmental Protection Agency (EPA) requires manufacturers of hearing protection devices to identify the noise reduction capability of all hearing protectors sold in the United States, and to present the NRR on the package label of the device¹ . We are aware that some manufacturers of hearing aids have also designed hearing protection into their devices with an assigned NRR.

To evaluate the adequacy of any hearing protector's attenuation, the employer must refer to the mandatory Appendix B to 29 CFR 1910.95, as required in paragraph 1910.95(j)(1). The NRR of the hearing protector is compared to an individual worker's noise environment to determine whether the exposure is attenuated to the level required by the OSHA standard. For employees with no STS, the hearing protector must attenuate noise exposure to an 8-hour time-weighted average of at least 90 dBA, as required in paragraph 1910.95(j)(2). For employees who have experienced an STS, the hearing protector must attenuate exposure to 85 dBA or below, as per paragraph 1910.95(j)(3).

Thank you for your interest in occupational safety and health. We hope you find this information helpful. OSHA requirements are set by statute, standards, and regulations. Our letter of interpretation explains 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 http://www.osha.gov.

If you have any further questions, please feel free to contact the Office of Health Enforcement at 202-693-2190.

Sincerely,

Thomas Galassi, Director
Directorate of Enforcement Programs

1. 40 CFR 211, Subpart B - Hearing Protective Devices