Two hard ceilings and one hierarchy. No octave or one-third octave band may exceed 145 decibels between 1 Hz and 40 kHz, and overall unweighted sound pressure may not exceed 150 decibels — below those levels there is no time limit on exposure. Day to day, the controlling number is the eight-hour time-weighted average dose, and the rule everywhere is that engineering controls come first: hearing protectors are what you use when engineering out the noise is not feasible, not the primary answer.
Readers asked this on CheckMyRegs and CheckMyAFI 2 times — this page answers it from the official catalogs and the publications’ own text.
| Branch | Controlling publication | Dated | Source |
|---|---|---|---|
| Air Force | DAFI 48-127 Current Occupational Noise and Hearing Conservation Program | 2026-03-17 | Official link |
| Coast Guard | COMDTINST M5100.47D Current Hearing protective devices and the controls hierarchy | 2021-07-27 | Official link |
| Army | AR 385-10 Current Army Safety Program | 2023-07-24 | Official link |
| Navy | OPNAVINST 5100.23H Current Navy safety and occupational health programme | 2020-06-05 | Official link |
| Marine Corps | MCO 5100.29C VOLUMES 1-9 w/CH-2 Current Marine Corps safety management system | 2022-02-08 | Official link |
| DoD-wide | DoDI 6055.01 Current DoD-wide safety and occupational health policy | 2014-10-14 | Official link |
No octave or one-third octave band level may exceed 145 decibels for frequencies from 1 Hz through 40 kHz, and overall unweighted sound pressure may not exceed 150 decibels; below those levels there are no time limits on exposure.
“3.2.1. No octave or one -third octave band level may exceed 145 dB for frequencies in the range of 1 Hz through 40 kHz, and the overall sound pressure level cannot exceed 150 dB (unweighted). There are no time limits for exposures below these levels. However, protecting hearing requires adherence to the hearing protection limits mentioned above, in addition to the ultrasonic evaluation requirements mentioned in the next paragraph, to protect against non - auditory effects of noise; this applies regardless of any hearing protection used.”
Bioenvironmental Engineering recommendations for engineering controls are the primary means of eliminating hazardous noise, with the goal of keeping an individual's daily dose within the eight-hour time-weighted average.
“2.12.2. Use BE recommendations for engineering controls as the primary means of eliminating exposure to potentially hazardous noise and protecting the hearing of assigned personnel to ensure an individual’s daily noise dose does not exceed an 8-hour time weighted average (TWA) of 85 decibels A-weighted (dBA). Limiting exposure time, increasing distance from noise sources (in some cases), and ensuring all workers are correctly using approved (Certified Protective Equipment List) hearing protection are secondary means of limiting the hazardous noise dose wh en engineering controls are not feasible to control hazardous noise. Explore and use all practical design approaches as recommended by BE to reduce noise levels to below hazardous levels.”
Coast Guard policy states it plainly — personal hearing protective devices should only be an interim measure while engineering controls are implemented, with administrative controls where engineering is not feasible.
“e. Hearing Protective Devices. (1) The use of personal hearing protective devices to limit noise exposure should only be an interim protective measure while implementing engineering controls. Where engineering controls are not feasible, units must employ administrative controls and/or the use of hearing protective devices. (2) Hearing protective devices must be able to reduce the member’s effective exposure at or below the OEL as specified in A.3. (3) Hearing Protective devices must be available at no cost to members and used when entering designated hazardous noise areas. (4) Hearing protective device must be worn in areas where operations generate noise levels above the OEL in Paragraph A.3.”
The occupational exposure limit is taken from established outside standards rather than invented, most commonly the current Threshold Limit Values published annually by the American Conference of Governmental Industrial Hygienists.
“3.1.1. Noise Exposure Limits on Hearing. The OEL is the most appropriate limit adopted from established, recognized standards (e.g., latest edition of the Threshold Limit Values ( TLV)® Booklet published annually by the American Conference of Government Industrial Hygienists, 29 CFR 1910.1000 Tables Z -1, Z-2, and Z -3 and 40 CFR 141) for noise and is intended to prevent damage to the hearing of exposed personnel. These noise exposure limits are sound levels and durations to which nearly all workers may be exposed without permanent adverse effect on their ability to hear and understand normal speech. Table 3.1. Health Protection Criteria. Hearing Protection* 85 dBA, 8-hours or equivalent exposure times Criterion level 85 dBA Exchange rate 3 dB Threshold level 80 dBA Maximum level 115 dBA Impulsive Noise LIAeq100ms=85 dBA. Reference MIL-STD 1474E Appendix B for impulsive noise”… (paragraph continues in the PDF)
Maximum attenuation from any hearing protector is capped by bone and body conduction, so a device advertising outstanding noise reduction still cannot deliver that figure in practice.
“5.4. Limits of Hearing Protection Performance. The maximum possible sound attenuation provided by HPs is limited by human body and bone conduction mechanisms. Even though a particular device may provide outstanding values of noise attenuation, the actual noise reduction may be less because the noise surrounding the head and body bypasses the hearing pr otector and is transmitted through tissue and bone pathways to the inner ear.”
Equipment producing ultrasonic exposure is evaluated separately against the limits in the DoD hearing conservation instruction and the current threshold limit values, using its ceiling table as the control guide.
“3.2.2. The impact of workplace equipment or other workplace conditions causing ultrasonic noise exposures will be evaluated. The limits specified in DoDI 6055.12 and the latest version of ACGIH Threshold Limit Values ( TLV) for Chemical Substances and Physical Agents should be used. Note these limits are designed to protect hearing. They apply at the ear, and hearing protective devices can be used to meet these limits. Consultation with USAFSAM/OE may be required in measuring or evaluating ultrasonic noise. Table 3.3. Exposure Guidelines for Upper Sonic and Ultrasound Noise. One-Third Octave-Band SPL (dB re: 20 microPascals (μPa)) Mid-Frequency of Third Octave Band (kHz) Ceiling Values 8-Hour TWA 10 105A 88A”
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Updated 2026-08-01. CheckMyRegs is an unofficial index — always cite the official publication.