Occupational Noise Exposure

Standards

Noise hazards are addressed in OSHA standards for recordkeeping and general industry. This section highlights OSHA standards and documents related to noise. For information on construction employment, see the construction requirements section.

Section 5(a)(1) of the OSH Act, often referred to as the General Duty Clause, requires employers to "furnish to each of his employees employment and a place of employment which are free from recognized hazards that are causing or are likely to cause death or serious physical harm to his employees". This section may be used to address hazards for which there are no specific standards, e.g. noise in agricultural operations.

OSHA Standards

Recording and Reporting Occupational Injuries and Illness (29 CFR 1904)
Recording and Reporting Occupational Injuries and Illness (29 CFR 1904)		Related Information
1904 Subpart (C)		Related Information
1904 Subpart (C)	1904.10, Recording criteria for cases involving occupational hearing loss.	Related Information

General Industry (29 CFR 1910)
General Industry (29 CFR 1910)		Related Information
1910 Subpart G - Occupational Health and Environmental Control		Related Information
	1910.95, Occupational noise exposure.	Related Information

State Plan Standards

There are 29 OSHA-approved State Plans operating state-wide occupational safety and health programs. State Plans are required to have standards and enforcement programs that are at least as effective as OSHA's and may have different or more stringent requirements.

Methods for Estimating HPD Attenuation
Permissible Noise Exposures

Conversion from Percent Noise Exposure or Dose to 8 Hour Time-Weighted Average Sound Level
Dose or percent	TWA (dBA)
50	85.0
55	85.7
60	86.3
65	86.9
70	87.4
75	87.9
80	88.4
85	88.8
90	89.2
95	89.6
100	90.0
105	90.4
110	90.7
115	91.1
120	91.3
125	91.6
Assumes 5 dB exchange rate and 90 dBA PEL.

Methods for Estimating HPD Attenuation

The actual effectiveness of any individual hearing protector cannot be determined under workplace conditions. However, OSHA's noise standards (29 CFR 1910.95(j)(2) and 29 CFR 1926.52(b)) require that personal hearing protection be worn to attenuate the occupational noise exposure of employees to within the limits shown in Tables G-16, G-16a, and D-2, respectively. Hearing protectors are evaluated under laboratory conditions specified by the American National Standards Institute in ANSI S3.19-1974 (OSHA's experience and the published scientific literature indicate that laboratory-obtained real ear attenuation for hearing protectors can seldom be achieved in the workplace).

Appendix B: Methods For Estimating the Adequacy of Hearing Protector Attenuation provides information on how to determine the adequacy of hearing protector attenuation using the noise reduction rating (NRR) of a given hearing protector.
Use the following formulas to estimate the attenuation afforded to a noise-exposed employee in a work environment by muffs, plugs, or a combination of both.
- A common method used for single protection (either muffs or plugs) is as follows
  1. Determine the laboratory-based noise attenuation provided by the HPD. This is referred to as the Noise Reduction Rating (NRR) and is listed on the packaging.
  2. Subtract the NRR from the C-weighted TWA workplace noise level, as follows:
    Estimated Exposure (dBA) = TWA (dBC) - NRR
    
    If C-weighted noise level data is not available, A-weighted data can be used by subtracting a 7 dB correction factor from the NRR, as follows:
    
    Estimated Exposure (dBA) = TWA (dBA) - (NRR - 7)
    
    Example:
    
    TWA=100 dBA, muff NRR=19 dB
    
    Estimated Exposure = 100 - (19-7) = 88 dBA
For dual protection (ear muffs and plugs are used simultaneously) use the following:
1. Determine the laboratory-based NRR for the higher rated protector (NRRh).
2. Subtract 7 dB from NRRh if using A-weighted sound level data.
3. Add 5 dB to the field-adjusted NRR to account for the use of the second hearing protector.
4. Subtract the remainder from the TWA as follows:
  Estimated Exposure (dBA) = TWA (dBC) - (NRRh + 5) , or
  
  Estimated Exposure (dBA) = TWA (dBA) - [(NRRh- 7) + 5]
  
  Example:
  
  TWA=110 dBA, plug NRR=29, and muff NRR=25 dB
  
  Estimated Exposure = 110 - [(29 - 7) + 5] = 83 dBA
OSHA's experience and the published scientific literature have shown that laboratory-obtained real ear attenuation for HPDs can seldom be achieved in the workplace. To adjust for workplace conditions,OSHA strongly recommends applying a 50% correction factor when estimating field attenuation. This is especially important when considering whether engineering controls are to be implemented. The equations above would then be modified as follows:
- Single Protection:
  Estimated Exposure (dBA) = TWA (dBC) - [NRR x 50%], or
  
  Estimated Exposure (dBA) = TWA (dBA) - [(NRR - 7) x 50%]
- Dual Protection:
  Estimated Exposure (dBA) = TWA (dBC) - [(NRRh x 50%) + 5] , or
  
  Estimated Exposure (dBA) = TWA (dBA) - {[(NRRh - 7) x 50%] + 5}

Comparison of Duration Per Day in Hours to Allowable Sound Level in dBA (Slow-Response SPL)
Duration per day (hours)	Sound level (dBA, slow response)	PEL = 90 dBA (TWA), or 100% Dose
8	90
6	92
4	95
2	100
1	105
½	110
0.25	115

PEL: The permissible exposure limit (PEL) for noise is 90 dBA, as an eight hour time-weighted average (TWA). The PEL is also referred to as a 100 percent "dose" noise exposure. [Table G-16]
Exchange Rate: The standard utilizes a 5 decibel (dB)exchange rate.
Maximum Continuous Noise: As interpreted from the table, exposure to continuous steady-state noise is limited to a maximum of 115 dBA.
- If the variations in noise level involve maxima at intervals of one second or less, it is to be considered continuous. [1910.95(b)(2)]
Impulse Noise: The standard states that exposure to impulsive or impact noise should not exceed 140 dB peak sound pressure level. [Table G-16]
Since the standard utilizes a 5 dB exchange rate, a TWA exposure of 95 dBA is equivalent to a dose of 200 percent, while a TWA exposure of 85 dBA is equivalent to a dose of 50 percent.
Most modern noise measuring instruments provide readouts in both noise dose and TWA.
Refer to 1910.95 Appendix A: Noise Exposure Computation for instructions and additional information for computing employee noise exposures.

Note: These are NOT OSHA regulations. However, they do provide guidance from their originating organizations related to worker protection.

Environmental Protection Agency (EPA)

40 CFR 211, Product Noise Labeling

Federal Railroad Administration (FRA)

49 CFR 227, Occupational Noise Exposure for Railroad Operating Employees. Requires railroads to conduct noise monitoring and implement a hearing conservation program for employees whose exposure to cab noise equals or exceeds an 8-hour TWA of 85 dBA. This final rule became effective February 26, 2007.
49 CFR 229, Railroad Locomotive Safety Standards
- 229.121, Locomotive Cab Noise

Mine Safety and Health Administration (MSHA)

30 CFR 62, Occupational Noise Exposure

National Institute for Occupational Safety and Health (NIOSH)

Occupational Noise Exposure. Publication No. 98-126, (June 1998). Includes revisions to previous 1972 recommendations that go beyond attempting to conserve hearing by focusing on preventing occupational noise-induced hearing loss.

U.S. Coast Guard

Recommendations on Control of Excessive Noise. Navigation and Vessel Inspection Circular No. 12-82, (June 2, 1982).

U.S. Department of Defense (DoD)

DoD Hearing Conservation Program. Instruction No. 6055.12, (December 3, 2010). Includes exposure limits and requirements for monitoring, control methods, hearing conservation programs, and more as part of the hearing conservation program.

U.S. Department of Transportation (DOT), Federal Motor Carrier Safety Administration

49 CFR 393.94, Interior noise levels in power units

Note: These are NOT OSHA regulations. However, they do provide guidance from their originating organizations related to worker protection.

American National Standards Institute (ANSI)

S3.1, Maximum Permissible Ambient Noise Levels for Audiometric Test Rooms. Specifies maximum permissible ambient noise levels (MPANLs) allowed in audiometric test rooms.
S3.44, Determination of Occupational Noise Exposure and Estimation of Noise-Induced Hearing Impairment.
S3.6, American National Standard Specification for Audiometers. Includes specifications and tolerances for audiometers and standard reference threshold levels for audiometric transducers.
S12.6, Methods for Measuring the Real-Ear Attenuation of Hearing Protectors. Specifies laboratory-based procedures for measuring, analyzing & reporting passive noise-reducing capabilities of hearing protection devices.
S1.4, American National Standard Specification for Sound Level Meters. Establishes performance and accuracy requirements for sound level meters.
S1.25, American National Standard Specification for Personal Noise Dosimeters. Contains specifications for performance characteristics of personal noise dosimeters.

American Conference of Governmental Industrial Hygienists (ACGIH)

ACGIH has established exposure guidelines for occupational exposure to noise in their Threshold Limit Values (TLVs) (85 dBA PEL with a 3 dBA exchange rate).