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Hearing Conservation: The Standards

Regulations intended to protect workers from the effects of noise have been in place in the US since the late 1960s. Familiarity with the regulations is an important part of providing hearing conservation services. This article will serve to offer the reader an overview of current regulations.

Important Caveat

As with most federal regulations, noise-related standards are subject to change, revision, and interpretation. The information contained here is accurate as of Spring, 2001, but it is advisable to check the current status of regulations and interpretative letters regularly. Website addresses and other contact information will be provided herein.

The Basics

Most regulatory criteria share common aspects.

  • Exposure assessment. The process starts with noise exposure surveys to determine who needs to be included in the program, what hearing protectors should be selected, and what noise problems should be considered for control.
  • Exposure limits. Regulations typically stipulate a permissible exposure limit and/or a level at which other program aspects, for instance, medical surveillance and/or hearing protection, are required.
  • Controls. Regulations typically require controlling hazardous noise by reducing it to safe levels, as the most desirable protection method of choice.
  • Hearing protection. Guidance is provided for the use of hearing protection. However, hearing protection is typically recommended after engineering controls are already in process or when engineering controls are insufficient to provide adequate protection from noise.
  • Recordkeeping. Most regulations contain requirements for noise exposure and hearing record maintenance and retention. OSHA's recordkeeping standard (CFR 1904) is separate from the hearing conservation rule. It details how hearing loss is to be managed as a recordable workplace illness/injury.
  • Training. Most standards describe training requirements for noise-exposed workers.
  • Medical surveillance. The general industry and mining standards contain requirements to monitor the hearing of the noise-exposed workforce to assess the effects of exposure and the effectiveness of hearing protection via regular audiograms.

Chapter 16 in the recently revised AIHA Noise Manual (AIHA Press, 2000) contains a useful table comparing some aspects of the OSHA, MSHA, and NIOSH criteria. A version of that table is provided here with permission, with the addition of construction criteria. The Noise Manual is a valuable reference for professionals involved with hearing conservation, and is available from AIHA Press at . The comments following and the table are not comprehensive lists of all requirements, but are intended to provide a comparison of key points among standards.


The OSHA Hearing Conservation Amendment (HCA) was developed in the late 1970's and early 1980's as the successor to the Walsh-Healy Act of 1969.

Noise monitoring is required to determine who needs to be in the hearing conservation program (HCP). Noise monitoring must be repeated as conditions change as there is the potential that more/other people may need to be in the HCP or that hearing protection devices (HPD) may not be sufficient for exposures. Exposure must be assessed via a sampling strategy designed to identify people for HCP.

Based on the HCA, sound levels below 80 dBA are considered zero in calculating exposure. The HCA guidelines assume; a 5 dB exchange rate (assuming the risk of hearing loss from noise doubles/halves with each 5 dB increase/decrease in sound level); 'slow' response setting on the measurement equipment; a ceiling limit or 'not to exceed' value of 115 dBA slow or 140 dBA unweighted fast response peak.

The HCA considers 8 hours exposure to an average of 90 decibels (dBA) as 100% of the permissible exposure limit (PEL), or 100% dose, called the 'criterion level'. HCP inclusion is required for people exposed to, or above 85 dBA TWA (time-weighted average) or 50% dose, also called the 'action level.'

The HCP requires hearing testing to assess the effect of noise on exposed workers. The first or baseline test is provided within 6 months of first exposure to noise above the action level. Up to 12 months is allowable before the baseline test if the employer uses a mobile testing service and if HPD is used in the interim. Fourteen hours of quiet is required before the baseline test to ensure no contamination due to temporary threshold shift (TTS) from noise exposure; HPD can be used to meet the 14 hour requirement. Allowable background level in the test environment are stipulated in Appendix D.

Annual tests are provided and compared to baseline to assess changes in hearing. Note that the purpose of the HCP is not to directly address hearing ability; it is intended instead to assess changes in hearing over time. There is no requirement for 'quiet time' prior to the annual test, as detection of TTS can be helpful in detecting deficiencies in HPD or other program aspects. Annual test results are compared to the baseline. The sentinel hearing change is called 'standard threshold shift' (STS), defined as a 10 dB averaged loss from baseline across the three identified frequencies, 2000, 3000, and 4000 Hz. Age correction per the tables in Appendix F is permissible; if age correction is used, it must be applied to all audiograms under consideration.

If STS is detected, the employer can retest the worker within 30 days to make sure the shift is persistent. If the STS is found to be persistent, the new test can be used as a revised baseline for future comparisons. The worker must be notified of the STS in writing within 21 days of determination, unless the HCP supervising professional determines that the STS is not work-related. Follow-up, including evaluating the HPD used by the worker to make sure it is sufficient, refitting the HPD, and retraining the worker is required. If deemed appropriate by the supervising professional, or if the STS is not related to work or to HPD use, referral to a hearing health professional is required.

The HCP must be supervised by a licensed or certified audiologist, otolaryngologist, or other physician. The person actually providing the test is responsible to the supervising professional, and must be certified by the Council for Accreditation in Occupational Hearing Conservation (CAOHC) or demonstrate equivalent competence. Interestingly, testers using microprocessor audiometers are excluded from the CAOHC certification requirement.

HPD is optional at 85 dBA TWA, except for workers who have demonstrated an STS. For exposures above 90 dBA TWA in general, and for workers with a known STS, HPDs are mandatory. HPD choices must be include 'a variety', interpreted by OSHA as at least one type of plug and one type of muff.
Follow-up compliance directives and letters of interpretation lead to using the noise reduction rating (NRR) to assess adequacy of HPDs. Unfortunately, the derating of NRRs is complex and may potentially confuse the wearer, or lead to a false sense of safety.

Noise control, or hearing protection until noise control is implemented, is required at the criterion level. Numerous qualifiers apply to noise control, including definitions of feasibility and significant benefit.

A copy of the regulation must be posted in the workplace. Hearing loss recordability is addressed under CFR 1904, OSHA's recordkeeping rule (discussed below).


The mining industry is covered by their own rule (30 CFR Parts 56 and 57 et al), which came into full effect in September 2000. Most of the requirements are similar to OSHA, including monitoring, with the additional stipulation that each mine operator establish a system to evaluate exposure sufficiently to comply with the rule.

The action level of 85 dBA TWA (50% dose), criterion level at 90 dBA TWA (100% dose), and 5 dB exchange rate are the same as the OSHA rule. The September rule contains hearing testing requirements, similar to those in the OSHA rule, that are new for most of the mining industry. The hearing test under MSHA is optional at the discretion of the miner, and that the person providing the tests must be CAOHC certified 'or equivalent'.

Hearing protection rules are similar as well, with the addition of a requirement for double HPD (earplug under an earmuff) where exposure exceeds 105 dBA. Choices of HPD are defined as at least two types of earplugs and two types of muffs. No method of HPD effectiveness evaluation is stipulated.
Feasible noise controls are required where exposures exceed the criterion level even if the control does not reduce exposure to less than 90 dBA TWA. Administrative controls are acceptable (limiting the time miners spend in hazardous noise via employee rotation or reducing the amount of time noisy equipment is operated); they must be provided to the miner in writing and posted at the worksite.

STS cases require 10-day notification, and, unless the STS is found not to be work-related, follow-up including retraining, reissuing and refitting of HPD, and review of controls to detect deficiencies are required.

MSHA uses a their own system for recording and reporting occupational injuries and illnesses. Recordable hearing loss is defined as a 25 dB average shift from baseline at 2000, 3000, and 4000 hz, requiring maintenance of separate baselines for STS calculation and recordability.


The construction industry is exempt from the requirements of CFR 1910.95. Noise is covered under 29 CFR 1926, with Part 52 defining exposure limits and Part 101 covering HPD.

The construction rule is far less detailed that either OSHA or MSHA, and is very similar to the Walsh-Healy Act that preceded the HCA. The basic requirement is the employer must administer a 'continuing, effective hearing conservation program' when exposures exceed 90 dBA TWA, but these terms are not defined. The construction rule has the same criterion level as OSHA and MSHA at 90 dBA TWA, and it infers the same ceiling limit of 115 dBA, but it has no specific requirements for monitoring or hearing testing which form the basis of the other rules.

HPDs must be selected and fit by a 'competent person' when exposures exceed 90 dBA TWA. Noise control is ostensibly required where exposures exceed the criterion level, but with no specific requirement for monitoring, this is difficult to assess.

NIOSH Criteria Document

NIOSH uses the Criteria Document process to inform OSHA of the need for rulemaking. The Criteria for a Recommended Standard: Occupational Noise Exposure issued by NIOSH in 1998 was an update of their 1972 Criteria Document, which led to the HCA in the early 1980's. The Criteria Document reflects the most recent research and science in the area of occupational noise exposure and hearing, and reflects a significant revision of thought regarding how to protect workers from the effects of noise. The changes are pervasive enough that NIOSH coined a new term for the new approach - the hearing loss prevention program (HLPP) replaces the HCP under the NIOSH recommendation.

NIOSH recommends replacing the dual action/criterion levels in OSHA and MSHA with a single recommended exposure limit (REL) of 85 dBA TWA, making the design goal for controls 85 dBA. Administrative controls are allowable, but they must not expose more workers to noise. Remonitoring noise exposure every 2 years is required under the Criteria Document for facilities with any exposure above the REL, using a 3 dB exchange rate rather than the 5 dB exchange rate currently in the OSHA and MSHA rules. Warning signs are required at entrances to areas with exposure routinely exceeding the REL.

Hearing testing is managed in the Criteria Document much like the OSHA and MSHA rules. Twelve hours of quiet is required prior to the baseline hearing test instead of the 14 required under OSHA and MSHA, and HPDs are not allowed to be substituted for 'quiet'. NIOSH also removes consideration of presbycusis, assuming that using population-based correction factors to interpret individual audiograms may mask hearing loss until the opportunity for intervention is lost.

NIOSH redefined the sentinel hearing loss event as well, defining significant threshold shift as a 15 dB change in hearing from baseline at any test frequency, confirmed with a follow-up test. They felt that frequency-averaged shift criteria allow too much noise-induced hearing loss to accrue before triggering intervention. STS follow-up is similar to OSHA, with 30 day worker notification and retraining requirements. NIOSH also recommends considering moving the worker to a quieter area.

HPD management is significantly changed under the NIOSH recommendation. The Criteria Document requires HPDs at the REL, with double protection recommended at 100 dBA TWA. HPD effectiveness is directly addressed, with the manufacturer's NRR to be derated by 25% for earmuffs; 50% for 'formable' or foam earplugs; and 70% for all other earplugs, unless the HPD has been evaluated using the updated lab methods in ANSI S12.6-1997 Method B.

Worker training is approached differently in the HLPP model. NIOSH refers to this aspect of the HLPP as education and motivation, addressing the essence of the desired goals. Education and motivation are required for all workers exposed at the REL or higher, and include new requirements for information about the effect of not just noise on hearing, but on hearing loss itself to motivate the worker to undertake appropriate self-protective behaviors.

OSHA Recordkeeping

Revisions to OSHA's recordkeeping standard have been under development for some time. The final revised rule was published in the waning hours of the Clinton administration in January 2001. The 60-day stay implemented by the Bush administration makes the effective date for the new recordkeeping rule March 2, 2002, pending further review and/or stay. The revised 1904 provides a comprehensive revision of workplace injury and illness forms, criteria, and reporting protocol. There are new specific aspects pertaining to hearing conservation.

  • Work relatedness. Hearing loss is assumed to be work related if the worker is exposed to action level or greater on the job. Final decisions regarding work relatedness are deferred to the medical professional responsible for hearing conservation program oversight.
  • Recordable hearing loss criteria. OSHA STS has been selected as the recordable event. This is a significant change from the previous recordability criteria of 25 dB average at 2000, 3000, and 4000 hz. 'Correction' for aging is allowable, but not required, per the presbycusis tables in Appendix F of the HCA. Retesting the worker to determine persistence of the STS is allowable prior to recording the loss up to 30 calendar days from detection of the shift.
  • Hearing loss has a specific location on the revised recordkeeping form. Hearing loss is to be recorded in Column M on the new Form 300 (replaces Form 200) within 7 calendar days of the confirming test, if any. This will enable NIOSH and other research agencies to accurately determine the scope of the occupational hearing loss issue nationally for the first time. Previously, hearing loss cases were recorded as generic occupational illness, and it was impossible to extract hearing loss data separately for analysis.

Compliance Doesnt Protect Hearing
While existing regulations provide a solid framework for preventing hearing loss in the workplace, compliance with regulation in itself does not ensure that workers will not lose hearing. Regulations may lead to detecting and recording hearing loss, but cannot guarantee hearing loss will be prevented. Early identification of susceptible individuals, effective intervention strategies, and above all, reducing or eliminating exposure by effective control of hazardous noise are the real keys to hearing loss prevention.

Key US Regulations and Documents
29 CFR 1910.95, OSHA's Hearing Conservation Amendment for general industry. OSHA standards and supporting documentation are available at www.osha-slc.gov/SLTC/noisehearingconservation/index.html
30 CFR Parts 56 and 57 et al , the MSHA hearing conservation rule for mining. MSHA has a 'one stop' page covering the mine standard at www.msha.gov/1999noise/noise.htm
29 CFR 1926 for construction. Part 52 covers exposure limits and Part 101 addresses hearing protection. Construction standards are currently under review, with an advance notice of proposed rulemaking (ANPR) expected soon. Access the construction standards through the Federal Register at www.access.gpo.gov/nara/cfr/
29 CFR 1904 is the federal rule covering recording and reporting of occupational injuries and illnesses. The recordkeeping rule was revised in January, 2001, with specific and far-reaching implications for hearing conservation which are discussed below. The recordkeeping rule and supporting documentation are available at www.osha-slc.gov/recordkeeping/index.html
The 1998 NIOSH Criteria for a Recommended Standard: Occupational Noise Exposure is a key leading indicator, as it reflects the most current research in hearing loss prevention and is indicative of 'best practices' in management of noise and hearing. The Criteria Document is available at www.cdc.gov/niosh/98-126.html.

Comparison of US Hearing Conservation Regulations and Recommendations (requires Adobe Acrobat)

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