Reference · 30 terms

Hearing Conservation Glossary

Plain-English definitions of the terms you'll encounter in OSHA 29 CFR 1910.95 and in day-to-day hearing conservation work — action level, PEL, TWA, NRR derating, STS, audiogram, CAOHC, OHC, and more. Every definition cites the relevant section of the standard where one applies.

Educational reference only — not a formal compliance audit, on-site noise survey, or legal review.

#1 term

29 CFR 1910.95 Standard & Program: The OSHA standard titled “Occupational Noise Exposure,” under 29 CFR Part 1910 Subpart G. It defines the action level, permissible exposure limit, monitoring requirements, audiometric testing, hearing protectors, training, recordkeeping, and program administration for general industry.See also:Hearing Conservation Program, Action Level, Permissible Exposure Limit

A9 terms

Action Level(AL) Sound & Measurement: An 8-hour time-weighted average sound exposure of 85 decibels (A-weighted, slow response). When employee exposure equals or exceeds the action level, OSHA requires the employer to administer a continuing, effective hearing conservation program.Cite:29 CFR 1910.95(c)(1)See also:Time-Weighted Average, Permissible Exposure Limit, Hearing Conservation Program
Administrative Controls Standard & Program: Workplace policies that reduce a worker's noise exposure without modifying the noise source — for example, rotating workers out of noisy areas, scheduling loud operations when fewer workers are present, or limiting time spent in noisy zones.Cite:29 CFR 1910.95(b)(1)See also:Engineering Controls, Hierarchy of Controls
Age Correction Audiometric Testing: An optional adjustment, applied per Appendix F of 29 CFR 1910.95, that accounts for hearing loss attributable to aging when evaluating whether a Standard Threshold Shift has occurred. Age correction must be applied consistently when used.Cite:29 CFR 1910.95 Appendix FSee also:Standard Threshold Shift, Audiogram
Annual Audiogram Audiometric Testing: A hearing test performed at least once per year for every employee exposed at or above the action level. Annual audiograms are compared to the baseline audiogram to detect a Standard Threshold Shift.Cite:29 CFR 1910.95(g)(6)See also:Baseline Audiogram, Standard Threshold Shift, Audiogram
Attenuation Hearing Protection: The amount of sound a hearing protector reduces, expressed in decibels. The labeled NRR is a laboratory measurement; OSHA's derating method estimates real-world attenuation, which is typically much lower than the labeled rating.See also:Noise Reduction Rating, NRR Derating, Hearing Protection Device
Audiogram Audiometric Testing: A graph or table showing an individual's hearing thresholds — the softest sound, in decibels, the person can hear at each frequency tested. Required tests use ANSI S3.6 audiometric zero as the reference.Cite:29 CFR 1910.95(h)(2)See also:Baseline Audiogram, Hearing Threshold Level, Audiometric Zero (ANSI S3.6)
Audiologist Roles & Credentials: A licensed clinical professional who diagnoses, evaluates, and manages disorders of hearing and balance. Under 1910.95, an audiologist (or otolaryngologist or other physician) is a “reviewing professional” who evaluates problem audiograms.Cite:29 CFR 1910.95(g)(3)See also:Occupational Hearing Conservationist, Reviewing Professional, Otolaryngologist
Audiometric Testing Program Audiometric Testing: The element of a hearing conservation program that establishes baseline and annual audiograms for exposed employees, identifies threshold shifts, and triggers required follow-up actions.Cite:29 CFR 1910.95(g)See also:Baseline Audiogram, Annual Audiogram, Standard Threshold Shift
Audiometric Zero (ANSI S3.6) Audiometric Testing: The reference sound pressure level used to express hearing thresholds in audiometry, defined by ANSI S3.6. Hearing levels on audiograms are reported in dB HL relative to this reference, not in dBA.See also:Audiogram, Hearing Threshold Level

B1 term

Baseline Audiogram Audiometric Testing: An employee's reference audiogram against which all future annual tests are compared to detect a Standard Threshold Shift. Must be obtained within six months of an employee's first exposure at or above the action level — or within one year if a mobile test van is used.Cite:29 CFR 1910.95(g)(5)See also:Annual Audiogram, Standard Threshold Shift, Audiogram

C1 term

CAOHC(CAOHC) Roles & Credentials: Council for Accreditation in Occupational Hearing Conservation. CAOHC certifies Occupational Hearing Conservationists (OHCs) and approves the course directors who train them.See also:Occupational Hearing Conservationist

D2 terms

Decibel(dB / dBA) Sound & Measurement: A logarithmic unit of sound intensity. OSHA noise measurements use the A-weighted scale (dBA), which approximates how the human ear responds to sound. Most 1910.95 thresholds — the 85 dBA action level and 90 dBA PEL — are expressed in dBA on slow response.Cite:29 CFR 1910.95(d)(2)(i)See also:Action Level, Permissible Exposure Limit, Time-Weighted Average
Dosimeter / Dosimetry Sound & Measurement: A wearable noise-monitoring device that measures a worker's cumulative noise exposure across the workday. OSHA accepts personal dosimetry as an integrated sampling method for determining time-weighted average exposure.Cite:29 CFR 1910.95(d)(1)See also:Sound Level Meter, Time-Weighted Average, Noise Dose

E2 terms

Engineering Controls Standard & Program: Modifications to equipment or the workplace that reduce noise at its source or along its path — for example, enclosures, mufflers, vibration damping, or replacing a tool with a quieter model. OSHA requires feasible engineering controls when exposures exceed the PEL.Cite:29 CFR 1910.95(b)(1)See also:Administrative Controls, Permissible Exposure Limit, Hierarchy of Controls
Exchange Rate Sound & Measurement: The rule for adjusting allowable exposure time as sound level changes. OSHA uses a 5 dB exchange rate (every 5 dB increase halves the allowable time); NIOSH recommends a more protective 3 dB exchange rate.Cite:29 CFR 1910.95 Appendix ASee also:Time-Weighted Average, Noise Dose

H4 terms

Hearing Conservation Program(HCP) Standard & Program: The set of activities an employer must put in place when employee noise exposure equals or exceeds the action level: monitoring, audiometric testing, hearing protectors, training, and recordkeeping. The program must be effective and continuing.Cite:29 CFR 1910.95(c)(1)See also:Action Level, 29 CFR 1910.95
Hearing Protection Device(HPD) Hearing Protection: A device worn over or in the ear to reduce noise exposure — earplugs, earmuffs, semi-insert plugs, or canal caps. Employers must offer HPDs at no cost to employees exposed at or above the action level.Cite:29 CFR 1910.95(i)See also:Noise Reduction Rating, NRR Derating, Attenuation
Hearing Threshold Level(HTL) Audiometric Testing: The minimum sound level at which an individual can hear a specific frequency, measured in decibels relative to ANSI S3.6 audiometric zero (dB HL). Reported on every audiogram.See also:Audiogram, Audiometric Zero (ANSI S3.6)
Hierarchy of Controls Standard & Program: The NIOSH-recommended order for addressing workplace hazards: elimination, substitution, engineering controls, administrative controls, then personal protective equipment as the last line of defense. PPE alone is not a substitute for engineering or administrative controls.See also:Engineering Controls, Administrative Controls, Hearing Protection Device

N3 terms

Noise Dose Sound & Measurement: The percentage of an employee's allowable daily noise exposure. A 100% dose corresponds to an 8-hour TWA of 90 dBA under OSHA's PEL; a 50% dose corresponds to 85 dBA TWA — the action level.Cite:29 CFR 1910.95 Appendix ASee also:Time-Weighted Average, Permissible Exposure Limit, Action Level, Exchange Rate
Noise Reduction Rating(NRR) Hearing Protection: A laboratory-measured number, in decibels, printed on the package of every U.S. hearing protector under EPA labeling rules. The higher the NRR, the more attenuation the device provides under ideal conditions. Real-world attenuation is typically much lower; OSHA derates the NRR for workplace use.See also:NRR Derating, Attenuation, Hearing Protection Device
NRR Derating Hearing Protection: OSHA's method for estimating real-world hearing protector performance. For dBA measurements: take the labeled NRR, subtract 7, then divide by 2 — estimated protection (dB) = (NRR − 7) ÷ 2. The result is subtracted from the unprotected exposure to estimate the protected level.Cite:OSHA Technical Manual, Section III, Chapter 5See also:Noise Reduction Rating, Attenuation, Hearing Protection Device

O2 terms

Occupational Hearing Conservationist(OHC) Roles & Credentials: A technician trained and certified by CAOHC to perform audiometric testing and to support an employer's hearing conservation program. An OHC is not an audiologist or physician; problem audiograms are referred to a reviewing professional.See also:CAOHC, Audiologist, Reviewing Professional
Otolaryngologist(ENT) Roles & Credentials: A physician specializing in ear, nose, and throat conditions. Under 1910.95, an otolaryngologist is one of the qualified reviewing professionals who can evaluate audiograms requiring follow-up.Cite:29 CFR 1910.95(g)(3)See also:Audiologist, Reviewing Professional

P1 term

Permissible Exposure Limit(PEL) Sound & Measurement: The maximum allowable 8-hour time-weighted average noise exposure under OSHA: 90 dBA. Above the PEL, OSHA requires feasible engineering and administrative controls in addition to a hearing conservation program.Cite:29 CFR 1910.95(b)(1), Table G-16See also:Action Level, Time-Weighted Average, Engineering Controls

R1 term

Reviewing Professional Roles & Credentials: An audiologist, otolaryngologist, or other physician who evaluates audiograms when a problem (such as a Standard Threshold Shift) is identified. The reviewing professional determines whether further medical evaluation is needed.Cite:29 CFR 1910.95(g)(3)See also:Audiologist, Otolaryngologist, Standard Threshold Shift

S2 terms

Sound Level Meter(SLM) Sound & Measurement: A handheld instrument used to measure sound pressure level in real time, typically for area monitoring or spot checks. OSHA permits sound level meters for sampling, but most workplace exposure assessments rely on dosimetry.Cite:29 CFR 1910.95(d)(2)(i)See also:Dosimeter / Dosimetry, Time-Weighted Average
Standard Threshold Shift(STS) Audiometric Testing: A change in hearing threshold of 10 dB or more, averaged at 2,000, 3,000, and 4,000 Hz, in either ear, relative to the baseline audiogram. When an STS is identified, OSHA triggers a sequence of required follow-up actions including notification, retesting, and use of hearing protection.Cite:29 CFR 1910.95(g)(10)(i)See also:Baseline Audiogram, Annual Audiogram, Age Correction, Reviewing Professional

T1 term

Time-Weighted Average(TWA) Sound & Measurement: An employee's noise exposure averaged over an 8-hour workday. OSHA's action level (85 dBA) and PEL (90 dBA) are both expressed as 8-hour TWAs. Calculated using the OSHA 5 dB exchange rate.Cite:29 CFR 1910.95 Appendix ASee also:Action Level, Permissible Exposure Limit, Exchange Rate, Noise Dose

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