Noise-induced hearing loss is permanent, preventable, and one of the most common occupational illnesses in manufacturing. Here is what OSHA’s noise standard requires when a hearing shift becomes recordable, and how to run a program that holds up.

Hearing loss is the injury no one notices happening. It is silent, gradual, and painless, accumulating over years of exposure until a worker realizes the ringing never stops and conversations have gone muffled. By then, the damage is permanent, because once the inner ear’s hair cells are gone, they do not grow back. Noise-induced hearing loss is one of the most common work-related illnesses in the country. The CDC estimates that about 22 million U.S. workers are exposed to hazardous noise each year, and manufacturing, with its presses, grinders, compressors, and other machinery, is among the loudest workplaces.

The standard that governs it, 29 CFR 1910.95, is well established, but two parts of it consistently trip employers up: the difference between the two noise limits and the rules for when a hearing shift must be recorded on the OSHA log. Get those wrong, and you either miss your compliance obligations or misreport your injury data. Here is what the standard requires, how recordability actually works, and how to run a program that protects hearing and survives an inspection.

The two noise limits, and the one that employers confuse

The single most common misunderstanding in hearing conservation is the difference between the action level and the permissible exposure limit.

The permissible exposure limit, or PEL, is 90 dBA measured as an 8-hour time-weighted average. That is the legal ceiling for routine exposure and equals a 100% noise dose. The standard uses a 5 dB exchange rate, which means that every 5 dB increase halves the allowable exposure time: 90 dBA is permitted for 8 hours, 95 dBA for 4 hours, 100 dBA for 2 hours, and so on. There is also a ceiling of 140 dB peak sound pressure level for impulse or impact noise, such as a stamping press or a sudden bang, that applies no matter how brief.

The action level is 85 dBA as an 8-hour time-weighted average, equal to a 50% dose. This is the number that matters most, because the full hearing conservation program kicks in at the action level, not the PEL. Once any employee’s exposure reaches 85 dBA, the employer must run the entire program: monitoring, audiometric testing, hearing protection, training, and recordkeeping. Employers who assume nothing is required until 90 dBA have already missed their obligation. For shifts longer than eight hours, the action level adjusts downward to about 83.4 dBA for a 10-hour shift, because the damage is cumulative.

One more distinction worth knowing: NIOSH, the research agency, recommends a more protective limit of 85 dBA using a 3 dB exchange rate. That is a recommendation, not an enforceable rule, but it reflects the scientific view that OSHA’s PEL is not fully protective, which is why good programs aim well below it.

The hearing conservation program

When exposures reach the 85 dBA action level, the standard requires a complete program with several core elements:

• Noise monitoring. Measure employee exposures to identify who is at or above the action level and must be enrolled, and to evaluate where controls are needed.
• Audiometric testing. Provide a baseline audiogram and annual hearing tests at no cost, supervised by a licensed or certified audiologist, otolaryngologist, or physician, and compare each annual test to the baseline.
• Hearing protection. Make hearing protectors available at no cost, offer a variety of suitable options, ensure proper fit, and train workers in their use. Protection is available at the action level and becomes mandatory above the PEL or after a worker experiences a hearing shift.
• Training. Provide annual training on the effects of noise, the purpose and use of hearing protection, and the audiometric testing program.
• Recordkeeping. Maintain noise measurements and audiometric records, with audiometric records kept for the duration of the worker’s employment.

The standard also expects employers to use feasible engineering and administrative controls to reduce exposure, not to rely on hearing protectors alone, a point we return to below.

Standard threshold shift and recordability

This is where employers most often go wrong, because two different thresholds are at play, and they are easy to conflate.

A standard threshold shift, or STS, is defined as an average change of 10 dB or more at 2,000, 3,000, and 4,000 Hz in either ear, compared to the worker’s baseline audiogram. When an annual test shows an STS, the employer may retest within 30 days and use that retest as the annual result, and may apply OSHA’s age-correction factors consistently and document them, since some hearing change is age-related rather than noise-related.

When an STS is confirmed, the standard requires specific actions: notify the employee in writing within 21 days; refit and retrain them in hearing protection and require its use; evaluate whether the shift is work-related; consider whether a revised baseline is appropriate; and make a medical referral if warranted. These actions are required for every confirmed work-related STS.

Recordability on the OSHA 300 log is a separate, higher bar. Under the recordkeeping rule, an STS is recordable only if it is work-related and the worker’s total hearing level in the affected ear, averaged at those same frequencies, is 25 dB or more above audiometric zero. The practical consequence is that many STS events do not meet the recordability threshold. So the rule to internalize is this: every confirmed work-related STS triggers program actions like notification and refitting, but only those that also exceed the 25 dB total hearing level threshold are recorded in your log. Employers err in both directions: some record every STS and inflate their illness numbers, while others ignore nonrecordable STS events and skip the required follow-up. Getting both halves right is the mark of a real program.

Why it matters

The case for hearing conservation rests first on permanence. Noise-induced hearing loss cannot be reversed, so every shift prevented is a hearing a worker keeps for life, along with freedom from the tinnitus that so often accompanies it. That is a quality-of-life issue that outlasts the job.

It is also a compliance and cost issue. The noise standard is regularly cited by OSHA. Hearing loss is a recordable occupational illness that feeds your injury and illness rates, and occupational hearing loss generates workers’ comp claims that, while individually modest, accumulate across a workforce and across years. A program that prevents shifts protects both the worker’s hearing and the employer’s record.

Running a program that actually works

Compliance is the floor; preventing hearing loss is the goal, and the two are not identical. A program that genuinely protects hearing does a few things well:

• Controls noise at the source first. The standard expects feasible engineering and administrative controls, not reliance on earplugs alone. Quieter equipment, enclosures, sound dampening, isolating noisy processes, and limiting time in high-noise areas reduce the hazard itself rather than just shielding the worker from it.
• Runs a quality audiometric program. Good baselines, consistent annual testing in proper conditions, and prompt comparison are what let you catch a shift early, while there is still time to intervene.
• Get hearing protection that fits right. A poorly fitted earplug provides a fraction of its rated protection. Variety, fit testing, and training matter more than the number on the package.
• Acts fast on a shift. When an STS appears, quick follow-up, refitting, retraining, and reducing exposure can keep a temporary shift from becoming permanent loss. Speed is protective.

Where HealthcareLive fits

Hearing conservation is heavily clinical and administrative, which is exactly where HealthcareLive’s occupational health support fits. The engineering controls that quiet a machine are the employer’s to install, but the rest of the program, the part that is medical and record-driven, is what HealthcareLive can run or support.

That includes the audiometric testing program, baseline and annual audiograms with the required licensed audiologist or physician oversight, coordination of exposure monitoring, evaluation of standard threshold shifts and their work-relatedness, the written employee notifications, and the recordkeeping that keeps both your program documentation and your OSHA 300 log accurate, including the recordability determinations that employers so often get wrong. With that clinical and compliance backbone in place, an employer can be confident it is meeting the program requirements at the 85 dBA action level and handling STS events correctly, while focusing its own efforts on controlling the noise at the source.

The bottom line

Hearing loss is preventable and permanent, which is a powerful combination: everything you prevent, the worker keeps for life. The OSHA noise standard makes the path clear: start the full hearing conservation program at the 85 dBA action level rather than waiting for the 90 dBA PEL, run quality audiometric testing, and handle standard threshold shifts correctly, remembering that every work-related STS requires action, but only those crossing the 25 dB total-hearing-level threshold are recordable. Control the noise at the source where you can, protect with well-fitted hearing protection where you cannot, and act fast when a shift appears. If you want help running the audiometric, surveillance, and recordkeeping side of a compliant program, HealthcareLive can help.

Frequently asked questions

What is the OSHA noise limit? The permissible exposure limit is 90 dBA as an 8-hour time-weighted average, using a 5 dB exchange rate that halves the allowable time for every 5 dB increase. There is also a ceiling of 140 dB peak sound pressure level for impulse or impact noise.

What is the difference between the action level and the PEL? The action level of 85 dBA triggers the full hearing conservation program, monitoring, audiometric testing, hearing protection, training, and recordkeeping. The PEL of 90 dBA is the legal exposure ceiling and triggers the mandatory use of hearing protection and the implementation of feasible engineering and administrative controls. The program starts at 85 dBA, which is the most commonly misunderstood point in the standard.

What is a standard threshold shift? A standard threshold shift, or STS, is an average change of 10 dB or more at 2,000, 3,000, and 4,000 Hz in either ear compared to the worker’s baseline audiogram. The employer may confirm it with a retest within 30 days and may apply OSHA age-correction factors. A confirmed work-related STS requires employee notification, refitting, and retraining on hearing protection, and evaluation of work-relatedness.

Is a standard threshold shift recordable on the OSHA 300 log? Not always. An STS is recordable only if it is work-related and the worker’s total hearing level in the affected ear is 25 dB or more above audiometric zero, averaged at 2,000, 3,000, and 4,000 Hz. Many STS events do not meet that threshold, so they require program follow-up but are not recorded on the log.

What are the elements of a hearing conservation program? Noise monitoring, audiometric testing (baseline and annual), hearing protection provided at no cost with proper selection and fit, annual training, and recordkeeping, along with the use of feasible engineering and administrative controls to reduce noise at the source. The program is required when any employee’s exposure reaches the 85 dBA action level.

Is noise-induced hearing loss reversible? No. Once the inner ear’s hair cells are damaged by noise, they do not regenerate, and the hearing loss is permanent. This is why prevention is the entire point of a hearing conservation program and why acting quickly on an early shift matters so much.

Sources and methodology

This guide reflects the current OSHA occupational noise standard, 29 CFR 1910.95, including the 90 dBA permissible exposure limit, the 85 dBA action level that triggers the hearing conservation program, the 5 dB exchange rate, the 140 dB peak ceiling for impulse noise, the definition of a standard threshold shift as an average 10 dB shift at 2,000, 3,000, and 4,000 Hz, the allowance for a 30-day retest and age correction, and the required actions following an STS; the OSHA recordkeeping rule (29 CFR 1904.10) under which an STS is recordable only when work-related and accompanied by a total hearing level of 25 dB or more above audiometric zero in the affected ear; the CDC estimate that roughly 22 million U.S. workers are exposed to hazardous noise each year; and the NIOSH recommended exposure limit of 85 dBA with a 3 dB exchange rate. Manufacturing is identified among the sectors most affected by occupational noise.

Service descriptions attributed to HealthcareLive’s occupational health support, including audiometric testing, exposure monitoring coordination, STS evaluation, and recordkeeping, reflect HealthcareLive’s own offering. This content is informational and is not legal or medical advice; confirm current obligations with OSHA and 29 CFR 1910.95.