Noise monitoring informational appendix

Employers must implement noise monitoring when employee exposures are at or above 85 dB averaged over an 8-hour workday so they can determine who needs to be placed in a hearing conservation program. This practice is described in the Monitoring Noise Levels Non‑Mandatory Informational Appendix to 1910.95 and aligns with the action level in 1910.95.

• Monitor when there are indications (e.g., employee complaints, difficulty conversing, signs of hearing loss) that exposures might reach or exceed 85 dB.
• Use measurements to estimate daily dose and decide who enters the hearing conservation program.

Signs that should trigger noise monitoring include employee complaints about loud noise, indications of hearing loss, and noisy conditions making normal conversation difficult. The appendix lists these practical indicators in 1910.95 App G.

• Also consider manufacturer data for specific machines and any previous measurements.
• If you observe these signs, take measurements to estimate employee exposures and determine whether a hearing conservation program is needed under 1910.95.

Area monitoring measures sound levels at fixed locations to estimate exposures in places where noise is relatively constant, while personal monitoring follows or is worn by a worker to measure the noise that worker actually experiences. The appendix explains both methods in 1910.95 App G and this distinction is useful for complying with 1910.95.

• Use area monitoring (sound level meters and sound maps) when noise is steady and employees are stationary.
• Use personal monitoring (dosimeters or meter near the worker) when employees move or noise fluctuates, because it better captures true individual dose.

Employers should use a dosimeter for personal monitoring when employees move around or when noise levels fluctuate, because dosimeters integrate noise over time and give an average exposure for the work period. The appendix describes this guidance in 1910.95 App G.

• Dosimeters are worn on the employee (microphone near the shoulder) and report dose for an entire shift.
• Sound level meters measure sound at one moment and/or location and are better for spot checks or making area sound maps.

A sound level map should be combined with information about where employees spend their time during the day to estimate individual exposures. The appendix outlines using sound maps with employee location data in 1910.95 App G.

• Map multiple sound level readings across the workplace.
• Track typical employee routes and durations at each location, then compute a time-weighted average exposure for the shift.
• Use this method (area monitoring) where noise is relatively constant and employees are not highly mobile.

For accurate personal monitoring the dosimeter microphone should generally be located on the employee's shoulder and remain there for the entire workday. The appendix provides this practical placement guidance in 1910.95 App G.

• Keep the microphone unobstructed by clothing.
• Follow the device manufacturer's instructions for mounting and use to ensure valid readings.

When using a sound level meter to estimate an individual's exposure, position the meter's microphone near the employee's head and take multiple measurements at different times as the worker moves; these readings can then be combined to estimate the overall exposure. The appendix explains this approach in 1910.95 App G.

• A person usually holds or follows the worker with the meter.
• Take enough samples to capture changes in noise levels and durations at each level to compute a time-weighted average.

Noise monitoring must be repeated whenever significant changes in machinery or production processes might increase noise levels, and many employers also choose to remonitor periodically (for example, annually or every two years) as a best practice. The appendix states this requirement in 1910.95 App G and it supports compliance with 1910.95.

• Remonitor after equipment changes, new processes, or layout adjustments.
• Periodic remonitoring helps ensure all exposed employees remain correctly classified for the hearing conservation program.

Instruments should be calibrated before and after each use as good professional practice to ensure accurate results. The appendix recommends following the manufacturer's instructions and calibrating devices before and after each use in 1910.95 App G.

• Always follow the operating manual for calibration procedures.
• Keeping calibration records helps demonstrate that measurements were conducted properly under 1910.95.

Employers should consider equipment cost, frequency of use, and in‑house technical expertise; smaller employers often find renting more economical while larger or frequent users may prefer to buy. The appendix provides typical price ranges and rental guidance in 1910.95 App G.

• Sound level meters typically cost about $500–$1,000; dosimeters about $750–$1,500 (per appendix estimates).
• If you lack experience, consider hiring industrial hygiene firms, audiological testing firms, or university departments for monitoring services.

When noise levels fluctuate, use personal monitoring with a dosimeter or take multiple timed sound level meter readings across the shift and calculate a time-weighted average exposure. The appendix recommends these approaches in 1910.95 App G.

• For fluctuating noise, personal dosimetry is generally more accurate.
• If using spot measurements, record the duration the employee spends at each level and compute the daily exposure (dose).

Yes; a sound level meter can be positioned near the worker's head and followed by an individual to gather measurements that—when taken at appropriate intervals and combined—can estimate personal exposure, but dosimeters are usually simpler for full-shift integration. The appendix explains using a sound level meter for personal estimates in 1910.95 App G.

• Ensure the microphone stays near the employee's breathing zone.
• Take enough readings to capture variability and compute a time-weighted average consistent with 1910.95.

Employers should prioritize monitoring employees who work in the noisiest areas, those who complain about noise, employees who perform similar tasks in multiple locations, and workers with potential hearing changes; the appendix recommends using area maps and job activity patterns to choose representative employees in 1910.95 App G.

• Select employees with varying tasks and movement patterns to capture different exposures.
• Use the resulting exposure estimates to determine who must enter the hearing conservation program under 1910.95.

Universities with audiology, industrial hygiene, or acoustical engineering programs and OSHA-supported consultation organizations can provide technical advice or noise monitoring services, often at low or no cost for small businesses, as noted in the appendix 1910.95 App G.

• Contact local university departments or OSHA consultation programs for help designing a monitoring program or conducting measurements.
• OSHA-supported state and private consultation organizations often prioritize small businesses and can provide on-site assistance.

The appendix advises employers to maintain the measurement data and any estimates used to determine employee exposure, so they can demonstrate how employees were evaluated for the hearing conservation program under 1910.95 and 1910.95 App G.

• Record instrument type, calibration checks, measurement locations/times, and employee time-at-location used to compute exposures.
• Keep data for the period required by any applicable recordkeeping policies and to support program decisions.

If machine manufacturers provide sound emission data, employers can use that information along with worker location and time-at-task to estimate exposures and decide whether monitoring is needed; the appendix suggests considering such information in 1910.95 App G.

• Use manufacturer noise levels as initial screening.
• Verify estimates with spot measurements or dosimetry when worker exposure patterns or workplace reflections might change actual exposure.

When employees move through several noise zones, employers should use personal dosimetry or combine area sound maps with a time-at-location log to calculate a time-weighted average exposure for the shift, as advised in 1910.95 App G.

• Equip employees with dosimeters for the entire shift when mobility is high.
• If using area maps, accurately log time spent in each zone to compute the employee's noise dose.

If an employer lacks expertise, reasonable steps include renting equipment, hiring qualified industrial hygiene or audiological testing firms, contacting university programs, or seeking OSHA consultation services as the appendix recommends in 1910.95 App G.

• Use rental equipment for short-term needs, and follow manufacturer calibration instructions.
• Consider contracting experienced consultants to ensure measurements meet professional standards and support compliance with 1910.95.

Employers should use spot checks when noise is stable and predictable, but use full-shift measurements (typically with dosimeters) when noise fluctuates or workers move, because full-shift data capture the integrated dose needed to decide hearing conservation program placement; the appendix explains these trade-offs in 1910.95 App G.

• If spot checks suggest potential exposures near or above 85 dB, follow up with full-shift monitoring.
• Full-shift dosimetry provides the clearest basis to determine employee dose under 1910.95.

Although not mandated, many companies choose to remonitor periodically—commonly once every year or every two years—to ensure continued identification of exposed employees, a practice noted in 1910.95 App G.

• Use periodic remonitoring to capture gradual changes in equipment wear, maintenance, or work practices.
• Always remonitor sooner if significant process or machinery changes occur that may increase noise.