Hearing Protection Fit Testing

The Noise Reduction Rating (NRR) on a box of earplugs is measured in a laboratory by trained subjects with careful fitting. Real workers usually get much less protection. Fit testing measures how much noise reduction you actually get from the protector you actually wear, so you can fix a bad fit before your hearing is damaged.

• Noisy Trades
• Safety Managers
• Industrial Workers

Why the label isn’t enough

• The NRR comes from laboratory tests under ideal conditions. In the field, protectors are often inserted too shallow, worn loose, shifted by glasses and hard hats, or used for only part of the shift.
• Studies show typical real-world protection is far lower than the NRR, and the difference between individual people can be large. Two people wearing the same earplug may get very different protection.
• For this reason, the OSHA noise rule (29 CFR 1910.95) and the NIOSH guidance both reduce the label NRR when estimating protection. See Hearing Protection and Noise.
• Employers in a hearing conservation program must ensure protectors attenuate noise to an acceptable level and evaluate the adequacy of the protectors for each employee. Fit testing is a good way to do this.

Derating the NRR (the quick method)

• OSHA method for A-weighted measurements: subtract 7 from the NRR, then divide by 2. This estimates the reduction in dBA. For example, an NRR 29 protector gives about (29 − 7) ÷ 2 = 11 dBA, not 29.
• NIOSH derating is more conservative for some types (reducing the NRR by 25% for earmuffs, 50% for formable earplugs and 70% for other earplugs), which shows the same trend.
• Derating is a rough guide, not a measurement. It assumes average performance and may overstate or understate protection for a given person. Fit testing gives a real number.

What fit testing is

• Field attenuation estimation systems (FAES) measure the personal attenuation rating (PAR): the noise reduction a worker actually gets with their protector, fitted in the field.
• The worker wears the protector while a test compares how well they hear a test sound with and without it, or compares the sound in the ear canal. A good system takes a few minutes per person.
• Common systems include NIOSH HPD Well-Fit, 3M E-A-Rfit (microphone-in-ear method), Howard Leight VeriPRO, and others. They use headphone-based or in-ear microphone methods, and different devices measure slightly different things.
• Results show whether the protector gives enough reduction for the person’s noise exposure, and the tester can help the worker refit, or choose a different protector.
• Fit testing is a training and selection tool, not a pass or fail test of the worker.

How to use the results

• Pick a target: aim to reduce the worker’s exposure below 85 dBA (8-hour time-weighted average) or lower, and many programs aim for at-the-ear exposure in the 70 to 80 dBA range. Avoid over-protection that isolates workers from warnings and communication. See Electronic Hearing Protection.
• Compare the PAR to the noise. Subtract the PAR from the worker’s measured noise level. Noise measurement comes from sound level meters or dosimeters. See Noise Monitoring & Dosimetry.
• Use the test to teach. When a worker gets low protection, show them how to roll, pull up the ear and insert the plug deeply, or try another size or style. Retest right away.
• Try different options: foam plugs, premolded plugs in different sizes, custom-molded plugs, banded plugs and earmuffs. Fit differs for everyone, and one person may need a different size in each ear.
• Combine protectors when needed. Double protection (plugs plus muffs) is used for very high noise, usually above about 105 dBA, and adds less than expected. Combined estimates add roughly 5 dB to the better protector. See Hearing Protection.
• Record results as part of the hearing conservation program, along with training and audiograms. See Hearing Tests (Audiograms).
• Retest at least annually, when changing protectors, after significant changes in weight, ear health or head gear, and with new hires.

Common fit mistakes

• Foam plugs inserted too shallow. They should be rolled tight, inserted deeply while pulling the ear up and back, and held in place for 20 to 30 seconds while they expand. A good fit leaves the plug’s end about even with, or slightly inside, the ear canal opening.
• Wrong size premolded plugs, or the same size in both ears when each ear is different.
• Earmuffs with a poor seal caused by glasses temples, long hair, hard hat straps, beards and sideburns. See Beards & Respirators for similar seal issues. Use thin-temple glasses or special seal pads.
• Worn-out protectors: stretched headbands, cracked or hardened ear cushions, dirty or deformed plugs.
• Taking protection out in noise even briefly. Removing earplugs for a short time greatly reduces the protection you get over a shift.
• Relying on the NRR alone or choosing the protector with the highest NRR without checking fit and comfort.

Program tips for employers

• Fit-test everyone in the hearing conservation program, especially new workers and people with early hearing loss. Include supervisors and those who go in and out of noisy areas.
• Train workers on inserting, wearing and caring for protectors, and when to wear them. Use signs and buddy checks.
• Offer a choice of at least several types. Workers who like their protectors wear them. See PPE Proper Fit.
• Replace protectors regularly, and keep protectors available where noise exceeds limits.
• Use fit-test results with audiogram trends to see if protection is working. A worker with a standard threshold shift may need better fit or a different protector. See Medical Surveillance.
• Check the quality and calibration of the fit-testing system, and follow the maker’s instructions and trained testers.

Hearing fit-testing checklist

• I know the label NRR overstates real protection, and I use derating or a fit test to estimate mine
• My fit test result shows enough protection for my noise exposure
• I insert foam plugs deeply and hold them in place, and I check my muff seals
• I use sizes and styles that fit each ear, and replace worn protectors
• I keep my protection in for the whole noisy time
• I am retested yearly and when my gear or ears change

Last updated: October 5, 2026