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Quantitative fit testing for hearing protection devices measures the actual attenuation an individual achieves with a specific HPD, producing a personal attenuation rating (PAR) rather than relying on the population-average NRR. Under OSHA 1910.95(i)(4), employers must ensure HPDs are properly fitted—and quantitative fit testing is the most defensible method to demonstrate that requirement has been met. Two established quantitative methods exist: the microphone-in-real-ear (MIRE) system and the real-ear attenuation at threshold (REAT) method. Both produce a PAR; the choice of method affects protocol, required equipment, and what information the system can additionally generate.
Soundtrace provides quantitative HPD fit testing using the REAT method—available as an in-house service (employer-run with Soundtrace equipment) or as an on-site managed service (Soundtrace technician comes to your facility). The Soundtrace platform delivers instant fit quality guidance, noise exposure assessment, and per-employee compliance records alongside every test.
Both MIRE and REAT are ANSI-recognized quantitative methods that produce a PAR. They use different measurement approaches and serve slightly different use cases.
| Feature | MIRE | REAT |
|---|---|---|
| How it works | Probe microphone at ear canal measures physical sound level difference before/after HPD insertion | Measures threshold shifts in the worker’s hearing with and without the HPD in place—same audiometric approach as a hearing test |
| Equipment | Probe microphone + sound field system | Audiometric booth or equivalent + audiometer; same hardware as audiometric testing |
| Output | dB PAR per frequency band | dB PAR per frequency band; threshold-based measurement |
| Dual purpose | Fit testing only | Fit testing + can simultaneously flag audiometric changes when paired with audiometry |
| Worker requirement | Passive (no active response needed) | Active (worker responds to tones, same as audiogram) |
| Used by Soundtrace | — | ✓ Yes |
Worker is tested without the HPD to establish hearing thresholds across test frequencies—identical to a standard audiometric test
Worker inserts the HPD using their normal, uncoached technique—the test captures real-world fit, not best-case coached performance
Thresholds are re-measured with the HPD in place across the same frequencies
The system calculates the difference between open-ear and occluded thresholds. This difference is the PAR—the actual attenuation this worker achieved with this device and this technique
Soundtrace immediately classifies the result, generates fit quality guidance, assesses against the worker’s noise exposure, and stores the result in the employee’s compliance record
After each REAT test, the Soundtrace platform instantly classifies the result into one of three fit quality tiers based on the PAR relative to the worker’s noise exposure and target attenuation. This gives the test administrator an immediate, actionable interpretation without requiring manual calculation.
PAR substantially meets or exceeds the required attenuation for the worker’s noise exposure. Worker is adequately protected with this device and technique. Document and continue.
PAR meets minimum attenuation requirements but with limited margin. Worker is protected, but retraining on insertion technique or a higher-attenuation device is recommended to build compliance headroom.
PAR falls below the required attenuation for this worker’s noise exposure. Retraining and retest required. If PAR remains inadequate, device change or custom-molded HPD should be considered.
This immediate classification removes the need for on-the-spot dB arithmetic by the test administrator. The guidance is worker-specific—the same PAR might be a “great fit” for a worker at 90 dBA and an “okay fit” for a worker at 100 dBA, because the required attenuation is different.
In addition to fit quality, the Soundtrace platform assesses the worker’s noise exposure as part of the fit testing workflow. By combining the measured PAR with the worker’s TWA from noise monitoring data, the platform calculates the worker’s protected exposure level and flags whether it falls within OSHA’s permissible limits. This closes the loop between noise monitoring, HPD selection, and fit verification—the three components that must align for a complete, defensible HPD program under 1910.95.
Soundtrace links the worker’s noise exposure TWA to their fit test result, producing a protected exposure dB value for the record
Platform flags whether PAR is sufficient to bring protected exposure below 90 dBA (or 85 dBA post-STS)
All results—PAR, fit tier, noise exposure, adequacy determination—stored per employee with test date and device for OSHA inspection
Year-over-year PAR trends visible per employee; declining PAR triggers early intervention before an STS occurs
| PAR Result | Soundtrace Tier | Action |
|---|---|---|
| PAR ≥ required attenuation (strong margin) | Great Fit ✅ | Document; schedule next annual test |
| PAR ≥ required attenuation (narrow margin) | Okay Fit ⚠️ | Retrain on insertion technique; retest recommended |
| PAR below required attenuation | Bad Fit ❌ | Retrain and retest immediately; try different size or type if PAR remains inadequate |
| PAR below required after retraining | Bad Fit ❌ | Switch HPD type; consider custom-molded earplug |
| Highly variable PAR across trials | Bad Fit ❌ | Inconsistent technique; additional training; consider earmuffs for consistent seal |
Establish baseline PAR for every new HCP enrollee before noise exposure accumulates
Timed with annual audiogram to catch technique degradation, physical changes, and HPD substitutions
1910.95(i)(4) refit requirement—fit test the replacement HPD to verify adequacy before returning employee to noise exposure
Any time a worker switches HPD type, brand, or size; PAR from old device does not transfer to new device
Running fit testing as a one-time onboarding event and never repeating it. A worker who passes at hire may develop technique degradation, switch HPD brands, or change physically in ways that affect fit. Annual fit testing timed with the annual audiogram catches these changes before they produce an STS. The Soundtrace platform flags employees whose next fit test is overdue alongside their audiometric testing schedule.
A PAR result per employee, per HPD, and per date is the evidence that OSHA’s proper fitting requirement under 1910.95(i)(4) has been met. Fit quality classification and noise exposure integration turn that result into an actionable compliance determination, not just a number.
See: Hearing Protection & Fit Testing: The Complete Employer Guide
Soundtrace delivers instant fit quality guidance, protected exposure calculations, and per-employee compliance records—in-house or via on-site managed service.
Book a DemoGet a quote for your facility →MIRE (microphone-in-real-ear) measures the physical sound level difference at the ear canal before and after HPD insertion using a probe microphone. REAT (real-ear attenuation at threshold) measures the shift in the worker’s hearing thresholds with and without the HPD, using the same audiometric approach as a standard hearing test. Both produce a personal attenuation rating in dB. REAT uses audiometric equipment, allowing it to share hardware with the annual audiogram workflow. Soundtrace uses the REAT method.
Quantitative HPD fit testing measures the actual noise attenuation a specific worker achieves with a specific HPD using their own uncoached technique. The result is a personal attenuation rating in dB that replaces the labeled NRR for that individual for compliance and documentation purposes. Two recognized methods—MIRE and REAT—both produce a PAR.
Soundtrace classifies each fit test result into one of three tiers based on the PAR relative to the worker’s noise exposure and required attenuation. Great Fit means the PAR substantially meets or exceeds required attenuation. Okay Fit means the PAR meets minimum requirements but with limited margin, and retraining is recommended. Bad Fit means the PAR falls below required attenuation and retraining or device change is required. The tier is worker-specific because required attenuation varies with noise exposure level.
Best practice is annual fit testing timed with the annual audiogram. Fit testing is also required after any confirmed STS under OSHA 1910.95(i)(4) when a worker is refitted, and any time a worker changes HPD type, brand, or size. The Soundtrace platform tracks each employee’s fit test schedule alongside their audiometric testing calendar and flags overdue tests.
First step is retraining on insertion technique and retesting. If the PAR remains inadequate, try a different HPD size or type. If no available HPD achieves adequate attenuation, custom-molded devices or earmuffs should be considered. The Soundtrace platform logs each attempt, result, and action taken, creating a documented response trail for OSHA compliance purposes.