2025 NHCA Annual Conference

The November 22, 2023 update to Department of Defense (DOD) Instruction 6055.12, "Hearing Conservation Program" promulgates a significant new requirement for hearing protector fit testing to be conducted for all DOD personnel who have noise exposures greater than or equal to 95 dBA 8-hour time weighted average (TWA) and who are enrolled in a service hearing conservation program (HCP).  This requires multi-frequency REAT or MIRE testing to identify the need for earplug fit training or alternative earplugs for an individual, which imposes significant time and instrumentation in the field setting.  A new acoustical physical methodology has been developed to precede in-field REAT or MIRE, not requiring REAT’s threshold tests or MIRE’s in/under-earplug microphones. The Leak-and-Attenuation Test (LAT) comprises an special instrumented headphone worn over the occluding earplug, and via analysis of resonance and sound path lengths that reflect the quality of an earplug’s seal, leaks are identified in a few seconds without requiring both occluded and unoccluded trials as in REAT or MIRE. Simulated ear canal data were reported at NHCA earlier, demonstrating the frequency shift and magnitude parameters that reflect different earplug leak sizes. This paper reports on actual human testing with the LAT headphone system, with a comparison of LAT data for earplug fits with no leaks and different-sized leaks against REAT data for each of the same fits on the same subject. Strong positive correlation between LAT and low-frequency REAT results resulted, evidencing that the LAT system is predictive of REAT results for both well-fit and leaky earplugs. Given such objective data from a very quick occluded-only test, the hearing conservationist can quickly decide whether to re-fit or assign an alternative earplug, before proceeding to the more lengthy REAT or MIRE testing.