Results of a pilot interlaboratory comparison of REAT measurements of hearing protectors, coordinated by ANSI S12/WG11

Abstract

ANSI working group S12/WG11 has been tasked with developing laboratory and/or field procedures that yield useful estimates of the real-world attenuation of hearing protection devices. The first goal selected was the development of a laboratory-based real-car attenuation at threshold (REAT) protocol that would estimate the protection that can be, or is being, obtained in the top 10%–20% of today's hearing conservation programs. A protocol was developed based upon ANSI S 12.6-1984, but with modified subject selection, fitting, and training procedures that were described explicitly and in substantially greater detail than in the standard. Pilot testing of two earplugs in four laboratories with ten naive subjects per facility showed subject-fit attenuation results comparable to available real-world studies. Although subjects achieved significantly greater attenuation after the experimenter demonstrated how to insert the devices (informed user fit), the interlaboratory reproducibility of the group data was not significantly improved. The indications are that a subject-fit protocol, in which experimenter involvement is minimized, yields the best estimates of real-world attenuation, and still provides acceptable reproducibility. The pilot results suggested refinements in the design of a full-scale interlaboratory comparison which should begin in the later part of 1990.