Experience with a new ANSI standard for measuring the real-ear attenuation (REAT) of hearing protectors (S12.6-1997)

Abstract

It has become increasingly apparent during the past 20 years that laboratory-measured values of hearing protector attenuation obtained in conformance with ANSI standards (S3.19-1974, S12.6-1984) bore little correspondence to those obtained by workers in actual occupational settings. The development of a new standard, ANSI S12.6-1997, Methods for Measuring the Real-Ear Attenuation of Hearing Protectors, addressed this problem. The new standard includes both experimenter-supervised fit and subject-fit methods. The latter method, designated as method B, requires the use of audiometrically experienced subjects who are naɪ̈ve in the use of hearing protection. This method is intended to approximate the upper limits to the attenuation that can be expected for groups of occupational users. It yields mean attenuation values, more so for earplugs than earmuffs, that are substantially lower, and standard deviation values that are higher than previously found using ANSI standards. This paper will describe the new S12.6, present method-B test data, compare and contrast the standard to the existing related ISO standard (4869-1:1990), and review the results of ongoing studies designed to evaluate aspects and assumptions of the Method-B protocol. The problems inherent in obtaining and utilizing test panels of inexperienced hearing protection wearers, as well as observations gleaned from working with those subjects for in excess of 30 evaluations, will also be examined.