scope:

This standard provides methods for the measurement of the insertion loss of hearing protection devices in specified continuous and impulsive noise environments. The microphone-in-real-ear (MIRE) method utilizes human test subjects and may be used for hearing protectors that enclose the ears and make supra-aural or circumaural contact with the head, whereas the acoustical test fixture (ATF) method employs an inanimate fixture and can be used for any hearing protection device. The standard contains information on instrumentation, calibration, and electroacoustic requirements including details regarding the sound field of test facilities, the acoustical characteristics of ATFs, and subject selection and training and location of ear-mounted microphones for MIRE testing. Methods for measuring or determining sound pressure levels in the ear are also specified as well as methods for reporting the calculated insertion loss.

This standard establishes uniform instrumentation requirements and procedures for the measurement of insertion loss at supra-threshold levels of continuous noise using the MIRE method with human subjects, and at supra-threshold levels with continuous or impulsive noise using the ATF method. These procedures utilize signals at sound levels representative of applications in which hearing protection devices are worn. The methods are intended to provide quick, economical, and repeatable objective (not psychophysical) measurement techniques that can be used as additions or complements to the real-ear attenuation at threshold (REAT) measurement method specified in ANSI/ASA S12.6.

This standard is intended for use in design, quality assurance, and verification of compliance with specifications for hearing protection devices. The MIRE subject selection and fitting procedures described herein correspond to Method A (trained-subject fit) of ANSI/ASA S12.6. An inexperienced subject fit MIRE method, corresponding to Method B of ANSI/ASA S12.6, is not provided because of the degree of subject/experimenter interaction required to ensure proper fitting of the MIRE microphones in the ear.