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This paper presents a field-microphone-in-real-ear (MIRE) method for the objective measurement of individual earplug field attenuation. This development was made possible by using a recently designed instrumented expandable custom earplug. From the measurement of the noise reduction (NR) through the earplug, this method predicts the attenuation that would be experienced by the wearer and that would be measured using the real-ear attenuation at threshold (REAT) method. Formulations presented include establishing the relationship between NR, insertion loss, and REAT, as well as defining the laboratory and field calibration procedures required to determine the correction factors to be applied to the measured NR. This method was validated experimentally by comparing the predicted field-MIRE attenuation values to the REAT values measured on a group of test-subjects. This method offers fast and accurate measurement of earplug field performance on an individual basis and could lead to further developments for effective hearing protection practices as well as for hearing protection device rating and labeling.
Voix et al. (Mon,) studied this question.