Abstract: A method and system of performing a MIRE test to determine the efficacy of an in-ear hearing protector utilizes both a novel microphone assembly designed to run a microphone through a vent in the hearing protector and an optional insertion tool that expands the vent temporarily to allow for insertion of the microphone assembly. The method obtains a true MIRE test result by performing a spectral scan of a known and intense broadband sound field in a chamber formed between the ear canal end of a hearing protector and an ear drum and comparing the results to simultaneous samples of the same signal taken by a similarly designed microphone outside of the hearing protector. A comparison of the differences in the two samples at nine discrete midpoint frequencies provides a reliable basis for measuring the efficacy of an in-ear hearing protection device in the field.