A field microphone in real ear hearing protector attenuation measurement system

Abstract

A Field-Microphone in Real Ear (F-MIRE) hearing protector Field Attenuation Estimation System (FAES) was developed for individual or group testing of any type or style of hearing protector device (HPD). Both occluded and unoccluded ear canal stimulus level measurements are made with a tiny Micro Electro-Mechanical System (MEMS) microphone mounted on a 2-mil thick flat flexible cable. The microphone is mounted inside of a conventional foam ear dam to protect the microphone and the ear canal and to facilitate insertion into the ear canal. The presence of the cable in the ear canal was demonstrated to have a negligible effect on attenuation measurements for both muff and insert-type HPDs. The system measures HPD attenuation in 1/1 or 1/3 octave bands and it is capable of simultaneously measuring HPD attenuation on up to eight human test subjects. Stimuli can be presented via headphones or loudspeakers. Human subject testing using both the laboratory based ANSI S12.6-2016 method and the F-MIRE system was performed using muff- and insert- type HPDs. Regression equations were generated from these data. These equations are incorporated in the F-MIRE software to allow valid comparisons between F-MIRE data and labeled HPD attenuation data.