Ear Protection Validation System

Phase 2 involves the continued development of the F-MIRE FAES system. The FAES system insertion loss measurements utilize a sub-miniature MEMS microphone mounted in the ear canal of the HPD wearer. An ultra-thin flat flexible cable connects the microphone to a signal conditioning unit and power supply. The microphone is mounted in a foam ear dam to protect the microphone and the sensitive ear canal. A custom software interface will run the automated F-MIRE test, perform 1/3 octave band analysis and data storage. Variable stimulus levels are required since the range of attenuation is large and test subject exposure must be monitored carefully. Test fixture verification tests have demonstrated that the F-MIRE measurements using the FFC and MEMS microphone are accurate to within about 1 dB for muff-type devices and to within about 2 dB for insert-type devices. Challenges include consistent placement of the microphone in the ear canal and consistent headphone placement for insert-type measurements. Besides further development, phase 2 will include extensive human subject studies comparing the FAES system to standardized methods. The proposed FAES system will be compatible with all HPD types and will meet all of the objectives set forth in the original project solicitation.