An Electroacoustic Hearing Protector Simulator That Accurately Predicts Pressure Levels in the Ear Based on Standard Performance Metrics

Report No. ARL-TR-6562
Authors: Joel T. Kalb
Date/Pages: August 2013; 56 pages
Abstract: Impulse-noise response pressure waveforms in the occluded volume under a hearing protector (HP) depend on energy transmission by means of its rigid motion, through its material and at skin-contact leaks. The Real Ear Attenuation at Threshold (REAT) and Microphone in Real Ears (MIRE) methods are common insertion loss measures of this process at a collection of low-level test frequencies. This paper describes a linear HP simulation with an electroacoustic (EA) simulator determined with an iterative fitting procedure using the insertion loss data. Combining this simulator with head diffraction and ear-canal models in the Auditory Hazard Analysis Algorithm for Humans (AHAAH) allows free-field pressure waveforms to be transformed to protected waveforms measured at various locations in real and artificial ears by solving the differential equations of motion. Applying the EA simulator to 384 REAT data-sets from an inter-laboratory study using ANSI S12.6 method B for inexperienced subject self-fits gives statistical frequency distributions of occluded volume, leakage elements, and predicted hazard with the four tested HPs and a rifle waveform. Further validation was obtained using manufacturer-supplied REAT data to predict and compare with protected waveforms on humans and manikins near impulse noise sources such as high-explosives, rifles, shoulder-fired recoilless rifles, and howitzers.
Distribution: Approved for public release
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Last Update / Reviewed: August 1, 2013