Hearing Protection Evaluation System

Selection of appropriate hearing protection devices (HPDs), such as earplugs and earmuffs, is important in mitigating noise-induced hearing loss among military personnel. The standard method of measuring the noise attenuation performances of HPDs is based on a psychoacoustic method involving human subjects, which is time-consuming, costly and inherently variable. It also cannot be used to measure the performance of earplugs with special acoustic features such as non-linear venting and active noise reduction, which are increasingly relevant for military use. An alternative is a physical measurement using a test fixture which has the advantage of being repeatable and efficient. However, conventional test fixtures are designed for the evaluation of earmuff-type HPDs and can be inaccurate for earplug-type HPDs. ATI is developing an advanced hearing protection evaluation system (HPES) which can assess a wider range of HPDs including earplugs. HPES is essentially a simulated human head with sufficient acousto-mechanical emulations for accurate evaluation of a variety of HPDs. The fixture is designed with the capability to accurately measure earplug attenuations, large microphone dynamic range and ability to take into account the bone conduction effect. This Phase II SBIR research will further refine the Phase I HPES design and develop a pre-production prototype.