Hearing Protection Evaluation System

The acoustic test fixture (ATF) type of hearing protection evaluation system (HPES) has been widely used in the past to evaluate hearing protection device (HPD) performances, in addition to the Real-Ear-Attenuation-at-Threshold method and the Microphone-In-Real-Ear method. Since the use of ATF devices does not rely on human subjects, they are more efficient, and in many cases indispensable, for testing HPDs in various application environments. However, one significant drawback of current ATF devices is that they lack agreement with human subject testing due primarily to the insufficiency of modeling the real human head regarding the hearing mechanism. The focus of this Phase I program is thus to develop novel approaches, based on finite element analysis, for building an advanced HPES that emulates realistic heads and allows for characterizing either circumaural or insert-type HPDs in both impulse and continuous noise environments across the dynamic range of human hearing. Means for imitating mechanical and acoustical characteristics of the human head and auditory system, as well as means for emulating bone conduction pathways, will be investigated in this program. A report describing the approach and demonstrating the feasibility and capabilities of an advanced HPES design will be provided at the conclusion of Phase I.