Advanced Hearing Protection

Some ground crews for aircrafts are exposed to ambient noise levels up to 150 dB SPL: at these levels, conduction of sound through tissues is significant and may be responsible for hearing loss. Protecting the ear canal with earplugs and earmuffs cannotprevent damage caused by tissue-conducted sound. Our research partners at University of Illinois at Urbana-Champaign, experts in bioacoustics and audiology, will use finite element analysis to investigate the reception and conduction of sound through hardand soft tissues of the head and torso. From their work we will determine the attenuation characteristics that protective gear should possess. We will demonstrate methods to increase the attenuation provided by passive earmuffs. Similar improvements canbe made to helmets and garments, but these will await completion of the tissue conduction analysis. Finally, we will begin to assess the feasibility of incorporating active cancellation of air-borne noise into headgear other than earmuffs; effectiveactively controlled earmuffs already exist on the market.The technology developed to protect the hearing from high-intensity sound can have numerous military and consumer applications. Potential military devices include 1) hearing-protection for aircraftground crew, and for maintenance, repair, and testing personnel of aircraft engines, 2) helmets for ear and brain protection of pilots in military aircraft, and 3) ear protective device for crews in the engine room of a ship. Potential commercial devicesinclude 1) hearing protection for patients and operating room personnel during extracororeal shock wave lithotripsy, 2) protective helmet for patients undergoing functional magnetic resonance imaging, and 3) ear protection devices for people in variousindustries using tools that produce high sound pressure.