Active and Passive Reduction of Noise Caused by Bone Conduction to the Head of US Navy Deck Crew Personnel with Helmets

"SYTRONICS proposes Bone Conducted Noise Reduction (BCNR) research to accomplish Phase I objectives, establish a foundation for further research and product prototyping in Phase II, and product testing and development in Phase III. The Phase I objectivesare: propose new design approaches to protect Naval deck crew personnel from bone conducted sound to the inner ear; establish a protocol for determining the path(s) of bone conducted noise to the inner ear; and develop a preliminary conceptual design for asolution to the problem. Proposed work includes: assessing current approaches to measuring bone conducted noise using distortion product oto-acoustic emissions (DPOAEs) technology; determining new methods for measuring bone conducted noise by generatingDPOAEs in a novel way to study the cancellation of bone conducted noise in the cochlea; performing a series of preliminary bone-conduction studies designed to explore the effect of level changes in air-conducted and bone conducted stimuli, examinecancellation of the bone-conducted tone, compare the sensitivity of DPOAE measures with conventional behavioral measures, and make a preliminary determination of bone conduction pathways to the inner ear; providing a concept demonstration of a potentialbone conducted noise reduction. We anticipate the benefits of this research to include (1) a better understanding of the pathways and practical effect of bone conducted sound to the inner ear;