Bone-Conducted-Noise Measurement Technique and Noise-Reduction System

"The goal of this project is to characterize the magnitude andtransmission paths of bone-conducted sound to the cochlea and touse this information to design an effective noise-reductionsystem for crew helmets. The need for improved hearingprotection is critical, given the scale of noise-induced hearingloss in the armed forces today and the increased sound levelsassociated with the next generation of fighter aircraft.However, an improved understanding of the transmission pathwaysfor bone-conducted sound must be acquired before effectivecountermeasures can be developed. There are no measurementtechniques available today that can distinguish the relativecontributions of air- and bone-conducted sound. In Phase I wedeveloped an objective measurement technique with this capabilityand supplemented our findings with detailed measurements madeusing a specially prepared human skull. In Phase II we willextend this approach to fully characterize the dominant bone-conduction mechanisms. We will then evaluate a series ofpotential hearing protection components in a number of iterativedesign/build/test cycles. On the basis of these evaluations, wewill select the optimum set of components and manufacture andevaluate a prototype device capable of providing protectionagainst bone-conducted sound.BENEFITS: The primary benefit provided by this research and development will be reduced hearing loss in personnel exposed to extreme noise environments.