Hearing Protection System for Extreme Noise Environments

Creare and Dartmouth College propose to design, fabricate, and test an effective system for hearing protection in extreme noise environments. Current Air Force ground crews work in close proximity to aircraft engines in sound environments that can resultin noise-induced hearing loss after brief exposures without sufficient hearing protection. The harmful effects of noise at such extreme levels is manifest through both air- and bone-conducted pathways. Current hearing protection is inadequate in theseenvironments. Furthermore, there are no existing measurement techniques that can distinguish the relative contributions of air- and bone-conducted sound to evaluate new designs.During the Phase I project, we developed an objective measurement technique that can measure the relative contributions of airborne and bone-conducted noise, and we supplemented our experimental results with analytical modeling. In Phase II, we willemploy this measurement with psychoacoustic tests to: (1) provide data with which to tune and validate our models; (2) perform specialized tests to characterize the dominant bone-conduction mechanisms; (3) extend testing to extreme noise environments; and(4) measure performance of active noise reduction techniques. We will then use the knowledge so gained to design, build, and test a hearing protection system to meet Air Force requirements. Creare's extreme noise reduction (ENR) system will reduce the harmful effects of long-duration exposure to high noise levels and will improve speech intelligibility. The ENR system will be valuable to tank crews, flight crews, flight deck personnel,mechanized infantry, and commercial operators of noisy equipment.