Novel Acoustic Materials for Passive Hearing Protection

Hearing loss is the number one disability of soldiers returning from todays battlefield. Issued hearing protection devices are often not worn by soldiers because it can reduce situational awareness through undesired acoustic attenuation. Current passive hearing protection options cannot offer protection against high intensity noise such as gunshots and explosions while allowing users to hear everyday noises. The current state-of-the-art nonlinear hearing protection systems using orifice limiters suffer from broadband loss across important acoustic bands. A successful hearing protection system technology would enable selectively attenuation of noise amplitudes at different frequencies and filter harmful noise levels while allowing everyday conversation. Newly developed acoustic metamaterials may be leveraged to address this problem. Metamaterials are composite materials that derive their properties through their composite geometry. In a Phase I effort, Oceanit showed the feasibility of a unique metamaterial design that can provide a tunable frequency selective acoustic filter with amplitude-dependent attenuation. In the Phase II effort, Oceanit will develop, test and demonstrate prototype passive hearing protection devices ear plugs and earmuffs based on this unique tunable, amplitude-dependent metamaterial and demonstrate them to a Technology Readiness Level of 6.