A conformal, helmet-mounted microphone array for auditory situational awareness and hearing protection

Hearing protectors often are considered detrimental to auditory situational awareness due in part to the distortions they impose on localization cues. The addition of a helmet or other head-worn equipment can exacerbate this problem by covering the ears and effectively changing the shape of the head. In an effort to design a hearing-protection system that maintains natural auditory localization performance, we have built a prototype conformal microphone array integrated into a helmet. The system involves beamforming for spatial selectivity, filtering with head-related transfer functions to reintroduce spatial auditory cues to the beamformed data, dynamic range compression to attenuate potentially damaging sound levels, and insert earphones to deliver binaural audio and provide additional hearing protection. All directions are auralized simultaneously to provide full spatial coverage around the wearer. In this paper we describe the design, implementation, and testing of a prototype 32-channel system, including 3D modeling and simulations, signal-processing approaches, real-time processing, and localization performance.