Michael V. Scanlon
Stephen M. Tenney
Army Res. Lab., AMSRL-SS-SH, 2800 Powder Mill Rd., Adelphi, MD 20783-1197
Two hearing augmentation devices developed at the Army Research Laboratory can enhance normal listening abilities and restore hearing degraded by encapsulating headgear. Surrounding sounds are localized with a head-mounted binaural pinna attachment that recreates the head-related transfer function associated with the normal listening. The user's brain interprets the recreated stereo signals that enter the ear canals through intra-aural speakers, giving excellent restoration of omnidirectional hearing. A hand-held, ultra-directional array extends the user's listening range. The use of delay and sum beamforming in the array assures maximum directivity in the pointing direction. The binaural long-range hearing device has two linear endfire arrays of eight cardioid microphones each. The slightly offset directivity patterns of the two arrays create stereo outputs, so that the user can interpret differences in amplitude, phase, time-of-arrival, and frequency content of sounds in the forward area. These devices provide aural protection and an intra-aural input for communications, without removing the user from his acoustic environment. Both devices can be monitored remotely, and are ideally suited for detecting speech, personnel, equipment, or vehicles during military or law enforcement missions. Performance measurements of various array configurations will be shown.