An array of pressure sensors and motions sensors is contained in a layered
material system that includes an acoustically compliant layer and an
acoustically transparent layer. The compliant layer (which vibrates in
accordance with acoustical influence thereupon) is the foundation for
both sensor types and is the vibratory medium for motion sensing. The
transparent layer is the matrix for both sensor types and is the window
permitting sound waves to reach the pressure sensors (which sense
pressure of the sound waves) and the compliant layer (the vibration of
which is sensed by the motion sensors). The compliant layer's exposed
surface can be attached to a structure's exterior for passive sonar
detection purposes. Since the pressure sensors are effective primarily
for low frequency sound waves, and the motion sensors are effective
primarily for high frequency sound waves, the invention is aggregately
effective for a broad band spanning low and high frequencies.