Subsurface Acoustic Sensor

The need for acoustic instrumentation to gather signatures under prohibited weather conditions or hostile natural and man-made barriers led to the placement of microphones below the ground surface. This paper will show how the idea was conceived and its initial implementation. Testing of the device at various sites will show its performance as an acoustic signaturegathering sensor. Equations will be presented to describe its performance. Further evolution of the sub-surface microphone will be discussed and some applications for the device will be shown.