Low Noise Infrasonic Sensor System with High Reduction of Natural Background Noise

Abstract : Physical Sciences Inc. has developed a new type of infrasound piezocable sensor system under this program's SBIR Phase 1 and Phase 2 funding from DTRA. The sensors consist of continuous lengths of off-the-shelf radially poled polyvinylidene fluoride (PVDF) coaxial cables, theoretically of arbitrary length, specially terminated and connected to state of the art, ultra high input impedance quiet amplifiers, tailored to the unique characteristics of the sensor outputs. Test data reported herein has primarily been collected with sensors of 100 m lengths deployed in the field after significant development, laboratory testing and system calibration efforts were undertaken. Pairs of such long line sensors deployed at right angles to each other can determine signal incidence direction and also eliminate the aliasing associated with the current infrasound sensors used at large spacing in the present designs of infrasound monitoring arrays, particularly in the higher frequency ranges of interest around 1 Hz. Prototype sensors have been utilized to collect data a Pinon Flat, CA (Infrasound Station-157US) with support from Scripps, UCSD, and a sensor array is also installed in Hawaii at 159US with support from ISLA, University of Hawaii. This report presents some of the key results of field test measurements to document the capability of these new, robust and inexpensive sensors.