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| Author: | Fred Kern |
| Institution: | Physical Sciences Inc. 20 New England Business Center Andover, MA 01810 |
| Email: | kern50440@att.net |
| Authors: | Fred R. Kern, Steven A. Africk, Ryan G. Chaves, and Paul A. Cataldi, Physical Sciences, Inc., Andover MA 01810 Michael A. H. Hedlin and Clint Coon, Laboratory for Atmospheric Acoustics, Scripps Institution of Oceanography, University of California San Die |
Abstract Title:
"A Novel Piezoelectric-Cable Infrasound Sensor - Initial Results " |
Abstract:
A novel infrasound sensor consisting of a long length of radially-poled commercially available piezoelectric polyvinylidene fluoride (PVDF) coaxial cable and a specially designed amplifier has been developed as a potential improved performance and lower cost replacement for microbarograph-based systems such as employed in the CTBT program. These cables are readily available and relatively inexpensive, supporting design of easily-replaced or expendable sensor elements. The purely electronic transduction mechanism provides uniform sensitivity to pressure along the sensor’s length (“at lightspeed”). This automatically gives rise to continuous spatial averaging (i.e. array gain) of both signals and environmental pressure fields such as wind to provide noise reduction. Electronic transduction also allows for combination of signals from multiple sensors to enable signal processing options not possible with many other types of infrasound sensors. Prototype sensors of 30 and 100 meter length were installed several inches deep in trenches at UCSD’s Pinon Flat Observatory in May 2003 and infrasonic data have been telemetered to UCSD in La Jolla continuously since then. Upgraded amplifiers and an automatic signal insertion calibration system have been installed to monitor system performance. Conventional, non-piezoelectric (RG 174a) coaxial cables of 30 and 100 meter length were installed in September, 2003 for diagnostic studies, including the detection of possible electromagnetic signals. The piezocable sensors have successfully detected acoustical events detected by the CTBT infrasound array and other diagnostic sensors at Pinon Flat with appropriate magnitude and good coherence. As anticipated, the longer sensors tend to be quieter than the shorter and appear to provide spatial filtering of higher acoustic frequencies. Two sensors placed at right angles appear to provide the potential to identify the direction of incoming signals. Work is continuing to further characterize and reduce the environmental noise of these sensors. This work has been carried out under a Small Business Innovation Research Contract from DTRA.
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| Keywords: | piezoelectric polyvinylidene fluoride (PVDF) coaxial cable infrasound sensor, Long Baseline, Array Gain |
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