A Theoretical and Experimental Investigation of Acoustic Dyadic Sensors
Final rept. Feb 2001-Jul 2001
SITTEL CORP OJAI CA
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This report sets the groundwork for a generalized theory of directional sensors using the Taylor series of the acoustic pressure it moves from the basic pressure sensor to the vector sensor, on to the dyadic sensor, then on to higher-order sensors depending on the number of terms in the Taylor series. A benefit of higher-order sensors is improvement in the 3-dB beamwidth 105 degrees for a vector sensor, 65 degrees for a dyadic sensor. An analysis shows 1 how finite-difference approximations can be utilized to estimate the 10 terms that define the dyadic sensor, 2 it is not prudent to employ finite differences to the estimation of 2nd-order partial derivatives of the pressure, 3 a dyadic sensor be realized with 18 accelerometers and a pressure sensor and 4 that this realization requires only 1st-order finite differences, which can be performed in the pressence quantization and wide band noise effects. A partial dyadic sensor three orthogonal accelerometer dipoles and a pressure sensor at the origin was tested at Seneca Lake during May 2001. The experimental in-water beam pattern measurements confirmed theoretical predictions.