Surface Impedance Modification of Plates in a Water-Filled Waveguide
NAVAL RESEARCH LAB ORLANDO FL UNDERWATER SOUND REFERENCE DIV
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The interaction of parallel waves, propagating in a water-filled cylindrical wave-guide, with a plate perpendicular to its axis is determined by the plates specific acoustic impedance, the product of density and wave speed. By means of an attached piezoelectric disk-shaped double transducer, sensor and actuator, the apparent surface impedance of the plate is modified to equal the impedance of the medium, thus establishing a no-reflection situation. The actuator voltage is regulated by a feedback loop, based on an algorithm for complex-root finding.