Surface Impedance Modification of Plates in a Water-Filled Waveguide
2007
Dubbelday, Pieter S.
The interaction of plane waves, propagating in a water-filled cylindrical waveguide with a plate perpendicular to its axis, vith the same cross section as the tube, is determined by the surface impedance at the plate relative to the specific acoustic impedance of the medium. By means of an attached piezoelectric disk-shaped double transducer (sensor and actuator) the apparent surface impedance of the combination may, in principle, be modified to equal the impedance of the medium, thus establishing a no-reflection situation. The actuator voltage is regulated by feedback loop, based on an algorithm for complex-root finding. The analysis of this concept is given and a figure-of- merit for the transducer material is presented. Efforts to demonstrate experimentally the feasibility of this concept were inconclusive.
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