AN EXPERIMENTAL BICONVEX LIQUID-FILLED ACOUSTIC LENS.
NAVAL POSTGRADUATE SCHOOL MONTEREY CALIF
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An experimental study has been made of the properties of a biconvex liquid-filled acoustic lens formed by pressurizing a refracting fluid between two deformable diaphragms. Trichlorotrifluoroethane was used as the refracting liquid and stainless steel sheets 76 cm in diameter and 0.3 mm 0.012 inch thick were used as the diaphragm material. Distortion of the spherical surfaces due to the weight of the liquid was negligible because of the tension developed by the internal hydrostatic pressure 1.4 atmospheres for focal length 1.2 meters. Acoustic diffraction patterns measured at f4.0 in water at frequencies from 200 KHz to 500 KHz compare favorably with patterns computed numerically. Multiple focal points were found and can be associated with multiple internal reflections. Author