A vibrating-blade, end-fire ultrasonic radiator

The technique of producing highly directional ultrasonic radiation in the end-fire direction consists of exciting a beam (blade) clamped at one end by applying an a.c. signal to piezo-electric strain gauges placed in the best position to produce flexural vibration in the beam. Due to the acoustic impedance mismatch between the material of the beam and the medium to which the beam is coupled standing waves develop on the beam. A general theoretical expression for the acoustic radiation pressure, based on wavelength coincidence principle and the piston type theory has been derived. A design philosophy for the radiator has also been developed.