Abstract
Unidirectional characteristics can be generated in cylindrical piezoelectric-effect transducers by splitting the elements parallel to their longitudinal axes. These characteristics, which have been called directional resonance effects, are being investigated at the U. S. Naval Air Development Center under its Foundational Research Program. It was observed that line transducers made of cylindrical elements showed deviations from uniformity in response patterns when elements were damaged by cracking. A working hypothesis for such behavior was formulated and applied to transducer design. Line transducers that provide unidirectional patterns at certain frequencies have been designed. For example, a 12-in. line made up of cylinders having a diameter of 112 in. when used without any reflector gave a unidirectional response pattern having a front-to-back ratio of approximately 10 dB at a frequency of 10 kc/sec. The hypothesis indicates that patterns occur at a series of frequencies. The presence of such patterns has been verified experimentally and the front-to-back ratio exceeded 30 dB. The hypothesis used, transducers designed, and the results obtained are shown.
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