Ring vibrations in an acoustic medium as a source of ultrasonicradiation

摘要

In this paper, the vibrational characteristics of ultrasonicntransducers consisting of a ceramic ring filled with a plastic disk arenconsidered. For axially symmetric resonances, the vibrational amplitudenon the surface of the plastic core is approximately described by antruncated Bessel function of zero order and first kind J0,nleading to an ultrasonic beam which is nondiffracting near thentransducer. The near- and far-field pressure distributions of suchntransducers are measured and compared with model predictions. In thennear zone, the width of the measured main lobe is narrow, which is innaccordance with the theoretical results for circular transducers with antruncated Bessel function amplitude distribution. By changing the innerndiameter of the ring, it is possible to control the resonance frequencynof the plastic core. On the other hand, the resonance frequency of thenring may be regulated by varying its width. The existing coupling ofnresonant vibrations of the ceramic ring and plastic core enablesnvariations of the bandwidths of the considered circularntransducers