Effects of coupled vibrations in cylindrical shell transducers

Abstract

Coupled vibrations in cylindrical transducers can have unwanted effects on the resulting radiation or reception of sound. An investigation of vibrations of piezoelectric cylindrical shell transducers using analytical and experimental methods shows the presence of an additional flexural resonant mode that was not previously reported [see J. F. Haskins and J. L. Walsh, ‘‘Vibrations of ferroelectric cylindrical shells with transverse isotropy,’’ J. Acoust. Soc. Am. 29, 6 (1957)]. The additional flexural mode can be strongly coupled to radial and axial modes in cylindrical shells with finite thickness. The effect can be substantial, resulting in unwanted resonances that may be in the frequency band of interest for both projectors and receivers. An equivalent circuit is derived, which describes the cylindrical transducer operation taking into account the effect of coupled vibrations. The results of calculations in terms of resonant frequencies and frequency responses for both transmit and receive modes are in good agreement with experiments. The overall performance of the cylindrical shell transducer can be greatly enhanced by using cylinders of appropriate height to diameter aspect ratio. [Work supported in part by ONR 321SS.]