Low-Frequency Acoustic Radiation from Free-Flooded Ring Transducers Driven through the Circumference, Thickness, or Height

Abstract

The normal velocity distribution of the surface of a free-flooded ring transducer completely determines its radiation characteristics in a given medium. The SHIP program is an algorithm for rapidly predicting the radiation characteristics of a free-flooded ring when the known surface velocity distribution is axisymmetric. The character of the radiation at low frequencies is extremely sensitive to the details of the velocity distribution which, in turn, depends not only on the geometry of the ring, but also on the manner in which the ring is driven and on the electromechanical parameters of the ring material. Gross differences in the directivity patterns predicted for different drive conditions occur at frequencies well below the first radial resonance for typical rings. Directivity patterns were obtained for a number of rings fabricated for different commonly encountered drive conditions (circumference, thickness, or height) and compared with patterns predicted by the SHIP program using simple models for the velocity distribution appropriate to each drive. Good agreement was obtained between the measured and predicted directivity patterns.