Water depth and drive voltage dependence of the acoustic parameters of a barrel-stave flextensional projector

Abstract

A low-frequency barrel-stave flextensional projector for sonar and general underwater acoustics applications has been built at the Defence Research Establishment Atlantic in Dartmouth, Nova Scotia. The projector was calibrated at the Seneca Lake sonar test facility at Dresden, NY, as a joint research venture with the Naval Undersea Warfare Center, New London, Connecticut. The transmitting voltage response (TVR), mechanical quality factor (Qm), electrical admittance, and electroacoustic efficiency (ηea) were measured for driving voltages up to 5.0 kVrms at four depths: 30, 61, 91, and 123 m. At 5.0 kVrms, the resonance frequency (f0) increased from 780 to 840 Hz, Qm decreased from 4.4 to 3.3, and ηea decreased from 87% to 71%, as the depth was increased from 30 to 123 m. The change in each acoustic parameter, averaged over the four depths of interest, was −10 Hz/kVrms for f0, +0.4 dB/kVrms for the TVR at resonance, and +0.1/kVrms for Qm, as the driving voltage was increased from 0.1 to 5.0 kVrms. The dependence of the parameters on depth and driving voltage are discussed in terms of the interactions between the rubber boot and the staves. [Work sponsored in part by the U.S. Office of Naval Research.]