VLF Flexural Disk Transducers Using Disks 1 Meter in Diameter
NAVAL UNDERWATER SYSTEMS CENTER NEW LONDON CT
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A series of underwater projector designs in which the driving elements are piezoelectric flexural-mode disks 1 m in diameter are studied. The disks are employed either as direct radiators or as drivers for Helmholtz resonators. All the proposed designs have a substantial depth capability 200- 500 m, which is obtained by use of liquid-filled interiors containing compliant tubes. The 1 m disk size was chosen because it is well suited to very low frequency VLF applications however, no piezoelectric disks this large have yet been built. Designs using smaller disks at higher frequencies can be obtained readily from the present results by linear scaling. Because of the low radiation damping of the VLF transducers, the resonance peaks in the response tend to be too high. They must be flattened by use of acousto-electrical feedback, electrical equalization, or both. Helmholtz resonator transducers are suitable either for broadband or narrowband applications, and a number of examples are presented illustrating both types of operation. Internal cavitation is a possible problem in Helmholtz resonators hence, these transducers have a minimum allowable depth, which may be as high as 100 m for some of the narrowband designs. The direct radiator transducers produce much less source level than the Helmholtz resonator types, but they are free of the minimum depth restriction.
- Test Facilities, Equipment and Methods
- Acoustic Detection and Detectors