Folded Shell Projector


  1. Purcell, C.J.
  2. Bonin, Y.R.
Corporate Authors
Defence Research Establishment Atlantic, Dartmouth NS (CAN)
Defence Research Establishment Atlantic (DREA) has recently disclosed a design for a flextensional transducer called the Folded Shell Projector (FSP). The FSP is a compact, low-frequency underwater sound source which has potential applications in low frequency sonar systems. The FSP can be described as a variation on the barrel stave projector (BSP). The BSP achieves the required values for stiffness and mechanical transformer ratio for its radiating surface by having slots in a solid axisymmetric shell or individual staves separately by slots. The slots must be waterproofed by a polymer membrane (e.g. neoprene) called the "boot". Under hydrostratic loading the boot is pushed into the slots leading to depth dependence of the resonance frequency and source level. Thus for some applications, the BSP may require a gas pressure compensation system to be fitted, with its attendant cost and complexity. There have been previous efforts as DREA to build bootless variants of the BSP, and the FSP in the most recent attempt. The FSP design uses folds instread of slots and since the resultant one-piece shell is inherently waterproof, the boot is not required (although some FSP applications may still need a corrosion proof coating). The basic concept of the folded shell projector is illustrated in Figure 1.
FSP (Folded Shell Projector);Barrel stave flextensional projectors
Report Number
DREA-SL-1999-015 — Reprint
Date of publication
01 Apr 1999
Number of Pages
Reprinted from
Proceedings of the Institute of Acoustics, vol 21, part 1, 1999), p 1-9
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