Underwater acoustic projector
AssigneeBBN Corporation
InventorJames E. Barger
Life of this patent
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Abstract
The underwater sound projector disclosed herein employs, as radiating surfaces or pistons, stiff, lightweight panels whose mass is substantially less than the inertial component of the radiation impedance over the operating frequency range. The panels are driven in opposition by a plurality of linear actuators, e.g., piezoelectric stacks, distributed essentially uniformly over the panels so that each stack drives an essentially equal area of the panel and flexing of the panel is avoided. The compliance reactance of the actuators is made to cancel the inertial reactance of the radiation impedance at all frequencies within an at least decade-wide frequency band. In this way, operation, similar to resonance with its high efficiency, is achieved continuously over a wide frequency band.
Claims16
An underwater sound projector for radiating sound energy over a range of frequencies F1 to F2 into a body of water into which the projector is immersed, said projector comprising:
- a pair of complementary, aligned and spaced-apart panels constructed as lightweight plates;
- means for flexibly sealing the peripheries of said panels to exclude water from the space between them;
- a plurality of actuators between said panels for driving said panels in opposition, thereby to radiate sound energy into said body of water, the inertial component of the radiation impedance being substantially greater than the mass of the panels over the frequency range F1-F2, the compliance of the actuators being such that
- C.sub.m .alpha.=1
- where .alpha. is the product of angular frequency and the radiation reactance of water within the range F1-F2 and C.sub.m is the compliance of the actuators.
An underwater sound projector for radiating a substantially constant amount of sound energy over a range of frequency F1 to F2 into a body of water into which the projector is immersed, said projector comprising:
- a pair of complementary, aligned and space-apart panels as stiff, lightweight plates which resist bending over said range of frequencies;
- means for flexibly sealing the peripheries of said panels to exclude water from the space between them;
- a plurality of linear actuators between said panels for driving said panels in opposition, said actuators being distributed essentially uniformly over the panels so that each stack drives an essentially equal area of the panel and there is essentially no flexing of the panel, thereby to radiate sound energy into said body of water, the compliance of the actuators being such that
- C.sub.m .alpha.=1
- where .alpha. is the product of angular frequency and the radiation reactance of water within the range F1-F2 and C.sub.m is the compliance of the actuators.
An underwater sound projector for radiating sound energy over a range of frequencies F1 to F2 into a body of water into which the projector is immersed, said projector comprising:
- a pair of complementary, aligned and spaced-apart panels constructed of stiff, lightweight honeycomb cored plates;
- means for flexibly sealing the peripheries of said panels to exclude water from the space between them;
- a plurality of actuators between said panels for driving said panels in opposition, thereby to radiate sound energy into said body of water, the inertial component of the radiation impedance being substantially greater than the mass of the panels over the frequency range F1-F2, the compliance of the piezoelectric stacks being such that
- C.sub.m .alpha.=1
- where .alpha. is the product of circular frequency and radiation reactance of water within the range F1-F2 and C.sub.m is the combined compliance of the actuators.
An underwater sound projector for radiating sound energy over a range of frequencies F1 to F2 into a body of water into which the projector is immersed, said projector comprising:
- a pair of complementary, aligned and spaced-apart panels constructed of stiff, aluminum plate which is divided into a plurality of equal area sections joined by relatively thin webs;
- means for flexibly sealing the peripheries of said panels to exclude water from the space between them;
- a plurality of actuators between said panels for driving said panels in opposition, there being three actuators driving each section, thereby to radiate sound energy into said body of water, the inertial component of the radiation impedance being substantially greater than the mass of the panels over the frequency range F1-F2, the compliance of the piezoelectric stacks being such that
- C.sub.m .alpha.=1
- where .alpha. is the product of circular frequency and radiation reactance of water within the range F1-F2 and C.sub.m is the combined compliance of the actuators.
Dependencies are inferred from the claim text.