Solid fill acoustic array

Details Solid fill acoustic array Solid fill acoustic array

1999-02-22

2001-07-17

Lobo, Ian J. (Department: 3662)

Communications, electrical: acoustic wave systems and devices

Signal transducers

Underwater type

C367S020000, C174S101500

Reexamination Certificate

active

06262944

ABSTRACT:

BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates generally to an array of acoustic sensors, and specifically to an improved acoustic array utilizing a solid fill material for controlling the buoyancy properties of the acoustic array.
DESCRIPTION OF RELATED ART
In order to measure a variety of different events or conditions in underwater environments, it is common to position an array of interconnected sensors in the underwater environment. For instance, acoustic arrays of hydrophonic sensors are used to sense sounds traveling through the underwater environment. These acoustic arrays are typically formed by arranging the hydrophonic sensors within a sealed flexible tube-like casing which seals the sensors from the external environmental elements. In order to provide the acoustic array with controlled buoyancy, the sealed casing is filled with a low density fill fluid. Many of these fill fluids are hydrocarbon-based fluids, which have the drawback of requiring strict handling requirements due to the environmental regulations associated with most underwater environments. Conventional acoustic arrays are formed of electrically active components, as they typically consist of piezo-ceramic (PZT) elements used for acoustic detection with copper wire used for the transmission of information to and from the array of PZT elements. These conventional components are inherently dense, thus requiring a fill fluid having a low specific gravity to generate a neutral buoyancy for the acoustic array in water. Additionally, the fill fluids that are chosen must also be good electrical insulators so as not to short the electrical pathways in the acoustic array. If a break in the sealed casing should occur, the fill fluid could leak from the acoustic array into the underwater environment. This loss of fill fluid can cause the acoustic array to lose buoyancy and sink. Further, water from the surrounding underwater environment would pass through the break: in the sealed casing into the acoustic array and potentially damage the electrical continuity of the array, since electricity can be conducted through the water now surrounding the internal elements of the array.
Clearly, there is a need for an acoustic array which is comprised of lightweight components in order to reduce the buoyancy and composition requirements of the fill fluids within an acoustic array. Moreover, there is a need for an acoustic array formed of electrically passive components in order to prevent electrical conductivity problems from arising from potential breaks in the sealed casing of the acoustic array.
SUMMARY OF THE INVENTION
It is a primary object of the present invention to overcome the aforementioned shortcomings associated with the prior art.
The present invention provides an acoustic array comprised of electrically passive components which allow the acoustic array to be formed from lightweight components. The lightweight components forming the acoustic array of the present invention reduce the buoyancy requirements of the acoustical array. The electrically passive components used to form the acoustic array of the present invention are also inert, which reduces the effects which the surrounding environment can have on the buoyancy and performance of the acoustic array from any leaks which may develop in an outer casing which seal the acoustic array from the surrounding environment.
The present invention still further provides an acoustical array which utilizes a solid fill material to provide controlled buoyancy properties for the acoustic array.
Moreover, the acoustic array of the present invention allows a water-based fluid to be used as a fill fluid for the transduction of acoustic energy into an acoustic sensor in the acoustic array, which eliminates the environmental concerns associated with fill fluids and reduces the effects which water from the surrounding environment can have on the buoyancy of the acoustic array when incidentally mixing with the fill fluid.
These as well as additional advantages of the present invention are achieved by providing an acoustic array including a plurality of acoustic sensors positioned along predetermined telemetry points for measuring acoustic energy from a surrounding underwater environment. The acoustic array is surrounded by a longitudinally extending outer tube-like hosewall. The acoustic sensors are each positioned within a fluid-filled pocket formed in the acoustic array, wherein each of the various fluid-filled pockets are separated from each other by a section of buoyant solid fill material. The solid fill material provides the buoyancy for the acoustic array, where the acoustic sensors are positioned in the gaps between the sections of solid fill material. The outer hosewall which encloses the acoustic array forms the fluid-filled pockets in the gaps between the sections of solid fill material. At least one strength member is extended longitudinally throughout the length of the acoustic array to provide a load bearing mechanism for distributing longitudinal tensile loads applied to the acoustic array. The acoustic array also includes support spacers situated within the acoustic array to provide radial support for the acoustic array and prevent the outer hosewall or strength member from collapsing inward.
The acoustic array is formed of a lightweight and electrically passive structure which allows a water-based fluid to be used as the fill fluid in the fluid-filled pockets to propagate the acoustic energy from the underwater environment to the acoustic sensors in the fluid-filled pockets. Using a water-based fill fluid provide an environmentally-safe fill fluid having buoyancy characteristics which are not significantly altered by its mixture with water from the surrounding underwater environment should a leak in the hosewall occur. Further, should the hosewall develop a rupture, the intrusion of water from the surrounding underwater environment into the water-filled pockets will not significantly alter the buoyancy of the array.


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