USA As Represented by Secretary of the Navy

Stanley A Fisher

Larry S Chandler

Aime S DeReggi

Gideon Maidanik

An array of pressure sensors and motions sensors is contained in a layered material system that includes an acoustically compliant layer and an acoustically transparent layer. The compliant layer (which vibrates in accordance with acoustical influence thereupon) is the foundation for both sensor types and is the vibratory medium for motion sensing. The transparent layer is the matrix for both sensor types and is the window permitting sound waves to reach the pressure sensors (which sense pressure of the sound waves) and the compliant layer (the vibration of which is sensed by the motion sensors). The compliant layer's exposed surface can be attached to a structure's exterior for passive sonar detection purposes. Since the pressure sensors are effective primarily for low frequency sound waves, and the motion sensors are effective primarily for high frequency sound waves, the invention is aggregately effective for a broad band spanning low and high frequencies.

Dual response acoustical sensor system

The invention is directed to a fiber-optic sensor for measuring acoustic signals originating from a single point remote from the sensor. The sensor includes a sensing cable formed with a light transmitting optical fiber core encased within an acoustically sensitive jacket that is bonded to the optical fiber core; a reference cable formed with a light transmitting optical fiber core encased within a protective jacket that is not bonded to the optical fiber core; a base structure forming a concave surface having a focal point that corresponds to the point in space from which acoustic measurements are desired; an acoustically sensitive surface formed by mounting the sensing cable and the reference cable in a collocated pair onto the concave surface; a coherent light source connected to and transmitting light to the sensing optical fiber and the reference optical fiber; and an electro-optic processor connected to and receiving transmitted light from the sensing optical fiber and the reference optical fiber and suitable for determining phase shift differences between transmitted light from the sensing and reference optical fibers.

Acoustic sensor for a point in space

A tubular prosthesis formed by an assembly of electrode segments enclosing n elongated inner chamber, is inserted into the inner ear of a patient for piezoelectric generation of electrical impulses and localized injection thereof in response to externally generated sound waves. Such electrical impulses are applied from the prosthesis to nerve endings adjacent to cochlea contact locations on the electrode segments so as to improve hearing adversely affected by biological damage to the inner ear.

Passive piezoelectric prosthesis for the inner ear

The invention is directed to an improved acoustic sensor system for detering the direction of underwater sound signals relative to a user is disclosed. The sensor system includes first and second sensing means for sensing incoming acoustic energy and for providing first and second acoustic energy signals in response thereto; separation means for separating the first and second sensing means a distance S=E(C.sub.W /C.sub.A) where E is substantially equal to the separation distance between the users ears, C.sub.W is the speed of sound in water, and C.sub.A is the speed of sound in air; detector means, operatively connected with the first and second sensing means, for providing first and second output signals in response to the first and second acoustic energy signals; and audio means, operatively connected with the detector means, for providing an audio output to the user in response to the first and second output signals.

Hydrophone for determining direction of underwater sound

An omni-directional hydrophone having a pair of fiber-optic windings wrapped around a resilient ball to form a spherical acoustic sensor is provided. The fiber-optic pair has a first fiber which has a bonded jacket and a second fiber which has an unbonded jacket. The fiber with the bonded jacket is sensitive to both vibration of the mounting structure and impinging acoustic signals. The fiber with the unbonded jacket is sensitive to vibration but insulated from the acoustic signals. By comparing the signals from the two fibers, the hydrophone detects acoustic signals by detecting the phase difference between the two fibers. As both fibers are equally affected by vibration, there is no phase difference caused by vibration. This mechanization permits the canceling of vibration induced signals while retaining full sensitivity to acoustic signals. The hydrophone uses a standard fiber-optic laser source and detection system to convert the acoustic generated phase change to amplitude dependent voltage signals. The hydrophone is pressure and temperature insensitive.

Omni-directional hydrophone

A fiber-optic hydrophone having a pair of jacketed fiber optic windings fed in a concentric planar spiral configuration in a layer of polyurethane is provided. One of the fiber optic windings has a fiber with a bonded acoustically sensitive jacket thereby increasing its sensitivity to acoustic energy. The second fiber optic winding, the reference winding, has a unbonded jacket enclosing the fiber resulting in reduced sensitivity to acoustic energy. Sensitivity to vibrational energy; however, is not reduced. The combining of signals from the pair of fibers provides a vibration-canceled acoustic signal.

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Boyds, MD, United States of America

Stanley A Fisher