USA As Represented by Secretary of the Navy

Mark S Peloquin

Andrew J Hull

Norman Lee Owsley

Stephen A Austin

A method is presented to calibrate the transfer function for a fluid-filled compliant cylinder as a function of wavenumber and frequency. An air-filled compliant cylinder has a first linear array of force sensors coupled to the cylinder's exterior surface. A turbulent flow field is generated in a fluid environment about the first linear array which generates an output indicative of pressure incident thereupon. A fluid-filled compliant cylinder identical in diameter to the air-filled compliant cylinder houses a second linear array of force sensors. A similar turbulent flow field is generated in the fluid environment about the fluid-filled complaint cylinder to generate an output indicative of pressure incident upon the second linear array. The ratio of outputs is indicative of the transfer function of the fluid-filled compliant cylinder. Each output can be further adjusted by a calibrated sensitivity of the corresponding first and second linear arrays. The method compensates for elastic scattered pressure fields and the wavenumber-frequency dependence of the air-filled compliant cylinder's sensitivity to pressure.

Calibration of the normal pressure transfer function of a compliant

A method and system are provided for frequency filtering compressional wave nergy. An elastic cylinder is filled with a fluid that is selected based on a fluid density .rho..sub.i and a dilatational wave phase velocity c.sub.i thereof. When the elastic cylinder so-filled is subjected to a compressional wave propagating in a fluid environment, a first radial resonance frequency of the elastic cylinder is controlled by the fluid density .rho..sub.i and the dilatational wave phase velocity c.sub.i. Further tuning of the first radial resonance frequency can be achieved by adjusting the radial wall thickness of the elastic cylinder.

Method and apparatus for frequency filtering using an elastic

A method and system are provided to optimize filtering of compressional wave energy in the wavenumber domain for a given frequency range using a fluid-filled elastic cylinder. The fluid is selected based on its fluid density .rho..sub.i and dilatational wave phase velocity c.sub.i. The selected fluid must satisfy the relationship ##EQU1## for the given frequency range where P.sub.i is the magnitude of the pressure field in the fluid at a point within the fluid defined by a distance r.sub.1 from the cylinder's central longitudinal axis and P.sub.o is the magnitude of the impinging compressional wave, and must control at least one of the breathing wave response, the extensional wave response and the fluid P-wave response.

Optimizing the compressional wave energy response of an elastic

A method and apparatus for locating artery stenoses in blood vessels incls providing an array of sensors on skin surface to acquire data for detecting, locating and analyzing energy emissions in three-dimensional objects. The array detects momentum transfer that exists in the object in the form of wave energy, and the detection is designed to occur on the surface of the object, thereby providing a non-intrusive method for locating artery stenoses, with localization of the artery stenoses being achieved through array signal processing by information detected on the surface of the skin with the plurality or array of sensors.

Device and method for locating flow blockage in a three-dimensional

A composite hydrophone array assembly is made from a compliant mandrel such s a hollow tube and at least one wrap of piezoelectric film adhered to the compliant hollow tube at a plurality of locations thereon. Each location defines a composite hydrophone channel. The centers of adjacent hydrophone channels are separated along the length of the compliant hollow tube. To shade a hydrophone channel, the wall thickness of the hollow tube can be varied along its length, the circumferential area of coverage of the wraps of piezoelectric film can be varied along their length, the longitudinal lengths of the wraps of piezoelectric film are varied, or a combination of these approaches can be used. Unwanted noise is rejected by eliminating hydrophone channel grating lobes and overlapping portions of the wraps of piezoelectric film of the adjacent hydrophone channels to create a wavenumber response for the composite hydrophone array that significantly reduces array grating lobes.

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Uncasville, CT, United States of America

Mark S Peloquin