Very-large-scale integrated (VLSI) analog binaural signal-processing circuits have been proposed for use in detecting and locating leaks that emit noise in the ultrasonic frequency range. These circuits would be designed to function even in the presence of intense lower-frequency background noise that could include sounds associated with flow and pumping. Each of the proposed circuits would include the approximate electronic equivalent of a right and a left cochlea plus correlator circuits.

Cochlear and Correlator Circuits, operating in conjunction with external scanning circuits, would implement stereausis.
A pair of transducers (microphones or accelerometers), corresponding to right and left ears, would provide the inputs to their respective cochleas from different locations (e.g., from different positions along a pipe). The correlation circuits plus some additional external circuits would determine the difference between the times of arrival of a common leak sound at the two transducers. Then the distance along the pipe from either transducer to the leak could be estimated from the time difference and the speed of sound along the pipe. If three or more pairs of transducers and cochlear/correlator circuits were available and could suitably be positioned, it should be possible to locate a leak in three dimensions by use of sound propagating through air.

The cochlear circuits would consist mostly of cascades of amplifier/delay units positioned along two orthogonal edges of a rectangular VLSI chip, as depicted in the figure in simplified form. In addition to introducing increments of delay, the cochlear circuits would filter the signals to reject frequencies below the ultrasonic range. The output of a given amplifier/delay unit in a cochlea would be fed to both the next amplifier/delay unit in the same cochlea and to a string of correlator circuits, which would form the analogs of the correlations between (1) the output of this unit and (2) the outputs of all amplifier/delay units in the other cochlea. The outputs of the correlator circuits would be scanned by the external circuitry and displayed or otherwise processed to determine which pairings of right and left cochlear units (and thus which differential signal delay) yields the greatest correlations.

This work was done by Frank T. Hartley of Caltech for NASA's Jet Propulsion Laboratory. For further information, access the Technical Support Package (TSP) free on-line at www.nasatech.com/tsp  under the Computers/Electronics category.

This invention is owned by NASA, and a patent application has been filed. Inquiries concerning nonexclusive or exclusive license for its commercial development should be addressed to the Patent Counsel, NASA Management Office–JPL; (818) 354-7770. Refer to NPO-18399.



This Brief includes a Technical Support Package (TSP).
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Analog Binaural Circuits for Detecting and Locating Leaks

(reference NPO-18399) is currently available for download from the TSP library.

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