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.

Topics:
Amplifiers Electronic equipment Electronics & Computers Logistics Noise Parts Pumps
This Brief includes a Technical Support Package (TSP).
Document cover
Analog Binaural Circuits for Detecting and Locating Leaks

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

Don't have an account?

Magazine cover
NASA Tech Briefs Magazine

This article first appeared in the May, 2003 issue of NASA Tech Briefs Magazine (Vol. 27 No. 5).

Read more articles from the archives here.

Overview

The document presents a technical support package from NASA's Jet Propulsion Laboratory (JPL) detailing the development of analog binaural circuits aimed at detecting and locating leaks that emit ultrasonic noise. The proposed technology utilizes very-large-scale integrated (VLSI) circuits designed to function effectively in environments with significant lower-frequency background noise, such as sounds from flow and pumping systems.

The core of the system involves a pair of transducers, analogous to human ears, which receive ultrasonic signals from different locations (e.g., along a pipeline). These transducers serve as inputs to cochlear circuits that process the signals. The cochlear circuits consist of cascades of amplifier/delay units that filter out frequencies below the ultrasonic range and introduce time delays to the signals. The outputs from these units are then fed into correlator circuits, which analyze the time differences in sound arrival at the two transducers.

By measuring the differential delays between the signals received by the transducers, the system can estimate the distance from either transducer to the leak. If multiple pairs of transducers are used, the technology can determine the leak's location in three-dimensional space by analyzing sound propagation through air.

The document emphasizes the innovative nature of this technology, which mimics the auditory processing capabilities of biological systems, specifically stereausis, the ability to perceive sound direction. The work was conducted by Frank T. Hartley at Caltech for NASA and is protected by a patent application, indicating its potential for commercial development.

The document also includes a disclaimer stating that the U.S. Government and JPL do not assume liability for the use of the information contained within and that references to specific commercial products do not imply endorsement. For further inquiries regarding licensing for commercial development, contact information for NASA's Patent Counsel is provided.

Overall, this technical support package highlights a significant advancement in leak detection technology, combining principles of biology with engineering to create a sophisticated system capable of operating in challenging acoustic environments.