Acoustic emission source location on plate-like structures using a small array of transducers

Claim 1

A small transducer array for omnidirectional monitoring of acoustic waves on a plate-like surface, comprising: a surface to be monitored; four substantially point receiver transducers acoustically coupled to said surface, each transducer being adapted to produce an output signal corresponding to received acoustic waves on said surface, said transducers forming an array on said surface wherein no three transducers are colinear, wherein said transducers do not lie on a circle, and wherein no two of said four transducers lie on a straight line which is parallel to the direction of a straight line passing through the remaining two transducers, said transducer array having a maximum dimension that is less than or on the order of the wavelength of the acoustic waves being monitored; circuit means responsive to output signals from said transducers for determining the location of the source of received acoustic waves, said circuit means including: means for determining the time difference at each of said transducers between the arrival of a first selected characteristic feature of said acoustic waves and the arrival of a second selected characteristic feature of said acoustic waves; means for determining from said time difference the distance from the transducers to the source of received acoustic waves; means for determining the time delays between the arrival of any selected characteristic wave feature at a first of said transducers and each of the remaining three transducers; and means for determining from said time delays, the direction of the source of the received acoustic waves with respect to the transducers.

Claim 10

The method of determining the location of a source of acoustic emissions on a plate-like surface, comprising: acoustically coupling four substantially point receiver transducers to a surface to be monitored, said transducers forming an array on said surface wherein no three transducers are colinear, wherein said transducers do not lie on a circle, and wherein no two of said four transducers lie on a straight line which is parallel to the direction of a straight line passing through the remaining two transducers; measuring the time of arrival of a selected characteristic feature of an acoustic wave traveling on said surface at each of said transducers; determining the time delay between the arrival of said selected characteristic feature at a reference transducer in said array and the arrival of the same selected characteristic feature at each of the remaining three transducers, determining from said time delay measurements the direction of the source of acoustic emissions producing said acoustic wave with respect to said reference transducer; determining from said time delay measurements the velocity of propogation of said selected characteristic feature; determining from said velocity of propagation and said time delay measurement, the three phase delays of said selected characteristic feature between said reference transducer and each of said three remaining transducers; and, determining from said phase delays the distance from said reference transducer to said source of acoustic emissions.

Claim 11

The method of determining the location of a source of acoustic emissions on a plate-like surface, comprising: acoustically coupling four substantially point receiver transducers to a surface to be monitored, said transducers forming an array on said surface wherein no three transducers are colinear, wherein said transducers do not lie on a circle, and wherein no two of said four transducers lie on a straight line which is parallel to the direction of a straight line passing through the remaining two transducers; measuring the time of arrival of a selected characteristic feature of an acoustic wave traveling on said surface at each of said transducers; determining the time delay between the arrival of said selected characteristic feature at a reference transducer in said array and the arrival of the same selected characteristic feature at each of the remaining three transducers, determining from said time delay measurements the direction of the source of acoustic emissions producing said acoustic wave with respect to said reference transducer; determining from said time delay measurements the velocity of propogation of said selected characteristic feature; determining from said velocity of propagation and said time delay measurement, the three phase delays of said selected characteristic feature between said reference transducer and each of said three remaining transducers; and, determining from said phase delays the distance from said reference transducer to said source of acoustic emissions.

Claim 14

The method of determining the location of a source of acoustic emissions on a plate-like surface, comprising: acoustically coupling four substantially point receiver transducers to a surface to be monitored, said transducers forming an array on said surface wherein no three transducers are colinear, wherein said transducers do not lie on a circle, and wherein no two of said four transducers lie on a straight line which is parallel to the direction of a straight line passing through the remaining two transducers; measuring the time of arrival of a first selected characteristic feature of an acoustic wave traveling on said surface at each of said transducers; measuring the time of arrival of a second selected characteristic feature of an acoustic wave traveling on said surface at each of said transducers; determining from the difference in the arrival times of said first and second selected characteristic features, and from the determined group velocities of said first and second selected characteristic features, the distance from said transducers to said source of acoustic emissions; determining the time delays between the arrival of any selected characteristic feature at a reference transducer in said array and the arrival of the same selected characteristic feature at each of the remaining three transducers; and, determining from said time delay measurements the direction of the source of acoustic emissions with respect to said reference transducer.

Claim 15

The method of determining the location of a source of acoustic emissions on a plate-like surface, comprising: acoustically coupling four substantially point receiver transducers to a surface to be monitored, said transducers forming an array on said surface wherein no three transducers are colinear, wherein said transducers do not lie on a circle, and wherein no two of said four transducers lie on a straight line which is parallel to the direction of a straight line passing through the remaining two transducers; measuring the time of arrival of a first selected characteristic feature of an acoustic wave traveling on said surface at each of said transducers; measuring the time of arrival of a second selected characteristic feature of an acoustic wave traveling on said surface at each of said transducers; determining from the difference in the arrival times of said first and second selected characteristic features, and from the determined group velocities of said first and second selected characteristic features, the distance from said transducers to said source of acoustic emissions; determining the time delays between the arrival of any selected characteristic feature at a reference transducer in said array and the arrival of the same selected characteristic feature at each of the remaining three transducers; and, determining from said time delay measurements the direction of the source of acoustic emissions with respect to said reference transducer.