Abstract: A method and apparatus for utilizing the sound and pattern recognition capabilities of the human auditory system, which takes information contained in typical instrumentation signals in the form of amplitude, frequency, and time characteristics, and converts this information into sound qualities and characteristics which are recognizable by the human listener. The method and apparatus digitizes the analog amplitude, frequency, and time information, and selects appropriate sound characteristics into which it may encode this information in standardized form that is recognizable to the human listener. The method allows for the testing or inspection of materials using nondestructive evaluation techniques in a manner that allows the tester to interpret the information provided by the testing system, either exclusively through his auditory senses, or through his auditory senses in conjunction with visual indicators.

Abstract: An ultrasonic piezoelectric transducer that is operable in very high and very low temperatures. The transducer has a dual housing structure that isolates the expansion and contraction of the piezoelectric element from the expansion and contraction of the housing. Also, the internal components are made from materials having similar coefficients of expansion so that they do not interfere with the motion of the piezoelectric element.

Abstract: Low pressure turbine disc rims are inspected by a method in which an ultrasonic beam is directed into a disc rim steeple from a location on the disc rim web. Reflected waves are received and signals indicative thereof are produced for display. A predetermined time window is established on the display, based on the time-of-flight difference between the top of the steeple and the disc rim. The presence of signals within the time window on the display is determined to indicate the presence of a crack. Cracks located along the steeple serrations and oriented in a generally tangential direction to the steeple cross section are detected by producing an ultrasonic beam directed along a line normal to the bottom of a steeple. Cracks located at the bottom of a blade groove at the steeple root and oriented in a generally radially direction can be detected by producing an ultrasonic beam skewed at an acute angle relative to the line normal to the bottom of a steeple.