| 摘要 |
PROBLEM TO BE SOLVED: To precisely detect the presence of an abnormal position of a conduit and specify its position by successively performing a preprocessing sufficiently considering both characteristics of leak sound and noise of the abnormal position, a correlation processing, and further a post processing. SOLUTION: The receipt signals of ultrasonic sensors 3a, 3b, and 3c are read in a receiving part 71 according to the instruction of a control part 7 to calculate a power spectrum by use of a plurality of specified expressions. The combination of two ultrasonic sensors, for example, 3a and 3b is selected, and the cross spectrum of the receipt signals received by the sensors 3a, 3b is calculated by a specified expression. The coherence is also calculated by a specified expression. The characteristic of a SCOT filter is determined to filter the cross spectrum by a filter having frequency characteristics of a specified expression. The filtered cross spectrum is transmitted to a correlation processing part 72b to calculate the mutual correlation function, and the envelope detection is performed in a post processing part 72c. When the frequency of envelope memory storage is equal to a predetermined repeat frequency of data read, the repeat is ended, the envelopes are averaged to determine the delay time to the receiving time of the ultrasonic sensor. One or both of peak values of the mutual correlation functions averaged between the sensors 3a and 3b and between 3a and 3c is compared with a predetermined threshold to judge the presence of an abnormal position 2, and its position is specified.
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