| 摘要 |
PURPOSE:To detect an acoustic signal due to cracking generated from an object to be detected discriminately from noise easily and accurately by measuring the two of the rise period, holding period and fall time of the isolated wave where the electrically converted signal of said acoustic signal presents. CONSTITUTION:A sensor 21 is held in contact with an object to be examined, not shown in the figure, and the acoustic signal due to cracking generated from said object is converted to an electric signal which is drawn out. When the isolated wave which presents in this electrically converted signal is on the rise (rise period), that is, when the leading edge of the isolated wave is under inputting, the current output of a peak holding circuit 31 is larger than the output of the peak holding circuit 31 of one clock before, and the output of a comparator 32 goes to a high level. However, if the isolated wave is on the fall (fall period), the output of the circuit 31 of one clock before attains the value larger than the current output and the output of a comparator 33 goes to a high level. In the period except either of these two periods, the outputs of the comparators 32, 33 are the low level. The acoustic signal due to cracking is detected discriminately from noise by measuring these periods. |
