| 摘要 |
PROBLEM TO BE SOLVED: To improve the reliability of judgment from percussive sounds at the time of judging the content of a can, etc. SOLUTION: While a can 1 is percussed with a hammer, the exciting force of the hammer is detected by means of a vibration detector 11 and the percussive sounds are detected by means of a microphone 3. The detected sounds are divided into a time-sequential signals in a plurality of frequency bands by means of analog BPFs 41 and the maximum values of the signals are stored in peak hold circuits 43. In a reference value setting mode, reference peak values and reference values are respectively stored in reference value setters 16 and 46. In a judgment mode, a ratio computing element 15 computes the ratios between the exciting force and the peak reference values and correctors 44 respectively correct the detected maximum values by using the ratios. Comparators 45 compare the corrected maximum values with the reference values stored in the setter 46 and, when the compared results do not meet a prescribed relation, output judgment signals to an alarm 18. Since the maximum values in the frequency bands are extracted for comparison from the time-sequential signals at every frequency band, the reliability of judgment is improved. |
