| 摘要 |
PROBLEM TO BE SOLVED: To judge a large quantity of fruits efficiently without requiring the skill of an expert by judging the ripeness of fruits according to the relationship of the differential frequency and the differential peak value of the frequency of an impact sound propagating through the outer skin part and the edible part of the fruits. SOLUTION: An impact sound generated by means of a hammer 12 and fruits 11 propagates through the outer skin part and the inner edible part of the fruits. An impact sound signal collected by sound collection microphones 13, 14 is amplified by an amplifier 15 and converted through an A/D converter 16 into a digital signal. A frequency analyzer 17 extracts both a gradually damping frequency of an initial impact vibration propagating through the outer skin and the vicinity thereof, and gradually damping frequency of an impact vibration propagating through the inner edible part. The propagation frequencies propagating through the outer skin and the edible part are varied from each other as the ripening progress at the edible part and frequencies having different peak values are obtained. The frequency interval (frequency level difference) and the frequency intensity difference (peak value difference) are calculated by a frequency analyzer 17 for the different peak frequencies and employed for judging the ripeness. |
