Nondestructive quality evaluation of fruits by acoustic impulse transmission

摘要

Acoustic impulse responses of several fruits were studied as a nondestructive means of evaluating produce quality. Acoustic signals induced by an impact were classified into a few types of waveforms: waves transmitted along the surface, internally transmitted waves and harmonic vibration waves. Experimental results were as follows: (1) Two kinds of waves were observed in watermelons and pineapples: a surface-transmitted wave and an internally transmitted wave. (2) The amplitude of the internally transmitted wave was related the firmness of watermelons-flesh. (3) The internal wave was not observed in internally cracked watermelons. (4) Only the wave transmitted along the surface was observed in muskmelons, apples, kiwi-fruit, Japanese pears and Japanese persimmons. (5) After the surface transmitted wave passed, harmonic vibration was observed in apples and Japanese pears. (6) The velocity of the transmitted wave along the surface can predict the firmness of flesh of muskmelons, apples, Japanese pears and persimmons.