Acoustical characteristics of pine nut and fractal recogition

According to the structure differences of open pine nuts and closed pine nuts, the acoustical characteristics of them were tested in order to distinguish whether the pine nut was open or not. In the experiment, pine nuts dropped from a certain height, the impinging sound on ceramic board was collected by a microphone. The sound wave graph and frequency spectral curves were obtained while the impinging sound was analyzed by computer. Fractal dimension was calculated on sound wave graph and frequency spectral graph of open pine nuts and closed pine nuts. The result of test and analysis show that the sound wave fractal dimension of open pine nuts was smaller than that of closed pine nuts. The even value of the former was 1.4097, while the latter was 1.6576. And the frequency spectrum fractal dimension of open pine nuts was larger than that of closed pine nuts. The even value on the frequency spectrum fractal dimension of open pine nuts was 1.3497 and the one of closed pine nuts was 1.1846. Fractal dimension of sound wave and frequency spectrum could be used as an important index to distinguish whether the pine nut was open or not.