抄録
Acoustic responses obtained by striking the fruit have been used for evaluating fruit firmness and maturity using a FFT method. However, those responses are often quite complex and uncertain. This study proposes a new technique to address such complex data. In the method, the attractor of the acoustic response is first described; then, its slope is calculated using the method of least squares. There was a close relationship between the slope of attractor and fruit firmness. The slope of attractor decreased in proportion to fruit firmness. Significant linearity was observed in the relationship between fruit firmness and the slope of attractor. This linearity was confirmed through simulation of a mechanical model (damped vibration model). These results showed that use of the attractor allowed quantitative evaluation of fruit firmness in the time-domain.