0023-6152

AA00697606

4363556

The percentage of ripened grains (PRG) is an important indicator affecting rice yield and quality, which is used for production management of rice. However, PRG can be evaluated only in test fields, because the current method of measuring PRG through quadrat sampling is time–consuming and laborious. Meanwhile, PRG can be estimated by particle density of rough rice, which is calculated by the ratio of mass to true volume of rough rice layer piled in a combine grain tank. Commercially available combines have already been equipped with the function of measuring mass of rough rice. However, the technology has not been available for measuring volume of rough rice layers in a grain tank. The objective of this study was to investigate whether volume of a rough rice layers in a container can be estimated using Helmholtz resonance. We used a closed–type cylinder resonator (volume: 770 cm3) for measuring volume of water, glass beads having diameter of 1 mm, glass fragments having width larger than 0.7 mm, and rough rice. For glass fragments and rough rice, three filling conditions, which included loose, free fall, and dense, were tested to investigate the effect of porosity in particle layers on the volume measurement. Moreover, volume of water and particle layers estimated using resonant frequency was compared with true volume. Estimated volume had a strong linear correlation (r>0.99) with true volume for all the filling conditions and materials. On the other hand, volume was more underestimated as porosity in a particle layer increased. A possible reason for underestimating volume was that vibration energy attenuated by porosity in a particle layer decreased resonant frequency