Volume Estimation Method of a Rough Rice Layer Using Helmholtz Resonance

Abstract

An estimation of the percentage of ripened grains requires measuring the volume and the mass of a rough rice layer in a combine grain tank. Helmholtz resonance can be used to measure the volume. However, its measurement accuracy lowers because the sound pressure attenuates through pores in a rough rice layer. This study clarified the characteristics of viscous damping coefficients α used in the volume estimation equation considering the attenuation and evaluated the volume estimation accuracy. Coefficient α, which had a strong liner relationship with the pore volume (R² ≥ 0.975), was estimated using rough rice mass (R²＝0.988). The relative error of volume estimates was generally within ±5 %, greatly improving from −20 % using the conventional equation without considering the attenuation.