Experimental Study of Sound Travel-Time Estimation Method in Stored Grain

One common and traditional method for detecting stored grain deterioration is to measure grain temperature by contact sensors. Many sensors are installed throughout the bin for this. Temperature maps can also be obtained using acoustic travel-time tomography, which would be more suitable for store grain due to its non-contact measurement. The measurement of sound travel-time in grain bulk was researched. A time-delay estimation method using triple correlation with wavelet transform is proposed for solving the problem of sound attenuation in grain bulk. A measurement system of sound travel-time based on virtual instrument was built. Sound travel-time in soybeans was measured by the proposed method, cross-correlation method, and cross-correlation with wavelet transform method. The results show that the proposed method is best in measurement stability and accuracy. Thus it is expected to be used in an actual acoustic temperature monitoring system for stored grain.