Research on Estimation of Acoustic Travel-Time in Soybeans

One common and traditional method of detecting stored-grain deterioration is by measuring grain temperature. The key to stored-grain temperature measurement by acoustic method is acoustic travel-time measurement. In this paper, a phase transform generalized cross correlation with wavelet transform (WT-PHAT-GCC) method for acoustic travel-time measurement is proposed. An experimental system of acoustic travel-time estimation has been realized. Acoustic travel-times in soybeans and in air have been estimated by PHAT-GCC method and WT-PHAT-GCC method respectively. The experimental results show that the estimation of acoustic travel-time in soybeans is proportional to the distance between two microphones. WT-PHAT-GCC can give better estimation than PHAT-GCC. A stable ratio of the travel-time in soybeans to the travel-time in air at same distance and same temperature can be calculated, which means the grain temperature can be reliably derived from the acoustic travel-time in grain.