Preliminary Research on Measurement of Stored-grain Temperature by Acoustic Method

One common and traditional method of detecting stored-grain deterioration is by measuring grain temperature. Key to stored-grain temperature measurement by acoustic tomography is discussed. Grain is a highly absorbing acoustical medium, acts as an acoustical low-pass filter, accordingly acoustical signal distorts seriously in transmission. An acoustic-attenuation-property weighted generalized cross-correlation method (for short AAP-GCC) is proposed. Using BCC (basic cross-correlation), PHAT-GCS and AAP-GCS, the estimations of acoustical travel-time in a grain bin of 10m diameter were computer simulated under various sound wave paths and various signal-to-noise ratios. Simulation results show that for a short sound wave path, all the three methods can give good estimation, and BCC is the best since it is the simplest; for a long path, AAP overmatch BCC and PHAT, which indicates that AAP can repair the signal distortion due to sound attenuation effectively. Examples of estimation by AAP, BCC and PHAT are given.