A model of ultrasonic radiation damping is presented to describe the dissipation of ultrasonic vibration energy in a solid processing system on the basis of vibration damping theory. Four kinds of polyethylene particles, with diameters varying from 0.15 to 0.85mm and bulk densities varying from 499.6 to 252.5kg center dot m-3, are put in a Plexiglas storage bin inserted with a Plexiglas bar, as powder material. Ultrasonic energies absorbed by these kinds of particles were detected by receivers at different levels. The results show that when distance between receiver and source of ultrasonic vibration is lengthened, the AE energy absorption increases, and it also increases when the bulk density of powder material is increased. It is also found that the ultrasonic vibration energy dissipates much more along the inserted bar than along the wall of a storage bin, because the inserted bar has greater radiation area. The results of experiments are accurately predicted by the radiation damping model presented in this article with a fairly good accuracy. Furthermore, a method of level gauging is developed to meet the requirements of different applications, such as online measurement of the particle material, to replace other level gauging methods.