In the utilization of the Kaiser Effect of AE as a method of estimating the gecstress in rock, it is very important to eliminate the noise induced at the ends cf a specimen, so sponge pads are put between the upper and lower end surfaces of specimens and bearing plates. In this paper, the attenuation behavior of sounds emitted by AE simulator and propagating in sponges are quantitatively measured. The eliminaion of noise by sponge effect is confirmed by the Kaiser Effect.