Abstract
The sound velocity in the mixtures of RTV silicon rubber and various powders is a function of only the concentration at low frequency. In this range, the sound velocity in the RTV silicon rubber compounded with low density powder is larger than that in pure RTV silicon rubber and increases monotonically as the concentration of the mixture increases. The sound velocity in the RTV silicon rubber compounded with high density powder such as zinc, iron, and wolfram, decreases with the concentration. Then the range of measured sound velocity for the various mixtures is between 730 and 1300 m/sec. The specific acoustic impedances of the mixture compounded with high density powder are nearly equal to those of the mixture compounded with low density powder while the sound velocities of them have a great difference. When the RTV silicon rubber is compounded with low and high density powders, it is possible to vary the sound velocity of this mixture by choosing the concentrations of low and high density powders without change of specific acoustic impedance.
