Sound velocity and absorption in amorphous silica

Velocity and absorption coefficient of sound have been measured in fused silica, in the range of temperature (30÷300) °K, and at the frequencies of 15, 25, 35, 45 MHz. The obtained results, while generally agreeing with similar data given by other authors in a different range of frequencies, show however some peculiarities not observed until now. In addition the possibility of comparison of data taken at the same temperature but at different frequencies allows a more detailed insight into the physical mechanism that originates the observed anomalies. A tentative theoretical explanation is proposed, that assigns the excess of absorption to a possible mechanism called “stochastic resonance» that would be peculiar to disordered structures. The experimental data well support such an explanation.