Factors Influencing the Acoustic Properties of Vitreous Silica

The acoustic properties of various types of commercial vitreous silica have been studied as functions of thermal treatment and impurity‐ion concentrations. The properties studied include density, shear‐wave attenuation, shear and dilatational wave velocities, and elastic constants. The measurements of acoustic properties are made on small sphere‐shaped samples using primarily a technique that sets the sphere into a resonant mode of vibration and then allows the vibration to decay freely. Both frequency and the decrement of the decay are measured. Use of this resonant sphere technique is particularly appropriate to the present study because it permits precise measurements on samples small enough to conveniently undergo laboratory modification, and it permits the study of velocity variations in a single block of material by measurements on many localized samples. The major findings of this study are the following: (1) An increase of one degree in fictive temperature (a parameter assumed to be related to the...