Magnetic Field Dependence of the Velocity of Sound in Ultrapure Cd and Cu

The change in the velocity of sound in very pure Cd and Cu as a function of the intensity of a perpendicular magnetic field has been measured for ql1. The velocity oscillates in phase with the oscillations in the attenuation. The amplitude of the relative changes in the velocity is about 10^-4. A standing-wave resonance technique which eliminates the effects of stray electrical signals is described. It takes advantage of the fact that transmitted signals for even and odd numbers of half-wavelengths within the sample differ in phase by 180^∘{}. The technique is readily adaptable to automatic recording systems.