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 $\mathrm{ql}\gg 1$. The velocity oscillates in phase with the oscillations in the attenuation. The amplitude of the relative changes in the velocity is about ${10}^{-4\mathrm{}}$. 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.