ATTENUATION OF LOW-FREQUENCY LONGITUDINAL SOUND IN METALS.

The viscous and induction mechanisms of the attenuation of sound in metals are considered simultaneously. It is shown that, in the long-wavelength limit, they make comparable contributions to the attenuation of sound. At T much less than THETA //D the contributions of nonequilibrium phonons and of the umklapp scattering to the attenuation are small. The relaxation times which appear in the induction and viscous terms contain the second Legendre polynomial of the cosine of the angle between the direction of propagation of sound and the electron momentum. On the other hand, the conductivity is governed by tau which contains the first Legendre polynomial.