There are two widely used theories of ultrasonic attenuation in the Akhieser ($\Omega \tau \ll 1$) regime. Woodruff and Ehrenreich used the Boltzmann equation and found that the attenuation was a function of the specific heat of the thermal phonons. Mason and Bateman obtained the fundamentally different result that the attenuation also involved the thermal energy. It is shown here that the Mason-Bateman theory contains both mathematical and conceptual errors and that its apparent agreement with experimental data on Si and Ge is fortuitous.

• Received 15 October 1969

DOI:https://doi.org/10.1103/PhysRevB.1.2538