Acoustic Attenuation in High-T_c Superconductors

We analyze the acoustic attenuation rate in high-$T_c$ superconductors, and find that this method offers an additional way to examine the anisotropy of the superconducting order parameter in these materials. We argue that it should be possible to distinguish the electronic contribution to the acoustic attenuation, which has a strong temperature dependence near $T_c$, from the lattice contribution, which does not show a strong temperature dependence near $T_c$. We propose that this can be utilized to measure the anisotropy of the order parameter by measuring the attenuation rate near $T_c$ in different directions.