The lattice loss coefficient &agr;lfor acoustic waves in low‐resistivity (0.6 &OHgr; cm) CdS was determined from the electric‐field‐dependent incubation time. At the frequency of the maximum gain, the value for &agr;llies between the extrapolated experimental curves as measured by Bateman and McFee [J. Appl. Phys. 39, 4471 (1968)] and by Zucker, Zemon, and Wasko [Proc. Int. Conf. Phys. Semicond. 9th Moscow, 1968 2, 904 (1968)]. Two simple theories for the field dependence of the incubation time were compared and critically analyzed.