  The temperature dependence of the ultrasound wave absorption in bulk
$p$-Cd$_{0.2}$Hg$_{0.8}$Te crystals free from low-angle grain boundaries has
been studied experimentally for the first time in the frequency range 10--55
MHz and the temperature interval 150--300 K, and the corresponding results of
measurements are presented. The maximum value of absorption coefficient is
found to increase and to shift toward higher temperatures, as the ultrasound
frequency grows. The results obtained can be satisfactorily explained in the
framework of the Brailsford model, which associates the ultrasound absorption
with vibrations of thermally activated dislocation kinks. The characteristic
parameters of this model for $p$-Cd$_{0.2}$Hg$_{0.8}$Te are determined; namely,
the frequency coefficient $f_{k}\approx $~6\,$\times $\,10$^{\,9}$\,Hz and the
kink diffusion activation energy $W_{k}\approx $~0.11\,eV. The dislocation
concentration is also evaluated ($\alpha \approx
$~2\,$\times$\,10$^{10}$\,m$^{-2}$), with the determined value being consistent
with that obtained by the selective etching method (0.7\,$\times
$\,10$^{10}$\,m$^{-2}$).
