  The properties of the aperiodic brightness variability for the dwarf nova HL
CMa are considered. The variability of the system HL CMa is shown to be
suppressed at frequencies above $7\times10^{-3}$Hz. Different variability
suppression mechanisms related to the radiation reprocessing time, partial disk
evaporation, and characteristic variability formation time are proposed. It has
been found that the variability suppression frequency does not change when the
system passes from the quiescent state to the outburst one, suggesting that the
accretion flow geometry is invariable. It is concluded from the optical and
X-ray luminosities of the system that the boundary layer on the white dwarf
surface is optically thick in both quiescent and outburst states. The latter
implies that the optically thick part of the accretion flow (disk) reaches the
white dwarf surface. The accretion rate in the system, the flow geometry and
temperature have been estimated from the variability power spectra and spectral
characteristics in a wide energy range, from the optical to X-ray.
