  In the fast rotating gas (with the velocity typical for Iguassu gas
centrifuge) three families of linear waves exist with different polarizations
and law of dispersion. The energy of the waves is basically concentrated at the
axis of rotation in the rarefied region. Therefore these waves decay on the
distance comparable with the wavelength. There is only one type of waves
propagating strictly along the axis of rotation with the law of dispersion
similar to ordinary acoustic waves. These waves are interested for the physics
of gas centrifuges. The energy density of these waves concentrates at the wall
of the rotor. These waves have weak damping due to the molecular viscosity and
heat conductivity. The damping coefficient is determined for this type of waves
by numerical calculations. Analytical approximations for the damping
coefficient is defined as well. At the parameters typical for the Iguassu
centrifuge the damping is defined by interaction of the waves with the rotor
wall.
