  The hydrodynamics, describing dynamical effects in superfluid neutron stars,
essentially differs from the standard one-fluid hydrodynamics. In particular,
we have four bulk viscosity coefficients in the theory instead of one. In this
paper we calculate these coefficients, for the first time, assuming they are
due to non-equilibrium beta-processes (such as modified or direct Urca
process). The results of our analysis are used to estimate characteristic
damping times of sound waves in superfluid neutron stars. It is demonstrated
that all four bulk viscosity coefficients lead to comparable dissipation of
sound waves and should be considered on the same footing.
