  Phenomenologically assuming a sharp decrease of shear relaxation time for
large wavevector $k>k_\xi$ density modes (where $k_\xi$ is of order of inverse
of several interatomic distances $a$), I develop a general elasto-hydrodynamic
theory describing the low-energy excitations of glassy and amorphous solids,
which are responsible for anomalous specific heat and thermal conductivity. The
theory explains the origin of collective two-level states and Boson peak. The
ratio of the wavelength of the phonon, $\lambda$, to its mean free path, $l$, -
universal property of sound absorption in glasses - is derived in this theory
to be $\lambda/l=(2/3) (c_t/c_l)^2 (k_\xi a)^3$, where $c_t$ and $c_l$ are
transverse and longitudinal sound velocities correspondingly.
