  High frequency sound is observed in lithium diborate glass,
Li$_2$O--2B$_2$O$_3$, using Brillouin scattering of light and x-rays. The sound
attenuation exhibits a non-trivial dependence on the wavevector, with a
remarkably rapid increase towards a Ioffe-Regel crossover as the frequency
approaches the boson peak from below. An analysis of literature results reveals
the near coincidence of the boson-peak frequency with a Ioffe-Regel limit for
sound in {\em all} sufficiently strong glasses. We conjecture that this
behavior, specific to glassy materials, must be quite universal among them.
