  Cascading gauge theories of Klebanov et.al. provide a model within a
framework of gauge theory/string theory duality for a four dimensional
non-conformal gauge theory with a spontaneously generated mass scale. Using the
dual supergravity description we study sound wave propagation in strongly
coupled cascading gauge theory plasma. We analytically compute the speed of
sound and the bulk viscosity of cascading gauge theory plasma at a temperature
much larger than the strong coupling scale of the theory. The sound wave
dispersion relation is obtained from the hydrodynamic pole in the stress-energy
tensor two-point correlation function. The speed of sound extracted from the
pole of the correlation function agrees with its value computed in
[hep-th/0506002] using the equation of state. We find that the bulk viscosity
of the hot cascading gauge theory plasma is non-zero at the leading order in
the deviation from conformality.
