  We present a novel interpretation of the Hawking temperature of acoustic
holes, the hydrodynamic analogue of standard black holes, by connecting the
geometrical properties of the horizon with the distribution function of the
spontaneously generated phonons. Using covariant kinetic theory to describe the
phonon gas emitted by the acoustic hole, we obtain the correct expression of
the Hawking temperature by equating the entropy loss of the acoustic horizon
with the entropy gain of the phonon gas. In doing this, we assume that the
entropy of the acoustic hole is proportional to the area of the horizon, as in
standard black holes. Since our method only depends on the geometrical
properties of the acoustic horizon and on the statistical properties of the
phonon gas, it is well suited to be extended to standard black holes and to
out-of-equilibrium systems.
