  We obtain the analytic solutions of the radial part of the massless
Klein-Gordon equation in the spacetime of both three dimensional rotating and
four dimensional canonical acoustic black holes, which are given in terms of
the confluent Heun functions. From these solutions, we obtain the scalar waves
near the acoustic horizon. We discuss the analogue Hawking radiation of
massless scalar particles and the features of the spectrum associated with the
radiation emitted by these acoustic black holes.
