  In this work we analyze the sound perturbation of Unruh's acoustic effective
geometry in both (2+1) and (3+1) spacetime dimensions and present an exact
analytical expression for the quasibound states of these idealized black-hole
configurations by using a new approach recently developed, which uses the
polynomial conditions of the hypergeometric functions. Our main goal is to
discuss the effects of having an event horizon in such effective metrics. We
also discuss the stability of the systems and present the radial eigenfunctions
related to these quasibound state frequencies. These metrics assume just the
form it has for a Schwarzschild black hole near the event horizon, and
therefore may, in principle, shed some light into the underlying classical and
quantum physics of astrophysical black holes through analog acoustic probes.
