  Since Alfven, dynamo and sound waves and the existence of general
relativistic black holes are well stablished in plasma physics, this provides
enough motivation to investigate the presence of acoustic black-hole effective
metric of analogue Einstein's gravity in dynamo flows. From nonlinear dynamo
equations, one obtains a non-homogeneous wave equation where it is shown that
the non-homogeneous factor is proportional to time evolution of the
compressibility factor. In the Navier-Stokes case for a finite Reynolds number
the acoustic black-holes also exists on the stretching plasma flows. In the
magnetostatic case the dynamo is marginal. Analog models are usually applied to
a superfluid analog spacetime, instead of the plasma setting used here. A
coupled nonlinear plasma flow solution is found for the dynamo equation where
the effective black hole solution of the scalar effective equation yields an
imaginary part of the growth of magnetic field. Therefore though the real part
of the growth rate of the magnetic field is negative or null, since there is a
temporal oscillation in magnetic field, the solution represents a slow dynamo.
Thus acoustic black holes are shown to definitely contribute to dynamo action
of the effective plasma spacetime. It is suggested that a fast dynamo effective
spacetime may also contain an acoustic black hole. I the case of planar waves
the effective metric can be cast in Kerr-Schild spacetime form. The Killing
symmetries are explicitly given in this metric and the growth of dynamo waves.
