  We study the Hawking radiation for the acoustic black hole. In the beginning
we follow the outline of T.Jacobson but then we use a different $2+1$ vacuum
state similar to the vacuum state constructed by W.Unruh. We also use a special
form of the wave packets. The focus of the paper is to treat the 2 dimensional
case, in particular, the case when the radial and angular velocity are
variable.
