  We present the results of numerical testing on determination of the sound
speed $c$ in the acoustic equation $u_{tt}-c^2\Delta u=0$ by the ${\it
boundary}$ ${control}$ ${method}$. The inverse data is a response operator (a
hyperbolic Dirichlet-to-Neumann map) given on controls, which are supported on
${\it a part}$ of the boundary. The speed is determined in the subdomain
covered by acoustic rays, which are emanated from the points of this part
orthogonally to the boundary. The determination is ${\it time-optimal}$: the
longer is the observation time, the larger is the subdomain, in which $c$ is
recovered. The numerical results are preceded with brief exposition of the
relevant variant of the BC-method.
