  We consider the emission of gravitational waves in the two proposed models
for the collapse of a massive star to a black hole: the prompt collapse, in
which nearly all the star collapses to a black hole in a dynamical time scale,
and the delayed collapse, in which a light black hole, or a neutron star, which
subsequently accretes matter, forms due to the fall-back achieving, in the
neutron star case, the critical mass for black hole formation. Recent
simulations strongly support this last scenario. We show that, due to the
slowness of fall-back, in the delayed collapse the main burst of gravitational
radiation is emitted depending on the parameters, mass and angular momentum, of
the initial, light, black hole. We estimate, under different assumptions, the
detectability of the emitted gravitational waves showing that such kind of
collapse is not particularly suited for detection by forthcoming
interferometric detectors. Detectors with high sensitivity at frequencies
greater than ~4-5 kHz would be well suited for this kind of sources. We
calculate also the final mass distribution function of single black holes.
