  The stochastic gravitational wave background produced by supernovas,
magnetars and merger of binaries constituted by a pair of compact objects is
reviewed and updated. The merger of systems composed by two black holes
dominates by far the background signal, whose amplitude in the range 10-100 Hz
is above the sensitivity of the planned Einstein laser interferometer (ET). The
background signal at 25 Hz estimated by the LIGO-VIRGO collaboration, based on
the available merger detection data, is in good agreement with the present
theoretical predictions.
