  Astrophysical sources of gravitational radiation are likely to have been
formed since the beginning of star formation. Realistic source rates of
formation throughout the Universe have been estimated from an observation-based
determination of the star formation rate density evolution. Both the radiation
emitted during the collapse to black holes and the spin-down radiation, induced
by the r-mode instability, emitted by hot, young rapidly rotating neutron stars
have been considered. We have investigated the overall signal produced by the
ensemble of sources exploring the parameter space and discussing its possible
detectability.
