  Superposition of gravitational waves generated by astrophysical sources is
expected to give rise to the stochastic gravitational-wave background. We focus
on the background generated by the ring-down of black holes produced in the
stellar core collapse events across the universe. We systematically study the
parameter space in this model, including the most recent information about the
star formation rate and about the population of black holes as a function of
redshift and of metallicity. We investigate the accessibility of this
gravitational wave background to the upcoming gravitational-wave detectors,
such as Advanced LIGO and Einstein Telescope.
