  We study the impact of young clusters on the gravitational wave background
from compact binary coalescence. We simulate a catalog of sources from
population I/II isolated binary stars and stars born in young clusters,
corresponding to one year of observations with second-generation (2G)
detectors. Taking into account uncertainties on the fraction of dynamical
binaries and star formation parameters, we find that the background is
dominated by the population of binary black holes, and we obtain a value of
$\Omega_{gw}(25 \rm{Hz}) = 1.2^{+1.38}_{-0.65} \times 10^{-9}$ for the energy
density, in agreement with the actual upper limits derived from the latest
observation run of LIGO--Virgo. We demonstrate that a large number of sources
in a specific corrected mass range yields to a bump in the background. This
background could be detected with 8 years of coincident data by a network of 2G
detectors.
