  We investigate the effect of the dark matter (DM) halos collisions, namely
collisions of galaxies and galaxy clusters, through gravitational
bremsstrahlung, on the stochastic gravitational wave background. We first
calculate the gravitational wave signal of a single collision event, assuming
point masses and linear perturbation theory. Then we proceed to the calculation
of the energy spectrum of the collective effect of all dark matter collisions
in the Universe. Concerning the DM halo collision rate, we show that it is
given by the product of the number density of DM halos, which is calculated by
the extended Press-Schechter (EPS) theory, with the collision rate of a single
DM halo, which is given by simulation results, with a function of the linear
growth rate of matter density through cosmological evolution. Hence,
integrating over all mass and distance ranges, we finally extract the spectrum
of the stochastic gravitational wave background created by DM halos collisions.
As we show, the resulting contribution to the stochastic gravitational wave
background is of the order of $h_{c} \approx 10^{-29}$ in the band of $f
\approx 10^{-15} Hz$. However, in very low frequency band, it is larger. With
current observational sensitivity it cannot be detected.
