  Stochastic gravitational waves can be produced during the preheating when
out-of-equilibrium particles are produced with an anisotropic stress-tensor. We
discuss the case where these particles carry spin 3/2. We compute the spectrum
of the gravitational waves generated by the transverse and longitudinal
components. We find a different scaling of the spectrum near the peak and the
longitudinal components lead to an enhancement when compared to spin-1/2
fermions with Yukawa couplings. We note, as expected, that the corresponding
typical frequency is too high for the current observation and calls for
ultra-high frequency gravitational wave detectors in the future.
