  We use a numerical code to compute the density perturbations generated during
an inflationary epoch which includes a spontaneous symmetry breaking phase
transition. A sharp step in the inflaton potential generates $k$ dependent
oscillations in the spectrum of primordial density perturbations. The amplitude
and extent in wavenumber of these oscillations depends on both the magnitude
and gradient of the step in the inflaton potential. We show that observations
of the cosmic microwave background anisotropy place strong constraints on the
step parameters.
