  We consider anisotropies in the Cosmic Microwave Background (CMB) generated
by spatially limited seeds; these objects could correspond to relics of high
energy symmetry breaking in the early universe. It is shown how the CMB
perturbation propagate beyond the size of the seed in the form of waves
traveling with the CMB sound velocity. Moreover, these waves are the
substantial part of the signal, both for polarization and temperature. The
explanation of this phenomenology in terms of the CMB equations is given.
  Observationally, this effect is threefold promising. First, it enlarges the
signal from a seed intersecting the last scattering surface to the scale of the
CMB sound horizon at decoupling, that is roughly one degree in the sky. Second,
it offers cross correlation possibilities between the polarization and
temperature signals. Third, it allows to unambiguously distinguish these
structures from point-like astrophysical sources.
