  The spherically symmetric perturbations in the spatially flat Friedman models
are considered. It is assumed that the Friedmannian density and pressure are
related through a linear equation of state. The perturbation is joined smoothly
with an unperturbed Friedmann's background at the sound horizon of
perturbation. Such junction is in accordance with the "birth" of a local
perturbation as a result of the redistribution of matter. The solution of the
Einstein's equations is obtained in linear approximation on a Friedmann's
background near the the sound horizon of perturbation.
