The Raman scattering of light from the ferroelectric fluctuations of the uniaxial ferroelectric lead germanate is analysed and found to be well described by models for which the self-energy has appreciable dispersion at frequencies comparable with the soft-mode linewidth. A model is developed to calculate the self-energy arising from phonon-density fluctuations of the modes belonging to the same branch. The model shows that this contribution to the self-energy of the soft mode is particularly large if the modes with which it is interacting are overdamped. In detail, however, the model suggests that close to T_c there is an appreciable contribution to the Raman scattering from the interference terms between the one- and two-phonon scattering.