[en] Neutrinos couple through a weak neutral current to the density of matter, in particular to the neutron density. Density fluctuations, or phonons, in the neutron fluid may be emitted or absorbed by neutrinos passing through the matter. At high densities, temperatures and neutrino energies the neutrino mean free paths for phonon emission and absorption can be < = 10⁶ cm. Significant changes in the neutrino momentum and energy accompany these processes. A model calculation is presented for neutrino scattering by phonons, and representative numerical results for the neutrino mean free path and mean energy and momentum changes for ksub(B)T and Esub(γ) both ranging from 1 to 27 MeV. (Auth.)