  Motivated by model calculations for the heavy fermion superconductor CePt3Si
predicting phonon anomalies because of anti-symmetric spin-orbit coupling we
performed a detailed experimental study of the lattice dynamical properties of
CePt3Si. In particular, we investigated the dispersion of transverse acoustic
and low energy optic phonon branches along the [110] direction using inelastic
neutron scattering. In these branches, we found deviations from our ab-initio
lattice dynamical calculations, which overall give a good description of the
phonon dispersion in CePt3Si. However, the agreement for the [110] transverse
modes can be improved if we neglect the Ce 4f states, done in an additional
calculation. We conclude that the lattice dynamics of CePt3Si are conventional
and that the observed deviations are not related to effects of anti-symmetric
spin-orbit-coupling. More likely, ab-initio calculations overestimate the
exchange between different phonon branches, particularly in the presence of 4f
electron states. Our results imply that the ASOC plays less a role in
non-centrosymmetric superconductors than commonly believed.
