  We discuss matter wave experiments in a near-field interferometer and focus
on dephasing phenomena due to inertial forces. Their presence may result in a
significant reduction of the observed interference contrast, even though they
do not lead to genuine decoherence. We provide quantitative estimates for the
most important effects and demonstrate experimentally the strong influence of
acoustic vibrations. Since the effects of inertial forces get increasingly
important for the interferometry with more massive particles they have to be
identified and compensated in future experiments.
