  We investigate the elastic scattering of Bose-Einstein condensates at shallow
periodic and disorder potentials. We show that the collective scattering of the
macroscopic quantum object couples to internal degrees of freedom of the
Bose-Einstein condensate such that the Bose-Einstein condensate gets depleted.
As a precursor for the excitation of the Bose-Einstein condensate we observe
wave chaos within a mean-field theory.
