  We have measured the effect of dipole-dipole interactions on the frequency of
a collective mode of a Bose-Einstein condensate. At relatively large numbers of
atoms, the experimental measurements are in good agreement with zero
temperature theoretical predictions based on the Thomas Fermi approach.
Experimental results obtained for the dipolar shift of a collective mode show a
larger dependency to both the trap geometry and the atom number than the ones
obtained when measuring the modification of the condensate aspect ratio due to
dipolar forces. These findings are in good agreement with simulations based on
a gaussian ansatz.
