  The role of electron-phonon interactions is experimentally and theoretically
investigated near the saddle point absorption peak of graphene. The
differential optical transmission spectra of multiple, non-interacting layers
of graphene reveals the dominant role played by electron-acoustic phonon
coupling in bandstructure renormalization. Using a Born approximation for
electron-phonon coupling and experimental estimates of the dynamic phonon
lattice temperature, we deduce the effective acoustic deformation potential to
be $D^{\rm ac}_{\rm eff} \simeq 5$eV. This value is in accord with recent
theoretical predictions but differs substantially from those obtained using
electrical transport measurements.
