  In Dirac-Born-Infeld inflation, changes in the sound speed that transiently
break the slow roll approximation lead to features in the power spectrum. We
develop and test the generalized slow roll approximation for calculating such
effects and show that it can be extended to treat order unity features. As in
slow-roll, model independent constraints on the potential of canonical
inflation can be directly reinterpreted in the DBI context through this
approximation. In particular, a sharp horizon scale step in the warped brane
tension can explain oscillatory features in the WMAP7 CMB power spectrum as
well as features in the potential. Differences appear only as a small
suppression of power on horizon scales and larger.
