Recent observations of sound-evoked vibrations in the cochlea’s sensory organ of Corti (ooC), using optical coherence tomography (OCT), revealed unanticipated and complex motions. Relative motion between different structures of the ooC is the key for mammalian ears to achieve remarkable frequency selectivity and sensitivity but is not well understood, especially in the low-frequency region that is essential to human speech perception. We mapped the ooC motions using multiple OCT viewing angles over an extended region in the low-frequency apex of gerbil cochleae. These resolve the “direction limit” with classical approaches and address low-frequency sound processing in the mammalian ear. Our data demonstrate the active structure of sensory outer hair cells moves with the traveling wave. In addition, they also move along an unexpected longitudinal direction. This motion is never predicted, adds another dimension to address the active process within the cochlea, and impacts the interpretation of cochlear vibrometry data.