(A–C) Ratios of the BM velocities, V/Vd1, for BC excitations at (A) 0.5 kHz, (B) 1 kHz, and (C) 7 kHz. Every V represents a relative BM velocity, ΔVBM = VBM– VB, for a given excitation direction. For this figure, the ME structure was not included. To see this figure in color, go online.