Figure 1

Schematic of optical accesses to the cochlear partition and vibrations of the reticular lamina and basilar membrane. (a) While the object beam of the interferometer accesses the cochlear partition through the round window in a non-perpendicular direction, it approaches the same best-frequency (BF) location through an opening in the cochlear lateral wall approximately in the transverse direction. (b) With a perpendicular optical axis, the object beam from the lateral wall opening reaches the BM and RL at the same longitudinal location (indicated by A and B in Fig. 1b). With a non-perpendicular optical axis, the object beam from the round window reaches the BM and RL at different longitudinal locations indicated by locations A and C. The time for a traveling wave to propagate over the distance between locations B and C can result in a phase difference between the RL and BM vibration. (c,d), The magnitude spectra of the RL and BM vibrations presented by displacements as a function of frequency at different sound pressure levels. (e,f) Transfer functions of the RL and BM vibrations presented by the ratio of the RL or BM displacement to the stapes displacement as a function of frequency at different sound pressure levels. (g,h) The phase spectra of the RL and BM vibrations shown by phase difference obtained by subtracting the stapes phase from the RL or BM phase as a function of frequency at different sound pressure levels. (i) Magnitude difference between the RL and BM vibration displayed by the ratio of the RL displacement to the BM displacement as a function of frequency at different sound pressure levels. (j) The phase difference between the RL and BM vibration obtained by subtracting the BM phase from the RL phase as a function of frequency at different sound pressure.