Figure 3.

Elastic propagating wave on the basilar membrane under uniformly distributed stimulation. Finite element models of the cochlear partition were subjected to pure tone stimulations. The stimulating frequency was 0.7 and 21.5 kHz for the apical (span of 1.6 mm centered at 10 mm from the basal end) and basal (span of 1.2 mm centered at 2 mm from the basal end) model, respectively. The force was uniformly distributed along the midline of the basilar membrane. (A) A sequence of basilar membrane vibration patterns of the apical model. As time advances, the wave propagates from thicker to thinner curves. The interval between curves is 0.2 ms. The shaded area indicates the envelope swept by the basilar membrane displacement waves. From top to bottom, the force amplitude was increased so that the amplitude of outer hair cell transduction current increases from 10%, 40%, and 90% of its maximum value. The basilar membrane displacement was normalized by the applied force. Scale bar: 70 nm/Pa. (B) Vibration patterns of the basal section. The time interval between the curves is 5 μs. Scale bar: 0.4 nm/Pa. The phase of the basilar membrane displacement with respect to the applied force at the apex (C) and the base (D). The wave number along the longitudinal location at the apex (E) and the base (F). The line colors correspond to the force amplitude in (A) and (B). Broken lines indicate the peak response location.