Figure 1: Longitudinally propagating waves of radial motion along the TM.

(a) TM segments were suspended between two supports separated by 390–480 μm in a wave chamber. Double-headed arrow indicates sinusoidal displacement of vibrating support at audio frequencies. Schematic waveform (green line overlaid on TM) is a displacement snapshot illustrating the wave-like nature of TM motion. (b) Schematic drawing of a decaying wave showing the peak amplitude (A), wave envelope (purple), wave decay constant σ and wavelength λ. (c, d) TM radial displacement versus longitudinal distance across basal and apical TM segments. Radial displacement was measured relative to a point on the TM, ∼30 μm from the edge of vibrating support. (c) Wave motion in response to 18-kHz stimulation for basal Tectb^−/− (red open circles) and wild-type (blue pluses) TMs. Best fitting wave parameter estimates were σ =110 μm and λ=330 μm for Tectb^−/− mice, and σ =200 μm and λ=415 μm for wild-type mice. (d) Wave motion in response to 3.5-kHz stimulation for apical Tectb^−/− (red open circles) and wild-type (blue pluses) TMs. Best fitting wave parameter estimates were σ =90 μm and λ=220 μm for Tectb^−/− mice, and σ =340 μm and λ=560 μm for wild-type mice.