Phase-locked component of the response (in nm) of a stereociliary bundle subject to sinusoidal deflection, over a range of drive frequencies (5–50 Hz in 1 Hz increments). Each stimulus frequency is presented for ten periods. The corresponding bundle motion trace is split into ten segments and then averaged. A single sine wave of fixed frequency is fit to the averaged response and its amplitude is extracted to obtain the phase-locked component. Linear interpolation was applied along the stimulus amplitude direction. Stimulus was applied at 4, 8, 12, 16, 20, 24, 28, 32, 36, 40, 60, 80, 100 and 120 nm (amplitudes refer to the base of the probe).