(a) The normalised BM amplitude at different sound pressure levels (SPL). All curves converge below 10 kHz, indicating linear response and equal gain, independent of the SPL. Measurements were performed using the Mössbauer technique in the basal turn of the guinea pig cochlea. Maximal response frequency is at about 17 kHz [43] (reprinted from Hearing Research, 22, Johnstone et al., Basilar Membrane Measurements and the Travelling Wave, 147–154, Copyright (1986), with permission from Elsevier). (b) Gain functions of the BM displacement measured in the basal turn of the chinchilla cochlea with laser Doppler velocimetry. Maximal response frequency is at about 8.5 kHz. Measurements are shown at two sound pressure levels, 75 and 95 dB, and in conditions of living and dead cochleas [44] (reprinted from Journal of Neuroscience, 11, Ruggero and Rich, Furosemide Alters Organ of Corti Mechanics: Evidence for Feedback of Outer Hair Cells upon the Basilar Membrane, 1057–1067, Copyright (1991), with permission from Copyright Clearance Centre).
