Each point on the basilar membrane responds best to one particular frequency. The base (near the oval window) is narrow and stiff and responds to high frequencies. The apex (near the helicotrema) is wide and flexible and responds to low frequencies. Stiffness falls roughly a hundredfold from base to apex. (von Békésy, 1960; Greenwood, 1990)
The wave always starts at the base and travels to the place of its characteristic frequency, where it peaks and then dies away. A low-frequency sound therefore moves a much longer stretch of the membrane, while a high-frequency sound stays within the first few millimetres of the base.
The sections in the right-hand panel let you explore types of hearing loss, a cochlear implant and a cross-section of the duct.
Drag to rotate; pinch or use the wheel to zoom. Tap a point on the membrane to hear that point's frequency. The space bar starts and stops the sound; the left and right arrows change the frequency by a third of an octave, the up and down arrows change the level by 5 dB.
© 2026 Ahmet Alperen Akbulut, Auditory Scene. All rights reserved. It may not be copied, reproduced or distributed without permission.
Vibration of the eardrum is carried by the ossicles to the stapes. When the stapes pushes the oval window in, the round window bulges out because the fluid cannot be compressed; the pressure difference between the two scalae moves the basilar membrane and the travelling wave begins. The cochlea is drawn here as a straight box; the membrane motion is the same as in the 3D model. (Voss, Rosowski & Peake, 1996; von Békésy, 1960)