• Background
  • Instructions
  • Illustration
  • Quiz


In temporal code theory (Wever & Bray, 1937), we determine the frequency of a sound by how fast a neuron fires. The auditory nerve attached to a hair cell will fire at the same point in a sound cycle, thus, the firing rate will match the incoming sound frequency. The fact that the opening of the ion channels is determined by the spread of the stereocilia is how this synchrony between sound cycle and firing rate happens.

In this activity, you can observe match between firing rate and sound cycle for one of the hair cells on the basilar membrane. Changing the frequency of the incoming sound changes the firing rate.


Full Screen Mode

To see the illustration in full screen, which is recommended, press the Full Screen button, which appears at the top of the page.

Illustration Tab


On the Illustration tab, you can adjust these parameters:

Play the Sound: check to start the animation and uncheck to stop the animation.
What Parts of the Ear to Show: Select what part of the ear you wish to examine: the Cochlea, or a single Hair Cell.
Show Vertical Movement: when only a single hair cell is shown, allow or not the vertical motion of the hair cell that results from the basilar membrane.
Show Rotation: when only a single hair cell is shown, show the rotation of the hair cell that results from the basilar membrane.
Frequency (Hz): adjust to see how the cochlea and basilar membrane respond to different frequencies.


Pressing this button restores the settings to their default values and allows you to adjust speed and relative size. It also resets the counter before you can indicate if you have the objects arriving at the same time.