• Background
  • Instructions
  • Illustration
  • Quiz


The frequency of a sound stimulus refers to the number of cycles in the sound wave that occur in 1 second. The perceptual correlate of frequency is pitch. Tones that have low frequencies are heard as being low in pitch, whereas tones that have high frequencies are heard as high in pitch. We define frequency as the number of cycles in a sound stimulus that occur in 1 second. Pitch is the subjective experience of sound that is most closely associated with the frequency of a sound stimulus.

In this illustration, you can play one octave of a piano keyboard and both hear the tone and see its frequency. This keybaord will only play a pure tone that is associated with the pitch of each key on the piano starting at middle C.


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


Below is a list of the ways that you can alter the illustration. The settings include the following:

Keyboard: click or touch a key to play the tone associated with that key. The tone lasts as long as the click or touch. The graph will plot that frequency until the next tone is played.
Show Intensity: If checked, draw a vertical line from the 0 value to the first peak. The height of this line is the intensity or amplitude of that wave.
Show Frequency: If checked, draw a line connecting the first two peaks of the wave. The longer the line, the lower the frequency.


Pressing this button restores the settings to their default values.