• Background
• Instructions
• Illustration
• Quiz

## Background

In most sounds several frequencies are present. It is usually the lowest, frequency, the fundamental, that determines the pitch. There is a very interesting phenomenon that happens when the fundamental is removed, or even several of the lowest harmonics as well. The pitch does not change. The frequency that supposedly causes the pitch is absent, but the pitch does not change. The sound changes timbre because of the change in harmonics, though.

You can also experience another interesting phenomenon that shows that in our hearing we do something akin to Fourier Analysis. Try turngin off and on any on of the components. You can pick out that component when, for most listeners, it is lost in the total tone most of the time. It is called Ohm's Acoustical Law and shows,when are attention is drawn to a single frequency, we can pick it out of a complex waveform, much like Fourier Analysis.

In this illustration, you can play a tone and remove the fundamental and the next four harmonics. By humming, you can convice yourself that the pitch does not change.

## Instructions

### 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.

### Settings

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

Play: start the sound. The button will then change to Pause and pressing it again will stop the sound. Restore Components: Turns back on all compotents that have been removed from the combined tone.
Fundamental Frequency: Change the fundamental frequency of the combined tone. All other components will change proportionally.
Remove #:: Removes the indicated component of the combined sound, that is, turns the volume of that component to 0 (0 is the fundamental and it counts up from there).

### Reset

Pressing this button restores the settings to their default values.