• Background
• Instructions
• Illustration
• Quiz

## Background

Pure tones are simple sine waves at single frequencies. However, in nature, pure tones are virtually nonexistent. Almost all sounds are complex sounds, which consist of mixes of frequencies. These frequencies combine to form a complex waveform. A complex waveform can be broken down into its composite frequencies through a mathematical formula known as Fourier analysis. Fourier analysis is a mathematical procedure for taking any complex waveform and determining the simpler waveforms that make up that complex pattern. The simpler waves used are sine waves. When we do a Fourier analysis, we break down a complex sound into its fundamental frequency and its harmonics. The fundamental frequency is the lowest frequency present in the complex sound and the one that determines the perceived pitch of that sound. The harmonics are all frequencies present in the stimulus that are higher in frequency than the fundamental frequency.

In this illustration, you can play different wave forms and see what frequencies are present in these complex waveforms. In other words, you will see both the waveform and the result of a forier analysis played in real time.

## 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. Waveform: chose one of the six different waveforms to play.
Frequency (Hz): change the frequency of the tone.
Intensity: change the intensity of the tone.

### Reset

Pressing this button restores the settings to their default values.