• Background
  • Instructions
  • Illustration
  • Quiz


Think of what happens when you clap your hands. The pressure of your hands against each other compresses the air between them, creating the pressure wave. This compression of the air between your hands causes the air molecules to collide with other air molecules in each and every direction around your hands, which then collide with air molecules farther away from your hands, and so on and so forth. As the air molecules are compressed in each area of space, just behind them is a small area in which the air pressure is lower because some of the molecules have been pushed forward. Thus, sound consists of pockets of higher pressure air followed by pockets of lower pressure air. Changes in air pressure propagate out- ward from the original source of the disturbance, in this case your hands clapping.

In this activity, you can play a click and then observe the sound wave propagate through simulated air molecules.


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:

X Position of Sound Source: move the brown dot horizontally to change where the sound begins.
Y Position of Sound Source: move the brown dot vertically to change where the sound begins.
Number of Molecules: choose the number of air molecules to simulate.
Sound Speed: adjust how fast the sound travels through the simulated air molecules.


Pressing this button restores the settings to their default values.