This java applet is a simulation of waves in a rectangular membrane (like a drum head, except rectangular), showing its various vibrational modes. To get started, double-click on one of the grid squares to select a mode (the fundamental mode is in the upper left). You can select any mode, or you can click once on multiple squares to combine modes. Also try clicking on the membrane itself and dragging up or down.

Full Directions.

Full screen version.

Java Version.

More applets.

Huge thanks to Bob Hanson and his team for converting this applet to javascript.