Sorry, you need a Java-enabled browser to see the simulation.
You might also want to try this version of the applet, which has sound but requires Java 2.

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.

Explanation how to use the Rectengular Membrane java applet.

Acknowledgement: This applet is courtesy of Paul Falstad.

Version 1.5, posted 21/11/05