This sound-wave synthesis tool comes from Paul Fasted's collection of physics applets. Thanks very much to Paul!
This java applet demonstrates Fourier series, which is a method of expressing an arbitrary periodic function as a sum of cosine terms. In other words, Fourier series can be used to express a function in terms of the frequencies (harmonics) it is composed of.
To select a function, you may press one of the following buttons: Sine, Triangle, Sawtooth, Square, and Noise. The function is displayed in white, with the Fourier series approximation in red. You can edit the function directly by clicking on it.
This applet has sound if you are using java 2. If you don't see a "Sound" checkbox, then you should get the Java plug-in.
Download zip archive of this applet. (double-click on index.html to run)
Version 1.6d, posted 4/21/14