Handheld Learning Forum

Here is a free one for PC/Mac/Linux/Unix that many of you probably already know about: Audacity

http://audacity.sourceforge.net

Make sure to download the app as well as the lame plug-in for Windows and Mac, which allows you to export your files as mp3. It's very easy to set up and use.

Mark is right.  I love this program.  This is an awesome piece of freeware.  Does tons for changing and converting audio (one downside: can't convert midi files to another form).

We have done several workshops where teachers create digital stories w/ narration, images, video, etc. and we do all of our voice-over recordings and editing in this; as opposed to a costly product like SoundForge or some other application where, while it can do the job, the learning curve is too great for short term use.

One of the coolest things is transforming voices: you can take an adult male voice, adjust the pitch and speed, and have it sound like it was recorded by a 5 year old girl.  (Graham, insert your joke about my manliness here. :) )

I have also used it for our Academic Olympiad competition where students have to identify a piece of music, but I play the track entirely backwards (amazingly enough the theme to The Simpson's TV show sounds the same forwards and backwards ;) ).  The kids love trying to figure these out.  A little "thinking outside the box" (or the box is backward in this case).  Takes a good ear and some serious concentration to listen to the patterns in the US National Anthem and play them backward in your mind.

(http://www.goldwave.com/images/inclogo.gif)

i luv goldwave - its ace - It even has an Expression Evaluator which allows sound to be generated from almost any equation.
For example, to generate a simple sine wave, the following can be entered:

    sin(2*pi*f*t)

General expressions for sine, triangle, and square waves are already provided, plus expressions for dial tones, effects, and noises.

and you can edit too, also has great add on modules which is great for all developers.