From Audacity Wiki
- Toolbox/Digital Audio - How audio waves are represented as a series of number, and the difference between lossless formats like .wav and lossy formats like 'mp3'.
- Toolbox/Audio Compression - Why you can't 'compress twice' and do better.
- Toolbox/Spectrograms - How sound is represented as frequencies
- Toolbox/Inside the Ear - How the ear works. (includes source separation)
- Toolbox/Inside a Microphone - How a (typical) microphone works
- Toolbox/Echoes and Reverb - Why a church 'sounds different'. (with samples)
- Toolbox/Radians vs Degrees - Why use radians to measure angles
- Toolbox/A Whirlwind Tour of Trigonometry - Sin, Cos, Pythagoras (with links)
- Toolbox/Why Complex Numbers - Why use the square root of -1 in Audio algorithms
- Toolbox/Audacity Classes
- Toolbox/Drawing Waveforms Quickly
- Toolbox/Drawing Spectrograms Quickly
- Toolbox/Cells and Overlays
- Toolbox/Real and Flyweight Widgets