Don't be fooled by its basic appearance, Audacity is an excellent audio sweet that can perform a whole heap of impressive functions to rival paid-for alternatives. That's right, despite its rich pedigree and awesome feature set, Audacity is completely free.
So what do you get with it? Well, for starters there's the recording function, which packs so many features that there's not enough space to list them all. You can record audio from both a microphone and from computer playback, while the sample rates go as high as 192,000 Hz (or up to 384,000 Hz for high resolution devices on Mac OS X and Linux). Level meters monitor the volume levels during recording, useful for spotting clipping. There's also support for recording at 24-bit depth on Windows, Mac and Linux.
You can import and export a ton of different file formats, then easily adjust your files with multi-track editing, smooth fading, labelling, syncing and more. And should the unthinkable happen, Audacity has a built-in crash recovery function.
It's clearly not just a simple, basic audio editor, and the wide range of effects and plugins just go to reinforce that. You can remove annoying hissing, humming and other background noises, perfect if you can't guarantee the quality of your recording environment.
Audacity can alter frequencies with its Equalization, Bass and Treble, High/Low Pass and Notch Filter effects, while the volume can be adjusted with ease thanks to the Compressor, Amplify, Normalize, Fade In/Fade Out and Adjustable Fade effects.
And if you feel like getting your hands dirty, there's support for plugins made using the Nyquist programming language, so you can create your own mods and run them in Audacity. There's also support for LADSPA, LV2, Nyquist, VST and Audio Unit effect plug-ins.
Verdict: Amazingly powerful and feature-rich, Audacity is a great free alternative to more expensive audio editors.