Audacity

Audacity is a free, easy-to-use audio editor and recorder for Windows, Mac OS X, GNU/Linux, and other operating systems. You can use Audacity to:

Record live audio.
Convert tapes and records into digital recordings or CDs.
Edit Ogg Vorbis, MP3, and WAV sound files.
Cut, copy, splice, and mix sounds together.
Change the speed or pitch of a recording.
Import and export WAV, AIFF, AU, and Ogg Vorbis files.
Import MPEG audio (including MP2 and MP3 files) with libmad.
Export MP3s with the optional LAME MP3 encoder library.
Create WAV or AIFF files suitable for burning to CD.
Import and export all file formats supported by libsndfile.
Open raw (headerless) audio files using the ??Import Raw?? command.


It supports all common editing operations, plus it will mix tracks and let you apply plug-in effects to any part of a sound. It also has a built-in amplitude envelope editor, a customizable spectrogram mode and a frequency analysis window for audio analysis applications.