Audacity is free, award-winning open source software for recording and editing sound. It runs on Mac OS X, Microsoft Windows, GNU/Linux and other operating systems.

The latest stable release of Audacity is 1.2.6, released on 15 November 2006. As of 13 May 2008, it was the 9th most popular download from SourceForge.net, with over 40 million downloads.[4] Audacity won the SourceForge.net 2007 Community Choice Award for Best Project for Multimedia.[5] Audacity is free software and is licensed under the GNU General Public License version two, but may update to GPLv3 after version 1.4.0.[6]
Some of Audacity’s features include:

Importing and exporting WAV, AIFF, MP3 (via the LAME encoder, downloaded separately), Ogg Vorbis, all file formats supported by libsndfile library
Version 1.3.2 also supports Free Lossless Audio Codec (FLAC)
Recording and playing sounds
Editing via Cut, Copy, Paste (with unlimited Undo)
Multi-track mixing
A large array of digital effects and plug-ins. Additional effects can be written with Nyquist
Amplitude envelope editing
Noise removal
Support for multi-channel modes with sampling rates up to 96 kHz with 24 bits per sample
The ability to make precise adjustments to the audio’s speed while maintaining pitch (Audacity calls it changing tempo), in order to synchronize it with video, run for the right length of time, etc.
The ability to change the audio’s pitch without changing the speed.
Converting cassette tapes or records into digital tracks by automatically splitting one wav (or the other supported types) track into multiple tracks based on silences in the track and the export multiple option.
Multi-platform: works on Windows, Mac OS X, and Unix-like systems (including GNU/Linux and BSD) amongst others.
The latest versions support Windows 98/ME/2000/XP/Vista, but Windows 95 and NT are not supported.[7]

- Fire