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.
• And more! See the complete list of features.

Audacity is free software, developed by a group of volunteers and distributed under the GNU General Public License (GPL).

link: http://audacity.sourceforge.net/about/