The Free, Cross-Platform Sound Editor.
Audacity® is free, open source software for recording and editing sounds. It is available for Mac OS X, Microsoft Windows, GNU/Linux, and other operating systems. Learn more about Audacity… Also check their Wiki and Forum for more information.
To install Audacity open a Terminal window (Applications -> Accessories -> Terminal) and copy+paste the following lines:
sudo add-apt-repository ppa:audacity-team/daily
sudo apt-get update
sudo apt-get install audacity
Some features are:
Record live audio.
Convert tapes and records into digital recordings or CDs.
Edit Ogg Vorbis, MP3, WAV or AIFF sound files.
Cut, copy, splice or mix sounds together.
Change the speed or pitch of a recording.