Audacity

Audacity is open-source audio editing software written in C/C++, enabling recording, playing and editing audio files. Audacity can import from, and export to a variety of audio formats (WAV, AIFF, Ogg Vorbis, MPEG, FLAC, AC3, WMA), with support for up to 32-bit samples and 384,000Hz sample rate. It can record live audio from a number of digital and analog sources such as microphones, mixer, digital CDs, USB/Firewire devices or video files. Editing features include various digital effects, spectrum analysis, unlimited undo/redo, sample point redrawing, noise reduction, volume automation/smoothing, MP3 metadata editing, etc. Audacity comes with a built-in plugin manager for adding/removing custom effects and generators.