Audacity X 2.0.0 RC 4 / 1.3.14 Beta
Audacity allows you to record sounds, play sounds, import and export WAV, AIFF, and MP3 files, and more.
Built-in effects include Bass Boost, Wahwah, and Noise Removal, and it also supports VST plug-in effects.
Use it to edit your sounds using Cut, Copy and Paste (with unlimited Undo), mix tracks together, or apply effects to your recordings. It also has a built-in amplitude envelope editor, a customizable spectrogram mode and a frequency analysis window for audio analysis applications.