Audacity

Audacity is an open source, cross-platform audio editor and recorder. Audacity can record and play sounds and import and export WAV, AIFF, MP3, and OGG files. Edit your sounds using cut, copy, and paste features (with unlimited undo functionality), mix tracks, or apply effects to your recordings. Audacity also has a built-in amplitude-envelope editor, a customizable spectrogram mode, and a frequency-analysis window for audio-analysis applications.

• Equalization effect now split into two effects, Filter Curve and Graphic EQ.
• Presets (using manage button) now active/working.
• Can now have two points at same frequency for steep steps.
• 'What you hear is what you get' for exports.
• Leading silence (blank space) not skipped over in exports.
• Quality setting on AAC/M4A exports.
• Removed Nyquist Workbench (use built-in nyquist features).
• Removed Vocal Remover (use Vocal Reduction).
• Removed On-Demand aliased files (copy files instead).
• Removed 'Normalize on Load' (Normalize as needed on export, instead).
• Over 150 bugs fixed since v.2.3.2