/Library/Audio/Plug-Ins/Components (system-wide plug-ins).~/Library/Audio/Plug-Ins/Components (user plug-ins).To add a new Audio Unit effect, place it in either of the following system plug-in directories: Each time you launch Audacity it will load all Audio Unit effects that it detects. > Audio Units (AU) are a system-level plug-in architecture provided on Mac OS X computers.
See 'How do I install VST plug-ins?' for more information.
Enable 'Rescan VST effects' in the Effects Preferences and restart Audacity when you want to add new effects. >On Windows and Mac, Audacity can load VST effects (but not VST instruments). To install new LADSPA or Nyquist plug-ins, place them in the Plug-Ins folder inside the Audacity installation folder.On Mac OS X, it is usually under 'Applications'.