- Apple純正のAudioUnitはファイルとして存在しない
- サードパーティ製のAudioUnitは/Library/Audio/Plug-Ins/Componentsか~/Library/Audio/Plug-Ins/Componentsに有る
だそうです。
Apple純正のものも含めて確認したい場合はauvaltoolを使うと良さげです。
こちらの環境での実行結果は以下の通りです。
$ auvaltool -a
AU Validation Tool
Version: 1.6.1a1
Copyright 2003-2013, Apple Inc. All Rights Reserved.
Specify -h (-help) for command options
aufx bpas appl - Apple: AUBandpass
aufx dcmp appl - Apple: AUDynamicsProcessor
aufx dely appl - Apple: AUDelay
aufx dist appl - Apple: AUDistortion
aufx filt appl - Apple: AUFilter
aufx greq appl - Apple: AUGraphicEQ
aufx hpas appl - Apple: AUHipass
aufx hshf appl - Apple: AUHighShelfFilter
aufx lmtr appl - Apple: AUPeakLimiter
aufx lpas appl - Apple: AULowpass
aufx lshf appl - Apple: AULowShelfFilter
aufx mcmp appl - Apple: AUMultibandCompressor
aufx mrev appl - Apple: AUMatrixReverb
aufx nbeq appl - Apple: AUNBandEQ
aufx nsnd appl - Apple: AUNetSend
aufx nutp appl - Apple: AUNewPitch
aufx pmeq appl - Apple: AUParametricEQ
aufx raac appl - Apple: AURoundTripAAC
aufx rogr appl - Apple: AURogerBeep
aufx sdly appl - Apple: AUSampleDelay
aufx tmpt appl - Apple: AUPitch
aupn ambi appl - Apple: AUSoundFieldPanner
aupn hrtf appl - Apple: HRTFPanner
aupn sphr appl - Apple: AUSphericalHeadPanner
aupn vbas appl - Apple: AUVectorPanner
aumu dls appl - Apple: DLSMusicDevice
aumu msyn appl - Apple: AUMIDISynth
aumu samp appl - Apple: AUSampler
aumu ssyn appl - Apple: SinSynth
aumu synt YMCK - Magical 8bit Plug
aumu Pas2 Demo - __MyCompanyName__: MyInstrument
aumx 3dem appl - Apple: AUSpatialMixer
aumx 3dmx appl - Apple: AUMixer3D
aumx mcmx appl - Apple: AUMultiChannelMixer
aumx mspl appl - Apple: AUMultiSplitter
aumx mxmx appl - Apple: AUMatrixMixer
aumx smxr appl - Apple: AUMixer
aufc conv appl - Apple: AUConverter
aufc defr appl - Apple: AUDeferredRenderer
aufc ipto appl - Apple: AUNotQuiteSoSimpleTime
aufc merg appl - Apple: AUMerger
aufc nutp appl - Apple: AUNewTimePitch
aufc splt appl - Apple: AUSplitter
aufc tmpt appl - Apple: AUTimePitch
aufc vari appl - Apple: AUVarispeed
auou ahal appl - Apple: AudioDeviceOutput
auou def appl - Apple: DefaultOutputUnit
auou genr appl - Apple: GenericOutput
auou sys appl - Apple: SystemOutputUnit
auou vpio appl - Apple: AUVoiceProcessor
augn afpl appl - Apple: AUAudioFilePlayer
augn nrcv appl - Apple: AUNetReceive
augn sspl appl - Apple: AUScheduledSoundPlayer
augn ttsp appl - Apple: AUSpeechSynthesis
auol tmpt appl - Apple: AUTimePitch
auol vari appl - Apple: AUVarispeed
左からタイプ、サブタイプ、製造元、ユニット名、だったと思います。
詳しくはauvaltool -hで確認願います。