--- title: AUAudioUnit framework: audiotoolbox role: symbol role_heading: Class path: audiotoolbox/auaudiounit --- # AUAudioUnit A class that defines a host’s interface to an audio unit. ## Declaration ```swift class AUAudioUnit ``` ## Mentioned in Adding Parallel Real-Time Threads to Audio Workgroups Rendering Spatial Audio from Bluetooth headphones ## Overview Overview Hosts can instantiate either version 3 or version 2 audio units with this class, and to some extent control whether an audio unit is instantiated in-process or in a separate extension process. Version 3 audio units should subclass the AUAudioUnit class. Version 3 audio unit components can be registered in the following ways: Package the component into an app extension containing an AudioComponents Info.plist entry. The principal class must conform to the AUAudioUnitFactory protocol, which will typically instantiate an AUAudioUnit subclass. Call the registerSubclass(_:as:name:version:) method to associate a component description with an AUAudioUnit subclass. Use the convention :