# AudioQueuePropertyListenerProc Called by the system when a specified audio queue property changes value. ``` typealias AudioQueuePropertyListenerProc = (UnsafeMutableRawPointer?, AudioQueueRef, AudioQueuePropertyID) -> Void ``` ## Parameters `inUserData` The custom data you’ve specified in the `inUserData` parameter of the [`AudioQueueAddPropertyListener(_:_:_:_:)`](/documentation/AudioToolbox/AudioQueueAddPropertyListener(_:_:_:_:)) function. `inAQ` The recording or playback audio queue that invoked the callback. `inID` The ID of the property whose value changes you want to observe. ## Discussion If you name your callback function `MyAudioQueuePropertyListenerProc`, you would declare it like this: ### Discussion Install this callback in an audio queue by calling the [`AudioQueueAddPropertyListener(_:_:_:_:)`](/documentation/AudioToolbox/AudioQueueAddPropertyListener(_:_:_:_:)) function. For example, say you want your application to be notified, after you call the [`AudioQueueStop(_:_:)`](/documentation/AudioToolbox/AudioQueueStop(_:_:)) function with the `inImmedate` parameter set to `false`, that audio has finished playing. Perform these steps: 1. Define this property listener callback function to listen for changes to the [`kAudioQueueProperty_IsRunning`](/documentation/AudioToolbox/kAudioQueueProperty_IsRunning) property. 2. Install this callback, using the [`AudioQueueAddPropertyListener(_:_:_:_:)`](/documentation/AudioToolbox/AudioQueueAddPropertyListener(_:_:_:_:)) function, in the playback audio queue that you want to monitor. --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)