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# Audio Route Change Reasons

Identifiers for the various reasons that an audio route can change while your app is running.

## Discussion

You encounter these identifiers as values in the <doc://com.apple.documentation/documentation/CoreFoundation/CFDictionary> object passed to your property listener callback function when it is listening for audio route changes. See the description for [`kAudioSessionProperty_AudioRouteChange`](/documentation/AudioToolbox/kAudioSessionProperty_AudioRouteChange).

## Topics

### Constants

[`var kAudioSessionRouteChangeReason_Unknown: Int`](/documentation/AudioToolbox/kAudioSessionRouteChangeReason_Unknown)

The audio route changed but the reason is not known.

[`var kAudioSessionRouteChangeReason_NewDeviceAvailable: Int`](/documentation/AudioToolbox/kAudioSessionRouteChangeReason_NewDeviceAvailable)

A new audio hardware device became available; for example, a headset was plugged in.

[`var kAudioSessionRouteChangeReason_OldDeviceUnavailable: Int`](/documentation/AudioToolbox/kAudioSessionRouteChangeReason_OldDeviceUnavailable)

The previously-used audio hardware device is now unavailable; for example, a headset was unplugged.

[`var kAudioSessionRouteChangeReason_CategoryChange: Int`](/documentation/AudioToolbox/kAudioSessionRouteChangeReason_CategoryChange)

The audio session category has changed.

[`var kAudioSessionRouteChangeReason_Override: Int`](/documentation/AudioToolbox/kAudioSessionRouteChangeReason_Override)

The audio route has been overridden.

[`var kAudioSessionRouteChangeReason_WakeFromSleep: Int`](/documentation/AudioToolbox/kAudioSessionRouteChangeReason_WakeFromSleep)

The device woke from sleep.

[`var kAudioSessionRouteChangeReason_NoSuitableRouteForCategory: Int`](/documentation/AudioToolbox/kAudioSessionRouteChangeReason_NoSuitableRouteForCategory)

There is no audio hardware route for the audio session category.

[`var kAudioSessionRouteChangeReason_RouteConfigurationChange: Int`](/documentation/AudioToolbox/kAudioSessionRouteChangeReason_RouteConfigurationChange)


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