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# CHHapticAudioResourceKeyUseVolumeEnvelope

A key for a Boolean value that indicates whether audio file playback fades in and out using an envelope.

```
let CHHapticAudioResourceKeyUseVolumeEnvelope: String
```

## Discussion

Fading, or ramping, the volume of an audio resource can prevent clicks during playback. It’s also useful in cases where the app modulates the envelope to use different attack and release times.

The default value is <doc://com.apple.documentation/documentation/Swift/true>.

---

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