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# measurement

A mode that indicates that your app is performing measurement of audio input or output.

```
static let measurement: AVAudioSession.Mode
```

## Discussion

Use this mode for apps that need to minimize the amount of system-supplied signal processing to input and output signals. If recording on devices with more than one built-in microphone, the session uses the primary microphone.

For use with the [`playback`](/documentation/AVFAudio/AVAudioSession/Category-swift.struct/playback), [`record`](/documentation/AVFAudio/AVAudioSession/Category-swift.struct/record), or [`playAndRecord`](/documentation/AVFAudio/AVAudioSession/Category-swift.struct/playAndRecord) audio session categories.

> Important:
> This mode disables some dynamics processing on input and output signals, resulting in a lower-output playback level.

---

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