---
title: kSpeechVolumeProperty
framework: applicationservices
role: symbol
role_heading: Global Variable
path: applicationservices/kspeechvolumeproperty
---

# kSpeechVolumeProperty

Get or set the speech volume for a speech channel.

## Declaration

```swift
let kSpeechVolumeProperty: CFString
```

## Discussion

Discussion The value associated with this property is a CFNumber object that specifies the speech channel’s speech volume. Volumes are expressed in floating-point values ranging from 0.0 through 1.0. A value of 0.0 corresponds to silence, and a value of 1.0 corresponds to the maximum possible volume. Volume units lie on a scale that is linear with amplitude or voltage. A doubling of perceived loudness corresponds to a doubling of the volume. This property works with the CopySpeechProperty(_:_:_:) and SetSpeechProperty(_:_:_:) functions.