---
title: kSpeechPhonemeCallBack
framework: applicationservices
role: symbol
role_heading: Global Variable
path: applicationservices/kspeechphonemecallback
---

# kSpeechPhonemeCallBack

Set the callback function to be called every time the Speech Synthesis Manager is about to generate a phoneme on the speech channel.

## Declaration

```swift
let kSpeechPhonemeCallBack: CFString
```

## Discussion

Discussion The value associated with this property is CFNumber object whose value is a pointer to an application-defined phoneme callback function, whose syntax is described in SpeechPhonemeProcPtr. Passing a CFNumber object that contains the value NULL for the value of this property disables the phoneme callback function. This property works with the SetSpeechProperty(_:_:_:) function.