# Core features

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The Video SDK for iOS lets users speak and hear each other in a session over VoIP using their device's microphone and speaker. Users who can't connect over VoIP can dial in by phone. For more information, see [Public Switched Telephone Network (PSTN)](/docs/video-sdk/ios/pstn/).

The core controls let you connect to audio, mute and unmute, and disconnect. For host-only controls, see [Host audio controls](/docs/video-sdk/ios/audio/host-controls/).

> Before using audio controls, you must **request permission to use the microphone**. Add an `NSMicrophoneUsageDescription` entry to your `Info.plist` and request permission at runtime. For details, see [Requesting authorization to capture and save media](https://developer.apple.com/documentation/avfoundation/capture_setup/requesting_authorization_to_capture_and_save_media).

The `ZoomVideoSDKAudioHelper` provides the methods used to manage a user's audio. Before changing any audio state, check whether the user is already connected to audio by reading the user's `ZoomVideoSDKAudioType`.

```swift
// Get the user's audioStatus.
if let audioStatus = user.audioStatus() {
    // Get the user's audioType.
    let audioType = audioStatus.audioType
}
```

```objectivec
// Get the user's audioStatus.
ZoomVideoSDKAudioStatus *audioStatus = [user audioStatus];
// Get the user's audioType.
ZoomVideoSDKAudioType audioType = [audioStatus audioType];
```

`audioType` is one of the values defined on `ZoomVideoSDKAudioType`.

| Value                             | Meaning                                                                                                            |
| --------------------------------- | ------------------------------------------------------------------------------------------------------------------ |
| `ZoomVideoSDKAudioType_None`      | The user is not connected to session audio.                                                                        |
| `ZoomVideoSDKAudioType_VOIP`      | The user is connected over VoIP (microphone and speaker).                                                          |
| `ZoomVideoSDKAudioType_Telephony` | The user is connected by phone dial-in. See [Public Switched Telephone Network (PSTN)](/docs/video-sdk/ios/pstn/). |

## Connect to audio

If the user is not already connected, connect to the audio through the `ZoomVideoSDKAudioHelper`.

```swift
if audioType == .none {
    // User's audio is not connected.
    if let audioHelper = ZoomVideoSDK.shareInstance()?.getAudioHelper() {
        // Connect the user's audio.
        audioHelper.startAudio()
    }
} else {
    // User is already connected to audio.
}
```

```objectivec
if (audioType == ZoomVideoSDKAudioType_None) {
    // User's audio is not connected.
    ZoomVideoSDKAudioHelper *audioHelper = [[ZoomVideoSDK shareInstance] getAudioHelper];
    if (audioHelper) {
        // Connect the user's audio.
        [audioHelper startAudio];
    }
} else {
    // User is already connected to audio.
}
```

## Mute and unmute a user

Once connected, you can mute a user's audio by calling `muteAudio` with the associated `ZoomVideoSDKUser`.

```swift
if let audioHelper = ZoomVideoSDK.shareInstance()?.getAudioHelper() {
    audioHelper.muteAudio(user)
}
```

```objectivec
ZoomVideoSDKAudioHelper *audioHelper = [[ZoomVideoSDK shareInstance] getAudioHelper];
if (audioHelper) {
    [audioHelper muteAudio:user];
}
```

Unmute a user's audio in the same way using `unmuteAudio`.

```swift
if let audioHelper = ZoomVideoSDK.shareInstance()?.getAudioHelper() {
    audioHelper.unmuteAudio(user)
}
```

```objectivec
ZoomVideoSDKAudioHelper *audioHelper = [[ZoomVideoSDK shareInstance] getAudioHelper];
if (audioHelper) {
    [audioHelper unmuteAudio:user];
}
```

When the local user is the session host, muting and unmuting behave differently for remote users. For more information, see [Host audio controls](/docs/video-sdk/ios/audio/host-controls/).

## Disconnect from audio

To disconnect completely from audio, use `stopAudio`. Use this only when the user explicitly disconnects. To silence the user temporarily, use `muteAudio` instead.

```swift
if let audioHelper = ZoomVideoSDK.shareInstance()?.getAudioHelper() {
    audioHelper.stopAudio()
}
```

```objectivec
ZoomVideoSDKAudioHelper *audioHelper = [[ZoomVideoSDK shareInstance] getAudioHelper];
if (audioHelper) {
    [audioHelper stopAudio];
}
```