# UNNotificationSound The sound played upon delivery of a notification. ``` class UNNotificationSound ``` ## Overview Create a [`UNNotificationSound`](/documentation/UserNotifications/UNNotificationSound) object when you want the system to play a specific sound when it delivers with your notification. To play the default system sound, create your sound object using the [`default`](/documentation/UserNotifications/UNNotificationSound/default) method. If you want to play a custom sound, create a new sound object and specify the name of the audio file that you want to play. For local notifications, assign the sound object to the [`sound`](/documentation/UserNotifications/UNMutableNotificationContent/sound) property of your [`UNMutableNotificationContent`](/documentation/UserNotifications/UNMutableNotificationContent) object. For a remote notification, assign the name of your sound file to the `sound` key in the `aps` dictionary. You can also use a notification service app extension to add a sound file to a notification shortly before delivery. In your extension, create a [`UNNotificationSound`](/documentation/UserNotifications/UNNotificationSound) object and add it to your notification content in the same way that you’d for a local notification. Audio files must already be on the user’s device before the system can play them. If you use a predefined set of sounds for your notifications, include the audio files in your app’s bundle. For all other sounds, the [`UNNotificationSound`](/documentation/UserNotifications/UNNotificationSound) object looks only in the following locations: - The `/Library/Sounds` directory of the app’s container directory. - The `/Library/Sounds` directory of one of the app’s shared group container directories. - The main bundle of the current executable. ### Prepare Sound Resources The system sound facility plays custom alert sounds, so they must be in one of the following audio data formats: - Linear PCM - MA4 (IMA/ADPCM) - µLaw - aLaw You can package the audio data in an `aiff`, `wav`, or `caf` file. Sound files must be less than 30 seconds in length. If the sound file is longer than 30 seconds, the system plays the default sound instead. You can use the `afconvert` command-line tool to convert sounds. For example, to convert the system sound `Submarine.aiff` to IMA4 audio in a CAF file, use the following command in Terminal: `afconvert /System/Library/Sounds/Submarine.aiff ~/Desktop/sub.caf -d ima4 -f caff -v` ## Topics ### Creating Notification Sounds [`default`](/documentation/UserNotifications/UNNotificationSound/default) Returns an object representing the default sound for notifications. [`init(named:)`](/documentation/UserNotifications/UNNotificationSound/init(named:)) Creates a sound object that represents a custom sound file. ### Getting Critical Sounds [`defaultCritical`](/documentation/UserNotifications/UNNotificationSound/defaultCritical) The default sound used for critical alerts. [`defaultCriticalSound(withAudioVolume:)`](/documentation/UserNotifications/UNNotificationSound/defaultCriticalSound(withAudioVolume:)) Creates a sound object that plays the default critical alert sound at the volume you specify. [`criticalSoundNamed(_:)`](/documentation/UserNotifications/UNNotificationSound/criticalSoundNamed(_:)) Creates a custom sound object for critical alerts. [`criticalSoundNamed(_:withAudioVolume:)`](/documentation/UserNotifications/UNNotificationSound/criticalSoundNamed(_:withAudioVolume:)) Creates a custom sound object for critical alerts with the volume you specify. ### Type Properties [`defaultRingtone`](/documentation/UserNotifications/UNNotificationSound/defaultRingtone) ### Type Methods [`ringtoneSoundNamed(_:)`](/documentation/UserNotifications/UNNotificationSound/ringtoneSoundNamed(_:)) --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)