The name of the sound file to play when a notification arrives.
- iOS 8.0+
- macOS 10.10+
- UIKit for Mac 13.0+Beta
- watchOS 3.0+
This property contains the string used to locate a sound file in your app’s bundle. That sound file is played as an alert when a push notification arrives on the user’s device. If the specified sound file does not exist, or if you specify the string
default for this property, the system plays the default alert sound.