How are some alarm apps such as Alarmy able to play a sound on iPhone when the app is in the background and the phone is on vibrate

There are few methods to implement this kind of functionality.For reference I recommend this link.

For actually playing the sound while the device’s ringer switch is set to vibrate

First off make sure to include the audio background mode in the capabilities, in order to play audio in the background.

Then,

Swift 4

do {  try AVAudioSession.sharedInstance().setCategory(AVAudioSessionCategoryPlayAndRecord, with: [.duckOthers, .defaultToSpeaker])  try AVAudioSession.sharedInstance().setActive(true)  UIApplication.shared.beginReceivingRemoteControlEvents()} catch {  NSLog("Audio Session error: \(error)")}

Here we set the shared audio session’s category to AVAudioSessionCategoryPlayAndRecord, so that we can play sound, while the device’s ringer switch is set to vibrate.

The .duckOthers is specified to make other audio quieter, if there’s any mixable audio playing, so that our alarm can be heard. You can leave that out or use another option, if you prefer a different behavior.

The .defaultToSpeaker is specified, so that the volume would go to the speaker, where it’ll be much louder and should wake up our user with ease.

beginReceivingRemoteControlEvents makes it so that the app handles the remote control options, like the play/pause buttons on the lock screen, in order to make it easier for our user to mute their alarm, once they wake up.

The way this can be done (I have implemented this in my app) is by starting an AVAudioPlayer and specifying a specific time to play. So:

1. Enable background audio in the app capabilities.

2. Start and audio session with .playback mode, and start a player at the time you like it to play:

   do {      //set up audio session      try AVAudioSession.sharedInstance().setCategory(.playback, options: [.defaultToSpeaker, .duckOthers])      try AVAudioSession.sharedInstance().setActive(true)      //Start AVAudioPlayer      player.play(at: time) //time is a TimeInterval after which the audio will start    }    catch {    ...    }

This does not play silence in the background, which violates Apple's rules. It actually starts the player, but the audio will only start at the right time. I think this is probably how Alarmy implemented their alarm, given that it's not a remote notification that triggers the audio nor is the audio played by a local notification (as its not limited to 30 seconds or silenced by the ringer switch).