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How to create 3D audio sound using SKAudioNode

Paul Hudson       @twostraws

3D audio is a feature where a sound is dynamically altered so that listeners think it comes from a particular location. Obviously they are looking at a flat 2D screen ahead of them, but using some clever mathematics iOS can make sounds "feel" like they are behind you, or at a more basic level adjust the panning so that sounds come from the left or right of the user's audio device.

As of iOS 9.0, you get these features for free: all you need to do is create an SKAudioNode for your sound and set its isPositional property to be true. That's it – iOS will automatically use the position of the node to adjust the way its audio sounds, and it even adjusts the audio as you move it around.

To give you a working example, this creates an audio node from a file called music.m4a (you'll need to provide that), then makes the audio move left and right forever. If you listen to this using headphones (which is the only effective way for 3D sound to work on iOS devices) you'll really hear a pronounced panning effect.

override func didMove(to view: SKView) {
    let music = SKAudioNode(fileNamed: "music.m4a")
    addChild(music)

    music.isPositional = true
    music.position = CGPoint(x: -1024, y: 0)

    let moveForward = SKAction.moveTo(x: 1024, duration: 2)
    let moveBack = SKAction.moveTo(x: -1024, duration: 2)
    let sequence = SKAction.sequence([moveForward, moveBack])
    let repeatForever = SKAction.repeatForever(sequence)

    music.run(repeatForever)
}

Available from iOS 9.0

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