Swift AVPlayer to ear speaker

I've got a simple audio player that works great. I'm playing a remote URL mp3. My code:

@IBAction func playAudio(sender: AnyObject) {
        let url = self.productAudio
        let playerItem = AVPlayerItem( URL:NSURL( string:url ) )
        player = AVPlayer(playerItem:playerItem)
        player.
        player.rate = 1.0;
        player.play()
}

But the audio is outputed by the loud speaker. How can I do to listen the audio at the ear speaking?

thanks!