ios – 使用AVFoundation有没有办法在swift 2.0中只用耳机的一只耳朵播放声音？

import UIKit
import AVFoundation

class ViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view,typically from a nib.
        testSound()
    }

    var audioPlayer = AVAudioPlayer()
    let alertSound = NSURL(fileURLWithPath: Bundle.main.path(forresource: "checkoutScAnnerBeep",ofType: "mp3")!) // If sound not in an assest
     //let alertSound = NSDataAsset(name: "checkoutScAnnerBeep") // If sound is in an Asset

    func testSound(){
        do {
            //        audioPlayer = try AVAudioPlayer(data: (alertSound!.data),fileTypeHint: AVFileTypeMPEGLayer3) //If in asset
            audioPlayer = try AVAudioPlayer(contentsOf: alertSound as URL) //If not in asset
            audioPlayer.pan = -1.0 //left headphone
            //audioPlayer.pan = 1.0 // right headphone
            audioPlayer.prepareToPlay() // make sure to add this line so audio will play
            audioPlayer.play()
        } catch  {
            print("error")
        }

    }

}