Best / Proper way to play a short sound - swift

Question

I'm trying to play a short sound in my Swift app.
The sound I want to play :
is very short (less than five seconds) ;
is one of the system sound (ex: sms received) ;
will most likely be played multiple time during the life cycle of my application ;
can be fired two time in less than the sound length time (i.e. fire the first one and a second one is fired before the first finish playing) ;
In addition to this, I would like to :
hear the sound only if the application is active and the "silent mode" is off ;
make the phone vibrate (regardless if silent mode is on or off).
So far, here is what I have :
import AVFoundation
class SoundPlayer {
// Singleton
class var sharedInstance : SoundPlayer {
struct Static {
static let instance : SoundPlayer = SoundPlayer()
}
return Static.instance
}
// Properties
var error:NSError?
var audioPlayer = AVAudioPlayer()
let soundURL = NSURL(fileURLWithPath: NSBundle.mainBundle().pathForResource("sound", ofType: "wav")!) // Working
//let soundURL = NSURL(string:"/System/Library/Audio/UISounds/sms-received1.caf") // Working
//let soundURL = NSURL(fileURLWithPath: NSBundle(identifier: "com.apple.UIKit")!.pathForResource("sms-received1", ofType: "caf")!) // Not working (crash at runtime)
init() {
AVAudioSession.sharedInstance().setCategory(AVAudioSessionCategoryAmbient, error: nil)
AVAudioSession.sharedInstance().setActive(true, error: nil)
audioPlayer = AVAudioPlayer(contentsOfURL: soundURL, error: &error)
if (error != nil) {
println("[SoundPlayer] There was an error: \(error)")
}
}
func playSound() {
if (audioPlayer.playing) {
audioPlayer.stop()
}
audioPlayer.play()
}
}
What I understand there are several ways to play a sound.
The two most common ways seems to be : AVAudioPlayer (like I did) and AudioToolbox.
From there, I'm asking myself three questions :
Which of those two is the most adapted (best / proper) for my situation ? (AVAudioPlayer is working correctly at the moment)
Are we allowed to play a system sound ? (Very small gain in size if in don't add my own sound to the project)
If so, is NSURL(string:"/System/Library/Audio/UISounds/sms-received1.caf") a good way to retrieve the sound ? Any better / proper solution ?
Is there a way to vibrate the phone at the same time the sound is fired ?