Default Ringtone on a VOIP app in iOS

Question

I'm trying to find a way to use the default ringtone of an incoming call on an iPhone device.

Currently, I'm using the AVAudioplayer, i.e.

NSURL *url=[NSURL URLWithString:@"CustomSound"];
AVAudioPlayer *aplayer=[[AVAudioPlayer alloc] initWithContentsOfURL:url error:NULL];
aplayer.numberOfLoops=-1;
[aplayer play]

Is it possible to find the default Ringtone sound of the user and play it?

Thanks