Используйте AVAudioPlayer:
NSString *path = [[NSBundle mainBundle] pathForResource:@"sound" ofType:@"mp3"];
AVAudioPlayer *audioPlayer = [[AVAudioPlayer alloc ] initWithContentsOfURL:[NSURL fileURLWithPath:path] error:NULL];
audioPlayer.numberOfLoops = -1; // infinite loops
[audioPlayer play];
Это делает работу.