-(void)viewDidLoad {

    CFBundleRef mainBundle = CFBundleGetMainBundle();
    CFURLRef    soundFileURLRef;
    soundFileURLRef = CFBundleCopyResourceURL(mainBundle, (CFStringRef)@"beat", CFSTR ("mp3"), NULL);
    UInt32 soundID;
    AudioServicesCreateSystemSoundID(soundFileURLRef, &soundID);
    AudioServicesPlaySystemSound(soundID);
}

@interface MyClass : AnyParentClass {
    AVAudioPlayer *audioPlayer;
}

// ...

@end

NSURL *URLForSoundFile = // ... whatever but it must be a valid URL for your sound file
NSError *error;

if (audioPlayer == nil) {
    audioPlayer = [[AVAudioPlayer alloc] initWithContentsOfURL:URLForSoundFile error:&error];
    if (audioPlayer) {
        [audioPlayer setNumberOfLoops:-1]; // -1 for the forever looping
        [audioPlayer prepareToPlay];
        [audioPlayer play];
    } else {
        NSLog(@"%@", error);
    }
}

if (audioPlayer) [audioPlayer stop];

// appDelegate.h
@interface AppDelegate : UIResponder <UIApplicationDelegate>
{
     UInt32 soundID;
}

//appDelegate.m
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    CFBundleRef mainBundle = CFBundleGetMainBundle();
    CFURLRef    soundFileURLRef;
    soundFileURLRef = CFBundleCopyResourceURL(mainBundle, (CFStringRef)@"beat", CFSTR ("mp3"), NULL);
    AudioServicesCreateSystemSoundID(soundFileURLRef, &soundID);
    AudioServicesPlaySystemSound(soundID);


    [NSTimer scheduledTimerWithTimeInterval:lenghtOfSound target:self selector:@selector(tick:) userInfo:nil repeats:YES];
    return YES;
}

-(void)tick:(NSTimer *)timer
{
   AudioServicesPlaySystemSound(soundID);
}