Can someone tell me why this is leaking? I am using CFRelease(), which I thought releases CFURLRef soundFileURLRef

**Call to function 'CFBridgingRetain' returns a Core Foundation object with a +1 retain count  

Object leaked: allocated object is not referenced later in this execution path and has a retain count of +1**

```
  -(void) playGuitarNote:(NSString *)noteVal {

    AudioServicesDisposeSystemSoundID(soundId);
    CFBundleRef mainBundle = CFBundleGetMainBundle();
    CFURLRef soundFileURLRef = CFBundleCopyResourceURL(mainBundle,CFBridgingRetain(noteVal), CFSTR("aiff"), NULL);
    AudioServicesCreateSystemSoundID(soundFileURLRef, &soundId);
    AudioServicesPlaySystemSound(soundId);
    CFRelease(soundFileURLRef);
    noteVal = nil;

}

```