My iPhone 32GS makes a noise that is not connected to any of the apps I have. The whoop is unconnected to any announcement, warning, notification, or messages. It is random, LOUD and makes me jump out of my skin. Could it be a virus or something? Any help in assisting me find out what the heck is causing the noise would be greatly appreciated. The noise itself is a triple whoop, reminiscent of a a police car.