Have you ever wondered why a flash unit makes noise?  No, not the kind of noise you get from low light or long exposure star photography.  The audible kind.  The loud kind.  My speedlights make a popping sound when fired and a high-pitched whine when recharging.  Why is that?  In a digital age, when we can put cameras into a silent mode, why is it that my flash is still making noises?  Learn more.