Oreo always howls when the police, ambulance, or fire trucks go by with their sirens on. I have always felt sorry for him when this happens, because I have always thought it's because the sirens hurt his ears.

Is this correct? (I see other people on here seem to think it's humorous when their dogs howl when the police or fire trucks or ambulances go by with their sirens on.) Is it possible that the sirens aren't hurting his ears? What other reason would he have to howl when he hears sirens nearby? That's the only time he ever does it.