The loudest I've heard from mine sound like 3 shrill whistles blown as hard as they can. Full lung capacity, every atom of oxygen fully dedicated to blasting air into that metal device.
I don’t know decibels, but I lived in an old building in an inner city for several years, and if you are familiar with the sound of pigeons mating on your fire escape or window ledge, it’s about that loud but more shrill.