Almost everytime when swinging the coil and I bumped the ground or something on the ground it sounded off with some kind of noise, mostly the same noise everytime it happened. I was set on Pro mode all metal, sensitivity was second from the top. It gound balanced at 81-82. When I turned sensitivity down a couple of noches it did not sound off as much. When I pick up the coil and tap it with my hand it sounded off. Also another question will the AT PRO lose much depth when you drop the sensitivty back? I have not sent the detector back for the upgrade as of yet. What do all of you think??????????????????