+1 on what AirmetTango said. I usually run mine at 1 or 2.
Cutting back the sensitivity in thick iron helps. The higher sensitivity the more sparky the iron becomes.
Pay attention to how repeatable those signals are. Falsing iron generally doesn't hit consistently, a good target usually will even if handicapped by iron and only in one direction.
Iron does have a different sound. You'll start to pick up on it as you put more time on the machine.
Good luck!
This....^^^^
You just need more experience.
Every detector I try to learn it was the same for me, at first not much is familiar and I dig all kinds of trash and iron...purposely and a lot that just fool me like high falsing iron.
Soon enough I started to understand and dug less and less garbage and more quality treasure.
Same with the Nox, everywhere I hunt is iron, sometimes massive amounts.
I run with between 1 & 4 most of the time and still get falsing but I am slowly learning the difference between good and bad, the more I learn the less garbage I dig...and there are some good iron indicating behavior.
At 9 nobody can say for sure but I say chances are you are missing most targets sitting near or around iron...you just won't see or hear them.
You don't like iron, don't want to hear it and don't want to dig it, we get it, but I don't think there are any magical detectors out there that will knock out iron and then act like it isn't there, all will be affected by iron whether you disc it out or in the case of the Nox turn up the bias high.
This is no miracle machine, it won't silence iron completely and it is not totally perfect at dealing with masking but it is extremely good at it and gets even better when you learn to understand it well.
A bit more experience than have now.
This guy says it, you have to find your own level you are comfortable with but you still have to learn more and you will always dig some iron no matter what.
Or at least dig some iron...a lot of those iffy,on the border, is it iron or isn't it iron signals might not produce positive results if you dig them but a few just might shock and thrill you.