You can check out all your gear and it's bonuses using the Unity companion app, and I noticed that some gear has a +% effect and some a -%.
I'm curious to know if my gear is causing me to be louder, looking at the screenshot. However, it's the Phantom set, which includes more lock picks and overall gives a large bonus to your Stealth attribute, so why would it make me louder?
If it's a positive bonus, why isn't is a -% to noise?
