I have two Access Points on my Network. One a few feet away (through a wall) and that measures about 50 db and the other is two floors below and two rooms over and that measures 85 db. Hope that shows you how it works.
I look at the graphs of signal strength vs time. I note that on a strong signal the s/n is pretty constant but on a weak signal the s/n varies (sometimes by quite a lot). I suppose it's like listening to the radio on a weak distant transmiter compared to a stronger local one. Hope you are all sorted!