It is very possible that the noise is from the shed.
I would not worry to much unless you see stringy saliva in its mouth or atleast some other sign.
If it were me I would live the substrate alone unless its not great for holding moisture, I like cypress mulch.
I would add damp moss to each hide. I have done this for years in my glass tank holding my ball. During a shed I keep it moist and during other times I allow it to dry out before making it moist again. This will create higher humidity in the hides and since this is where the snake will usually be it benefits from it greatly.