Do u have any other gadgets in the cage ? Waterfall, mister etc ? If its coming from your snake, check its nose, do u spot any mukus or bubble ? Is your snake yawning alot ? Coz this may hint that hes have respository problems.

What substrate are you using ?

If the sound is indeed coming from your snake, id take it to vet asap. Theres no knowing till a vet check it.