When a player or mob is in both powder snow and lava, a constant "hissing" sound will be heard, as they continually catch on fire and then extinguish. This is louder than the normal extinguishing sound that is heard, and, during my testing, I saw the sound level jump up into the high twenties and low thirties mostly just from this sound.
Hey there!
This appears to be a duplicate of MC-207397 which hasn't yet been resolved. Feel free to add a vote to it, nonetheless.