That is most likely the atty cooking the
juice. If you have an adjustable voltage see if tuning it down diminishes it. I'm use and Ego twist and Provari and with my cartys I get a sizzle sound I don't with the CE. I have never gotten that on my ego t. If you run at too high a voltage the atty will get hot sometimes too hot if the Ohm are too low. If the vapor burns a lot at a higher voltage it may be too high.
I'm still a newbie but i
vape a lot so that is just what I have noticed so far.