Chemistry station is great for raising the heat, although enough forges/fires/cement mixers going will spawn lots of screamers too. Yes, construction noise too...sneak if you are not looking to draw attention. Same for chopping trees and mining. The workstation produces some noise but should be very little compared to the above.
You can press F8 twice (edit: in debug mode) to see chunk heat and what adds to it. I did some testing, but nothing very rigorous.
Forge when "On" (regardless of whether it is smelting anything) = +6% heat, steady
Torch = +heat gradually over time
Upgrading wood frame through cobble to wet concrete = +0% heat (did not expect this result)
Destroying wet concrete using steel pick = +0.5%
Destroying wood frame using claw hammer = +1.2% heat
Firing pistol = +0.4%
Firing M60 = +0.65%
Above 50% the heat meter turns yellow, meaning maybe that's when the chances of screamer spawns start? Above 80% it turns red. At 100% a screamer will almost always spawn. Possibly it's always always and I just missed one during my testing somehow.
Also, heat seems to linger for a
long time. Over an hour and a half of game time passed after I turned off forges and removed torches and the heat % did not budge. Also also, surrounding chunks appear to get the same heat value as the chunk containing the forges/torches. Needs more testing.
Want a screamer? 14 running forges ought to guarantee it. Or shoot a couple of magazines of M60 - I got a lot of screamers when testing how far sound travels.