I live in SoCal so we don't need heaters much over here, but for the sake of testing I put mine on "HI" and let it run for a while. It's quiet as a mouse outside the car, inside the blower fan is louder than anything else in the car by far.
For the record my car just took the .7 update.
Also, the (refresh) heater heats the interior better than my previous 2 Model S's that were a 2014 & 205.