Some may be interested in my sound levels, which don't actually vary that dramatically despite me not being happy with he constant whirr of the fans at Apple's minimum of 1320. I am only using an app on my iPhone, so theses aren't going to be terribly accurate, but at least give an idea of the differences. I used the NIOSH app.
So, 1m min front of the Mac Studio, my room measure 25.6dB maximum. From he same position with he fans at 1320, it is 27.1dB Max, so only a tiny increase. With fans at 1100, it is 25.8dB max, so pretty much the same as my room, and the reason I then cannot hear it much. So yes, there is less than 2dB difference from this distance, which on paper would certainly look like hardly anything. Yet, to my ears, it is difference enough - so all definitely subjective!
For info, holding the meter right up to the front of the Mac, the readings were 29.3dB max at 1100 and 33.8dB max at 1320 - so much more of a difference.
If anyone is interested, I can do some recordings with my Tascam portable recorder comparing room with different fan speeds