I have been working the same issue for a couple of days.
I have 2 new T9's . I would like to move the heat from one of them into the house for now, and cut the noise.
What works -
Don't do anything. Mining room gets to 100f. Not really a problem. Rigs run 90-96c. Living space too cold with door closed but noise tolerable. Leave the door open house heats up, but noise!
What doesn't -
I started with the 4" adapters on the exhaust. I ran 4" flex house from each to a T then down 4" flex to a register. Fail. Temps too high and they shut down.
Took one out of the equation. Works but temps over 100c.
Set the other with 4" intake from outside. Works but again around 100.
Currently running 4" exhaust to 6" flex. Temps 84 to 94c. Progress. Off to Home Depot for 6" diameter register box! Hoping for not too much noise. Might need one of these
https://www.ebay.com/itm/6-Inch-Inline-Muffler-Noise-Reducer-Silencer-for-Duct-Fan . result = Noise from register but tolerable. Heats room nicely.
I am going to have 6 miners (4 S9's on the way!) I am going to run 4 to 6 inch reducers/increasers to flex duct off of each, to a wall which is in an out of the way place. Unless I find a better answer.
Thanks