Honestly this is the best way to reduce noise of the antminer s9 if you don't have a cooled server room : r/Bitcoin
Antminer S9 noise level? - The most accurate Antminer noise level - like a Train - YouTube
Antminer noise reduction ideas. Just printed this part and added to the output fans, and now I am thinking to add also the same part to the intake fans with a quiet
BITMAIN Water Cooling BTC Miner AntMiner S9 Hydro 18T With Power Supply APW5 Asic Bitecion BCH Miner,Low Noise,Energy Saving!|Block Chain/Miner| - AliExpress
Amazon.com : AntMiner S9 ~13.5TH/s @ 0.098W/GH 16nm ASIC Bitcoin Miner with Power Supply and Cord : Electronics
How to easily lower the noise of Antminer S9 2020 - ASIC BITMAIN DIY - YouTube
ANTMINER S9 NOISE/SOUND LEVEL TEST | CLOSE & FAR RANGE - YouTube