I think the fan is rather noisy, when owrated in otherwise quiet room. I am running it in an environment with a new M1 MacMini, which does not have a fan at all. As the OWC was the only source of noice in my office, I decided to relocate it to the room across the wall. The fan runs all the time and at constant speed.

The fan runs continuously and at the same speed, when connected to a computer. I would not call it "noisy" but it is clearly audible, and might be disturbing for sensitive persons in a very quiet environment. I got used to it, even if I would have preferred a silent unit. It is difficult to place it far from the computer due to the short length of the TB3 cable provided with it. Note: my MacBook Pro M1 Max remains completely silent and the bay itself contains only SSD, therefore the fan is the only source of noise in my configuration.. Out of topic but may be interesting: it is connected to the Mac over a OWC TB4 Dock and I am absolutely satisfied with the performance.

It does emit some noise and it does so all the time wile it is on. It's a low decibel hum noise, less disturbing than the fans kicking in on my 2018 Macbook Pro.

I never realized any dominant fan noise.