How loud is the Ubiquiti UDM-Pro?

I had some time on my hands this evening, so I figured it was as good a time as any to take the Ubiquiti Unifi Dream Machine Pro (UDM-Pro) out of the rack and put it in a quiet place to record how loud it is generally, and at maximum fan speed. Unfortunately, while I was at it, I found another issue with the device. Fortunately, after some messing about I was able to discover why it wouldn’t boot, and was able to document how loud it gets.