The 40TB Mobius 5-Bay/Thunderbolt produces a loud hum.
The loud hum that comes from the 40TB Mobius 5-Bay comes from the accumulated noise of the Seagate 8TB hard drives, particularly when the drives are in an idle state. The following video was sent to us by an Oyen Digital customer.
https://www.youtube.com/watch?v=mQKOppqkW8Y
This sound has also been noticed in other types of enclosures as well, such as the ones found in these videos:
https://www.youtube.com/watch?v=RSIuicB00ho
It is common for this to happen and doesn't indicate an issue with the Mobius or the hard drives. The noise will sometimes subside after a minute or so.