I believe I found some more pictures about the case in aan application:http://www.cooldrives.com/quswsa23gmuh.html
This spec list is the nail in the coffin of this particular external case:
* Enclosures has 1- 80-MM Ball Bearing Low Noise temperature controlled Power Supply Fan.
It also has one 80-MM Ball Bearing Low Noise Exhaust fan
* All Four Bays also have independent 20mm-ball bearing fans, to make sure hard drives have constant movment of cool air over and below the drive mechanism.
* Aluminum material construction
That's a total of six
fans, none of which will be quiet (although you can at least swap out the 80mm fans for quiet ones), plus the almost-inevitably resonant aluminum case construction. Adds up to a recipe for noise to me.