The SSL 11u computer rack was always noisy with all those many fans giving out their characteristic sound. They are directly fixed into a large metal box which, in turn, is housed in a large metal 19" rack hence all the resonance. Perhaps there could be 15-19 fans giving it some gun at any one point (11u rack, 1 computer and 2 console PSU's plus a changeover unit perhaps, especially if you have a larger console?).
How about mounting the fans via rubber grommets (this was done by SSL at some point) to provide some isolation from the computer rack? Then, fit some more grommets or nylon bushes to the computer rack M6 fixing positions in the 19" rack and also put some rubber or other material on the computer rack shelves. Also, position the whole 19" rack off the hard floor area on some form of softer material. Try to isolate the fans from the 19" units and also the units from the rack (direct metal to metal contact will resonate more when the fans are on and vibrating!).
Basically, any fixing screws need to be isolated, via rubber grommets and/or plastic bushes from the fastenings they are screwed into.
The SSL computer 19" rack should be in a separate place (machine room?) to the console behind closed doors of course!
Hope this helps from Jim Lassen