2 of the same fan blowing air in over the heatsink but there is a noise like
a variable direction wind or slightly gusty wind as though one fan has a
bearing problem.
It would seem one fan is fighting the other to some extent, significant ? or
just one of those things ? .
I was thinking of putting a dividing baffle between the 2.

Disconnecting each in turn and they run perfectly normally with no change of
sound. I may dig out a strobe if i can remember where it is and see if the
blade speed does vary in the double active case.

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/