You can check directly with the manufacture since they sometimes add specific sounds in order to identify problems and they should have their own testing utilities.
I would suggest to make sure you have your data backed up since sounds on within the HDD usually indicate that they are about to fail.
I'm managed to "solve" the problem, at least temporarily:
HDD Guardian was able to modify the S.M.A.R.T attributes of both disks, even in the raid array. I set the AAM & APM to their max value (254) and the drives have stopped clicking ever since. I guess they're constantly spinning at full speed now. I don't think I can make the change to the smart settings permanent though (or set at startup, since the drives reset to their default smart attributes upon reboot).
What I still find odd is that both disks started clicking at the same time. What are the odds of simultaneous disk failure....? This is why I posted in the chipset part of the forum.
for future reference if this should be useful to anyone:
Disabling APM in an intel raid array (raid0)
I created two schduled tasks in windows as administrator to start at boot with smartmontools for Windows
smartctl.exe -s apm,off /dev/csmi3,3
smartctl.exe -s apm,off /dev/csmi3,5
I managed to find the /dev/xxx devices with hdd guardian (both disks of my raid array)