Köszi, közben ezt találtam én is! :-]
If using AHCI or Legacy controller mode, fan noise will occur. There is no possibility in lowering the fan speeds in this modes to a lower value. It is going to be BIOS/iLO safe ranges.
The solution is "to configure the B120i in RAID mode. That would mean configuring at least one disk as a RAID-0 array." The end result, reportedly, is that the fan speed drops from about 37~39% to 22%.