My rack server was destroying my eardrums with the fan speeds being too high. I plan to replace the fans with Noctua's, but in the meantime this fix works great. It's not silent, but much quieter.

Run these commands inside of IDrac SSH

racadm set system.thermalsettings.FanSpeedOffset 255
racadm set system.thermalsettings.ThirdPartyPCIFanResponse 0
racadm set system.thermalsettings.ThermalProfile 2

That's it! Still a little noisy but tolerable.