Some systems have firmware update for the PSU's, but the 1850 does not.  It is doubtful that something like speedfan could control the integrated PSU fan on a regular system, not to mention one whose hardware it does not know how to talk to.  Servers just aren't quiet, rack systems are worse, and the smaller it is, the noisier.  Also, the older they are, generally, the worse they are.  Not sure there is much else you can do to make it quieter.  Dismantle fan to remove the fan, put it in another room, etc.?
i got an 1850 off of ebay to do some practical networking to go along with my IT program, and was wondering if theres any way to get the psu fans to throttle down, Ive gotten the main fans to get quiet with a esm and bios update, but both my psus continues to run at full blast.  i tried programs like speedfan, but im assuming everything is proprietary because nothing shows up, and i cant find any settings in the bios or server manager. anyone have any thoughts?
poweredge 1850 psu fan noise