Yes, fans are noisy, but in most cases they should ramp up to full during boot and then slow down.
Did you notice a recent increase in the noise?
Is it in a hotter location that previously?
I would suggest accessing the Cisco Integrated Management Console (CIMC) to see if you have any hardware warnings or failures.
See the link below on how to configure it, if you haven't. You'll likely have more issues with getting a device functional with Flash.
https://content.cisco.com/chapter.sjs?uri=%2Fsearchable%2Fchapter%2Fwww.cisco.com%2Fcontent%2Fen%2Fus%2Ftd%2Fdocs%2Fnet_mgmt%2Fcisco_secure_access_control_system%2F5-4%2Finstallation%2Fguide%2Fcsacs_book%2Fcsacs_hw_ins_ucs.html.xml#46885
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