If it was quiet before, as said you can attempt to clean it but odds are it needs to be REPLACED.
If you need to REPLACE it, contact Sony. You MAY be able to buy a different model but you need to know the basic details if you want to go to Newegg or wherever to look for one (get a quality one such as a Noctua if possible):
a) PWM or Voltage?
b) size? (i.e. 92mm)
d) Variable? (probably. Such as 500RPM to 1800RPM though it need not be exact)
e) Voltage? (probably 12V I believe but confirm)
FAN CONTROL SOFTWARE:
Fan control software varies in its setup and may not require any BIOS settings to be changed but here's the basics:
a) BIOS (see if enable/disable settings exist)
b) SOFTWARE (see support site for software downloads for you computer if this software isn't on your PC).
c) Enter software and set a Fan Profile (should be at a LOW speed such as 50% then speed up as it gets hotter.)
EXAMPLE: 50% at 40degC, ramp up to 100% at 80degC