Computer Fan Making Noise
My computer fan is making a lot of noise.
The fan speed in a computer is typically activated by a thermostat that determines how fast the fan needs to be running in order to keep the heat down. You might hear more noise from your computer fans if one fan is not working properly because it would cause the other fans to over compensate. Another reason for fans to run faster is if the thermostat were to become defective. If the processor fan isn't working, this might also cause the computer to heat up resulting in other fans running faster. These characteristics are actually quite similar for desktop computers and notebook computers.
If your fan is making a rattling noise it may be an indication that the bearings or mechanism are failing or worn out.
With most of the above circumstances it would be good to have the computer serviced.