Which fan is causing the sound the power supply fan on the top or the Processor fan inside the computer tower?
Try and update the computer with the latest BIOS update for your computer from support.dell.com.
If still problem persists, Reseat the power supply connection to the motherboard(Big white Connector)
Reseat Heatsink Assembly if its the processor fan.
If this still does not fix the issue. you might be having a bad processor fan or power supply fan and need to replace it..
Its also gud to use a blower to do a dusting inside the computer.
Thanks for the quick response. The fan is the processor fan beside the heatsink. I have used compressed air to try and clean out any dust that is around but the issue still happens. I have also updated the BIOS, but have not reseated the heatsink. If I reseat the HS and the problem still occurs do you think I just need a new fan?
Replacing the entire Heatsink assembly along with fan will be best. as replacing only the fan might result in having the same issue if it is the jack of the assembly that is the root cause of the problem.
I recommend replacing both. You can get it done FOC(Free of charge) if your system is still in warranty.