Noisy fans could due to obstructions (wire hitting fa blades e.g.) or dirty fans or the fan's bearings are going bad.
With power cord disconnected. I would open your Computer case and make sure all the fans are clean from dust and debris.
Turn each fan with one finger. It should turn easily and smoothly without any noises (checking your bearings) If the Fan noise increases the faster the fan rotates could indicate the bearings are going bad.
There are some Youtube videos that shows how in some fans you can relubricate them to make them less noisy.
Make sure nothing might be hitting the fan blades like a cable or wire.
