Quote (Ghot @ Mar 5 2019 06:01pm)
You can use a wooden spoon or dowel rod as a stethoscope, to find exactly which component is making the noise.
Put one end to ear flap and touch the other end to various parts. The one making the noise will be extremely loud.
I know, I've used that trick several times on cars. It doesn't feel like anything is hitting, it's too constant and it happens even when the fans aren't spinning.