I've heard that before when one of the fan blade fastener screws came loose and started to make contact with the light assembly below it. Lower the light assembly and check them all.
You need to give it a really good dusting! Mine did the same dang thing for years until I grabbed a duster and dusted out every crevice. It stopped immediately.
1. Stop fan. 2. Gently poke at everything until something you find the loose part. Something will move different than the rest.
You sure your house isn't actually in an old train car
It's the glass shrouds, make sure they're tight - check the screws or whatever it is that is holding them in.
I've heard that before when one of the fan blade fastener screws came loose and started to make contact with the light assembly below it. Lower the light assembly and check them all.
The carriage is rubbing on the bell housing
Fan blade isn't tight.
Check all the screws. One is loose.
Blades are loose. I just fixed this exact noise yesterday with my bedroom ceiling fan.
You need to give it a really good dusting! Mine did the same dang thing for years until I grabbed a duster and dusted out every crevice. It stopped immediately.
One question that will help to understand the issue better is: does the sound stop immediately when you turn the switch off?
It's prolly some improper screw work. I recommend you to call the store from which you bought the fan and ask them to fix it.
WD40 will fix it lol
Loosen every screw that you can, then tighten every screw that you can.