Toilet makes a terrible noise

[arriba59]

Our home is 12 years old and we've never had a plumbing problem. Beginning 3 days ago, whenever we flush the toilet in the master bathroom we hear a loud noise coming from under the house. I would describe it as a pulsing, grinding, almost "swishing" sound. It lasts about 20 seconds until the toilet refills. (It is extremely loud) This does not happen when the other toilet is flushed, when faucets are running, or when the washer is in use. Our pipes are not frozen and there are no leaks that we can see. Water pressure is normal.

We're stumped!

 

[Terry]

It's either the shutoff at the wall, (Open the valve all the way)

Or the fill valve (Repair or replace)