This happened a few years ago but now has returned.I've been told I have high water pressure,but it's just the one low flow toilet that makes it.I have to turn off water for now,and was hoping not to call a plumber.
Thanks.

What is your water pressure? If you do not know go buy a small pressure gauge and bib at the hardware store and attach to your garden spigot. Should be in the ballpark of 45 psi

Agree with Harold. Adjust water pressure first.

The noise is most likely generated by either Fill Valve or Angle Stop. Do this: Close and Open angle stop ( the valve supplying toilet with water ). See if that helped. Then, make sure your supply line is not kinked. Also, there may be debris in fill valve. Close water supply to the toilet. Then, depending on what type of fill valve you have, I would take it apart and flush it clean. Reinstall and see if that helped. Back to you. Milo

Thanks for your quick response.I got a gauge and it shows 100 psi!
So I guess I should have a Pressure Regulator installed?

100 psi is high, If you don't have a PRV you would need to install one, Please read the following.

What is considered normal water pressure? There really is no such thing as "normal" water pressure. Since water pressure is influenced by the elevation of the reservoir that serves your neighborhood versus the elevation of your water meter, water pressure varies from property to property. Water pressure in the District typically ranges from 45 - 125 psi; however, typical residential systems are designed to function best under a pressure of 40 - 60 psi. If the water pressure entering you home exceeds this level, you should install a pressure regulator in the line to reduce the pressure to an acceptable range. This protects your equipment and piping in your home from damage from excess force exerted by the water. Symptoms of high pressure include "clanging" or "rattling" of pipes that occur when a faucet, dishwasher, or washing machine shuts off; water heater pressure relief valve malfunctions, and reoccurring leaks. The symptom of low pressure is typically a noticeable reduction of flow.