Maybe it's the repair shop calling? Sounds bearing like. What model do you have?

Check at the rear of the machine, where the engine sets on the steel square part, and under that part you will find the drive mechanism. There will be a flat round aluminum disc, with a small driven wheel that runs on the disc. It has a rubber "tire" on it, that wears off in time, and if that little wheel has worn off its rubber, there is where you will get the ringing sound. If you find that is true, go to the place that sells them and buy that little wheel.
It will come with the'tire' glued on it.Make sure you install that wheel the correct way. HTH: Rusty J.
Note: Some of the newer discs have a brake lining inside of them, and you may have to remove the brake lining to make it fit the older machines.

"Note: Some of the newer discs have a brake lining inside of them, and you may have to remove the brake lining to make it fit the older machines."

Last I knew, the rubber tired driven wheel was offered both ways, "with and without" liner.

Walt Conner

Well, Walt, the place where i bought the wheel, didn't have one as old as the wheel already on my machine, to fit my 1983 year model, but they told me i could/ may have to/remove or not install (whatever) the brake lining furnished with the new wheel/disc. I then found out that my old machine had a small brake shoe inside it, that didn't accept the inner brake lining. So, i didn't use the brake lining (furnished with the new drive disc) and it worked ok.
When i bought the new disc,wheel,whatever, i did not go to just any old lawn mower repair shop--no--i went to the dealer of Snapper Products, who has been a personal friend for many years, and whom i trusted to steer me correctly in how to use the new disc/wheel/brake lining/paper cover/etc!
After i got the disc installed the correct way, i have used the machine for about 5 years, using the new disc/wheel/rotor/or whatever, and it has performed magnificently all of that time, since installation!
Howzat, Walt? Rustyj, The Mower Man