I am having the same problem as others with a low frequency hum. I want to try your remedy with the toilet, but I am very unfamiliar with the different parts. Would you mind explaining it all to me in a way I could understand - someone who has never worked with toilet. Where is the ballcock and the flapper. Please don't think I am too stupid. If you have a little time, I just need some help understanding what to do. Thanks. Debi

No problem Debi,
The ballcock's the thingy with the float ball on a rod. The flapper's the rubber looking dude on the end of a chain that lifts when you flush. There are a few things that will set up a vibration , (hum). We'll go through them one at a time.
First remove the tank lid and check the water level. It should be 1/2" beneath the top of the white overflow tube. Any higher then that let me know.
Now the flupper. With the lid still off flush the toilet. While the flapper's up run your fingers around the flat edge. It should have no wavey edges or rough spots. If so let me know. Check those and get back to me. Please post on the plumbing page, E-Mails and PM's make for more work for me. More questions? I'm as close as a click. Tom

Thank you