I talked about this a little in my longwinded answer to your other post, but you seem more urgent here. The fill valve in the toilets are famous for making strange noises, especially if you have high pressure. You can turn the valve off at the toilet (make sure that it actually does shut off completely) and see if this makes a difference. Toilet fill valves are fairly easy to change as a rule, but there is really no such thing as a truly straightforward plumbing job, any job can go bad at any time.
Someone else mentioned checking the water pressure, a really good idea. You can buy an inexpensive pressure gauge that will connect to a hose outlet (called a hose bib). Excess pressure should be reduced with a pressure reducer (required by code if above 80 psi). A pressure reducer is located on the main line as close as possible to where the water comes in the home. You could have one that is bad or you could need one. Check these things out and then get backto us.