When I flush my toilet it makes a loud whinning sound

Had to answer as my toilet is doing just the same thing. My boyfriend said its called Hammer something and he made an adjustment. It went away for a bit and now its back. I live in a block of flats and have heard others making the same noise above but as yet I have not called anyone in. Guess it's a job really for a qualified plumber. Its so Loud.

Sounds like your ballcock (flush) valve. Next time you flush, take the tank top off and lift the float. If noise goes away, replace the valve.