humm
If you know that the toilet fill valve is totaly shutting off, you can tell, when it's humming and you lift the float in the tank and the humm goes away.
I think you could check the toilet shut off. Turn the house water off, relieve the pressure by opening a faucet. Put a pan under the valve in question and turn the hex bonnet counter clockwise and turn the handle and stem to the left, till the whole asse. comes out. There should be a washer on the end of the stem. Also look real good inside that opening to see if there is anything loose inside, like pieces of the washer .
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