What you hear is the washer vibrating against the ballcock seat. The reason it stops when you turn the water on is that you have lowered the pressure by opening a valve. You can go at this two ways. (1) you can lower the pressure by turning the angle stop located below the tank until the noise stops or, (2) you can shut off the stop and remove the three screws on top and cup your hand over the top and just crack the stop enough to flush out any trash that may be in there. After you do that pull the washer out of its holder and flip it over in its holder and reinstall the top and float. One of the two should do the trick. If not click on back and
replace the flush valve. Joe