You need to restict the flow a little, if there are inline valves to the taps try turning them half off. I had this problem with a toilet cistern and solved it by putting a stainless steel washer inside the pipe to restrict the flow.
John
no its nothing to do with the flow, your toilet was screaming because the ball valve is faulty and the cold water pipework was vibrating, had the same problem a few months back and fixed it for a fiver.
and yes i would also suggest that your tap washers need replacing, if that doesn't work it could be the jumper washer on the main stopcock.