the problem is often caused by a hairline crack in any of the ballcock water assembley inlet or deteriation in the rubber seals and as you flush the toilet it can suck air in and vibrate the pipes do not rip your floor up until you check this they are only £4 60 in b@q new
always go for the ballcock first water inlet gear turn off supply of water dismantle it and clean reassemble put water back on if still there replace it easy and cheap to do
