Every time my toilet is flushed, it makes a loud sound as the water finishes rising. It sounds like a tuba or a large steamship and it lasts a good 5 - 7 seconds. It appears that the large round flotation device and the arm it's attached to may be the problem as they vibrate when the noise begins and stop the minute I hold the ball and arm still. Please forgive my lack of knowledge of plumbing terms, but I hope this is clear.

Any advice will be greatly appreciated.