There are two sounds heard during each heart beat. These are called Lub-Dub noises by doctors. The paper flap on the canister creates a sound similar to that made by heart valves. If the valves do not close properly and leak, the sound will not be clear but blurred. Medical professionals call this a murmur.
Rheumatic fever is a disease that can damage the heart valves.
Accumulated fat deposits in the heart can also affect the function of the valves. If the valves become too small or leaky due to either of these conditions, they can be surgically replaced with artificial valves. The heart contains valves which direct the flow of blood in one direction. Blood is forced through the flexible membranes which form the valves. Once the blood passes through the membranes, the valves collapse into a barrier, preventing the blood from flowing backwards.