When you go to a physician for a checkup, more than likely he/she will use a stethoscope on your chest to check your heart sounds.
The normal heart sound is typically described as "lub-dub." The "lub" sound is usually softer and longer than the "dub", and it is associated with the closing of the A-V valves at the beginning of systole. The sounds are also amplified by the chest, making them more audible. The sounds of the heart are only from the valves closing, not opening. The "lub" is the first heart sound. The "dub" sound is shorter and louder than the "lub" sound. It is associated with the closing of semilunar valves (aortic and pulmonary). The sound is shorter and louder because the cusps of the valves are more rigid than the mtral and tricuspid valves.
Although doctors use stethoscopes often, phonograph can also be used to record heart sounds as well. This machine is basically a microphone used to hear low-frequency sounds. It produces phonocardiograms which display heart sounds as waves. Using these machines, third and fourth heart sounds can be heard as well. They are much fainter than the first and second ("lub-dub").The third heart sound occurs during diastole. It is the reverberation that occurs when the ventricle is almost full and blood is still rushing in. The fourth sound occurs when the atria contract. The actual sound heard is the blood rushing into the ventricles (very similar to third sound).
Just by listening to your heart sounds or using a phonograph, a doctor is provided with a wealth of information regarding the state of your heart. If the valves are not completely closed (or opened partially), heart murmurs are produced. The doctor can hear murmurs and can actually tell which valve is stenotic or insufficient (just from the sounds!). To hear a sound of the damaged valve check out our interview with Mrs. Hartfield, Medical Technician in CAT lab.