Auscultation is the process of listening to the internal sounds of the body to assess for any underlying disease. Physicians use this method to evaluate the frequency, intensity, duration, number and quality of various internal sounds. It is used in both routine medical examinations and in diagnosing specific conditions. Auscultation is performed through the use of a stethoscope, which allows a physician to listen to the heart as it contracts and relaxes.

The normal "lub-dub" sound of the heart made during the "one-two" sound of the heart is made during the two stages of a heartbeat:

• The second stage (diastole) makes a sound as the other two valves of the heart close. One valve is the aortic valve between the left ventricle and the aorta, and the other valve is the pulmonic valve between the right ventricle and the pulmonary artery. The closed valves keep blood from leaking back into the left and right ventricles, respectively.

Abnormal sounds may be heard through the process of auscultation. For example, the physician may hear clicks, whooshes, snaps or other sounds that characterize a heart murmur. A heart murmur may be a sign of valvular heart disease, or it may be "innocent," with no underlying disease. The physician may also hear abnormal heart rhythms (arrhythmias).

In evaluating the cardiovascular system, a physician will also listen to the lungs, checking for any abnormal breath sounds, such as shallow breathing, wheezing and crackling. These and other abnormal sounds could indicate conditions such as reduced airflow to the lungs, overinflation of a portion of the lungs, or air or fluid in the lungs. They could also indicate conditions such as asthma, emphysema, bronchitis and pulmonary edema (swelling).

A blood pressure reading can be taken with a stethoscope and a blood pressure cuff (sphygmomanometer) that is wrapped around the patient's arm. The physician can also place the stethoscope directly over an artery to listen to the sound of the blood flow. For example, he or she may hear a turbulent, rough sound, called a bruit, which could be a sign of obstruction within the vessel. When heard in the carotid artery in the neck, it is known as a carotid bruit and is seen as a risk factor for stroke.

Ideally, the physician places the stethoscope on the patient's bare skin for the clearest sounds. The patient may also need to move around or take deep breaths in order to obtain the best sounds.