A stethoscope is used by a doctor to listen to a patient's heartbeat. Specifically, doctors listen for the sound of heart valves closing and irregularity of heart beat, both of which provide important information about a patient's heart health.
One of the first things that a doctor listens for while using his stethoscope is the closing of one set of heart valves followed by the closing of the other. In between the closing beats there should be silence, and a lack thereof may indicate health problems. Stethoscopes alert a doctor to the presence of heart murmurs, which indicate blood leaking backward. They also allow doctors to hear a rapid beat that may indicate heart failure and permit doctors to hear sounds indicative of high blood pressure or heart damage.