The stethoscope is an acoustic medical device for auscultation, or listening to, internal sounds in a human or animal body. It is most often used to listen to heart sounds and breathing. It is also used to listen to intestines and blood flow in arteries and veins. Less commonly, "mechanic's stethoscopes" are used to listen to internal sounds made by machines, such as diagnosing a malfunctioning automobile engine by listening to the sounds of its internal parts. It can also be used to leak check vacuum chambers for scientific purposes.