About stethascope

A stethoscope works on Bernouulli's Principle, which is in fact the Law of Conservation of Energy.

A stethoscope consists of a large diaphram which is placed over the patient's cheat. The diaphragm moves slightly according to the vibrations sent from the beating heart. When the diaphragm moves, it moves the enclosed air behind it. It transfers energy to the air that is in contact with the inner surface of the diaphragm. As the air moves away from the diaphragm the enclosure becomes narrower and narrower, but the energy of the waves stays the same, so instead of having the distance parallel to the diaphragm to move in, it moves more and more in the direction perpendicular to the diaphragm; that is, it moves back and forth in the tube with more force. As the space continues to narrow, it goes back and forth with more and more amplitude.

Bernoulli's Prrinciple states that when a moving liquid or gas is restricted in a pipe, the gas or liquid in the narrow part of the pipe will move the fastest. Since the sound pressure waves are moving back and forth, they move back and forth faster. This sort of focalization of the energy of the diaphragm into a high energy narrow tube is then used to move another smaller diaphragm near the listener's ear. Since this diaphragm is much smaller, it will vibrate with more amplitude since it is being driven by the energy from the larger diaphragm, making it sound as if the sound wave had been amplified.

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