A Stethoscope is an acoustic medical device for auscultation, or listening to the internal sounds of human or animal body (Chest Examination). It is often used to listen to lung and heart sounds. It is also used to listen to intestines and blood flow in arteries and veins. In combination with a sphygmomanometer, it is commonly used for measurements of blood pressure. 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. Stethoscopes can also be used to check scientific vacuum chambers for leaks, and for various other small-scale acoustic monitoring tasks. A stethoscope that intensifies auscultatory sounds is called phonendoscope
The stethoscope was first invented in France in 1816 by René Laennec at the Necker-Enfants Malades Hospital in Paris. It consisted of a wooden tube and was monaural. However, following several years of other refinements made to stethoscopes by other professionals, it was until in the early 1960s, when:
David Littmann, M.D., (1906–1981) was a German cardiologist and Harvard Medical School professor and researcher, created a new stethoscope that was much lighter than the previous versions or models and had improved acoustics. Along with Gus Machlup, Dr. David Littmann founded Cardiosonics, Inc. to sell his stethoscopes. At that time the stethoscope line consisted of two key models, the Doctor's stethoscope and the Nurse's stethoscope. 3M acquired the stethoscope company on April 1st, 1967, and hired Dr. Littmann as a consultant. 3M currently produces the range of Littmann brand stethoscopes today.
Later, in the late 1970s, 3M-Littmann introduced the tunable diaphragm, a very hard (G-10) glass-epoxy resin diaphragm membrane with an over-molded silicone flexible acoustic surround which permitted increased excursion of the diaphragm membrane in a "z"-axis with respect to the plane of the sound collecting area. The name Littmann has since become well known in the medical field for the patented Littmann Stethoscope reputed for its acoustic performances for auscultation.
3M Types of stethoscopes
Acoustic
Acoustic stethoscopes are familiar to most people, and operate on the transmission of sound from the chest piece, via air-filled hollow tubes, to the listener's ears.
Electronic
An electronic stethoscope (or Stethophone) overcomes the low sound levels by electronically amplifying body sounds. However, amplification of stethoscope contact artifacts, and component cutoffs (frequency response thresholds of electronic stethoscope microphones, pre-amps, amps, and speakers) limit electronically amplified stethoscopes' overall utility by amplifying mid-range sounds, while simultaneously attenuating high- and low- frequency range sounds.
Recording stethoscopes
Some electronic stethoscopes feature direct audio output that can be used with an external recording device, such as a laptop or MP3 recorder.
Fetal stethoscope
A fetal stethoscope or fetoscope is an acoustic stethoscope shaped like a listening trumpet. It is placed against the abdomen of a pregnant woman to listen to the heart sounds of the fetus. The fetal stethoscope is also known as a Pinard's stethoscope or a Pinard, after French obstetrician Adolphe Pinard.
MIC Global offers Littmann and a variety of stethoscopes; you can check this page http://www.micglobal.co.uk/stethoscopes-c61.html for more details

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