Back to medical ancient history, physicians used to place their ears directly on a patient’s front chest of back in order to listen to the heart and lung sounds. This technique is also called as “immediate or direct auscultation”. However this well known practice has been used in little since it introduce some kind of discomfort to the physician and much more to the patient. It was in 1816 which is 10 years before he passed away, Dr. Rene Theophile Hyacinthe Laennec incvented the first stethoscope. He is also the author of the classic treatise De auscultation's Mediate (On Mediate Auscultation), published in August, 1819.
In the preface of the book he did tell us how he has been inspired to invent the instrument. He said,
"In 1816 I was consulted by a young woman labouring under general symptoms of diseased heart, and in whose case percussion and the application of the hand were of little avail on account of the great degree of fatness. The other method just mentioned [direct auscultation] being rendered inadmissible by the age and sex of the patient, I happened to recollect a simple and well-known fact in acoustics, . . . the great distinctness with which we hear the scratch of a pin at one end of a piece of wood on applying our ear to the other. Immediately, on this suggestion, I rolled a quire of paper into a kind of cylinder and applied one end of it to the region of the heart and the other to my ear, and was not a little surprised and pleased to find that I could thereby perceive the action of the heart in a manner much more clear and distinct than I had ever been able to do by the immediate application of my ear."
Since then, the world start to discover that internal sounds could be isolated and amplified through a tube, making examinations less intrusive and easier to interpret and thus, many studies has been done for improvisation of the instrument. Start from just a rigid wooden cylinder with a funnel, stethoscope has evolved into the modern instrument which typically has two chest pieces connected to the ear pieces by tubing such as what Littmann Lightweight II SE Stethoscope looks like today.
Littmann Lightweight II SE Stethoscope consists of a shallow bell-shaped device with a clear stiff diaphragm, connected to the ear pieces by flexible tubing and a hollow metal headset. The chest-piece consists of two sides that can be placed against the patient for sensing sound - a diaphragm (plastic disc) or bell (hollow cup). Literally, Littmann Lightweight II SE Stethoscope will operate on the transmission of sound from the chest piece, via air-filled hollow tubes, to the listener’s ears. For example, if the diaphragm is placed on the patient, body sounds vibrate the diaphragm, creating acoustic pressure waves which travel up the tubing to the listener's ears. In the other hand, if the bell is placed on the patient, the vibrations of the skin directly produce acoustic pressure waves traveling up to the listener's ears. While the diaphragm transmits high frequency sounds, the bell transmits low frequency sounds. Both have its own diagnostic quality, thus it is a need for the medical health personnel to auscultate using both sides during the physical examination.
Littmann Lightweight II SE Stethoscope...