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The stethoscope is one of the common devices used by the physician for auscultation examination. Stethoscopes were first invented by a French physician, René Laënnec, in 1816. The prototype consisted of a rolled paper cone and a wooden tube, the purpose being to hear the heart’s sounds. In 1819, it was improved by replacing the wooden tube with a rubber tube. In the following years, many improvements were made to the design, with the introduction of the diaphragm, bell, and binaural version. In 1956, several further improvements were implemented, resulting in the current stethoscope now used by doctors [16]. The evolution of the rubber-based stethoscope is given in Figure 2.5.

Figure 2.5 Evolution of rubber-based stethoscopes.

The evolution of the stethoscope is not limited simply to design and appearance, but involves functionality, accuracy, and outcome. The first stethoscope only allowed doctors to hear the pumping of the heart through one ear, whereas the binaural stethoscope design, allowed its users to hear and compare sounds of each bell. Then came the stethoscope with its classic design of two sides and one bell, which helped physicians use it for the respiratory and cardiovascular systems. After that, the diaphragm was introduced, helping to distinguish low-pitched and high-pitched sounds for accurate diagnosis.

After several years, the development of digital stethoscopes began. A digital stethoscope (seee Figure 2.6) has the ability to convert acoustic sounds into electronic signals, which can be transmitted to a computer for further processing. The digital stethoscope has three different modules, namely data acquisition, preprocessing, and signal processing. The main benefit of these modules is to enhance the quality of the sound acquired [17]. Other recent improvements include embedded noise reduction and cancelation features that give better accuracy.

Figure 2.6 A digital stethoscope.