Electronic Acoustic Sensor
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Electronic Acoustic Sensor Vivek Bharti* Corporate Materials Research Laboratory Fred L. DeRoos Corporate Research Analytical Laboratory 3M Company 3M Center St. Paul, MN 55144-1000
Abstract: The Stethoscope (acoustic sensor) is a fundamental tool for the diagnosis of diseases and conditions of the cardiovascular (CV) system. It serves as the most commonly employed technique for diagnosis of such diseases and conditions in primary health care and in circumstances where sophisticated medical equipment is not available, such as remote areas. The piezoelectric sensor was used as an acoustic sensor. The sensitivity of the sensor was improved more than 20 times with our new design. The signal-to-noise ratio was further improved by using unique sensor housing and by using an electronic amplifier in the differential mode.
Introduction: The function of the heart is to provide the body with blood that is full of oxygen. All of the parts of the heart, like the chambers and valves, work together to ensure that blood always flows on the same path on its way through the heart and the lungs. The blood flow in the heart valves creates a specific lubb-dubb heart sound. Depending on the condition of the heart, this sound changes. In the early stage, the auscultation used to be performed by placing the physician’s ear to the patient's chest. At the beginning of the 19th century, Dr. R.T. Laennec introduced a tool, the stethoscope, for transmitting of sound from the heart to ear. The first improved stethoscope was designed with only a bell chest piece. This stethoscope was outstanding in picking up low frequencies, but was less effective at picking up the higher frequencies. In the early 1960s Dr. Littmann, a cardiologist at the Harvard School of Medicine, invented the first stethoscope chest piece that included a bell on one side and a diaphragm on the other side. This resulted in a stethoscope that provided both high and low frequency response from the same instrument. In 1967 3M acquired the IP and company started by Dr. Littmann and launched a stethoscope with “Littman” brand name. Limitation with Existing Stethoscopes: The diagnosis of heart sounds with a stethoscope is based on three critical parameters 1) location of the stethoscope, 2) time of the sound, and 3) shape of the sound wave.
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Therefore, one can imagine that detecting relevant symptoms and forming a diagnosis based on sounds heard through a stethoscope are skills that can take years to acquire and refine. The acoustical detection of abnormal activity is a challenge, because heart sounds are often separated from one another by very short periods of time and because the signals characterizing cardiac disorders are often less audible than normal heart sounds. As reported by Dr. Barrett, Cardiologist and Director of the Cardiac Clinic at Drexel University, the ability of medical students to correctly recognize heart murmurs is poor. In one study, only 13.5± 9.8% of the students were able to diagnose heart murmurs correctly and this percen
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