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Phonocardiography

Phonocardiography. Engr. Hinesh Kumar (Lecturer). Definition. Phonocardiography is the recording of heart sounds. The heart. like any mechanical pump, produces characteristic sounds as it beats . These are the sounds the physician hears with a stethoscope.

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Phonocardiography

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  1. Phonocardiography Engr. Hinesh Kumar (Lecturer)

  2. Definition • Phonocardiography is the recording of heart sounds. • The heart. like any mechanical pump, produces characteristic sounds as it beats. These are the sounds the physician hears with a stethoscope. • Certain heart murmurs produce sounds in the 1000-Hz range, and some frequency components exist down to 4 or 5 Hz.

  3. Heart Sounds Generation • The first heart sound is generated at the end of atrial contraction, just at the onset of ventricular contraction. • This sound is generally attributed to movement of blood into the ventricles, the atrioventricular(AV) valves closing, and the abrupt cessation of blood flow in the atria. • The second heart sound corresponds to the closing of the aortic and pulmonary valves.

  4. Cont… • Third heart sound corresponds to the cessation of ventricular filling. • Fourth heart sound is correlated to the atrial contraction. • This last sound has a very low amplitude and a low-frequency component.

  5. Cont… • The phonocardiograph transducer is a contact or air-coupled acoustical microphone held against the patient's chest (shown in fig). • Various types of microphones are used, but most are the piezoelectric crystal or dynamic type of construction.

  6. Cont… • The crystal microphone generally costs less and is more rugged than the dynamic type. • Also, the crystal microphone produces a larger output signal for a given level of stimulus • The dynamic microphone uses a moving coil coupled to the acoustical diaphragm. • The dynamic microphone is used when it is desirable to have a signal frequency response similar to that of the medical stethoscope. • An air-coupled microphone with a 2-s time constant is often used in apex phonocardiography.

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