الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
The stethoscope remains the centerpiece of diagnostic tools for clinicians performing cardiac examinations of their patients. Many cardiac and pulmonary abnormalities can be diagnosed at the bedside with the use of the stethoscope. Auscultation is one of the most cost-effective diagnostic tests for patients with cardiac and pulmonary abnormalities.
Digital stethoscopes are designed to overcome the disadvantages of the acoustic stethoscopes. Digital stethoscope electronically amplifies body sounds. Digital stethoscope uses sound waves, which are converted from analog to electrical signals that are amplified and provide much lauder and clearer sound. This makes identifying problems quicker and easier, and it allows the recording and playback of sounds picked up, making it useful for references or in the teaching for students.
In the present work, digital stethoscope system was designed and constructed. It consists of a function generator circuit for generating a sound signal with appropriate frequency and waveform to the constructed lung model by a mini-speaker inserted into the simulated trachea. Electrets condenser microphone at the surface of the model receives the sound signal and converts it into an electric signal. The signal then was amplified and filtered with a suitable gain and transmitted through an electrical cable to the sound card of a personal computer for further monitoring and analysis of the output sound signal.
The results of the simulated model showed that:
• The amplitude of the output sound signal increases with the increasing of solutions (Water, Sodium chloride, Glucose), and gel quantity.
• The sound attenuation decreases with the increasing of solutions quantity.
• The coefficient of attenuation decreases with the increasing of solutions quantity.
Digital stethoscope array system was developed for monitoring and diagnosing obstructive lung diseases which are associated with accumulation of lung fluids and cardiovascular diseases which associated with heart murmur like systolic and diastolic murmur from different auscultation points. Parameters such as sound attenuation and attenuation coefficient
The results of heart sound analysis showed that:
• The frequency spectrums of all normal and abnormal heart sounds were 64 Hz.
• The amplitude of normal heart sound at the apex auscultation point was -17 dB, while at the aortic and pulmonic auscultation points were -10 dB.
• The amplitude of abnormal heart sounds S3 and S4 at the apex auscultation point were -18dB.
• The amplitude of split S1 at the apex auscultation point was -22 dB, while the amplitude of split S2 at the pulmonic auscultation point was -16 dB.
• The amplitude of early, mid, late and holo systolic murmur at the apex auscultation point were in the range of -24 dB to -22 dB.
The results of lung sound analysis showed that:
• The amplitude of all normal and abnormal lung sounds was in the range of -50 dB to -30 dB.
• The frequency spectrum of normal vesicular lung sound was 120 Hz.
• The frequency spectrum of coarse crackles sound was 330 Hz.
• The frequency spectrum of inspiratory stridor sound was 275 Hz.
• The frequency spectrum of pleural friction sound was 58 Hz.
• The frequency spectrum of wheezing sound was 198 Hz.