Tasks on the theme - 45 minutes
1. Peculiarities of sound propagation in different mediums. 2. Physical characteristics of sound wave. 3. Physiological characteristics of the sound sensation and their dependence on the physical characteristics of sound wave. 4. Weber law, Weber-Fechner law. 5. Sound measurings. Audiometry. 6. Doppler effect. 7. Ultrasound. 8. Action of the ultrasound on a substance (mechanical, thermal). 9. Usage of the ultrasound in medicine.
Break - 10 minutes Students’ independent work - 30 minutes Problems solving. Problems: 1. In medicine in order to determine the movement speed of separate biological structures (for example blood, heart valves) the Doppler effect is used. How is the changing of ultrasound signal frequency at reflection from the moving object with its speed connected? 2. The level of loudness is 120 phon and the level of quiet talking in the same distance is 40 phon. Determine the ratio of intensities. 3. The maximal level of sound intensity of the radio is 80 dB. What will be the maximal level of sound intensity of two same simultaneously working radios? 4. Sound intensity is 10-2 W/m2. Find the sound pressure if the acoustic resistance of the medium (air) is 420 kg/m2s. 5. Determine the amplitude value of sound pressure for the clear tone with 1000 Hz frequency at which the rupture of the eardrum can happen if it happens at the loudness level LE=160 phon. (The answer has to be in Pa and atm.).
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