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# Ch12 (2)

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### Ch12 (2)

1. 1. Chapter 12 Waves and Sound
2. 2. Ch12.1 Properties of sound
3. 3. Compression Rarefaction Simple sinusoidal (sin) vibration– pure tone
4. 4. 疏 密  Wave-front surface 波前
5. 7. Wave in time domain and space domain 空間 位置 z 時間 z=0
6. 8. Compression Rarefaction Intensity Frequency Simple sinusoidal (sin) vibration– pure tone Speed of sound at 20℃, in air 3.3×10 4 cm/sec in water 1.4×10 5 cm/sec Total pressure P P a : ambient air pressure P o : maximum pressure change due to the sound wave Intensity I ~ I : amount of energy transmitted by a sinusoidal sound wave per unit time through each unit area ⊥ the direction of sound propagation ρ: density of medium
7. 9. Ch12.2 Some properties of waves Ch12.2.1 Reflection and refraction
8. 10. Ch12.2.2 Interference In phase Constructive interference Out of phase Deconstructive interference R=A+B Same frequency
9. 11. Standing wave
10. 12. close open
11. 13. Standing wave Resonant frequency Ch12.2.3 Diffraction
12. 14. Ch12.3 Hearing and Ear
13. 15. Figures from Urone, College physics Also see Text on p175
14. 16. Ch 12.3.1Performance of the Ear Loudness, Pitch, Quality cps cycle per second frequency = + + +
15. 17. frequency/ pitch
16. 18. <ul><li>C D E F G A B C ’ </li></ul><ul><li>Do Re Mi Fa Sol La Ti Do </li></ul>中央 C f C =256Hz 中央 C 之上的 A f A =440Hz
17. 19. Ch12.3.3 Intensity and Loudness For human ear Threshold of hearing 10 -16 W/cm 2 , at 3000Hz Threshold of pain 10 -4 W/cm 2 Ex 12-3
18. 20. Also see Text on p175 Resonance at 3000Hz, Pressure is increased by another factor of 2 . Mechanical Advantage MA
19. 21. Ch 12.4 Bats and Echoes Ex 12-6
20. 22. Ch 12.5 Sound produced by animal Ch 12.6 Acoustic Trap Rattlesnake Vocal cord
21. 23. Ch 12.7 Clinical uses of Sound Ch12-8 Ultrasonic Wave
22. 25. Doppler effect(1)
23. 26. Car moving  wavefront profile change
24. 27. Car moving  wavefront profile change 右邊的人聽到的 :
25. 28. Car stop  wavefront profile did not change 右邊的人聽到的 :
26. 29. 利用超音波及都卜勒效應 量測生物體內液體流速 Urone, College Physics Ex16.7 A diagnostic ultrasound echo is reflected from moving blood and returns with a frequency 500Hz higher than its original 2MHz.The speed of the ultrasound is 1540m/s. (a)What is the velocity of the blood? (b) What frequency does the blood receive?
27. 30. Self-practice <ul><li>Exercise 12-3, 12-6, 12-8 </li></ul>