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Sound Waves

Sound Waves. Sound is a longitudinal wave in a medium Audible range of human ear is 20 to 20000Hz. P 1. P 2. Bulk modulus. Please estimate the speed of sound in water, the bulk modulus of fresh water at 20 o C is about 2.28 ×10 6 Pa. 150 B. 340 C. 710 D. 1480 E. 3000 m/s.

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Sound Waves

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  1. Sound Waves Sound is a longitudinal wave in a medium Audible range of human ear is 20 to 20000Hz

  2. P1 P2

  3. Bulk modulus

  4. Please estimate the speed of sound in water, the bulk modulus of fresh water at 20oC is about 2.28×106 Pa. • 150 B. 340 C. 710 • D. 1480 E. 3000 m/s

  5. 空氣的bulk modulus 若為等溫過程，pV=nRT， 用此結果代入所得之聲速較實際值小。在聲音的傳遞，速度很快，空氣和周圍來不及做熱交換，要考慮絕熱過程，即 。

  6. Characteristic impedance or specific acoustic resistance

  7. Energy in Wave Motion For sinusoidal wave with wave function given as The speed of the displacement would be The instantaneous rate of doing work at the point x and timet is

  8. Energy in Wave Motion The instantaneous rate of doing work at the point x and timet is

  9. Sound Velocity and Gauge Pressure intensity of a sinusoidal sound wave definition of sound intensity level

  10. The maximum sound wave pressure human can tolerate is 28Pa above the atmospheric pressure. Find the max displacement if frequency is 1000Hz. Given speed of sound is 344m/s • 11 nm B. 0.11μm C. 11 μm • D. 0.11 mm E. 1.1 mm

  11. Sound Attenuation Which thunder is heard as a higher frequency crash? A. distant one B. nearby one C. same Why distant thunder is heard as a low rumble while nearby one is a higher frequency crash. High or low frequency is better for long distance communication?

  12. Sound Attenuation Which material will have largest displacement under same sound pressure variation? A. Steel B. Alumina C. water D. Air

  13. Sources of Musical Sound What factors would affect the frequency of sound generated from a guitar string?

  14. The Doppler effect Moving listener and stationary source

  15. Moving source and moving listener

  16. Shack Wave (Sonic Boom) H.W. Estimate the speed of the fighter. http://en.wikipedia.org/wiki/Sound_barrier

  17. 2smcosw't Beats 拍音 拍音可利用來做樂器的調音。人類可感覺之拍音約<7Hz

  18. People used Doppler flow meter to measure the blood flow rates. The speed of sound in blood is known to be 1570 m/s and a typical red blood cell has a radius of 5μm. Please estimate what would be the frequency for the flow meter? If the frequency shift measured by the Doppler flow meter is 100Hz (the meter was operated at 107Hz), please find the average velocity of blood flow. • 3.5 mm/s B.1.5 cm/s C. 23 cm/s • D. 65 cm/s E. 120cm/s

  19. 橫波(transverse wave)彈性體所產生之形變為剪應變(shear strain)

  20. 縱波(longitudinal wave)彈性體所產生之形變為拉伸應變(tensile strain)恢復力為拉伸應力(tensile stress)

  21. =5.75×1011 Pa (a)鋼之密度為7.83×103 kg/m3，G=8.3×1010 Pa，橫波在鋼中傳遞之速率為 (b)鑽石的橫波聲速高達12800 m/s，密度為3.51×103 kg/m3，他的shear modulus為

  22. Can bat tells what’s its prey? Insect has its own characteristic flapping frequency The echo is modulated by the beating wing of prey, as a result, the motion of wings impose a “warble” to the echo. In air or water, which is easier to detect via Doppler shift?

  23. Hearing The otolith organs are the primary means by which we sense linear acceleration of the head and the orientation of the head with respect to Earth's gravity. Each of these otolith organs contains a small sensory area known as a macula. Each macula contains several thousand vestibularhair cells. The cilia are embedded in a gelatinous matrix called the otolithic membrane. This membrane contains small piles of calcium carbonate crystals (CaCO3), called otoliths, a word which literally means "ear stones."

  24. Hearing In most animal, a change in pressure is heard There is a problem for terrestrial animals. Energy propagation at interfaces. Newton’s 3rd law at the interfaces

  25. The amplitude of sound transmitted into water is only about 1/1800th that in air

  26. The intensity of sound transmitted from air into water is about ? • 50% B. 20% C. 1% • D. 0.1% E. 0.01% How can terrestrial animal hear?

  27. A eardrum = 43mm2A stirrup = 3.2 mm2 V fluid =1500m/s The Anatomy of Human Ear

  28. http://www.sfu.ca/sca/Manuals/ZAAPf/e/equal_loud_cont.html

  29. Sound Amplifier When the size of an air bubble in water is smaller than sound wavelength, it can function as a sound amplifier More realistic model is to treat the bubble as a damped oscillator system

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