P221_2008_week15

# P221_2008_week15 - Sound waves You can think of a sound...

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Sound waves You can think of a sound wave as an oscillating pattern of compression and Expansion ( P), or as an oscillating position for small packets of Air [s(x,t), which leads to the above picture]. REMEMBER this is a longitudinal wave! Ι = ½ ρ ϖ 2 s m 2 v s = ½( p m ) 2 /v s ρ p m = ρ ϖ s m v s

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Chapter 17 Problems NOTE: ρ =1.21 kg/m 3 v=343 m/s At T=20 o C FIRST: What is the ratio of the Intensities between the two cases? e). What is the pressure difference that corresponds to each of these intensities? Finish off this to start off on Monday.
Interference with Sound waves Suppose the difference L2-L1 is 1.70 m and S1 and S2 emit sound at A frequency of 100Hz. How will the intensity at P change if the phase Offset between S2 and S1 is changed from zero to π ? (assume v=340m/s)

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Chapter 17 Problems
Reflections at a Boundary

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Standing waves: Pipes The resonance frequencies of pipes depend on the conditions at the two ends. A closed end needs a NODE , and an open end needs an ANTINODE . The book gives you formulae for the two cases that you can remember, OR you can just remember these two conditions and draw pictures! (I find this way of doing it MUCH easier.) Question: Why do we not consider the case of both ends closed? What would be the condition in that case?
Chapter 17 Problems

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If the amplitude of a sound wave is doubled, by what number of dB does the intensity of that sound wave increase? As usual, please provide a brief explanation for your answer (16 did not answer) if the amplitude of a sound wave is doubled then the
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## P221_2008_week15 - Sound waves You can think of a sound...

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