Lecture_20 - Sound Sound as a Wave Sound as a Wave Ip v...

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Sound

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Sound as a Wave
Sound as a Wave v sound = f λ v sound = Y ρ , in solid v sound = B ρ , in liquid v sound = 343 m / s + 0.6 m /( s o C )×( T 20 o C ) , in air I p amp 2 I 1 r 2 Acoustic Thermometry, can be used to measure temperature. Ex: Oceans Can be dependent on T.

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Sound as a Wave Sound will reflect (mirror -like for relatively large objects, scattered for relatively small objects – compared to λ) Sound will interfere Sound will refract
Decibels The lowest (approximately) intensity sound detectable by the human ear is I 0 = 1.00x10 -12 W/m 2 . This value is related to the smallest pressure difference detectable by the human ear ~ 2x10 -5 Pa. Examples: I 0 = 0dB. 10xI 0 = 10dB 100xI 0 = 20dB 50dB = ? β= 10 log ( I I 0 ) , intensity measured in decibels, dB

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Hearing
Sound and Standing Waves Sound can create standing waves. Harmonics will depend on whether the pipe is closed at ends (node) or open (antinode)

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Standing Waves f n = n v sound 4 L = n f 1, n odd One end opened Both ends closed f n = n v sound 2 L = n f 1, n an integer
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This note was uploaded on 12/07/2011 for the course PHYS 220 taught by Professor Chang during the Fall '09 term at Purdue University-West Lafayette.

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Lecture_20 - Sound Sound as a Wave Sound as a Wave Ip v...

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