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HELMHOLTZ RESONATORS
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More examples: Whistling Jar
Pre-Columbian Whistling Jar Basic Principle of Operation
Image from: http://www.prices4antiques.com/ Image from: http://www.mountainsocarina.com/lessons/lesson02-a7b.html
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Yet more examples: The Ocarina
Ocarinas Basic Principle of Operation
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Spring Mass System in Disguise
Air plug in neck “bobs” in a big sea of air molecules
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Resonant Frequency
• vsound velocity of sound waves in air
• L length of plug of air in neck
• S neck cross-section• V chamber volume of air
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Assumptions…you know what they say
• Which variable(s) is changing among these Coke bottles?
• How do these Coke bottles compare to the simple physics model?
• How would you determine S, L, and V?
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Lab Experiment
• Tune bottles• Compare actual frequency to theory
• Do better than these guys!
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Resources• Univ of New South Wales Acoustical Physics group:http://newt.phys.unsw.edu.au/jw/Helmholtz.html
• Eric Heller’s “Why you hear what you hear” chapter 13: http://www.whyyouhearwhatyouhear.com/subpages/chapter13.html
• Mountain Ocarinas: http://www.mountainsocarina.com/lessons/lesson02-a7b.html
• The Bottle Boys website: http://www.thebottleboys.com