HELMHOLTZ RESONATORS

Bottle Band

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

Yet more examples: The Ocarina

Ocarinas Basic Principle of Operation

Spring Mass System in Disguise

Air plug in neck “bobs” in a big sea of air molecules

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

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?

Lab Experiment

• Tune bottles• Compare actual frequency to theory

• Do better than these guys!

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