What factors affect the frequency of harmonics in a soda bottle?

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Discussion Overview

The discussion revolves around the factors affecting the frequency of harmonics produced when blowing across the open end of a soda bottle. Participants explore the relationship between blowing intensity and harmonic frequencies, as well as the underlying physical principles involved.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant questions whether the frequency of the next harmonic depends on how much harder one blows into the bottle.
  • Another suggests conducting an experiment to observe how the frequency changes, expecting a jump from 250 Hz to 500 Hz.
  • Some participants note the physical setup of the bottle, mentioning the presence of a node at the closed end and an antinode at the open end, which relates to the wavelengths involved.
  • There are inquiries about the relationship between blowing intensity and the speed of sound, with some confusion expressed regarding how blowing harder affects harmonic frequencies.
  • One participant introduces the concept of the bottle acting as a Helmholtz resonator, describing the air column dynamics and referencing basic physics texts for further understanding.
  • A later reply mentions a video that illustrates how the speed of air blown into the bottle affects which harmonic occurs, although access to a referenced article was restricted.

Areas of Agreement / Disagreement

Participants express various viewpoints on the relationship between blowing intensity and harmonic frequencies, with no consensus reached on the exact mechanics or implications of blowing harder. Multiple competing views remain regarding the factors influencing harmonic frequencies.

Contextual Notes

Some participants highlight the complexity of the harmonics in relation to the bottle's structure and the behavior of air, indicating that the discussion may involve unresolved assumptions about the physics involved.

bahtiyar
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I saw a question
"If you blow across the open end of a soda bottle and produce a tone of 250 Hz, what will be the frequency of the next harmonic heard if you blow much harder?"
the answer is 750 Hz
but I'm curious about "if you blow much harder" part, is it really depends on how much harder you blow or something else?
 
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Do the experiment and you'll be the expert !
 
When you run the experiment check how the frequency changes. Jumping an octave is what I'd expect (from 250 Hz to 500 Hz).
 
I think the point is that it is closed at one end and open at the other; there is a node at the closed end and an antinode at the open end, so it goes from 1/2 wavelength to 3/2 wavelength.
 
mjc123 said:
I think the point is that it is closed at one end and open at the other; there is a node at the closed end and an antinode at the open end, so it goes from 1/2 wavelength to 3/2 wavelength.
Didn't give that any thought. I believe you have the right of it.
 
isn't that about the speed of sound, if it is right how it much harder blowing effect on it. What is the logic here can anyone explain?
 
bahtiyar said:
isn't that about the speed of sound
The speed of sound is near 750 MPH, 750 Hz is oscillations per second...
 
bahtiyar said:
isn't that about the speed of sound, if it is right how it much harder blowing effect on it. What is the logic here can anyone explain?
Think about the speeds of the molecules which are needed for each harmonic mode.
 
I think this is pretty complicated, since a bottle like that is an example of a Helmholtz resonator. The column of air in the neck of the bottle is acting like the piston, and the air in the main portion of the bottle is acting like the spring. The basic linear theory is pretty simple - it is explained in basic sophomore level physics texts (eg Electromagnetic Vibrations, Waves and Radiation by Bekefi and Barrett). The harmonics are not as easy for me to understand. A quick google search did find an article that may be of interest:
http://iopscience.iop.org/article/10.1088/1361-6552/aa532b/meta

Jason
 
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  • #10
jasonRF said:
I think this is pretty complicated, since a bottle like that is an example of a Helmholtz resonator. The column of air in the neck of the bottle is acting like the piston, and the air in the main portion of the bottle is acting like the spring. The basic linear theory is pretty simple - it is explained in basic sophomore level physics texts (eg Electromagnetic Vibrations, Waves and Radiation by Bekefi and Barrett). The harmonics are not as easy for me to understand. A quick google search did find an article that may be of interest:
http://iopscience.iop.org/article/10.1088/1361-6552/aa532b/meta

Jason
thank you
the video on the page clearly shows which harmonic occurs depend on the speed of air that we blow. I can't reach the article it requires purchase the article but video was enough for me
 

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