Wine glass acoustics - wavelength not what expected

In summary, a lab experiment was conducted using a latex glove to stimulate a tone from a rotating wine glass on a turntable. The wavelength of the emitted tone was found using the equation lambda=v/f and was expected to be a quarter of the length of the glass, but was actually closer to half. This is because the rim of the glass vibrates like a bowstring rather than the air inside vibrating in a standing wave. There is also a quadrupole configuration of four nodes and four antinodes, which may be caused by two waves at the same time or a more stable configuration.
  • #1
neural_jam
18
0
Hi,
I have been conducting a lab experiment using a piece of latex glove to stimulate a tone from a wine glass that is rotating on a turntable. I used the equation [tex]\lambda[/tex]=v/f (using an audio spectrometer setup to find f) to find the wavelength of the emitted tone.
We expected the top part of the glass would be a quarter of the length of the wavelength, as in an organ pipe with one closed end. What I found though, was that it was very close to half.
Does anyone know why my initial assumption was wrong?

Thanks

-Jam
 
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  • #2
The air in the glass isn't vibrating like a standing wave down the length of the glass as in an organ tube, the rim of the glass is vibrating like a bowstring.
Imagine that two opposite points on the rim are staionary and the curve between them vibrates.
 
  • #3
omg thanks, that's been annoying me for weeks!
Thankyou!:biggrin:
 
  • #4
ok, that leaves me with a second question;
I just did a rough calculation, and it turns out that the wavelength is about the same as the circumference of the glass, which would lead me to expect to observe two nodes and two antinodes as I moved a microphone around the glass, i.e., two 'quietest' points, and two 'loudest' points.
However, my previous research (and observation) suggests that there is in fact a quadrupole configuration, that is, there are four of each such nodes and antinodes.

Why would this be?
 
  • #5
Perhaps 2 waves at the same time and this is the most stable configuration?
(only a guess)
 
  • #6
hmm... that was my initial thought too, but then the wavelength of the wave on the glass rim is then half that of the emitted tone...
ok, thanks for your help :-)
 

What is the phenomenon of "wine glass acoustics"?

"Wine glass acoustics" refers to the scientific study of how sound behaves when traveling through a wine glass. It explores the relationship between the shape and material of the glass and the sound waves produced by tapping or rubbing the glass.

Why is the wavelength not what is expected in wine glass acoustics?

The wavelength in wine glass acoustics is often not what is expected due to the complex shape and material properties of the glass. The glass can act as a resonator, causing the sound waves to reflect and interfere with each other, resulting in a change in the expected wavelength.

What factors affect wine glass acoustics?

There are several factors that can affect wine glass acoustics, including the shape and size of the glass, the thickness and material of the glass, and the type of sound source used to produce the sound waves. Temperature and humidity can also play a role in the behavior of sound in a wine glass.

How is wine glass acoustics studied?

Wine glass acoustics is studied through various experimental methods, such as tapping or rubbing the glass with a finger or using a specialized device to produce sound waves of different frequencies. Measurements are taken to analyze the sound waves produced and the changes in wavelength and frequency.

What are the practical applications of wine glass acoustics?

Studying wine glass acoustics can have practical applications in fields such as material science, acoustical engineering, and musical instrument design. It can also provide insights into the properties of different types of glass and how they may affect the quality of sound produced in wine glasses used in musical performances or wine tasting events.

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