Acoustic Resonance Chamber Design- Wine glass shattering

[taylaron]

Greetings PFers,

I'm designing a demonstration unit for use in grade schools demonstrating the principle of resonance upon wine glasses (shattering them). I intend to put a wine glass into an acrylic chamber of some geometry, hand the student a microphone and see if they can generate the glass' resonant frequency. Their voice will be amplified through an audio amplifier and projected through a medium size (8-12'' diameter) speaker

Device requirements:
1. Demonstrate phenomenon of acoustic resonance using wine glasses
2. Utilize a speaker and amplifier to generate the sound waves
3. Device should be able to fit on a desktop
4. Sound outside of the device shouldn't be unbearably loud (enclosed container for sound isolation)
5. Capable of handling input from frequency generator or a microphone
6. Protective shroud to isolate observers from flying glass
7. Wine glass should be observable through the top and around most of the wine glass
8. Able to handle varying sizes of wine glasses (varying pedestal height)
9. User should be able to see the wine glass vibrating (likely via strobe light)
10. Built-in canister for broken glass and a lid to insert another wine glass

I have three primary concerns in designing this demonstration unit
1. Geometry of the container causes as little deconstructive interference within the chamber as possible

design chamber so node length corresponds with typical radial distance to glass surface​

2. The sound outside* the device shouldn't be deafening, with the demonstrator able to speak over the noise

single or double acrylic walls for sound isolation. Vacuum between walls? Sound cancellation with another speaker?​

3. Geometry of the speaker orifice

Some good examples of this principle are the following videos:




I'm not worried about the electronics-that's relatively simple. But I do need help designing the container. I presume a cylindrical container with a hole in one side where the sound enters would make the most physical sense because the glass would be the same distance from the chamber at any angle. Wine glasses resonate typically between 450 and 650 Hz. How do I make a chamber that can handle this wide range of frequencies? I want the chamber to be a resonance chamber so the speaker amplitude doesn't have to be really loud (or soft for a long period of time...) The videos show a simple straight hole as the orifice. Should the hole be parabolic in shape to aid dispersion? I'm thinking that I should test the geometry in a water chamber to see if deconstructive interference is an issue.

I have access to Solidworks 2012 student edition with simulator,but I don't think it does acoustic simulation. Does anyone know of a free acoustic simulator?

Thanks for your time!
-Taylaron

 

[Achy47]

I would like to offer some suggestions and considerations for your demonstration unit:

1. Consider the material of the container: Acrylic may not be the best material for sound isolation. You may want to consider using a material with better sound absorption properties, such as foam or rubber.

2. Experiment with different container shapes: While a cylindrical container may seem like the most logical choice, it may not necessarily be the most effective for sound resonance. You could experiment with different shapes, such as a cone or a sphere, to see which one produces the best results.

3. Use a frequency generator instead of a microphone: While a microphone can pick up the resonant frequency of the glass, it may also pick up other ambient noises, leading to inaccurate results. A frequency generator can produce a pure tone at a specific frequency, ensuring more precise resonance.

4. Consider safety precautions: While it is important to isolate observers from flying glass, it is also important to consider the safety of the user. Make sure to provide proper protective equipment, such as safety glasses, for anyone using the demonstration unit.

5. Test different speaker orifice shapes: The shape of the speaker orifice can also affect the resonance of the wine glass. Experiment with different shapes, such as a parabolic or rectangular orifice, to see which one produces the best results.

6. Look into acoustic simulation software: While Solidworks may not have acoustic simulation capabilities, there are other free software options available, such as COMSOL Multiphysics or ANSYS Student.

7. Consider using a strobe light: A strobe light can help visualize the vibrations of the wine glass, making the demonstration more engaging and educational for students.

Overall, it seems like you have a good understanding of the principles involved in this demonstration. I would suggest conducting some experiments and simulations to determine the best container shape, material, and orifice design for optimal resonance. Good luck with your project!