Resonance Testing Method for Studying Chamber Resonance: Homework Questions

[eskenig]

Homework Statement

Hello,
I'm working on a semester project a measurements class at my college. We are measuring the affects of different materials on the resonance of chambers. We are testing two chambers, one in the shape of a rectangular prism, one in the shape of a cylinder. We will be taking measurements at various positions in the rectangular prism on two axes and the cylinder will be tested axially. I have been trying to find precedence of such experiments but have not had much luck for one reason or another. (If you know of any links that talk about this, it would be appreciated if you responded with them)

In any event my questions are about a few things that have not been decided with the method.
1. Where do we mount the speaker that emits the frequencies we're testing? Does it to go inside, outside? Centered/off center? Does it even matter?

2. What step in frequency should I use? Or would it be better to to a continuously varied frequency at each position we test at and then run an FFT on those results to find the frequencies.

3. Since I'm dealing with basic geometric shapes (more or less, they will be slightly affected by the materials lining the insides) are there existing equations for calculating resonance frequencies?

Any other thoughts on the project are welcome, I'm just trying to finalize our method so we can actually begin the experiment.

 

[Valkarie]

Homework Equations N/AThe Attempt at a Solution 1. The speaker should be mounted outside of the chamber, as any resonance inside the chamber will affect the measurements and give false results. It should also be centered, if possible, but it is not absolutely necessary.2. It is best to use a step-by-step frequency method in order to get more accurate results. The FFT approach would be faster, but may not give the same accuracy. 3. Yes, there are equations for calculating the resonance frequencies of basic geometric shapes. These equations are based on the shape's geometry and the speed of sound in the medium.

 

[Mene]

I would suggest the following responses to the questions posed in the content:

1. The placement of the speaker can affect the results of the experiment, so it is important to carefully consider where to mount it. Ideally, the speaker should be placed in a position that is representative of where sound would enter the chamber in real-life scenarios. This could be inside the chamber, at a specific location on the wall, or outside the chamber. It may also be helpful to test multiple positions to see if there are any significant differences in results.

2. The choice of frequency step should depend on the specific goals of the experiment. If the goal is to measure the resonant frequencies of the chambers, it may be more effective to use a continuously varied frequency at each position and then analyze the results using FFT. However, if the goal is to compare the effects of different materials, it may be more useful to use a set frequency step to ensure consistency in the measurements.

3. There are existing equations for calculating the resonance frequencies of basic geometric shapes, such as rectangular prisms and cylinders. These equations take into account the dimensions and material properties of the chamber. However, as you mentioned, the materials lining the inside of the chambers may affect the resonance frequencies, so it may be necessary to adjust the equations accordingly or perform additional experiments to account for this variable.

Overall, it is important to carefully plan and consider all aspects of the experiment, including the method and potential variables, to ensure accurate and meaningful results. Additionally, it may be helpful to consult with experts or previous studies on chamber resonance to gain more insights and ideas for the project. Good luck with your experiment!