Sound Absorption Experiment: Research and Testing

[Hazemm]

hey,
I'm starting this experiment regarding Sound absorption, and I am having a little trouble finding sufficient research to describe the physics behind it. Basically, I have a wooden chamber, which i will be testing inside. I will have a signal generator at one end, and a microphone hooked up to an osilliscope, in order to see differences in amplitudes. What I'm testing is how the density and shape of a material(im testing three types of foam, and the empty chamber) affect the amount of sound absorbed. If anyone can help me tie this in more with actual theory, and/or think of any other possible ways to analyze the resulting sound wave it would be a great help. At the end of the experiment i will be writing a 4000 word essay about what I did for my physics course. Anyways, thanks alot
peace

 

[pallidin]

The article here might be of some help, specifically Part IV:

http://stason.org/TULARC/physics/acoustics-faq/index.html

Here's another site: http://www.soundprooffoam.com/

And here: http://www.engineeringtoolbox.com/accoustic-sound-absorption-d_68.html


Not sure if the above helps, but worth a look.

 

[pavan0007]

hello sir
i am a designer basically into Diesel generators. we are starting freshely into market and i am struggling to design of sound proof cannopy for desiel generator .so please suggest some sites or formulas and what is the starting point of designing of this cannopy.

 

[Ivek]

If you mean what type of element absorbs most sound it will probably be the thickest foam, and least empty chamber because as a violinist i can say wood is a very good sound conductor. Maybe a bad choice of chamber:/

 

[PJC01]

Hello,

It sounds like you have a very interesting experiment planned. Sound absorption is a complex phenomenon that involves the interaction between sound waves and materials. The physics behind it can be explained using the concept of acoustic impedance.

Acoustic impedance is a measure of how much resistance a material offers to the transmission of sound waves. It is affected by the density and shape of the material, as well as its surface properties. In your experiment, you will be testing different types of foam, which have different densities and shapes, and an empty chamber, which has no material to absorb the sound.

When sound waves enter the chamber, they will encounter the different materials and their respective acoustic impedances. The sound waves will then either be absorbed or reflected depending on the material's impedance. Materials with a high impedance, such as dense foams, will absorb more sound waves, while materials with a low impedance, such as the empty chamber, will reflect more sound waves.

To analyze the resulting sound waves, you can use the oscilloscope to measure the amplitude of the waves. As you change the materials in the chamber, you should see a difference in the amplitude of the sound waves, indicating the level of absorption.

In addition to measuring amplitude, you can also analyze the frequency of the sound waves. Different materials will have different absorption coefficients at different frequencies. By testing a range of frequencies, you can determine the material's absorption properties across the spectrum.

I would also recommend researching the different types of foam you are testing to understand their composition and how it may affect their acoustic impedance. Additionally, you may want to consider the surface properties of the materials, as rougher surfaces can also contribute to sound absorption.

I hope this helps with your experiment and essay. Good luck with your research!