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In Reply to: RE: 8th grade science project posted by Jim D. on January 30, 2009 at 15:09:53
You've got to be able to see the SPL meter, unless you're using a mic connected to a computer outside the box and equipped with sound analysis software, so you may wish to consider a glass side, preferably a double glazed glass side.
What you're describing will illustrate absorption, ie the reduction of sound within the "room" since the meter is inside the box, but it won't illustrate how well different materials block transmission of sound from one room to another.
What you want is 2 meters, one inside the box and one outside . Make the box with the speaker in one end wall and the opposite end wall open but able to be closed by panels of your test materials. The first control measurements are taken with the end of the box opposite the speaker open, then further measurements with the box sealed with various materials. These could include a standard plasterboard wall section one of your materials, then similar wall section panels with various materials in the space between the 2 plasterboard sides of the section.
If you're using computer software you can even show frequency spectrums for the sound being measured by the 2 meters, showing the different absorption and transmission spectrums and illustrating how it is much easier to absorb and/or to block high frequency sound than it is to do the same with low frequency sound.
If some of your panels to close the box are materials like fibreglass boards with known absorption/transmission properties, you can show how your measurements confirm or differ from the material's published specifications. You won't get similar measurements to the specifications because your test chamber is very different to the standard test chamber but there should be some broad correlation between what you measure and the published specs.
David Aiken
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