124.186.229.142
In Reply to: RE: 8th grade science project posted by Jim D. on February 01, 2009 at 04:47:47
No, not all 6 sides, just the one opposite the speaker. I'd try and make the other sides as non-transmissive as possible. Sound will leak but if you've got a "reference reading" made with the switchable side open, you can compare that reading to readings with that sized closed by various materials/constructions and you can then see the effect that each switchable side has had in blocking transmission.
I thought about the 2 compartment enclosure, actually my first draft had that in it, but in the end I figured that it would make the box quite large and that could be a problem. The smaller box is easier to display and a lot easier to build and carry.
Measuring absorption within the box can be done but I wonder how useful the results will be in an extremely small box. They're not going to be accurate and they won't match the published data though you would expect to see somewhat similar curves for absorption at different frequencies. The small enclosure volume and small area of material being measured are going to have an effect on the results and it's going to be hard to do the standard mountings with spacings 4" away from a surface and have reasonable space for the mic or meter in a small box. The high frequency reflectivity of glass and its low frequency "leakiness" will also have an effect on the results if you're using a side with a window of some kind.
David Aiken
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