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William Wilson wrote:
Well that is sure spiffy.
In addition to reducing high frequency noise, it looks like the filter smooths out the frequencies in the lower regions which will make for a less "noisy" sounding exhaust even if it's not actually any quieter. It would probably also be easier for ANR headsets to filter out.
You could try experimenting with ceramics. I think PVC and wood have a natural muffling effect that metal pipes won't have. Ceramics can withstand the high temperatures and may be easier to work with, especially in development stage, since clay is very easy to shape. Plus, they do it on the F-117, so it's got to be good.
One step at a time. The first step is to determine if there is actually anything to this cockamamy idea that an arrangement of objects can filter sound. The next step is to build a prototype from materials that have been used successfully and see if it is effective. If that works well, I might consider novel materials.
So now I will test the empty box with the frequency sweep, and then I will run some test using actual recorded sounds from an un-muffled rotary. I think I have a recording here somewhere.
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http://www.ernest.isa-geek.org
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