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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.
On Mon, May 18, 2009 at 7:30 PM, Ernest Christley <echristley@nc.rr.com> wrote:
Tracy Crook wrote:
Your mathematics are sound George and using that approach will certainly keep back pressure to a minimum. But I think it is doomed to be noisy. That's just my understanding about how mufflers generally work and I could be wrong.
During a test of mufflers at a rotary fly-in some years back I was amazed at how effective the muffler became and how small the power loss was when we installed a 1" diameter muffler outlet pipe on the test stand engine (13B). 1" is admittedly too small but we learn by going to extremes sometimes.
Tracy
http://ernest.isa-geek.org/Delta/Experiments/PhononicBandgapFilter.html
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