Episode 82 of "shut that noise up"
Upon the eve of Easter, while out looking out over the distant full moon lit
pastures
for a pink and white rabbit an idea emerged instead...
With feverish reckless abandon i quickly searched through some 12,000 images of
my electronic memory and found photos of 181's CKT exhaust.
Rushing back to the table with assumptions in mind the computer was turned on
and
the images again reviewed,.. using the burn markings of the CKT muffler a model
of what could possibly be a similar internal structure, three absorber sections
with a central expansion chamber, was modelled and then sent through the
acoustic analyser with results being spat out shortly after.
What was found??? The CKT absorber/reflector style muffler provided better
overall
attenuation than the factory Rotax reflector style unit; broader low range,
medium, and high range attenuation.
On a broadband level the CKT styled unit provided on average 4db greater
attenuation
than the Rotax. Low range was shown to be affective from 50Hz upwards where
as the Rotax offers none until 320Hz. Peak attenuation levels on the CKT styled
unit happened between 2000Hz and 3200Hz where the Rotax is 450Hz to 4000Hz
with most attenuation taking place within this band.
So the CKT style Absorber/Reflector muffler is more quiet on a broadband basis
and works best at attenuating more mid-field frequencies than the factory Rotax
unit.
Happy Easter to all...
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=510600#510600
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