Today has been spent crunching numbers again by adding the butyl layer to 181's
air box. The untreated air box was also rerun through the same analysis matrix
settings as a control for comparison purposes.
Several criteria were examined on both models; the modal natural frequency, the
harmonic response, and the harmonic acoustic qualities.
Two sets of solutions were applied overall based upon 1 cylinder cycle and 4
cylinder
cycles from 3000rpm to 5800rpm; both provided similar attenuation plot
results. The images attached are from the 4 cylinder cycle solutions.
The attached images relate to distortion of the air box at a nominated frequency
of 8200hz, being 4100rpm. Blue represents zero distortion, red maximum measured
distortion. The two images clearly show how well the butyl layer attenuates
excitation frequencies of the air box; being the image with the most blue.
The attached graphs are related to the amplitude of applied frequencies being
projected
---From the air box to the surrounding environment, measured at a near field
specific position to the air box being 100mm above the air filter opening,
behind the rear at the firewall, inside under the air filter, and corollate
to (x2) rpm.
The db attenuation qualities of applying the butyl has proven much better than
expected. One point to note is the material density applied. The DCI product
presents
a density of 1310kg/m3 against standard 900kg/m3 of other similar products.
It was surprising to make the distinction between the lower amplitude levels on
the graphs to the different power setting rpm selected in real flight
situations;
they are identical to where the smooth running points are being perceived
to be.
Again these tests are not for determining induction noise affects, they are for
determining the inherent acoustic qualities of the air box and how it is
affected
by environmental frequencies along with its ability to adsorb vibrational
frequencies. Can it or can it not absorb and dissipate a specific kind of
kinetic
energy.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=510520#510520
Attachments:
http://forums.matronics.com//files/a36fd941_1515_4c04_b9fc_0d14389760b0_191.jpeg
http://forums.matronics.com//files/61ad6bda_5185_488d_ba0b_3f8573defecb_173.jpeg
http://forums.matronics.com//files/71bda7a8_4377_49aa_8b92_faa9a3fe50c3_650.jpeg
http://forums.matronics.com//files/e0f1a51a_5b31_4743_926c_b7eaf6d216da_106.jpeg
http://forums.matronics.com//files/3b843e40_1bf6_498e_85b9_a2e3aaeb69bf_110.jpeg
http://forums.matronics.com//files/36823efb_a9da_43af_b444_24f772356014_184.jpeg
http://forums.matronics.com//files/54d66213_a643_42a1_93d2_5483cc7be7d3_951.jpeg
http://forums.matronics.com//files/4db4f5b3_52d3_4cd7_991f_757fc0a54a36_207.jpeg
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