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Evaluatig Noise Reduction and Insertion Loss

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Hello, everyone.

I'm trying to evaluate Noise Reduction and Insertion Loss for open-end tube onto acoustics fields.
fortunately, I did calcalate Transmission Loss successfully. Because setting the outlet tube boundary contion is pretty simple. I assume anechoic termination at the end of tube, so I put the impedance Z_0 likes rho*c(speed of sound in air).

But I cant use that impedance when I calculate Noise Reduction and Insertion Loss, because these cases are NOT anechoic terminatio. So I put the equation likes..
Z_0 = rho*c*(0.25*(k*r0)^2+j*0.6*k*r0) (subject to k*r0<0.5)
This equation came from Levine and Schwingers' study(1947).

I tryed to calculatre this problem so many times whit COMSOL, but I cannot reach satisfy results.
That contains too many negative values.I expect your briliant advices.




Best Regards

0 Replies Last Post 23 juil. 2012, 02:13 UTC−4
COMSOL Moderator

Hello Kee Seung Oh

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