Air filter Noise analysis: simulation and testing

Dear all

I have been facing a problem since few weeks. I gotta single cylinder 4s engine and Its regarding the noise generated by the induction system consisting of pipe which connects to engine inlet valve through carburator, air filter with the filter element. I use paper filter as the medium for filtration. The induction system creates a very annoying noise from 3000rpm and there on. when the engine is at idle condition, it runs very smooth without any problem with induction noise. As soon as it crosses 3000-3400rpm til the max rpm it creates a very highly irritating noise (like ooorrrrrrrr). Mayb something similar to a race engine (just a guess). Initially I felt it might due to the sound radiated from the panel of the air filter due to insufficient stiffness in the strucutre. However, stiffening experiment failed with the same noise persistant still with high stiffness created through ribs and thickness increase. Lateron, I got doubtful about any air column resonance inside the whole induction system. I tried both firing and motoring the engine, the noise radiated in both cases. I tried measuring the noise with a microphone placed at certain distance from the engine and found a dominating peak in the overall spectrum at around 300-350hz and 650hz for which I designed one helmholtz resonator for both frequencies and fitted into the duct running from air filter box to carburator. The sound was reduced dramatically for the resonator desgined for 650hz but not worked for the one at 350hz.

I was wondering how to get this analysed in an analysis software like Ansys where capabilities of doing a fluid analysis, fluid-structure analysis are vast. I am doubtful about the boundary conditions to be given at the both end of the meshed system. And why does the resonator worked for 650hz but not for 350hz. I got some results but unable to get a conclusion without much simulation .

Finally the target is to desgin an induction system without irritating noise and without a resonator. Any inputs?

Thanks

Vinay