Noise from a body vibrating at its n-th natural frequency

[IngMilano]

Hi all,

I have to predict through LMS Virtual Lab Acoustics (Sysnoise...) the acoustic field radiated from a rod (of known geometry) wich is vibrating in is n-th (generic) longitudinal natural mode of vibration, with a known amplitude. Could anybody help me on how to solve this problem? Could anybody say to me how to enter the above vibration information as a boundary condition in the BEM analysis?

Thanks

EngMilano

 

[IngMilano]

Obviously when I say "in his n-th (generic) longitudinal natural mode of vibration", I mean that I have to predict the acoustic field: first when it is vibrating in the first frequency, then for the second, and so on ...

 

[electricpete]

That is far out of my area of knowledge. But if you are studying the longitudinal vibrations of a long thin uniform cylindrical bar, than it seems the only interface with the air that matters is at the ends (not the sides). Right?

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[GregLocock]

I don't know how to solve it in LMS, but, to continue with ep's train of thought, you have a dipole source. I'd be surprised if here wasn't a simple analytical solution.

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[IngMilano]

It's right that the greater contribution to acoustic field comes from the ends of the rod ... but I would like also to consider the influence of the expansion and contraction of cross sectional areas of the rod due to the Poisson modulus of the material ... in fact the rod is not so thin (diameter/length = 0.16) ! Isn't it right?

Anybody expert of Virtual Lab Acoustics or Sysnoise?

Thanks very much!