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Acoustic Analysis

I am trying to analyze the noise heard by the passenger inside the cabin (of vehicle) due to some external acoustic source as well as base excitation due to road.

I am using NVH application with Optistruct solver. I am able to analyze the base excitation due to road.

But I am not sure how to perform the analysis for noise generated by a far field source.

To be more precise how can I create acoustic cavity mesh for fluid outside the cabin and define acoustic source. (Acoustic cavity tab asks only to select structure components and seat components).

Thanks

Anmol

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anmolk

I found the method in this thread. but I am wondering how can I define CACINF4 element type for only outermost elements because I need to specify grid points in definition.

Is there a way to extract element connectivity table for the faces or some other way please let me know?

Thanks

Altair Forum User

Hi,

You can extract faces, move to a different component and change the element type to CACINF4

anmolk

Okay Thanks. For now I just made a very simple planar ambient field instead of sphere just to verify. I am getting same error as described in previous thread, ' *** ERROR 1684: FLUID element 1736620 points to non-fluid GRID 210175.'

I see that for some grids cd = -1. How do I resolve this. These grids lie inside the vehicle cavity.

Altair Forum User

Hi @anmolk

To resolve this issue you need to card edit all the fluid grids and choose CD= -1 for them. (This has to be done for all the nodes except the constrained node). You can card edit all the fluid grids at the same time.

anmolk

Appreciate your help that worked.

I have couple of questions though about this procedure.

1. I ran the analysis for low frequency ranges <200Hz. Is it valid for higher frequencies as well f=1-2kHz? If it is how may I improve the accuracy?

2. Can I use infinite elements approach to analyze noise inside Composites structures as well?

Please let me know

Thanks

Subash Karthikeyan

Hi anmolk,

I'm planning to do the same kind of analysis where i want to analysis the noise levels outside of a cabin,

can u help on me that.

It will be hepful

Regards & Thanks

Subash K