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ANSYS ACT ACoustics and Diffuse sound (TRansmission loss)

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Old   February 19, 2016, 08:08
Smile ANSYS ACT ACoustics and Diffuse sound (TRansmission loss)
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Liam
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Hi everyone,

I have a few questions regarding acoustic and structural modeling in ANSYS WB.

My goal is to obtain an accurate prediction of transmission loss through a multi-layer structure. There are 5 layers of different materials, the central one is a porous media. I have modeled it using a JCA equivalent fluid model.There is a wood frame surrounding the porous material. The structure is attached to a room (PML).

Questions:

1. The TL obtained is quite different from test data, mainly in the low frequency range (below 200 Hz). I am computing the result in 5 subintervals (1/3 octave) in Analysis settings, latter I make an average of the TL values in order to obtain a good prediction for the central frequency. Is this number of intervals enough? Is there any kind of rule of thumb for this?

2. I have available experimental structural damping measurement for each material. Where is the right place to set it? In Engineering data under "constant damping coefficient"? Or is this wrong and I have to include it under alpha damping factor? Or beta?

3. What happens if I define this value of damping under Damping controls in Analysis settings? Will be this damping value applied to all the materials available in the model? And what will happen if these value is defined in Analysis settings and also in each material in Engineering Data? Which one will overwrite each other?Or this means that this value will be double in magnitude when it is defined in both places?

4. I have defined all the properties for the porous material, but, which Acoustic-Structural Coupled body Options is suitable for my analysis? For the other zones I have used the settings according to Transmission loss (Diffuse Sound) tutorial for air and PML.

5. How can I apply a viscoelastic attachment in my model (where I can provide elastic constant and viscous damping coefficient)? Is this available under Supports menu? Or is it something more related to Connections branch?

6. My structure is attached to a room. In the diffuse sound tutorial the displacement in the lateral faces of the leaf are set to zero. So is it enough to constrain the inner layer faces of ny structure (in contact to the room) via a fixed support or zero displacement condition or have I to apply this condition to all the lateral faces of each layer?

Thanks in advance, I am quite new to ANSYS ACT and also acoustic simulation. I apologize for any mistake in English use.

Best,

Many
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