Tips & Tricks

Radiation efficiency for a trimmed panel
How does VA One calculate radiation efficiency for a trimmed panel?, The process is that we compute a radiation efficiency analytically of the bare panel, then compute ...
Emna Ben Ali Vibro-Acoustics

Getting the DLF for a foam
How do I get the DLF for a foam? The loss factor is defined as...
Emna Ben Ali Vibro-Acoustics

DLF>1 when damping computed "from NCT"
This can be due to a bad conditioning of the transfer matrix used by foam module to calculate the NCT impedance to submit to the panel.
Emna Ben Ali Vibro-Acoustics

Getting Cosmic run error
I get a Cosmic run error - what may be the cause? First look at the log file, to see if there is any errors or warnings.
Emna Ben Ali Vibro-Acoustics

FE area junctions : Why is my FE area junctions discontinuous?
Its most likely due to the nature of the meshes. A fundamental assumption for FE->FE Acoustic junctions is that the FE mesh must be finer than the acoustic mesh
Emna Ben Ali Vibro-Acoustics

What is the difference in TL from the VTL and Effective TL?
The difference is that with Effective TL you select a single area junction and with VTL you select a set of panels. The only practical difference is in the area of the connection between the cavities
Emna Ben Ali Vibro-Acoustics

Why is TL dependent on the size of the panel? Shouldn't TL be independent of the shape and size of the panel?
There are some small area/perimeter dependencies in CLFs through a panel but these should usually only cause small differences. Basically, when calculating non-resonant TL AutoSEA2 needs an expression for the impedance of the fluid on either side of the panel
Emna Ben Ali Vibro-Acoustics

Can I extract results when running VA One on Linux?
Can I extract results when running VA One on Linux?, Yes, here is few options: 1. One way to do this is to execute a QuickScript on Windows, while leaving the va1 file on Linux. Eg. solve on the Linux box, and run a QS script on Windows to extract the results, while working on a Linux file system (no need to shuffle the file over). This requires no extra license, but one needs to write the script. Eg: solver file.va1 vaone -script export_script.ebs
Emna Ben Ali Vibro-Acoustics

How does VA One calculate damping from NCT?
The equation can be found in reference [1] as Eq. (21), in which • T+U ~ 2T = 0.5*m*|v|^2, where m is the mass per unit area of the SEA panel. • Pdiss = 0.5*Re{z}*|v|^2, where z is the impedance of the base of the trim. In the ratio, the wave magnitude |v| disappears and one is left with eta = Re{z}/(omega*m).
Emna Ben Ali Vibro-Acoustics

Defined absorption in VA One FEM/BEM
Can I add user defined absorption in VA One FEM/BEM?, Yes, this application of User Defined Impedances to Surfaces of BEM Fluids and FE Acoustic Cavities is implemented in VA One 2007.5
Emna Ben Ali Vibro-Acoustics