01-29-2019 10:08 AM - edited
Hi,
We are working on experimental modal analysis of a vehicle acoustic cavity. I want to extract the correct natural frequencies and mode shapes of cavity. One of my problems is deciding about the model size for calculating the stability diagram. By increasing the model size, the software finds more stable modes. How can we adjust this parameter for obtaining the right number of modes?
01-30-2019 07:24 AM
Hi, and thanks for posting this question!
The problem you are trying to solve is indeed a difficult one, as the modes of the cavity are generally highly damped, and normally coupled with the one of the surronding structure as well making the modal density quite high.
My colleagues have recently posted and article explaining the basics of the stabilization diagram and how the poles shoudl be selected (see: Getting-Started-with-Modal-Curvefitting). This can be used in general to select the modes in standard scenario, but to better approach your problem i would suggest you to take some time in reading also this other article about the MLMM solver (see: Maximum-Likelihood-estimation-of-a-Modal-Model-MLMM)
The MLMM solver was specifically developed with the acoustic cavity modal analysis scenario in mind. As the selection of the poles in the stabilization diagram is difficult, and often the estimates end up to be be not fully reliable, MLMM will take your initially selected poles and optimize them to better represent the data that you measured.
So in your case, my suggestion would be:
I hope this can help you
If you want to discuss more in details the applications or have still some question, feel free to reach out to us.
02-01-2019 05:03 AM
Thanks for giving the answer for the above query.