Hi

It depends a bit as to what you refer to as a higher order model.

Perhaps a look at the theroy of a Single Degree of Freedom system is a good place to start

http://qringtech.com/TryMe/wp-content/uploads/2014/01/sdof.pdf

Then, take a look at the B&K Structural testing  and HP application Note 243-3

http://qringtech.com/learnmore/recommended-reading/

For links to freeware that makes Experimental Modal Analysis (EMA), see here

https://www.researchgate.net/post/References_for_MDOF_experimental_modal_analysis

This EMA freeware is planned for release in 2016

http://www.openmodal.com/

Sincerely

Claes

Hi

I advice you to see these documents. You will find what you need.

I hope that I helped you, let us know if you have another questions or you need more details.

Best regards

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