You are already helping a lot!
Where should I try to explain the method?
A new thread, PM, E-mail?
Give you al link to a web site that explains it, might be the best option.
http://www.danmarx.org/audioinnovation/impanalyzer.html
Let me know if there's anything that's unclear.
The device on the site is not really necessary, this is more to make a nice plot possible.
A simple resistor can do the job, if all you're interested in, is the resonance frequency.
B.

edit:Great! This is my 50th post