Separate static echos from acoustic signal (ICA?)

Question

I am using acoustic waves to measure the thickness of material. My problem is that the acoustical lens produces static echos in the signal. I try to separate both because there is a short interference between both.

The frequency of the material echo and the static echo has nearly the same frequency. So spectral subtraction is not a valid method to separate the signals.

I will try the following: The first measurement is without any object. So I am able to measure the static echo of the acoustic system. The second measurement I collect the signal with the object to measure.

My idea: So I got two signals from different signal sources. Maybe I can separate both with Independent Component Analysis (ICA).

Do you think that this solution will work? Or is there a better method to separate static and echo signals (with noise) out the measured data.

Thanks for your help.

Answer 1

This probably should be a comment, but I didn't earn that option yet. You can try measuring instrument impulse response. If I understand correctly, your system is essentially one-dimensional. Then if you use thin plate or plate of known thickness instead of thick object/material, your output signal will be an approximation of impulse response. Using it as deconvolution kernel will allow you to measure response specific to material, or object.

Answer 2

I would suggest looking into Adaptive Signal Processing techniques like RLS. http://researchtrend.net/ijet21/ijetnew/9%20Binod%20K.pdf

Component separation with ICA is possible provided the signal sources have the following characteristics.

1. They are non-gaussian.
2. Statistically independent from each other.
3. Time of Arrival are approximately the same.
4. Number of signal sources is at-least as large of number of estimated components.(You will have to account for the noise in the echo signal)

The drawbacks are the correct ordering of the estimated components, scaling and sign cannot be determined with ICA.