How to filter an underwater acoustic signal for TDOA localisation
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Hi,
I'd like to filter some ultrasonic signals in order to improve SNR on received signals. I'm trying to do an algorithm for underwater localisation based on the TDOA (Time Différential of Arrival) method. Actually, I use three kind of pass-band filters (filtfitlt(), bandpass() and filter()) to do that. However, I don't think I use properly those filters since when I apply a cross-correlation (gccphat() function) to the signals in order to get the TDOA , I don't get good results (time delay is almost always 0 which is false) so I can't estimate the localisation of the source. I don't have much experience doing digital signal processing, so any help would be very appreciated.
Regards,
Jorge.
4 Comments
Star Strider
on 10 Jul 2019
The filtfilt function is phase-neutral for all filters, so there should not be any phase distortion. The output should be a filtered version of the input, so the arrival times should not be affected. As I mentioned, I have no experience with ‘TDOA’, so I am only addressing your filter implementation.
Your best option may be to filter your signal before recording it, using a hardware filter. The Bessel filter is a phase-neutral (linear phase) filter that is frequently used to avoid phase distortion in the filtered signal. The cutoff frequency in a lowpass Bessel filter must be no higher than the Nyquist frequency (½ the sampling frequuency), although it may be lower.
Amit Galor
on 15 Jul 2019
Hi Jorge,
I'm working on a similar problem for the purpose of localizing underwater sources. I'm currently contemplating between the pros and cons of TDOA compared with the DOA algorithm for this purpose.
Can you post your script to help me compare the results with what I get with DOA for sample signals?
I might also be able to help you after seeing your noise filters implementation, we implemented de-noising with pca and bandpass filters.
Kind regards,
Amit
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