Here is the video
https://www.youtube.com/watch?v=1rIPQMkI0w8
You won't need any special hardware other than a 4 channel ADC. I use the NI 9234 which is a Sigma-Delta ADC from NI. You can use other ones though you may need anti-aliasing filters. Sampling is at 50kHz divided by 4 or 12.5kHz per channel. You can change this too.
The way the mics are arranged is crucial to the working. Co-ordinates are given on the front panel. (
Mic1 (-0.25,-0.25)
Mic 2 (-0.25 0.25)
Mic3 (0.25 0.25)
Mic 0 (0,0)
You can change this too but you may have to change the graphics to match.
The algorithm works by finding the delays between microphones using the generalized cross-correlation method (which uses FFTs and coherence, the Hannan Thomson mehod).
Once you find the time-delays for a source to a pair of mics you can fix the (x,y,z) co-ordinates. The radius control on the front panel is only like a zoom for the graphics and nothing more. a simulation of this method can be found here
https://decibel.ni.com/content/docs/DOC-16771
For theory see
Passive Acoustic Bearing Estimation
Using the Spherical Intersection Method.
(Smith and Abel IEEE Trans ASSP,vol assp-35,
no 12,Dec 1987
Unrar the file, arrange the microphones (see video). You can use a radio for the source.
