USB microphone & interface selection As a part of my thesis work -in which I am using both acoustic and visual information- I am looking forward to implement a real time sound source localization sub-system. From the geometric principles, I know that at least 4 non-coplanar microphones are needed for 3D localization.

However, as I understand, using only a laptop to interface 4 microphones is impossible. I read that one sound card can only support 2. I also search through 4 microphone usb interfaces and found out quiet expensive solutions. I have also encountered to PS Eye, I'm not sure its sensory information is accessible through MATLAB or CLAM/C++ though.

As I only need an approximate information, I then decided to use only the azimuth angle information (planar confidence) of the source. For that, I know 2 microphones are enough. But I read about another theoretical problems for this case, like the need of calibration, harder sound seperation etc.

I have to ask is there a cheap interfacing solution, using 3 or 4 USB microphones? If not, would it be feasible to build up something from scratch and use amplified electret mics? I am really confused about hardware selection. Neither my advisor, nor the academic papers have too much practical information.

Thanks in advance.
Just get a multi-channel recording interface and some regular analog microphones. For example http://www.sweetwater.com/store/detail/Scarlett18i20/ has plenty of channels and microphone pre-amps.