I searched for days trying to find a commercial sound localization sensor or info on how to build one. Sound localization is what the human ear does when it determines that a sound is coming from the left or right. After talking to some gentlemen over at the Arduino forums I realized that it wasn’t going to be as simple as I thought.
I finally hacked together something that works great for my first try, there is a lot of work to be done though. The sensor works fairly well from a foot or so away, after that you really feel the limitations of my circuit and only doing a volume comparison from the microphones.
I am aware that the LM324N is not specifically a comparator but can work as one, it seems to do the job.
If you are interested there are some videos on YouTube regarding sound localization but they only demonstrate the sensors and give no helpful information on building one yourself.
I may in the future try to use an ARM Cortex M3 proto board I purchased from Texas Instruments (EKK-LM3S811 Evaluation Kit) to do phase shift comparison calculations for sound localization, the Arduino is nowhere near fast enough to do this. After reading some information I believe you need to be able to sample and do a calculation in 10-50 micro seconds in order to get usable data.