I believe the type of problem you are working on is called DOA (direction of arrival) Estimation. Lots of research has been carried out in this area, but all the algorithms I've seen are very complex, very computationally intensive, and use many more than two sensors. On the plus side, some can achieve good directional resolution and can resolve multiple signal sources at once. The algorithms I've seen pretty much have to be run on multiple DSP's.

One way to make your system more resistant to noise and more sensitive to direction is to analyze a narrow band of frequencies, i.e. use a tight bandpass filter on both sensors. Analyzing only a narrowband case reduces the burden on your algorithm.

- Lee