sound source localization - finding source vector
In general, 2 microphones are not enough.  In 3 dimensions, you actually need 4 (non co-linear) for the 3 polar coordinates. 

There are cases where if you can bring more information to your problem, like knowing the signal of the source and the transmit and receive times of the signal, you can estimate the range for simple known geometries.  

A good reference is:

Strang, Gilbert, and Kai Borre. Linear algebra, geodesy, and GPS. Siam, 1997