How is pan computed for 3D AudioSource?

Are there any details on how the 3D Audio in Unity 3 computes pan?

I have a game with an AudioListener at (0,0,0) and a 3d AudioSource moving around the x/y plane (with z = 0). It pans from left to right as I move in the X axis, but there is a "dead zone" when x is between -100 and 0 where no sound is played. I cannot work out why this is happening.

I am unsure, but try raising your Z to 0.1 (or something small and insignificant) and see if you experience the same problem.

As far as I am aware Unity uses the deafult 3d panning in FMOD. If so there should be no 'dead zone'. Note that panning occurs in the X-Z plane relative to the listener. (i.e. There is no 'up' speaker in a 5.1 system) Moving along the Y axis will only reduce how hard the panning is and attenuate the sound.

You might need to rotate the listener to point so that the sounds are panning correctly.