Several posts have been made in the forum about playing wave files in stereo...

There's an alternative to playing stereo wave files in 3D GameStudio. You can split the wave file into two, and position the sounds according to the position of the camera.

For example, left wave file - camera - right wave file.

Note, however, when you pan a camera, you will need to do a calculation to get the wave files play at the exact position with the pan.