Yesterday I released the first beta of SPi-V 1.4, adding support for (streaming) directional audio, amongst other things. Here's a demo showing streaming directional audio.
Note how the directional audio not only changes in volume as you move past, but the sound actually travels from left to right (and when you are looking 180 degrees from the sound source, the left and right channel are actually reversed!).
The panoramas in the demo were taken years ago, and the 4-5 looping soundbites were 'found', not recorded by myself. Because they each loop at different intervals, the resulting soundscape seems to be a very long loop.
Instead of using the audio engine in Shockwave, I decided that it would be better to use Flash for audio. SPi-V already included a bridge to Flash in the form of a LocalConnection object, and now it creates a Flash Sound object for each sound. It was just easier to get streaming mp3 to work with the Flash functionality than it would have been with pure Shockwave/Lingo. And the Flash sound object has more control over panning and mixing the left/right channels.
For more information about the beta, see SPi-V dev.