There is the method "setListenerOrientation" (been around since the very first release, actually). With this method you specify the "look" and "up" directions for the listener. If you are writing a first-person shooter where "up" doesn't change, then you could use your direction parallel to the ground for "look", and for "up" you'd just use floats 0,1,0 (core SoundSystem) or SimpleVector 0,-1,0 (SoundSystemJPCT). If your game is not as simple as a first-person shooter like Wolfenstein and you need "up" to change, then you'll need to use "setListenerOrientation" to specify both the "look" and "up" directions, since there are an infinite number of possible orientations if you only know one axis. Of course they don't necessarily have to be "look" and "up" - if you know any two directions then you can use a little vector math to calculate "look" and "up" and plug that information into the "setListenerOrientation" method. You could also get this information from the Camera (SoundSystemJPCT has a version of "setListenerOrientation" that takes a Camera argument, and also has automatic Camera/listener syncing if that is something you need).
If the "setListenerOrientation" method is not what you are after, let me know what kind of method you'd like to see, and I'll see if it is something worth adding.
BTW, to anyone waiting for the next release of SoundSystem, it may be a couple months - I've had no time for programming between school, work, and the baby. When I finish the class I'm in, maybe things will slow down a bit and I'll have more time for fun.