The listener's orientation plays a strong role in 3-D effects processing. DirectSound approximates sound cues to provide the illusion that a sound is generated at a particular point in space. For more information about these cues, see Perception of Sound Positions.
An application can set and retrieve the listener's orientation by using the IDirectSound3DListener::SetOrientation and IDirectSound3DListener::GetOrientation methods. By default, the front vector is (0,0,1.0), and the top vector is (0,1.0,0).
For an illustration of the front and top vectors, see Listeners.