An application can set and retrieve a listener's position in 3-D space by using the IDirectSound3DListener::SetPosition and IDirectSound3DListener::GetPosition methods.
To set or retrieve the velocity value that DirectSound uses to calculate Doppler-shift effects for a listener, use the IDirectSound3DListener::SetVelocity and IDirectSound3DListener::GetVelocity methods. Velocity is measured in distance units per second—by default, meters per second.
As with buffers, a listener's position and its velocity are completely independent. It is entirely up to the application to set an appropriate velocity for the listener.