The IDirectSound3DListener::GetVelocity method retrieves the listener's current velocity.
HRESULT GetVelocity(
LPD3DVECTOR lpvVelocity
);
If the method succeeds, the return value is DS_OK.
If the method fails, the return value may be DSERR_INVALIDPARAM.
Velocity is used only for Doppler effects. It does not actually move the listener. To change the listener's position, use the IDirectSound3DListener::SetPosition method. The default velocity is (0,0,0).