You can call those functions from LabVIEW by using some VIs which we did not put in the palette. In vi.lib/sound2.llb you will find GetNumDevices.vi and Sound Device Info.vi. There's also a Sound Output Set Volume.vi, which is on the palettes. We will consider adding the other two VIs to the palette.
If you are trying to call these from C, then you can use the function prototypes given in the Call Library Nodes in those VIs. We do not support this usage, though.
If you have any other questions about the LabVIEW Sound API, I'd be happy to answer them.
