To me "displaying" the audio stream means showing a graphic representation of things like the wave form or frequency response, but probably you mean something else. Could you elaborate a bit?
If you mean displaying the number of available audio streams in a video file, I don't think that info is stored in any library field. It can only be discovered by playing the file and using the "right-click on display" DirectShow tools & features. If you know the file contents you can naturally create a new user field and type the info there.