How do I get the current overall System's volume?

I simply want to make a Music Visualizer that grabs the current volume on your system and makes a graph go up and down.

I have tried using NAudio, but the .dlls don't seem to be compatible with Unity. (They are .NET 3.5 libraries). I just can't follow any tutorials to get NAudio to work, I've tried putting the dlls in the assets folder and including them in my source file's header, but even doing that breaks the program.

I have no experience with interfacing with dlls. Detailed help is greatly appreciated. Thank you!