It is a bit tricky but not impossible. Assuming you are not writing any malicious code or something to spy on people by turning on the mic or anything, here is how it could be accomplished:
1. Load a dll into explorer.exe and hook into either ShellExecute or CreateProcess. Not sure which, but one of them should work
2. Intercept when sndvol.exe is being started
3. When sndvol process is loaded and starts to accept window events, find it's window handle
http://s10.postimage.org/nd8xgzk3t/Capture1.png
4. Find a child window of type TileListView
5. Find a child window of type TileSled
6. Enumerate child windows
7. Find the window handle of the volume mixer tile of your "invisible" app
http://s10.postimage.org/6e4kfgya1/Capture2.png
8. Set it's Visible property to false, Width to 0
http://s10.postimage.org/ct3lc54zt/Capture3.png
9. Slide the remaining tiles to the left to fill the gap
10. Resize & relocate the main sndvol window
11. ???
12. Profit
kolay gelsin