I've created a mockup for a simple version of the panel with per-application settings. Instead of volume sliders for each application, a tri-state button (muted, low, high) can be used to give priority to the focused application. Usually only one application would have high volume, clicking High on another application would set the previous focused app to low. This is to avoid micro-managing of the panel. But it could be allowed to set several applications at High with Ctrl+click, like multiple selection in lists.
Attachment:
sound panel.png
Description: PNG image
