The answer to 'why is my stink bug scratching sounds' is that stink bugs make a scratching or clicking sound when they are disturbed or trying to communicate with other stink bugs. This is a common behavior and not a cause for concern.
Stink bugs use their mouthparts to make these sounds, which can be heard when they are moving around or when you accidentally disturb them. The sounds are part of their natural behavior and are not a sign of a problem. As long as you are not seeing an excessive number of stink bugs in your home, the occasional scratching sounds are normal and nothing to worry about.