Clear Vacuum / Vacuum Cleaner

How can we know if a vacuum cleaner works or not?
The only that we could rely on is guessing from hearing the sound from it.
It, also, is not easy to recognize when a large dust block the brush nozzle.

Almost everyone who is using a vacuum cleaner keep their eyes on near the end of the brush nozzle.
If the brush nozzle can be made from transparent materials, then we could see if it is blocked by others, or if a vacuum cleaner works or not.
Then we are not going to guessing, but we could see with our eyes directly.
This is not only giving more values on a vacuum cleaner itself, but also giving users more achievements.