I have checked the autofocus noise of the Panasonic 25mm F1.7 again, because I received a lot of questions about it.
If you are doing fast focusing with the single autofocus (S-AF), then there is a humming noise and a click when the lens finds focus. But in my opinion this sound is not loud enough for people around you to notice it. I set my camera to silent mode and turned of the stabilization, so this noise is definitely from the lens not the camera.
However, during video recording using the slower continuous autofocus (C-AF) this noise does not appear, even when changing the focus point using the touchscreen.
In my opinion the autofocus noise of the Panasonic 25mm F1.7 is therefore not a problem.
Here is a video that demonstrates the sound it makes: