There is no sound, the button is a soft touch, so there is nothing to be heard inside or out. BTW, you can do both - use motion sensor to capture movement outside your door, and manually press the button to see who is at your door in real time. If you use the motion sensor, the pictures can be used after the fact, if you have a security breach.
In my case the motion sensor is always on.
Every time it detects someone he does not turn the screen. Just flash a small red light in the upper right corner of the screen.
If you want to see what is on the other side of the door will have to push the button.
I honestly do not know if the ability to set the screen to turn on whenever it detects someone there.
One thing I know it's possible to configure is that you can choose if you want her to do a short film or take pictures every time it detects motion.