Will our dogs always bark at imaginary intruders?

Can you train a dog to not bark whenever a door opens or whenever someone walks up and down the stairs?

If you can, is it too late for us? Our dogs are 8 years old.

I’m startled at least 15 times a day because our dogs bark whenever they hear a door open or whenever one of our children walk downstairs. They also start barking when I walk upstairs. It’s so hard to enjoy a peaceful moment in our home. They weren’t as bad when we lived in a smaller house.

Can we teach these old dogs a new trick?