Many dogs will alert bark at the sound of the door bell, a knock or a person at the door. They are initially startled by the sound. The door bell is one of the few sounds the human members of the pack have to get up and hurry to answer. So many dogs join in and become excited.
If the dog is shy or fearful they well feel stressed at the sound. A dog who tends to thinks that it is his job is to protect the territory will be on high alert. The friendly, social dog can barely contain itself that a friend might be at the door. All of these dogs will get into the habit of vocalizing by barking. Once the habit is well established it is hard to change.
If you want your dog to let you know when a car dives in the driveway or someone is walking up to the door be sure to teach a quiet cue. I use “Thank You That’s Enough”.
One way to make the sound of the bell meaningless is to buy a wireless door bell and ring it randomly ignoring both the dog and the door. You can also teach the dog that when they hear the bell or a knock it is a signal to the dog to go lie on a mat out of the way of the door. If your dog is a happy barker you can teach him to pick up a toy which usually stops the barking.
If you want to prevent a dog from dashing out the front door teach the dog to "Sit" when you put your hand on the door knob and to Stay in a Sit until the visitor comes into the house. Depending on the configuration of your entry way you chose a place for the dog out of the way of the door.
If you own a dog that tends to protect its territory or is fearful of new people coming into the house you can manage the situation by putting the dog either in the back yard or behind a baby gate when some one comes to the house. Though we want our dogs to be part of the family sometimes it is kinder to the dog to give it a pass on visiting with everyone who comes into the house.
With a little retraining your dog can learn to be quiet at the door.