To better understand the behavior of dogs barking at doorbells, it helps perceiving the world from your dog's perspective.
You see, when you first got your dog as a puppy, the doorbell was a neutral stimulus. In other words, something that had no meaning other than perhaps soliciting an orienting response such as turning their head towards the noise and wondering "hey, what was that?"
Through repeat associations between the noise of the doorbell and people coming over, your dog likely learned to put two and two together so he now reacts to the doorbell because he knows it means guests!
By observing how your dog behaves when guests are coming over, you'll be better equipped on understanding doorbell barking in dogs and how to curb it if it's excessive.
Hey, Owner, Somebody's at the Door!
There is barking and barking at the door. If your dog barks when the door bell rings or somebody knocks at the door, there are chances that your dog is just letting you know.
Some dogs are prone to alerting their owners about anything going on in the home and surroundings.
The term "watch dog" is there for a reason, it's used to depict those dogs who keep an eye on people that come and go and will bark to alert their owners. Some dog breeds are more prone to this type of barking than others.
Often these dogs give a couple of alarm barks and quiet down once their owners acknowledge that there's somebody at the door. Once the guests are in, the barking morphs into sniffing and possibly greeting behaviors.
Course of action: If your dog is prone to bark more than you would like, try to stay calm, walk by your dog and say something like "thank you" and slip him one, two treats that you keep at the entrance purposely for this training.
Hey, Owner, Yay, There are Guests!
Some dogs may bark from being very excited about having guests coming over. Dogs who bark excitedly at the noise of the doorbell are often dogs who are excited about guests.
Turid Rugass in her book "Barking: The Sound of a Language" describes excitement barking in dogs as being a high frequency sound that may sound a bit hysterical. The barking is more or less constant or it may present as a series of barks with some pauses in between. Whining may also be present in the middle of barking.
The moment guests enter the door, these dogs may are full of happy anticipation, some dogs may jump, some dogs lick faces and many greet guests like if they were long lost friends.
Course of action: To lower this type of overly excited, aroused barking, you may want to practice working with your dog under threshold by keeping him at a distance from the door (a leash can come handy) and teaching him an alternate behavior than the excited barking.
Have a helper ring the doorbell or knock at the door several times but without coming in the door. Every time the doorbell rings, ask your dog to perform a behavior such as sitting, lying down or going to his mat. When he performs the behavior, make sure to lavishly praise and reward with high value treats.
Once your dog's brain is in operant mode, he may be less likely to bark, and if you practice this often enough, he'll automatically know what to do. If you want to kick the training up a notch, practice it with guests coming over.
The more you practice the better you'll be able to lower your dog's arousal. Once your dog is much calmer, you can then unleash him and your guests may also participate in asking your dog to sit, lie down or go to his mat in exchange for some tasty tidbits.
Hey Owner, Stranger Danger!
Some dogs aren't that eager to meet people at the door. This may stem from territoriality or fear or perhaps a mix of the two.
Dogs who weren't much socialized may dread having guests over, rather than greeting them happily as some other dogs do.
Unlike the dog who was is barking excitedly and can't wait to go greet the guests, this type of barking is a distance-increasing signal that is trying to tell the guests to go away. The message may be "get off my turf!" or "I am not comfortable having you around"
Course of action: These fellows do best being kept in a separate area when guests are over as this will spare them from being exposed to an overwhelming and often stressful situation.
Then, if you wish helping your dog become more comfortable around guests, enroll the help of a dog behavior professional to help you desensitize and countercondition your dog so he can learn that guests mean great things so he'll be better able to relax.
Now That You Know...
As seen, dogs may bark at doorbells because they're just adhering to their watchdog duties, they're overly excited or they are concerned about people invading their turf. To each their own.
Once you are able to understand what type of emotion is behind your dog's barking at the doorbell behavior, you should be able to implement the best method to effectively reduce it.