Alert/warning barks
These are the type of barks some owners encourage. They want their dog to alert them to the presence of danger. Warning barks tend to become more rapid as the intruder approaches. Aggressive barks are low in pitch and may be combined with growls. We need to be able to distinguish warning barks from barks due to fear.
Attention-seeking barks
Most often used by puppies to get you to focus your attention on them. They can become very insistent and hard to ignore, but ignore them we must.
Play/excitement barks
Usually short and sharp. These barks are common if the dog gets too excited with the game. Often a time-out is in order.
Self-identification
This what you might hear when your dog seems to be answering other dogs he hears barking in your area. It is his way of saying, “Hello, I am over here.”
Lonely/anxious barking
This usually happens if your dog is experiencing separation anxiety. Anxious barks tend to get higher in pitch as the dog becomes more upset. This type of barking can be especially annoying for your neighbours and needs addressing before you get complaints!
As you can see, there are many reasons for barking and most barking is a normal behaviour.