You need to teach your dog the command quiet..
Training your dog to be quiet:
When you see your dog barking excessively at visitors we often find ourselves disciplining them rather than praising quiet behaviour. We are also often inconsistent in when we apply this discipline. Consequently our dogs do not develop any learned behaviour around when and where barking is allowed. Here are a few tips on training your dog to be quiet:
* Each time your dog barks at a passer-by, after several barks, praise your dog for informing you, then gently ask him or her to be QUIET. If they remain quiet for a few seconds, praise them. You may need to show them a very tasty titbit initially to help them concentrate on you and calm down. Give them the titbit the second they are quiet and slowly increase the amount of time they have to be quiet before giving them the titbit.
* If they continue to bark, raise your voice or use body language to strengthen the command, but praise them as soon as they are quiet.
* It will take a few sessions (depending on the number of visitors you get!) but, over time, build up the duration of time you expect them to be quiet. You might find it useful to count out the seconds as an added means to hold your dog's attention away from the passer-by.
* Always be consistent- many attempts to train a dog to be quiet fail through inconsistency.
* NEVER reprimand dog barking. Only reprimand them for disobeying your command to be quiet. But the second they obey, praise them warmly.