Step on his tail. But seriously, I would trade you if I didn't like my Wonder Dorg so much. When my doorbell rings, people in the next county know that I have dorg. (Even if they do mistake her for a dog; it's a common mistake.)

It is a dog's natural instinct to bark.I would say you are lucky he doesn't bark inside. Training a dog to bark is a hard thing to do. It involves shaping the behavior and reinforcing it. But first you have to get him to do it and teach him a "cue" so he associates barking with that word. (like "speak") When you hear him bark next time, keep repeating your "cue" word until he learns it.You will know he learns it when you say the word and he barks! Then you have to knock on the door at the same time, using the "cue" word. All during this training you have to "reinforce" any behavior that even closely resembles what you want him to do ("shaping")--he won't do it all at once!!! Shaping is done by rewarding him with treats and lots of praise. After the behavior is established you withdraw the treats but continue to praise him. He will learn to bark on cue when you knock on the door. Keep rewarding him and soon everytime he hears the knock on the door he will bark.

Actually, as a rule, it's pretty easy to teach a dog to bark...getting them to stop barking on command is usually more challenging. Debee did give you some great tips on how to get there! You want to make it a big FUN GAME! Have someone outside ring the bell...and YOU get excited over it! (treats that he loves in hand!) Jump around.. (have them keep ringing) while you ask him.."Who's THAT?!! Lets go see! as soon as he vocalizes at all...REWARD HIM...PRAISE AND TREATS. A trick I use is to have each human (inside and out) on a cell phone or walkie-talkie...so that the person outside can definitely HEAR when the dog barks...just in case they can't hear through the door. They STOP ringing the bell when the dog has barked...any bark, at all qualifies to start. Once the dog understands the GAME...I usually will add training the dog to then SIT calmly...while the person is let into the house...and the dog must stay sitting to then be acknowledged, greeted, petted by the "visitor." This is good to do, so that the dog, which you have stimulated to bark...doesn't become a pain in the butt when people come to visit...you don't want to create a yapping, jumping monster! Ideally, you want to train daily for no more than about 20 to 30 minutes over and over...if the dog is less than 14 months old...shorten your training time. Always remember to END TRAINING on a "good note" ask for a behavior the dog KNOWS rock solid how to do..so you can reward with treat and praise for a job well done!