I understand why they bark when someone’s at the door, or they see someone outside in their yard, and that type of barking directed at something.
Bu every day when I let the dachsie out, he barks. Right out of the door, as he runs to the back gate, before he can even tell if there’s anyone else around.
Then he stands there, barking. Not at anyone or anything as far as I can tell.
Is it just territorial?
“I’m here! I’m here! Didj’a get that? I’m here! And I’m one tough dachshund!”
Barks can mean a few different things, often based on what type of dog is doing the barking. Pack hounds bark and howl by habit to keep together, some herding dogs bark as part of herding, but not all. Some dogs will bark when their having fun. Mostly, barking is both an alert and a warning, with little yappy dogs doing it too much.
Here’s a wikipedia article on the subject.
It’s sometimes claimed that frequent barking in domestic dogs is retention of what is a juvenile trait in wild canids. A couple theories:
From http://www.hilltopanimalhospital.com/barking%20dogs.htm
He could be hearing or seeing things which you can’t detect. He may be able to hear another dog barking in the distance, or might see a squirrel hidden in the bushes. (My dogs have been known to bark at birds which dared to invade their territory.)
cuz they can’t talk?
This is a very helpful thread to me as I was wondering the same thing. I month or so ago I adopted a 4 month old Affenpincher. He very rarely made a sound. Just lately he has taken to barking when ever the front door opens, the garage door opens or any kind of louder than typical noise outside. I couldn’t figure out how he learned that behavior. The worst part of this is his bark in the middle of the night which wakes me up. I guess it would be good if there *were * actually an intruder rather than the neighborhood kid’s car stereo with the bass too high.
I was just going to say that!
Huh. I always thought the answer was “just to piss me off”.
I have a ten year old lhasa apso/shitzu mix. I inherited her from my parents. She barks when she plays with/ kills her toys. Which is very cute. She would totally bite your ankles to death.
But she also barks when she hears anything that she doesn’t like. She has far better hearing than I and when she doesn’t like something you know it. But she’s not a barker.
I encourage her to bark when she is uncomfortable, tell her she’s a ‘good dog’, b/c I want that warning the day I need it. She isn’t intrusive. She’s not some dog barking all night long in a yard.
She barks to alert.
Because if they meowed or tweeted, they’d sound weird? 
I have no evidence for this, but I’ve always considered that barking is one of several things they do to mark their territory. It’s also a warning alert to the “alpha male of the pack” (that’s you, NP!!) that there’s something the dog considers improper trespassing on your domain.
Based on past experience, though, typically dachshunds consider that they are really vertically-challenged great danes, and act accordingly. One of my favorite memories is a friend’s two pets, an elderly black cat and a young dachshund, sunning themselves on her porch when a neighbor’s eclectichound (ancestry ranging across a fair part of the canine genetic spectrum) decided to check out the front yard. The neighbor and my wife and I were having coffee on the porch. The dachshund moved to the foot of the steps and stood there, telling off this other dog about five times its size for having the temerity to trespass on her territory. With a sigh, the old cat got up, looked over at us with an expression that said, as clearly as if the cat had opened its mouth and said it in English, “Well, I guess I need to go pull the dog’s chestnuts out of the fire, before the young fool gets herself killed.” Cat proceeds down steps, stands alongside dog, begins hissing and arching back, fur standing on end. Neighbor dog eyes the two of them. Together they take one step forward, menacingly. Neighbor dog looks again, and remembers a pressing engagement elsewhere that he needs to go attend to right now. Dog and cat come back up on porch. Dog settles down with a “Did you see how I told him off!?!” smug expression. Cat looks at dog, then at us, shakes its head, and lies back down. 
I’m reminded of a Gary Larsen Far Side cartoon showing a street full of houses with a barking dog in every yard, captioned “What dogs are really saying.”
Every dog is saying "Hey! Hey! Hey! Hey! . . . "
I asked my dog this question, and he provided a qreat answer. I have transcribed her reply for your learning pleasure.
Woof woof,
Bark bark ruff. Whine bark woof growl. bark bark BARK BARK BARK wuff grrr… bark. Bark bark bark. Ruff bark bark. Bark.
Bark,
Goldie
About seven years ago I had the pleasure of watching a group of Great Danes grow from palm-puppy sized to full-on-scoobys. One of the funniest things I saw was when Rio’s voice dropped.
He’s running around the Garden, barking at the kids over the fence and his voice goes from Bark Bark Bark! to Bark Bark Bark!
The only other adult male in the pack is far far too lazy to bark so he’s never heard anything like it. Scared the hair from his back nearly! He runs inside the house and hides behind the table for the next hour. I miss that dog.