ANSWER - Tricky one. I think probably I'd go with something to calm the dog down. If you can get a bit of its hair, try sealing it into a small plastic bag with some chamomile and placing into the freezer. Freezing the essence of the dog should slow it down and hopefully make it less stressed and agitated. In conjunction with the calming properties of the chamomile, you should see the dog happier and more content.
I'd also suggest that it may well be worth experimenting with playing different types of music outside the window to the dog. Classical music can have a very calming effect on animals, particularly anything by Mozart. You may feel a bit silly pointing your speakers out the window, but hey if it works, peace is always worth looking a little silly for.
I'd also suggest you go to your local pet store and buy a secret supply of pig's ears. When the dog barks, you can throw one over the fence and likely it will be distracted enough with the chewing to shut up for a while. The dog is probably bored so giving it something to chew may generate enough interest to stop the boredom barking.
If all else fails, weird though it sounds, St. John's Wort has been clinically proven to have a beneficial reduction on anxiety in dogs. You could try getting a bottle and giving the dog a dose every day to see if medication has the desired calming effect. I wouldn't normally suggest people go round giving medicine to other people's pets but as the dig sounds pretty miserable and you get the dosage right (check first with a vet perhaps....) then you'll probably improve its quality of life while getting yourself a quieter working environment into the bargain.
I'd be very interested to know how this one turns out. Keep me posted!
Image http://www.sxc.hu/browse.phtml?f=view&id=1420563 (Leesa)