Once I nearly went insane due to a poor little beagle who was basically abandoned in his people's back yard.  I tried the usual courtesy-spoke to the neighbor (they lived behind us) to let her know that the dog would bay and bark constantly. At first it was all nice and full of apologies, but it disintigrated because I am an animal lover and felt the pet was being abused.  So, I did the following,  First, call the Police Department if Animal Control is not open. In the case of renters, go on the internet get the number of the Assessor's Office and you can get the name and address of the owner. If you are dealing with renters, write a letter to the owner letting them know of the problem. Remind them that they can be held financially responsible for the disturbance caused by their tenant.  Document each time you call Animal Control (and for how long the barking went on and whether the owner of the dog were home or not) and if you can make a friend at AC, that certainly helps. In our case the pet was not licensed and had no record of shots.  Large fines come with these violations.  AC is always willing to go and contact people with unlicensed and pets that have not had shots.  Or pets that constantly escape and end up in neighbor's yards and cause destruction.  We ended up moving  before we ever learned what happened to the poor little dog. Now, just to infuriate as many people as possible, I nearly died when the owner told me that she was only able to afford the $700 dog because her Section 8 voucher saved her so much on rent.  Normally, I wouldn't care and I had no idea, but I did know that at least half the time when I called her on the number she gave me, she would tell me that they were "out to dinner," or "at the mall," and I think her kids were often home with the dog.  As someone who worked hard to achieve what we had, I was a little taken aback by her candid comments. I really hope that you can resolve the situation amicably since you all have to live together. I cannot imagine what kind of noise Danes can make, but it must be just annoying beyond description.  pholub gave uo some really good things I never even though of..Good Job!  Also, great thoughts from  "jhd1200" as well.  If they are renters, you do have more resources.  And to reiterate, you can call AC weekly, or when you cannot stand it,call every day for a week.  They will find someone to go to the house.  I guarantee it.  

From my experience, those devices are a waste of money.

Smokey, I am sooooooooooo happy to hear you got some sleep, and that the dogs have not barked since 6 last night.  That is how it should be.  My neighbors have dogs and they are big dogs, and I RARELY if ever hear them bark.  Folks need to realize that owning an animal comes with "responsibility".  Think things all the way through before getting any pet. 

I'm hoping more Happy Zzzzzzzzzzz's in your future Smokey.