If they are barking ONLY when you are away, it could be that your dogs get anxious in your abscence.

Again, I HIGHLY recommend alone training. This allows the dog to cope with your abscence instead of using the quick fix.
Generally, you restrict their access to the house. I keep my dogs in the living room and yard ONLY. They don't do well in crates, so they stay in the living room with access to the yard. I close all the curtains and turn on the TV or radio to a medium volume. Then, I give the puppers a frozen Kong on their beds and leave nonchalantly. I walk around for about five minutes, then come back, take the Kongs away, and turn off the TV in one calm motion. Gradually, I increased the time. Now, my dogs are each other's stress reliever and I can leave home for 8+ hours (had to do that, unfortunately) if need be. Trust me, Alone training DOES work. I always recommend alone training any new dog. It boosts their confidence and helps acclimate them to their surroundings. You might also want to look into the DAP Diffuser and/or Rescue Remedy. Good Luck!