Strange snarls and growls

It was getting late, probably around 11:30pm. My wife had just finished with the computer and had come into the kitchen where I had just entered myself, having brought the dogs in after their night walk. I had taken a seat at the kitchen table and my wife was standing beside the kitchen sink spreading blackberry jelly on a piece of bread. Suddenly, from the direction of the dining room we heard this snarling growling commotion. I started to yell at my dogs, assuming they were the reason for the commotion. It wasn't my dogs; They were still in the kitchen with us. The older dog was beside my chair and the younger one was laying partly under the kitchen table. They both started, their ears up, but neither followed through and the snarls in the dining room were over. The whole episode had to have been well under a minute in length. But if it wasn't our dogs, what made the racket? It definitely sounded like my little female when she goes after our male for being too forward. But both of our dogs were in the kitchen with us. There definitely were no other dogs in the house. Dog noises from other than our own dogs seem to occur from time to time here. It would just satisfy a curiosity itch if I could figure out how they come about.