Yes, it sounds unusual. But when your dog growls he is giving you a present. He is opening a window into his mind for you. What is he saying? He is probably saying I am uncomfortable with something or some situation. It is up to you to figure out what that situation is but many times it is obvious. Is it some children that are making him uncomfortable or a strange person with a hat? You have to determine that and move him away from that thing, person or situation before it gets worse or turns into aggression. One thing you shouldn’t do is ever punish the growl or stop it in any way. As I said, it is a gift because you are a getting a clear signal from Rover. If you punish the growl, Rover will suppress it and in the future, give you no warning signals. That is when people say, “my dog bit someone and it came out of nowhere.” If you have aggression issues, it is extremely important that you get help from a trainer or behaviorist who is qualified to deal with such behavior. It, many times, is a result of owner/dog misunderstandings that have built up over time. Fixing those issues can take time and expertise.