It seems like it's somewhat of an age thing.
Miko didn't make any barks (of any kind for any reason) until he was 1 year old. One day, he just barked. I was sooo grateful it wasn't a yappy bark. Since then, he only barks at noises outside. If he needs to go out, or playing, etc, he rarely barks. (well, I take that back, he does more so now because of our loud mouth other dog). Miko is definitely not a barker. But, when he does bark, it sounds like a big dog.
Koji on the other hand, was always verbal. He whined more than barked in the beginning. And I knew Miko was teaching him a bad habit of barking at knocks on the door, etc. But I had hope. Koji didn't start barking till he was almost 1. Since then, he barks for attention, food, attention, wants to lie on you, attention, going out, attention, someone outside. You get the point.
I'd say, enjoy it. When it was only Miko, I sure didn't enjoy it as much as I do now, hehehe.