One of the quietest breeds I've ever had is the Australian Cattle Dog, aka Heeler. A primary goal in the development of the breed was to produce a herding dog who worked without barking.
My Heeler/German Shepherd mix, Scout, generally follows the book. She rarely barks. But put her in the car, and all bets are off.
As soon as her paws hit the seat, she starts belting out her own special noise with great intensity. She sounds like a hungry monkey who's spotted a bunch of bananas that's just out of reach.
It's not barking. It's more like an over... More