I've had two. In my limited experience, they do not bark a great deal. Mine will bark at strangers who approach their fence or yard, but are generally quiet in the house and around people in general.
my toller does bark at strangers and other animals. The breed is known for what is called a "toller scream". It is truly a scream, and the dogs will emit this when they are excited, or frustrated. They are not the breed for a crowded neighborhood where noise is a problem. For examples of a toller scream, just search Youtube for "toller scream" and there are several examples on there.
If properly socialised and trained they will only bark to sound an alarm, as will most dogs. They are a breed that requires lots of mental stimulation and should not be left alone for long periods.