Terriers have a reputation for being barkers, but this is a rather broad characterization of an entire group of dogs, and it simply doesn’t apply to every terrier breed. Glen of Imaal Terriers, for example, are on the quiet side, and for a very good reason: They were bred that way.
The Glen is not a “sounding” terrier. Their work style is to silently dig out their quarry, and indeed, during traditional hunting trials, a Glen was disqualified if s/he barked or sounded at the quarry. Consequently, Glens were bred to work “mute to ground.”
This isn’t to say Glen of Imaal Terriers have no voice. A doorbell or outside disturbance will likely compel a Glen to share his opinion, and then it comes as a surprise because the breed’s voice is unexpected for a dog his size. The deep baritone bark can be mistaken as coming from a much larger dog, a welcomed attribute that makes the Glen of Imaal Terrier an acceptable watchdog.
Image: Glen of Imaal Terrier fine European Porcelain Plate made in Denmark is available here