“They are all silent dogs; they cannot bark, dreaming, lying down, loving to slumber.”
Our late Shih Tzu was not a silent dog, but he was probably as close as you’ll ever get. He almost never barked, and when he did, about the most you’d get from him was a polite, solitary “Arf.” If you didn’t respond to that, you were on your own.
A non-barking dog is world’s greatest pet when you live in an apartment and want to maintain some sort of decent relationship with your neighbors. But our little guy would not have made much of a watchdog.