Gruffness is the quality of speaking, or sometimes acting, in that rough, unfriendly-sounding way. It is the noun: not the person, and not how they speak in one sentence, but the manner itself. “There was a gruffness in his voice” means you could hear that short, coarse tone. People sometimes use it for a blunt manner in general, not only the voice. It feels a little more formal than just saying “he sounded gruff.”