mumbler

/ˈmʌmblər/
noun
  1. A person who speaks quietly and unclearly, often with their mouth partly closed, making it hard to understand them.
    • In the movie, the villain was a creepy mumbler whose threats were barely audible.
    • My grandfather is a gentle mumbler, especially when he's tired.
    • The teacher asked the mumbler to speak up so everyone could hear.
Antonyms
What does "mumbler" mean? | whatsthatwordmean | whatsthatwordmean