mumle

verb
  1. To speak in a low, indistinct manner, often with the mouth partly closed, making it difficult for others to hear or understand. verb
    He tends to mumle when he's nervous, making it hard to catch what he's saying.
    The teacher asked her to speak up because she was mumbling during her presentation.
  2. A low, indistinct sound or utterance made by someone who is mumbling. noun
    All I could hear from the other room was a soft mumle.
    The mumle of the crowd grew louder as the speaker approached the podium.