to speak very softly or quietly, usually to avoid being overheard by others who are nearby
ささやく
to speak in a low, soft voice, often in a way that is difficult to hear or understand
呟く
to speak in a low or unclear voice, often so that the words are difficult to understand
もごもご言う
to repeat or perform something again, often to make it clearer, better, or to emphasize specific points
反復する
to say a word or words incorrectly, especially with regards to the proper pronunciation
誤って発音する
to talk rapidly and incoherently, making it hard for others to understand what is being said
支離滅裂に話す
to release a long deep audible breath, to express one's sadness, tiredness, etc.
ため息をつく
to speak with involuntary repetitive sounds or interruptions in the flow of speech
どもる
to talk in a low, soft voice, particularly to express contentment or to convey seductive charm
ゴロゴロ言う