mutter
US /ˈmʌt̬.ɚ/
UK /ˈmʌt̬.ɚ/
1.
to speak quietly and in a low voice that is not easy to hear, often when you are worried or complaining about something:
:
•
Stop muttering and speak up!
1.
(the sound of) words being said very quietly:
:
•
I heard the soft mutter of voices in the next room.