The caller's answer came out as a mumble, so the agent politely asked again.

來電者的回答只是一陣含糊的咕噥聲，所以客服人員禮貌地再問一次。

During the budget meeting, a low mumble of disagreement spread around the table.

預算會議上，一陣低聲的不滿咕噥在桌邊蔓延開來。

The pilot's announcement was just a mumble, and few passengers caught the gate change.

機長的廣播只是一片含糊的聲音，很少乘客聽清楚登機門變更。