老人在电话里咕哝着说话，我几乎听不清他在说什么。

The old man ___mumbles on the phone, making it hard to catch his words.

奶奶因为假牙不太合适，吃东西时总是咕哝着咀嚼。

Grandma ___mumbles her food because her dentures don't fit well.