If a sound is muffled, you can tell something is making noise, but you cannot hear it clearly — as if a door, a wall, a coat, or a blanket is sitting on it. A voice in the next room, a phone in a bag, drums under a cloth: they come out dull and round, not sharp.

If a sound is muffled如果一個聲音是muffled（悶悶的）you can tell something is making noise你可以知道有東西在發出聲音but you cannot hear it clearly但聽不清楚as if a door, a wall, a coat, or a blanket is sitting on it好像有一扇門、一面牆、一件外套或一條毯子蓋在上面一樣。A voice in the next room隔壁房間的說話聲a phone in a bag包包裡的手機聲drums under a cloth蓋著布的鼓聲they come out dull and round聽起來都悶悶鈍鈍的not sharp而不是清脆的。

This is ordinary English for sound, not slang.

This is ordinary English for sound這是形容聲音的普通英文not slang不是俚語。

People also say someone is muffled up when they are wrapped in scarves, but the sense here is about hearing.

People also say someone is muffled up人們也會說某人muffled upwhen they are wrapped in scarves意思是裹著圍巾but the sense here is about hearing但這裡講的是聽覺的意思。

Though actually, writers use it for feelings too — a muffled laugh, muffled anger — meaning the thing is held in and not fully let out. The opposite feel is a sound that rings out clear.

Though actually不過其實writers use it for feelings too作家也會用這個字形容情緒a muffled laugh, muffled anger像是muffled laugh（悶住的笑）、muffled anger（壓下來的怒氣）meaning the thing is held in and not fully let out意思是那個情緒被壓住、沒有完全發洩出來。The opposite feel相反的感覺is a sound that rings out clear是一個響亮清楚的聲音。