muffled
adjective uk/ˈmʌf.əld/ us/ˈmʌf.əld/
（声音）变轻微（或低沉）
A muffled sound is quiet or not clear.
I could hear muffled voices next door but couldn't make out any words. 我听到隔壁有人压低声音说话，可听不清说什么。
The muffled roar of traffic could be heard in the distance. 远处隐隐传来过往车辆的轰轰声。