她用低沉的声音说话，以免吵醒婴儿。

She spoke in a ___low voice so as not to wake the baby.

大提琴可以发出优美、饱满而低沉的音符。

The cello can produce a beautifully rich and ___low note.

威胁是以平静但令人恐惧的低沉声音说出的。

The threat was delivered in a calm but menacing ___low voice.