murmur, mutter, whisper

名詞 whisper:

1. speaking softly without vibration of the vocal cords
   同義詞：whispering, susurration, voicelessness
2. the light noise like the noise of silk clothing or leaves blowing in the wind
   同義詞：rustle, rustling, whispering

動詞 whisper:

1. speak softly; in a low voice

1. She said it in a whisper, so I didn't hear.
   她是悄聲說的，所以我沒有聽見。
2. The wind was whispering in the roof.
   屋頂上風聲颯颯。
3. The children were whispering in the corner.
   孩子們正在角落里低聲耳語。

whis.per

n.（名詞）
Soft speech produced without full voice.
低語：壓低嗓音說出的輕聲話語
Something uttered very softly.
耳語輕聲細語：非常輕聲溫柔地說出的話
A secretly or surreptitiously expressed belief, rumor, or hint:
耳語，私語：秘密或私下里表達出的看法、謠言或暗示：
例句：
whispers of scandal.
關于丑聞的竊竊私語

A low rustling sound:
低低的颯颯聲：
例句：
the whisper of wind in the pines.
風吹過松林間颯颯作響

v.（動詞）
whis.pered,whis.per.ing,whis.pers
v.intr.（不及物動詞）
To speak softly.
低聲說
To speak quietly and privately, as by way of gossip, slander, or intrigue.
私語：暗中秘密地及私下里說，如通過說閑話、誹謗或搞陰謀的方式
To make a soft rustling sound.
發(fā)颯颯聲，產(chǎn)生低聲颯颯作響的聲音
v.tr.（及物動詞）
To utter very softly.
耳語
To say or tell privately or secretly.
私語：私下里或秘密地說

來源：
From Middle English whisperen [to whisper]
源自 中古英語 whisperen [說悄悄話，耳語]
from Old English hwisprian
源自 古英語 hwisprian

【引伸】
whis.perer
n.（名詞）
whis.pery
adj.（形容詞）