murmur

/ˈmərmər/

a low continuous indistinct sound; often accompanied by movement of the lips without the production of articulate speech

中文释义：低语声；喃喃声

A murmur of conversation filled the library, disturbing those who were reading.

图书馆里充满了低语声，打扰了正在阅读的人。

The doctor listened to the patient's heart murmur with a stethoscope.

医生用听诊器听病人的心脏杂音。