murmuring

Murmuring is the act of speaking in a low, soft voice, often indistinctly or privately.

It can suggest intimacy, secrecy, or discontent depending on context.

When people murmur among themselves, there's often an implication of complaint or dissatisfaction: There was murmuring in the ranks about the new policy.

The word also describes continuous soft sounds, like water or wind: the murmuring of the brook.

As an adjective, murmuring characterizes something that produces such sounds: murmuring voices in the next room.