I hear voices but I can't see anybody; it's audible but invisible
A set phrase from a mid-Edo folk song, used to express that someone's presence is felt but they cannot be seen, or more broadly that something is known indirectly but not directly observable.
In the fog, I could hear voices but couldn't see anyone, and it felt eerie.
Online, it's a situation where you hear voices but can't see faces.
A set phrase originating from a mid-Edo period folk song. The exact derivation is uncertain, but it has become a fixed expression in modern Japanese.