speaking tube

a tube for conveying the voice over a somewhat limited distance, as from one part of a building or ship to another.

Origin of speaking tube

First recorded in 1825–35

The speaking-tube used was of woven material, not of rubber, and a pad of felt was kept in the tube near the diaphragm box.

Harvard Psychological Studies, Volume 1 |Various
He slouched across to the speaking-tube and whistled up the engine-room, while Slyne sat watching him with sombre eyes.

The White Blackbird |Hudson Douglas
Watching the barometer carefully, Cobb soon put his lips to the speaking-tube, and called to Lester: “That will do.”

A. D. 2000 |Alvarado M. Fuller
She flew to a speaking-tube and asked who on the fourth floor wanted her.

As Seen By Me |Lilian Bell

Thank you, sir, said Thomas, and called down the speaking-tube.

The Exiles of Faloo |Barry Pain

speaking tube

a tube or pipe for conveying a person's voice from one room, area, or building to another