Sotto voce

Then a man called for her, and began to make coarse jokes. But Mr. Pappleworth nodded his head in the direction of the boy, and the talk went on sotto voce.

‘Hello?’ she shouted, but still her voice came out barely louder than a sotto voce whisper.

The Boyz also regularly speak in sotto voce, mimicking the grave, hushed tones often adopted by nature/wildlife programming hosts.

"I am not your dear; I cannot lie down. Send me to school soon, Mrs. Reed, for I hate to live here." I will indeed send her to school soon," murmured Mrs. Reed sotto voce; and gathering up her work, she abruptly quitted the apartment.

“Darling,” she says, “a working-class hero is something to be. “Of course,” she adds, sotto voce, “I wouldn’t know.”