If you want students to use quiet voices in your classroom while they work, you too will use a quiet voice as you move through the room helping youngsters. A standard item in the classroom of the fifties was the clerk's bell. A shiny nickel bell sat on the teacher's desk. With one tap of the button on top he had everyone's attention. Teachers have shown a lot of ingenuity over the years in making use of nonverbal cues in the classroom.
Some flip light switches.
Others keep clickers in their pockets. Nonverbal cues can also be facial expressions, body posture, and hand signals. Care should be given in choosing the types of cues you use in your classroom. Take time to explain what you want the student to do when you use your cues. A classroom can be a warm cheery place.