Then the gentle hum as the platform started to lower.

The computer was working steadily, with a gentle hum and a regular flashing of lights.

She was singing when the man came in; now her voice dropped to a gentle hum.

He could hear the soft gentle hum of machinery over the rise.

There came a gentle hum as the door through which they had entered closed.

The gentle hum of the ship dropped to a low moan and then went silent.

There was a gentle hum as bright lights bathed her from above and below.

At the same time a buzzing could be heard, like the gentle hum of a bumblebee.

Smith heard the gentle hum through the red receiver.

Then suddenly the gentle hum of engines sounded in the still summer air.