There was a slight hum that rose into ultrasonics.

She opened her eyes and saw a gray metal bulkhead, sensed a slight hum.

He could hear the slight hum of the fans turned by the wind as it whistled past.

Watson pushed a slider bar up and there was a slight hum.

She heard nothing, no footsteps, no voices, just a slight hum from the central heat.

His answer came in a slight hum from behind the shield.

A slight hum of satisfaction ran round the hall.

The gray-haired woman pressed an unseen bell; the major could hear a slight hum.

Her friend Ebony Brown nodded with a slight hum of approval.

With all the reactions going on in the core, they make a very slight vibrational hum.