To make a continuous low-pitched droning sound
A continuous low-pitched droning sound
She smiled and began to hum, ever so quietly.
The hum of the translator was gone.
His energies flexed, the hum between them growing stronger.
The souls of his forefathers inhabited the obelisk, making it hum with immense power.
By the use of a key in the battery circuit as well as an interrupter or current reverser, signals can be given by breaking up the continuous hum in the telephone into long and short periods.