I.
noun
ADJECTIVE
▪ low
▪ distant
▪ constant , continuous , steady
▪ monotonous
VERB + DRONE
▪ hear
PREPOSITION
▪ with a ~
▪
The planes flew overhead with a low ~.
▪ ~ of
▪
the continuous ~ of the engine
II.
verb
Drone is used with these nouns as the subject: ↑ voice