Meaning: The children were paying attention to the sound of the fire burning.
Choice of Words: Listened means to pay attention to a sound. "Crackling" is the sound made by a fire when it burns.
Alternative Expressions
They heard the fire crackling.
Meaning: This means that they perceived the sound of the fire burning.
Choice of Words:Heard is a verb that means to perceive a sound. Fire is a noun that refers to the burning of something. Crackling is a verb that describes the sound of something burning or breaking. When you put them together, "They heard the fire crackling" means that they perceived the sound of the fire burning.
The crackling of the fire reached their ears.
Meaning: This means that the sound of the fire burning arrived at their ears.
Choice of Words:Crackling is a noun that describes the sound of something burning or breaking. Fire is a noun that refers to the burning of something. Reached is a verb that means to arrive at a place or to come into contact with something. Ears are the organs that we use to hear. When you put them together, "The crackling of the fire reached their ears" means that the sound of the fire burning arrived at their ears.