To crackle is to make short, sharp cracking noises. A roaring fire in your wood stove crackles as it burns.
Fires crackle, as small branches pop and snap from the heat, and a voice over an intercom might crackle with static. You could also describe the sound of your feet on dried leaves and branches as you walk through the woods as a crackle. A visual crackle, as opposed to one you hear, appears as tiny cracks in the surface: "I like that crackle effect on your table."
Primary Meanings of crackle
make a crackling sound
the sharp sound of snapping noises
to become, or to cause to become, covered with a network of small cracks
glazed china with a network of fine cracks on the surface
having the surface decorated with a network of fine cracks, as in crackleware