Article: Text is frequently incorporated into comics via speech balloons, captions, and sound effects. Speech balloons indicate dialogue (or thought, in the case of thought balloons), with tails pointing at their respective speakers. Captions can give voice to a narrator, convey characters' dialogue or thoughts, or indicate place or time. Speech balloons themselves are strongly associated with comics, such that the addition of one to an image is sufficient to turn the image into comics. Sound effects mimic non-vocal sounds textually using onomatopoeia sound-words.

Now answer this question: What type of words are used to do sound effects in comics?
onomatopoeia