Sound effect text appears untranslated even though the post may otherwise be translated. Sound effects are often skipped because they can be inferred from context, ambiguous, and are less critical to understanding. It's also common when a post's translation is taken from another, hard-translated source (such as a manga scanlation aggregator).
Sound effects can be translated in a number of ways. For example, ゴゴゴゴ could be translated as:
*rumbling* What the sound effect represents (a verb or an adjective)
gogogogo A romanization of the katakana that preserves the reading
brbrbrbr How the sound effect might be spoken in English
You can include more than one translation to help different kinds of readers.
Translating sound effects doesn't require much Japanese proficiency. Please feel free to try it! You can usually just look up the katakana and pick the meaning that fits best.
