SFX translation is not merely a definition, it's an understanding.
There is a few common translations that can be listed but if you're translating ALL SFX then it's not very useful as a reference. Especially since SFX is just
one of several types background text FX.
* I should add an edit here, in case my comment actually does get used for reference.
There is no definitive guide on text FX because artists often get really creative with it. The best way to translate it is always
context-dependent. Just like the textbox translations, you are free to word the SFX in whatever way you think makes the chapter more fun to read.
As an example: the Chinese character Hong 轰 (boom). It's SFX for all things loud and bang-y. It's used everywhere in Manhua, from actual explosions to just loud knocking sounds. Or even less. Door knocking 轰轰。 Car door slamming 轰。 Nuclear explosion 轰。To translate that literally: Boom boom, boom.... boom. But to translate that in a way that's fun to read: Knock— Knock—, SLAM, EX-PLOOOOOOOO-SION!
The biggest trouble you will find is determining what characters are actually used in the SFX, as OCR will not (almost never) be able to recognise characters that are styled in any way. Chinese/Kanji/Hanja characters are especially hard to recognise if they appear in cursive script, don’t even mention software.
For Japanese manga, you can start on several websites,
like Tofugu for example, to get the most common SFX,
you can use Jisho for ones that don’t appear there (after figuring out the SFX characters),
Google Translate as a last resort, and then following that you will have to learn why SFX is an art of understanding.
There are SFX that don’t have direct translations because... they SOUND like the FX.
ドウオオオオオオ DO-UOOOOOOOOOOOO (crowd cheering)
It’s just the same as English comics, when
*crowd cheering* is replaced with
WOOOOOO!
Thus to be able to translate all SFX, you need to know the characters
and their sounds. This is the pretty much the same for Korean Manhwa, with some small differences. Either way I would recommend you get some high definition/vector charts of the Hangul alphabet or Kana (Hiragana + Katakana) syllabaries so you can have a quick reference... or to actually learn the characters so you can see by looking. Now, obviously you only need to worry about Hangul if you're doing Korean Manhwa, and vice-versa. Manga SFX is normally done in Katakana alone, but the other text FX are treated as normal words/sentences with Hiragana and Kanji included, so either way you will come across much more FX combinations than a simple list can contain.
If you don't have the time to learn a bit of each chart, you need to have stroke input software (like Google Translate) in order to figure out what the character is. Nes370 has a comment below me with really important information I had forgotten about, which is small form kana. They modify both the sound of the word and its translation. Remember about it when you can't figure out why a SFX doesn't sound right.
For Chinese Manhua it works differently.
Assuming you can figure the SFX character being used, there will 100% be an onomatopoeia definition or common translation associated with it because there are just
so damn many Chinese logograms.
For Hanja (Korean) and Kanji (Japanese), they’re all Chinese (Hanzi) characters asides from modified definitions, and because there are thousands in common use and tens of thousands in existence, you need to try and stroke them with software to figure out what the character is
closest to. This applies to all of the above languages.
As I mentioned earlier, Hanzi in cursive script makes this extremely hard, sometimes... near impossible. But try your best.
For this, I recommend the mobile app Pleco because of its exceptional character recognition and suggestions despite incorrect stroking, otherwise Google Translate; browser or mobile, it has a pretty good recognition system.
After you’ve managed to figure out what the character is,
Yabla or its equivalents will give you the definition.
On some manguwa text FX will continue off-screen and you will just have to make guesses as to what the full character looks like. Sometimes IMEs or dictionaries can assist you by suggesting complete words.
As with all manguwa, the context will give it away. SFX isn't a critical part of the translation, so
as long as it fits, you're good to put whatever you feel like.
