Russian and Ukrainian are real sentences, you can use them if you want to ask someone not to make noise.

Does that mean those 2 languages could be translated as follows?

[#1844225] Don't make a sound. (CK) *audio*
[#1275396] Be quiet. (jakov) *audio*
[#477063] Don't make noise. (CK)

Literally "Тише!" means "be quieter", i.e. we can use it when someone makes noise and we want them to stop it. "Тихо!" (literally "be quiet") we can use both if we want to stop someone from making noise or just want to ask someone to stay quiet.
"Don't make noise" has its own translation into Russian, that has been already added before.
I'm not sure about "Don't make a sound", if it sounds rude or not in English. If yes, it doesn't match.

"Quieter" is an elliptical sentence where the first part "I want you to be.." is understood.
http://thewindlike.blogspot.ca/...l#.Vg1nAvlVhHw

1. I don''t translate from Japanese
2. I must have adopted the sentence because in my consideration it is correct.
3 .I unadopted the sentence.
4. Do what you want.

'Be more quiet', then, maybe?

The difference between "Quieter" and ""Be quieter" is only the level of politeness. You can say "Sit!" to a dog and I would claim that that is a sentence.
So the way to resolve this is to look at the Japanese and determine whether it is polite or rude and fix the sentence accordingly. (You''ll have to adopt it because I''m washing my hands of it."")

I personally agree with Dejo on all of his points and I give my approval for the sentence. "Quieter!" seems very natural to me albeit kind of abrupt and impolite. I've heard this particular expression used alone before both in real life and books/media. I have most likely used it a few times in my life before as well though in a playful way. "Quieter!" in my experience is often used when the speaker begins to feel flustered and fed up to the point where they decide to put strict emphasis on just that single word as a command. Also, like Dejo, I don't think I'm qualified to determine the exact suitability of the Japanese sentence that is linked to this one.