will it also cut other important sound , like ambiant sound or voices ?
The sound of the text scroll ARE the "voices" of the characters-- that's their purpose!
But no, there's no voice acting and any important sounds (there's not a lot of sound affects, mostly just music) are on a different sound channel; meaning the music slider controls the music and the sound slider controls the sound affects. The voice slider only makes quiet the beeps; as it is the character's "voice".
Hope that makes sense!