Where is sign language used?

1) This language is mainly used in the culture of the deaf and hard of hearing for the purpose of communication.
2) If it is necessary to observe silence; in the theater, at a concert, on the set of a movie, at an exam, at a lecture, at a meeting or meeting, so as not to interfere with the speaker and not to distract other participants, on a hunt, reconnaissance, and ambush.
3) If necessary, communicate in a noisy environment.
4) If there is a long distance or sound barrier between communicating,
5) With insufficient knowledge or even complete ignorance of the sound languages of the interlocutors.