One should not talk with a loud voice in the hospital.
Гӯсфандон аз паси чӯпон мераванд, чунки овозашро мешиносанд.
The sheep follow the shepherd because they recognize his voice.
бо як овоз: with one voice, unanimous
овоз додан: to announce, to vote
аз овоз мондан: to not be able to speak
The first sentence uses third person plural, which is more common than using the passive voice. You could also translate it as, “They don’t speak with a loud voice in the hospital”.