Please stop talking. 请不要讲话.
Listen carefully. 注意听.
Please be quiet. 请安静.
Please keep quiet. 请保持安静.
Don't push others. 不要推其他人.
Please pay attention. 请注意.
You are too noisy, please stop. 你太吵了,请停止.
Please don't make noise. 不要吵.
Return to your seat. 回到你的座位上去.