None. When you walk through that door it's an act of free will, and I will not have anything other than complete silence.

走过那道门,是你的自由，我不会做其他事,除非保持安静。

麻省理工公开课 - 固态化学导论课程节选

When you walk through that door, it's an act of free will.

当你走进这个门的时候，这是自由意志的选择。

麻省理工公开课 - 固态化学导论课程节选

All right, turn them off. If they have to make noise as you turn them off, turn them off, but that's it. So, when you walk through that door, it's an act of free will.

好了，把它们关掉，如果一定要发出声音,当关机的时候，也要关机，就这样，当你走进那扇门，这是自由意志的选择。

麻省理工公开课 - 固态化学导论课程节选