Five hours is contact time. That's three hours here, and two hours with the recitation instructor.

联系时间是5个小时，这有三个小时，其余2小时是和背诵课的讲师。

麻省理工公开课 - 固态化学导论课程节选

What we've got here is the following, this idea of partials that Eva was talking about with ratios, two to one, three to two, four to three, five to four, six to five and so on, and the point here is that the way we differentiate between instruments.

接下来,我们要讲的是,伊娃刚谈到的泛音的高低比率,二比一,三比二,四比三,五比四,六比五,等等,这里我要讲的是,我们区分乐器的方式

耶鲁公开课 - 聆听音乐课程节选