如果在一根振动弦的中部轻轻一触，它就发出高八度的音。

If a vibrating string is lightly touched at its midpoint, its pitch goes up an octave.

youdao

Here is the pitch in--of--a string an octave higher so you can see it this way. As you probably know, if you take a long string and pluck it, it's going to take that long string a long time to pass that sort of cycle, if you will, just one pass through that cycle.

这也是个音高,一个高八度的音弦,你可以这样这样看 你们可能知道,如果你拨动长弦,长弦要经过很长时间,才能完成一个震动周期,如果你想,可以尝试下

耶鲁公开课 - 聆听音乐课程节选