反弹到空中，所以马上又变成失重状态，来回振动。

So it goes back into the air so it goes immediately to weightlessness again and then it oscillates back and forth.

youdao

波会来回振动，而使两列波相遇你会得到一列新的混合波。

Waves oscillate back and forth. Add two waves together and you get a new composite wave.

youdao

振动的本质就是来来回回，牵拉再释放使其反弹再牵拉的过程。

A vibration, by its nature, is back and forth, a pull and release with bounce back and a return to a pull.

youdao