translation.en: This is a plot of frequency against time -- sort of like musical notation, where the higher notes are up higher and the lower notes are lower, and time goes this way.
translation.zh: 这是幅频率对时间的图表-- 有点像音符， 高处的标记表示频率较高，低处的标记表示频率较低， 时间朝这个方向流逝。