What does this sound mean? What is the function of sound? How to use it? I am studying Liu Xie.

In the content of Yin Na in Sixty Jia Zi, there is no sound, only five elements. Then why is it called "Yin Na"? Where is the sound? In fact, since the pre-Qin period, the ancients have corresponded the five elements with the five tones. Therefore, in Yin Na of Sixty Jia Zi, five actions are obvious and five sounds are hidden. It is expressed as five elements, followed by five tones (Gong, Shang, Jiao, Zheng and Yu, equivalent to notation 12356). Therefore, the "sound" of the ancients refers to the five tones endorsed by the "five elements". See "Study on Yin Na in Sixty Jiazi", published in the fourth issue of Cultural and Art Research in 2009.