What does the poem "You can't judge a person by his voice" mean?

It means that no one is seen, only voices are heard, which comes from the original text of Chai Lu as follows:

Author: Wang Wei

No one can be seen in the silent valley, only the voice is heard.

The shadow of the sunset shone into the depths of the forest, and the scenery on the moss was pleasant.

Translation:

The mountain was empty and silent, and no one could be seen, only people's voices could be heard.

The golden light of the setting sun went straight into the deep forest and shone on the moss in the dark.

Extended data:

Creation background

During the reign of Tang Tianbao, Wang Wei bought Wangchuan's other business at the foot of Zhong Nanshan. Chai Lu is one of Wang Wei's scenic spots in Wangchuan. There are 20 scenic spots in Wangchuan. Wang Wei and his good friend Peidi wrote poems one after another and compiled them into "Wang Chuan Bie Ji". This poem is the fifth.

This poem is about a lonely empty mountain and towering ancient forest, which is intended to create an ethereal and profound realm. The first sentence first describes the empty mountain positively, focusing on the empty mountain and cold mountain. After that, the second sentence comes out, using local and temporary "sound" to set off the whole and long-term emptiness. The third and fourth sentences describe empty mountains and then deep forests, from sound to color.