The voice "who knows" carries with it a sense of mystery and doubt. It is not just a simple statement but also a well-kept secret, an unknown that cannot be easily revealed. Its sound can reflect surprise, or disappointment when faced with an unforeseen truth. This voice is full of challenge and discovery, while creating an atmosphere of mystery and intrigue. It can be said that it is an expression of curiosity and exploration of the unknown, as well as a challenge to current understanding.