Before the popularity of videophones, most people used ordinary phones.

Do not think that you can not see your body, language, and mental state of your posture, smile, movement and expression when you talk at the two ends of the phone. In fact, the tone, speed, tone and content of the call can be a secret spy.

The voice is lazy and sleepy, it must be just waking up or being sleepy; weak and listless voice shows depression; sweet and crisp voice will make people think you are spirited and happy at the moment; the tone of the call conveys the spirit of the caller.

Similarly, body language or mental state can also affect sound in turn.

For example, if you are blushing and stammered on the phone, the other person will feel your nervousness.