How is the sound recorded?

At the earliest, the horn was used to pick up the sound, and the vibration was transmitted to the pen tip, recorded on the rotating wax bucket, and rotated in the opposite direction during playback. This is mechanical recording and playback. After discovering the principle of electromagnetism, human beings can convert vibration into electric energy. Microphones with pickups are actually the same thing as headphones and speakers for broadcasting. It is transmitted through wires and amplified by triodes. There are two ways to record words:

1 is mechanical: the diaphragm of the loudspeaker is made into the shape of a needle tip, the microphone picks up the sound, and it is amplified by a triode, which drives the recording head (that is, the pointed horn) to record the rotating vinyl disc, and it is reversed when playing, and amplified mechanically by the loudspeaker. This is a phonograph. The development after World War II is to burn the metal master, then make it into a template, inject it into modern black film, and pick it up with a pickup head (similar to a small pointed microphone) when playing back.

2. It is electromagnetic: the current picked up by the microphone is recorded on the magnetic sensitive material (steel wire at first, then developed into magnetic tape) through the magnetic head, which is picked up by the magnetic head during playback and then driven after amplification: headphones or speakers; Wireless antenna, short wave, medium wave, etc.