The loudspeaker consists of electromagnet, coil and horn diaphragm. The speaker converts the current frequency into sound. According to the principle of physics, when an electric current passes through a coil to generate an electromagnetic field, the direction of the magnetic field is the right-hand rule. Suppose the speaker plays the key C, and its frequency is 256Hz, that is, it vibrates 256 times per second. The speaker outputs 256Hz alternating current, and the current changes 256 times per second, emitting a C-tone frequency. When the electric coil vibrates with the loudspeaker diaphragm, it pushes the surrounding air to vibrate.