The sound system refers to the use of a microphone to convert the acoustic signal of the original sound field into an electrical signal, and according to certain requirements, the electrical signal is processed by some electronic devices. Finally, the electrical signal is converted into an acoustic signal and replayed by a speaker. The entire composition from the microphone to the speaker is the sound system. The microphone and speaker are both referred to as transducers. Although the electrical signals in the audio system are different in terms of energy form and dimension from the acoustic signals of sound waves, as signals, the essence of the information between them is consistent, that is, their amplitudes have a corresponding relationship of relative magnitude, and their frequencies also correspond. Therefore, the electrical signals in the audio system are within the sound frequency range of 20Hz~2000Hz in frequency, and are called audio signals. Audio signal, which is an important feature of the audio system.