In 1915, there was an American named E. S. Electroacoustics was born when Pridham put a contemporary telephone receiver on a horn that played a record sound that could be heard by a crowd celebrating Christmas in the city of San Francisco. After the end of the First World War, at the inauguration of President Harding in the United States, the Bell Corporation of the United States connected the dynamic receiver of the telephone to the horn of the record player at that time, which could transmit the sound to the inauguration of the president. The large crowd of people at the ceremony has produced a lot of professional audio research and developed the knowledge of sound reinforcement engineering. Audio researchers are not simply trying to improve audio equipment, but also experiment with various types of audio to understand how humans respond to hearing. But the most advanced audio research people understand that acoustics is a holistic study, to understand every link of audio equipment, and human physiological response to hearing, they have made a great contribution to this.