In 1915, an American named E. When S. ridham attached a telephone listener of the day to a horn playing a recording system, the sound could be heard by a crowd celebrating Christmas in San Francisco. Electroacoustics was born. After the end of world war I, in the United States President Harding (Harding) his inauguration, the telephone bell companies in the United States of moving coil to connect at the time of the horn on the record player, will be able to pass the sound to watch the inauguration of a large group of people, thus creates a lot of professional audio research and development the amplification engineering this science. Sound researchers are not only trying to improve sound equipment, but are also experimenting with different kinds of sounds to understand how humans respond to hearing. But the highest level of sound research people understand that sound is a holistic study, understanding every part of the sound equipment, and the human physiological response to hearing, and they have made a great contribution to that.