自从1919年发明声音广播,至今已有70多年的历史。这期间世界上有200多个国家和地区办起了声音广播,各类收音机达十多亿部。由于电台日益增多,调幅广播音质不佳,30年代后期又发展了超短波段的调频广播;40年代以后发展成为调频立体声广播。虽然调频立体声广播具有抗干扰能力强、音频频率宽、声音有空间感等优点,但是它也有一个最大 It has been more than 70 years old since its invention of sound broadcasting in 1919. During this period, more than 200 countries and regions in the world set up sound broadcasting, with over 1 billion radios of all kinds. Due to the increasing number of radio stations, the sound quality of AM broadcasting is poor. In the late 1930s, FM radio broadcasting in the ultra-short wave band was developed. After the 1940s, FM radio was developed. Although the FM stereo radio with anti-interference ability, wide audio frequency, sound space and other advantages, but it also has a maximum