The advent of radio broadcasting, electrical recording of disk records, and sound motion pictures all in the 1920's stimulated the development and commercialization of high quality studio microphones as follows: The omnidirectional condenser and dynamic microphones of the 1920's. The bidirectional velocity and omnidirectional microphones of the early 1930's. Microphones are still classified in these three basic types of directivity. Important and significant state-of-the-art improvements have been made through the years to the present time.
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