Showing papers by "Dolby Laboratories published in 1971"

Level setting in noise reduction systems

Abstract: A special test tone at a predetermined level is recorded or transmitted to enable the level to be set correctly on playback or reception. To enable the tone to be identified, it is intermittently and briefly frequency modulated to give the aural impression of a constant tone with intermittent "blips" therein. Because the amplitude stays constant, the modulation does not interfere with level meters and the like.