“…in 1951, John Cage spent some time in… an anechoic chamber at Harvard. In the dead acoustic environment of the chamber, Cage experienced an epiphany. After a while, against the silence of the room, he became aware of two sounds, one high-pitched and the other low. Later, the technician on duty informed Cage that the sounds he heard were, respectively, his nervous and circulatory systems at work. Cage told the story repeatedly for the rest of his life.” (Seth Kim-Cohen, In the Blink of an Ear, p. xvi)
The two sounds cage heard represent the fundamental Rhythm & Drone of the body. Even in ‘silence’ these sounds are present.