In 1948, John Cage joined the faculty of Black Mountain College, where he regularly worked on collaborations with Merce Cunningham. Around this time, he visited the anechoic chamber at Harvard University. An anechoic chamber is a room designed in such a way that the walls, ceiling and floor will absorb all sounds made in the room, rather than bouncing them back as echoes. They are also generally soundproofed.
Cage entered the chamber expecting to hear silence, but as he wrote later, he “heard two sounds, one high and one low. When I described them to the engineer in charge, he informed me that the high one was my nervous system in operation, the low one my blood in circulation.”
Cage had gone to a place where he expected there to be no sound, and yet sound was nevertheless discernible. He stated “until I die there will be sounds. And they will continue following my death. One need not fear about the future of music.”