The perfect noisy silence

This is the physical experiment which proofs that
in absence of air there is no sound.

But, the complete silence is almost impossible to experience. As John Cage said, there is always something to see and to hear. He also said that even in one of this special anechoic chambers - a room designed in order to avoid any sort of echoes - he was able to hear two sound: his nervous system in action and his blood in circulation. So, only when we die we will experience the real silence.