Acoustic space, as such, is discontinuous, 
resonating continuum. The continuum is a figure 
without a ground because it just goes on and on 
without ground. Voice has figure/ground. And 
most sensory modes have figure/ground. By the 
way, visual space is manmade. It is not a normal 
form of experience. It does not exist in nature.

On Campus with Marshall McLuhan  , Media Centre, 
University of Toronto, Jan. 22, 1979.