When Robert talks about the entirety of the teachings is found within Silence, he does not mean external silence or even internal calmness. As he says many times he means you go deep within, so deep you lose awareness of anything, sometimes even of awareness itself. It is like being asleep yet the body is fully awake; only the mind sleeps leaving no-self and no-world. This is Samadhi. The Nath tradition connotes this experience as being submerged in the Causal Body.
Even though it is quite "silent," in fact it takes a lot of "energy" to get there. The more perfectly you sit, the easier it is to enter this silent state. For example, in a Zen monastery you sit cross-legged in Lotus, and almost naturally your "center of gravity" of awareness descends into your heart and Hara, revealing the Void.
The feeling is quite different from merely falling asleep, because when you fall asleep, you can feel the body also going asleep. But when you go consciously into sleep, the body remains perfectly awake, so for a few minutes before going silent, you feel the body as very powerfully awake, solid, rooted into the ground, then it fades away from your awareness.