At first glance, a "silent echo" would seem to be a contradiction of terms. An echo by very definition is something audible. Yet, this is precisely how the Midrash describes the Sinai experience. God spoke in a thunderous voice that produced no echo (See Devarim 5:19).
Why would the audio quality of Sinai be an essential point to emphasize. Also, if the echo produced no sound, why mention it all?
The Lubavitcher Rebbe noted that the more an object absorbs, the less it echoes. At Sinai, the message became fully integrated and absorbed within the essence of our being. The only echo that was produced, was the sounds that continues to reverberate within us.
When we close our eyes, our mind produces images from our subconscious. Apparently our heart echoes as well.
We have been endowed with a heavenly GPS - t
he true gift of Sinai.