Seeing Sound: Making Sense of Sinai

All the people saw the sounds and the lightning, the voice of the horn and the mountain smoking; and when the people saw it, they fell back and stood at a distance.

"And all the people saw the sounds and the lightnings": They saw what was visible and heard what was audible. These are the words of R. Yishmael. R. Akiva says: They saw (what was audible) and heard what was visible.

(2) [THEY] SAW THE SOUNDS—they saw that which should be heard, something which is impossible to see on any other occasion.

(3) THE SOUNDS which issued from the mouth of the Almighty.

This is like ולבי ראה, “and my heart ‘saw’” (Kohelet 1:16). They meditated on the idea of the sounds, but they were unable to endure it. As it's said, “Let me not hear the voice of the LORD my God any longer or see this wondrous fire any more, lest I die” (Devarim 18:16).

And all the nation saw the sounds: I have previously explained the intent of seeing the sounds. All sensations join together and are processed at one point. And this is the meaning when they saw the sounds and the lighting. This drove a person to be afraid, and the voice of the shofar was something never heard before. And the mountain itself was smoke. When they saw these wonders, they trembled.

And the text says: All the people saw the thunders. It's not written "thunder (hakol)," but rather "thunders (hakolot)." Rabbi Yochanan teachs that When God’s voice came forth at Mount Sinai, it divided itself into seventy human languages, so that the whole world might understand it, and every nation heard it in their own language.

We have to understand how they could seen the sounds ... It sounds reasonable that each word the G-d spoke became palpable and tangible to the extent that it took on physical form and could be seen in the air as floating letters as is they were written in front of them.