When the god Yahweh confirmed with Moses that the he would be looked upon as an Elohim by the people of Israel Moses brought the people's words to Yahweh. And Yahweh said: Behold, I shall be coming unto thee in a thick cloud, enabling the people to hear when I speak with thee. so that in thee too they shall have faith."
During the landing, Yahweh indicated to Moses, that it would create a danger to anyone coming too near. "Thou shall set bounds round about." the Mount. Moses was told to keep the people at a distance asking them to not even dare touch the Mounts edge "for whosoever touched it shall surely be put to death."
And Mount Sinai was completely engulfed by smoke, for Yahweh has descended upon it in a fire. And the smoke rose up like that of a furnace and the whole mount quaked greatly. And the sound of the (Kol) Shofar continued to wax louder; As Moses spoke the Elohim answered him a loud voice.
The word “kol” heard and described at Sinai is the same kol that went walking in Gan Eden right after the first sin.
Bereshit (Genesis) 3:8 And they heard the voice (kol) of HaShem God walking in the garden in the cool of the day: and Adam and his wife hid themselves from the presence of HaShem God amongst the trees of the garden.
Shemot (Exodus) 19:16 And it came to pass on the third day in the morning, that there were thunders (kol) and lightnings, and a thick cloud upon the mount, and the voice (kol) of the shofar (horn) exceeding loud; so that all the people that [was] in the camp trembled.