It is written of the Children of Israel at Sinai that all the people saw the sounds.
One may ask: How could it be that they saw the audible and heard the visible?
We are accustomed to distinct systems of reaction to stimuli, each sense having its own nervous apparatus and brain connections.
Is there not an organ of reception that does not bother about the receptor, a profoundly acute brain center where distinguishing and understanding take place?
Could this not be stimulated directly?
If so, it makes no difference what the channel of nerves or the nature of the reaction to a perception.
Sounds could be "seen" and sights could be "heard."
This is possible because the infinite Light is without limit or definition.
It cannot be put in any particular category.
It cannot be grasped except if it is contracted and "clothed" by something finite.
As the Maharal says in his discussions on the Rambam:
According to the (intellectual approach) of the Rambam one should perhaps speak of the Mind (HaSechel) as Blessed Be He, instead of the Infinite (Ein Sof), which has no possible definition, certainly none in terms of human knowledge and wisdom.
–Rabbi Adin Steinsaltz
From In the Beginning by Rabbi Adin Steinsaltz