Synesthesia, Cymatics, and Different Ways of Knowing

I had no idea that there were people whose senses overlapped like those who are synesthetic.  The thought of having a conversation with a person, or reading a book, and seeing different types of color and shapes intrigues me.  It also, in the more experimental form, allows me to imagine a whole different world of perceptual presentation in film.  I immediately see two actors speaking words, gun shots exploding, simple body movements that make sound with color (specifically, in my mind's eye I am seeing the scene from the Wachowski brothers 1999 film The Matrix, where Keanu Reeves is fighting Hugo Weaving and in slow motion dodging bullets from his gun).  The thought of cymatics is truly interesting as well.  I always knew sound had the capability to create movement but the precise and intentional creation of shapes through it was never something I considered.  Once again, in an experimental context, I could see the potential of cymatics.  It makes me think of films from Stan Brakhage in which he uses closes ups of intentionally colored and manipulated film stock throughout as a visual experience.  I imagine doing the same with a close up of sand or some type of lighter material, while manipulating it with sound waves.  I am sure this would create an intriguing visual experience.