Cymatics and Synesthesia

Both cymatics and synesthesia are very interesting concepts. In cymatics there have been many neat tests and art forms created through the use of sound.  I find it interesting now that I think about it, when I was growing up there were many times where I experienced cymatics but did not know of the concept. It was always neat to see something move due to the vibration of sound, but it is even more intriguing that people are intentionally manipulating sound to create motion and shapes.  I will be curious to see where cymatics can be applied in the future with the integration of technology and further cymatic advances.  Who knows what applications cymatics might unlock in the future.  One question that came to my mind while watching the video was are we truly seeing sound? Because if we are then that sound should then have the same pattern every time right?  But if we changed the thickness or area of the material vibrating to the sound, then would that change the pattern?  If so we are not necessarily observing sound solely, but we are observing sound in conjunction with the vehicle in which sound travels. Will the same pitch appear differently when using different surfaces or materials?  That is the question that kept coming to my mind.  As for synesthesia, I am a little uncertain as to what the definition means exactly, especially with regards to grapheme, or color synesthesia.  According to Wiki it stated that synesthetes perceive a letter or number with a color.  What I am unsure about is do the people actually see the color when they look at the letters or do they think of the color when they see or think of the letter or number?  Because in my mind when I think of the letter 'A' I also picture the color red in my head, but I know that this is due to programming and memory growing up.  The whole 'A' is for Apple, and the apple being red comes to mind.  I also think of images with sound, but again it is due to memory and programming over time.  If I hear a screeching sound I think of tires and a car accident, but the screeching could be something else.  Even though it may not be a tire or accident about to happen, my brain immediately associates that sound with what I am most used to.  I feel like this is why Foley sounds can be created so well and trick people's brains, because they are using sounds that are similar to the sound they may be imitating, but may lack fidelity.