As a related thing, I have sound/vision synesthesia.

It is a little like what was shown in the movie Ratatouille where the mice see colors related to what they smell only for me it is sound related. If you want to know more feel free to ask.

Sounds (pun intended ;-)) intriguing. Is a specific visually perception related to specific sound, e.g. like the classic example of a musical note evoking the perception of a specific colour?

On a slightly related note, being colour blind Neil Harbisson - the world's first legally recognized cyborg - had an antenna implanted in his skull that allows him to perceive colours as sounds (musical notes and even chords, specifically); so, the inverse route in a way.

Specific types of sounds result in the same types of shapes and colors and unexpected sounds particularly when my eyes are closed produce the strongest illusions. There are some color/sound overlaps I can only "see" when my eyes are closed however an unexpected dog bark will result in an effect I perceive in full day light.

The related shapes I "see" are also based on the sound I hear.

For example, a vaccum or motor gives me gentle waves or pulses of blue that start low in my "vision" while that surprise dog bark will be a bright white explosion usually in the top right of my "vision"