Synesthesia

Ok, confession time. Prepare to not believe me. 

I can see sound. 

Not all the time. Only when I'm relaxed. Like when I'm lying down and my mind is drifting, and some sound would find my ear. 

A wooden door closing on a wood frame: it's a brief sound that doesn't persist, so the image wouldn't either. It's always a red and black checkerboard. That was the first one I can remember, and it's been consistent. 

Two sheets of paper sliding across each other: glistening sand falling, but only as long as I hear it. It's never very long. 

Those are the two most common. Many others have happened.

What usually happens is I see the colors, and get so excited that my brain is no longer "resting", and it's gone. It's bizarre, and it makes me wonder how my brain is wired. But, it's fun. I just wish it happened more often.