The thread below about audible brain sounds was closed (reasons unknown), so I am starting it again, because I may have some sort of partial answer..
http://www.medhelpinternational.org/forums/Symptoms/messages/838.html
Really wanting to get to the bottom of the brain-squish-crunch concern, I spent ages looking around for what could be the possible cause of it. I am constantly aware of the spot that the sound comes out of, feeling like cotton wool. I felt I had some sort of benign lesion / bloodclot / aneurism.
Every few years it gets me to the point of going to the doctors to get a CT scan (although I always asked for an MRI). Doctors ignored my insistance that the sounds were coming from my brain, and they told the radiologists to look for air trapped in my ear canal, or another time, to look in my sinus.
After some time I came across the Wikipedia definition of Asperger's Syndrome. I was astonished to find that it read like a biography..
Focussing my reading on Asperger's Syndrome publications, I found several radiological studies on Asperger's brains...
The spot in my brain where the sound comes out of, is quite different in over 80% of Asperger's people.. Sometimes that bit can be missing, other times there may be a dense neural growth there, and usually some bit has grown at 90 degrees to the norm.
As soon as I hand in my PhD thesis (in chemistry, unrelated to the stuff here) I am off to get my head read by the giant magnets of the MRI.
Any other head crackle people out there fit into the Asperger's category?