I’m aware that it’s in my head rather than a real sound occurring in the room. The timbre is usually somewhere between humming and breathing mixed with an orchestra. It gets extremely vivid when I’m tired or stressed, to the point where it can keep me awake. Sometimes at moments of extreme emotions (positive or negative ones) I start to perceive colours too, in the same way that anyone can see anything in their mind, but it’s always the same colour (a neon green on a background of very pure white and black).

http://iheartguitarblog.com/2012/06/musicophilia-musical-hallucinations-and-synesthesia.html?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+blogspot%2FCNYC+%28i+heart+guitar%29&utm_content=Google+Reader