I've only read a bit of this thread, but most seem to be high pitched sounds, i get the opposite, i've got low frequency tinnitus in my right ear, i don't hear it at all usually through the day or if i'm active at night, but i get it if i've been laid down in bed for anything from a few minutes to hours and BOOM it's like there is a lorry idling outside my room, so i have to sleep with a fan on, have done for about 10 years now.
When it originally started, i went a little crazy ie very crazy due to lack of sleep, because i thought it was an actual noise, even so much to go out and walk for miles at the early hours to find it, i obviously never did, but one day inbetween me going mad, i was laying in bed on my left side and i could hear it coming from above me, to which i got the ladders out and listened to my ceiling, but because the normal sounds you make when moving it had gone away, so i laid back down on my right side this time and almost straight away it came from down below, thats when i realised it was my ear and not a sound, ive got a fan for in the house to cope with it and when away i have a LectroFan which is brilliant really.