My hissing also gets louder when I lie down - not more noticeable... just louder
Erik, yours Mike's and mine do all sound very similar then? Especially the 'having a few good, a few bad, a few ok days' pattern.
I've eliminated and reintroduced all the food that I eat. Chinese sauce makes mine immediately 'spike' but nothing else seems to make any difference. I've never cooked with or added salt to anything so not sure what salt would do. I also don't think that magnesium rich foods etc. made it any better.
The one thing I cut out completely and didn't re-introduce was Volvic mineral water. I drank a lot more mineral water when I moved to Cornwall because of the change of area (wanted to gradually get used to whatever the Cornish water board adds to theirs) and, although Volvic isn't a particularly 'high in calcium' water, I was worried that the added calcium had caused the T. I'm back in Hampshire now (house sale down there completes on Friday - yippee!) and, although I always used to drink Volvic, I haven't had any since cutting it out.
The reason I'm scared of too much calcium is that, way before the T, too much calcium used to make my head go a bit weird.
I still think that the ENT I saw was wrong... he said it was caused by stress and that it would go away but I am beginning to wonder. Maybe nothing else was involved. Maybe I had stress that was subconscious (because I wasn't aware of any).
If the hissing is there, when I stick a finger in my ear and pull down, it lessens.
When there is less air in the house (I'm a fresh air freak) the hissing gets louder. I thought this was because it was evening but it isn't. Opening the back door changes it so it goes down again (this isn't 'masking with external noise' because I have the rain sounds on all the time). That's why I suspect air pressure is affecting it.
Sometimes I can actually 'feel' the hissing or electrical noises when I trace my fingers over my skull. Also, when I brush my hair the hissing gets worse. Has to be related to nerve endings/signals/central nervous system...?
Apologies for scribbling down rambling thoughts here