Not sure what caused it but observed the continuous high piched hissing sound on awakening in the morning.
Welcome to the forum. There are many causes which can trigger or aggravate tinnitus including but not limited to drug reaction or side-effects from ototoxic drugs, ear wax build-up, ear or Eustachian tube infection or ETD, ear drum injury, fluid build-up in ears feeling pressured or fullness, sinus infection & congestion, TMJ, TTTS, high blood pressure or blood circulation problem, loud noise exposure or acoustic trauma/shock, head trauma & injury, neck injury or muscle problems, hearing loss, Meniere's Decease, barotrauma from sudden change of air pressure such as during landing & taking off on flights especially with blocked nose causing failure to balance the pressure changes, slapping of the ears, deep grief for the loss of loved ones, untreated sleep apnea, extreme, extended stress, anxiety & panic disorder, etc., etc. T can also be caused or made worse by unhealthy diet such as too much salt, sugar, caffeine, MSG, alcohol etc. or lacking some mineral or vitamin supplements, such as Magnesium, Zinc, B12, D3 etc.
Many members report the same thing, awakening to a loud T in the morning or after taking a short nap. This phenomenon has been referred to as 'Awakening Response' by some as it has to do with the brain trying to make sure your vital signs are ok when you wake up to be ready for the day. A doctor once wrote a more detailed explanation:
"I have always felt it to be due to the role of the reticular formation in tinnitus perception. The reticular formation is a primitive structure in the brain stem. It's a "vital sign monitor." When you wake up, the RF checks to see whether or not you are alive! It looks for heartbeat, respirations, blood pressure, temperature - basic bodily signs. It does not care whether or not these signs are good or bad - just that they are present. And as far as the RF is concerned, tinnitus is part of "expected" body function in an individual suffering from severe intrusive tinnitus. So when you wake, your RF checks to see whether or not tinnitus is present. And if it doesn't immediately find the tinnitus, the RF seeks it with a vengeance - - especially in the post-nap state, when there has been inadequate REM sleep and when, therefore, the RF is on already "high alert" that something might not be quite right. Theoretically - very theoretically - this RF hyperactivity in seeking tinnitus, which in a person with severe intrusive tinnitus it equates with life, results in temporarily markedly augmented tinnitus perception."