I have it. Previously went for 2 operations to clear my ear passage.. and subsequently I suffer from occasional bouts of labyrinthitis, an infection of the inner ear. The "yin"-ning sound gets very loud each time.. it's better these days.
The ear specialist I saw at the time told me the sound is caused by air passing thru the small holes in your eardrum, infections, or wax blocking the ears. He said tittinus is mostly harmless itself, it's only a symptom.. most notedly he said this - hearing problems are usually caused by wear and tear o the eardrum (that's why u lose hearing as u grow older), but with loud earphone/headphone usage or prolonged exposure to loud deep sounds, the process speeds up dramatically.. he singled out earphones with deep bass sound, and/or the ear bud designs that keep noise out, as the worse offenders..
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Tinnitus