The cause of such ear damage ?

According to Professor Axelsson,
one cause of tinnitus is exposure to loud noise.
Thoses who wear stereo headphones, for example,
often do themselves harm by playing their music at high-decibel levels.
Tinnitus is one possible result.

Of course,
it's good to keep in mind the comment made by Richard Hallam in his book Living With Tinnitus:
" The body is not a completely silent place and so a certain degree of " tinnitus' is normal.
Sound result from the mechanical movement of muscles, bones, blood and air....

It is supposed that in everyday conditions,
theses background noises are masked by the louder sounds in the environment-- they are simply not heard."

Reading this articule may have made you more aware of thoses background noises.
However, they are not a problem for most people.