[rikk009]

Never been in a soundproof room so can't say but right now I am wearing foam earplugs and I hear ringing. Is this tinnitus?

 

[Ancipital]

Yes, simply. Lack of input causes it, to simplify (sometimes it's a mechanical thing, sometimes it's in the brain- similar things happen with long-term sight loss, often).

 

[old tech]

Is this normal? I dont listen to very loud music but everytime I enter a sound proof room (I play drum kits) and I hear a very soft ear ringing in my ear. I dont usually notice its there but its there. Does anyone experience this problem or is it totally normal? thanks.

What you are hearing is your brain's noise floor.
 
It is the same with vision in a totally dark room, or closing your eyes at night - the star like patterns you see is also your brain's white noise.

 

[edstrelow]

I spent my years as a graduate student with access to scientific grade sound proof rooms and would  hear noises when I went in.  However it was not ringing, rather you could hear things like the sound of your own pulse.  Too much white noise or ringing could indeed be tinnitus.