Yes, that is tinnitus. Very mild tinnitus like this is not uncommon. I don't agree with your ENT that everyone has it from birth, though.
It wasn't the ENT exactly, it was another worked who conducts the hearing tests. They didn't specify this as tinnitus either though, they said something along the lines of this being something everyone gets at birth and compared the phenomenon to the noise you hear when you hold a sea shell to your ear.
But yeah, I think I've had this "tinnitus" for as long as I can remember. I don't know if it's changed since I was young. If it has, it's been very, very gradual and subtle. It has exacerbated at times since I developed hyperacusis, but it hasn't been consistent. But the tinnitus I've been referring to is distinct from this, it's comparable to the kind you'd experience when a very loud, sudden noise goes off, and was the most persistent, obvious indicator of the development of hyperacusis. I think my regular tinnitus exacerbated in the leadup too, but nothing like this.
I'm still experiencing after-effects of that "test" from yesterday. At one point last night, after my post, I started to experience the closest I've ever had to the beginnings of genuine "pain", and the general tinnitus got quite noticeable. I remember eating pretzels last night and I was actually rather irritated by the sound of chewing- first time anything like that has ever happened. It's all largely died down today, and things like an electric razor right by me ear were mostly tolerable, or having the window down on a busy freeway. There was even a situation where some worker was using a small power saw near me- I avoided that, but my reaction wasn't much worse than a normal person might expect without earplugs, which I'm sure the worker was wearing.
The generalized tinnitus has been quite noticeable this evening though (I even experienced that noticeable, "intermittent" hyperacusis I've been describing in this thread, probably the first time it's happened two days in a row in a long time), and throughout the day, I've often had a kind of on-edge feeling with various noises I experience, like I feel like I'm close to a threshold (even with typing right now). But it's really hard to tell if this is heavily psychological. I'm likewise still surprised how sensitive I am to audio from speakers/artificial sources. It really does seem like unclear audio is what gets me though- I generally can't stand static or low-quality sound, but getting irritated from phone speakers was new. My computer speakers might not be as high-quality as I thought if this is the case. Altogether though, the after-effects of my "test" are the worst I've experienced since this all first began, and in some ways even worse. I really hope this didn't do anything, but some of my behaviors early on weren't conductive to recovery anyway.
Is this tinnitus I've experienced since early childhood really anything to worry about? It's never been much of an issue and I seldom pay attention to it. I can't think of anything that could have caused it and I've never really had hearing issues before. I'm guessing tinnitus like this isn't treatable? If it isn't, it's not a big deal. But what is it indicative of or even caused by? Is it indicative of any other ear or hearing issues that atleast might manifest later on? Even though my hyperacusis is nothing compared to people's experiences with it from this thread and elsewhere, I'm hesitant to say if my "mild" case is really something to take solace in. After all, look how it's progressed over the past year+.
I didn't get a chance to contact any other specialists today, but I'm also wondering if the ENT really tested me as much as they should (or if they could have done more.) Both hearing tests- last year and a couple of months ago- were perfectly within normal range, but I don't think those captured tinnitus or much else.
Also, someone please clarify the privileges required to PM on this board.