Yes, right. Not freaking out from onset is much easier said than done, even though it looks like the sensible thing to do in hindsight
Yes, the physiological mechanisms of t are in place. That's for sure.
I take lorazepam, and it reduces my sounds a lot. So for me, I know on top of the mechanisms, it is anxiety that drives my t and the volume switch.
Having said that, we are all different.
Also, just on a side note to a comment above, I remember silence, sitting in sound proof rooms, or the stillness of a quiet night. I am a musician, and pick up the smallest of sounds. For me, the idea that everyone has t (although soothing) does not seem accurate somehow.