Great post and good points.
The last example nails it, it would probably be hard to live near a subway/railroad/whatever until you became accustomed to it and no longer noticed it actively.
Tinnitus of course is a bit different since once you have chronic tinnitus you can't choose not to have it. The fight-or-flight response kicks in rather easily, but often not so when it comes to external frequent noises like railroad.
But once you get over that and accept that this is nothing to worry about, just noise like anything else, it's not going to kill me and I have no reason to fight it, then the habituation process usually starts by itself.
That's what I think happened in my case but I guess it varies from one to another.
EDIT/PS. It's very hard to rate one's tinnitus loudness, but it's obvious that there are huge variations in the (perceived) loudness scale. My tinnitus was and is of the sort that I can hear it easily over normal tv/movie volume if I listen to it, but it doesn't nowadays take the front seat like it used to (thanks to some sort of habituation).
Then there are those who describe their tinnitus like overwhelming and really really loud (terms like jet engine) that takes central place even when walking on a busy road. I would imagine that overcoming the fight-or-flight response will be harder in these cases and habituation process might take longer. I can't speak for everyone, but I would think that habituation is possible even if the perceived volume seems louder than the "average tinnitus".
Anyway, at some point it could be interesting to create a thread about tinnitus noises and how loud one thinks their tinnitus is.
And while I'm on the subject (albeit continuing slightly offtopic);
The loudness of tinnitus is evaluated by adjusting the loudness of an external tone that most closely matches the sounds of the tinnitus. The test proceeds until the external tones are as loud as the tinnitus.
- Using this technique, the actual loudness of the tinnitus is measured. Typically, it is more of a whisper than a shout, between 4 and 7 decibels (or dB) above the threshold of hearing. This finding presents somewhat of a puzzle. Frequently, people describe their tinnitus as being "very loud," when in fact the measurable "loudness" is in the very low range of 4 to 7 dB.
- Because of the difference between actual loudness and perceived loudness, another test known as the Visual Analog Scale is administered.
- This scale is a horizontal line marked off in equal units (like a ruler), from zero to 10. A rating of zero means "no tinnitus" while a 10 means the "loudest tinnitus one can imagine."
- The person selects the number on the scale that best represents the loudness of their tinnitus. Using this scale, 70 percent of people tested chose a value of six or above. This seems to confirm that tinnitus is perceived as a loud noise.
(source)
No doctor has ever evaluated the loudness of my tinnitus using that technique. An audiologist might do this, but I've only once been to an audiologist and it didn't include this test. I didn't know to ask for it though at the time.