It's true, it fires a rifle cartridge from a "pistol"... but the barrel is 15" long, only 1" shorter than many rifle barrels.
It's also true that almost every handgun I've ever fired is noticeably louder than my Encore. Even .380acp and 45acp. My Glock 33 in 357sig with a 3.46" barrel is possibly the loudest gun I've ever fired. While I acknowledge that you said not to try this with 357mag or 10mm, and 357sig would no doubt also make your list, what am I to do if those are the cartridges I'll be using for defense?
It's also true that a single exposure to a sound as loud as gunfire, even outdoors, can result in immediate and permanent hearing loss. Being indoors makes it much, much worse. See links:
http://www.entusa.com/noise_hearing_loss.htm
http://www.freehearingtest.com/hia_gunfirenoise.shtml
http://en.wikipedia.org/wiki/Sensorineural_hearing_loss
http://www.asha.org/public/hearing/C...oss-in-Adults/
I would also make the argument that, potential damage or no, firing a single shot "just so that your brain will know how loud it is", is pointless. First, as you point out, we've all heard it before. We know how loud it is.
Second, when we're in the middle of a home invasion or burglary, we are most likely to be experiencing Auditory Exclusion, making sounds like gunfire completely irrelevant. Anyone who hunts has experienced Auditory Exclusion when they shoot animals. We don't "notice" the gunfire. The same thing will happen in a crisis.
So,
1)Single gunfire events can damage your hearing.
2)We already know what it sounds like.
3)Our brains won't be processing the sound under crisis anyway, having heard it before is not relevant.
Incidentally, I complete agree with your assessment of the potential pitfalls that might come from using a suppressor for defense. Legal or no, its one more thing for the prosecutor to use to make you look like the bad guy. If I weren't concerned about the legal aspects, I'd use one (if I could in NY) but the "nutjob with a silencer" aspect is enough to keep me from trying it.