Ok guys, a few of you have requested the white papers on alot of the studies. There's a handful of others but I'm not sure how relevant they are to this very discussion, so we'll just start with these. Copy and pasting directly to head-fi proved to be really tricky (it looked a mess and the graphs wouldn't show up). So I've uploaded two of them and they're avalible for you to download as a PDF file.
http://www.pdf-archive.com/2016/03/31/asius-aes-paper/
http://www.pdf-archive.com/2016/03/31/asius-ica-paper-montreal2013/
first, thanks for providing those papers. I wish I had seen such paper a few years back when I was desperately trying to make sense of audiophiles claims about hearing. overall it's instructive.(for others, the second paper is mostly a short version of the first one just showing a different implementation of the same concept with the same results).
ok so let's see if I get this right:
A/ the basic concept is that the listener will look for a desired perceived loudness, and because our protection mechanism reduces our sensitivity to sound, when triggered, we tend to increase the volume to compensate for that reduced sensitivity thus making the protection mechanism even more needed.
this makes sense to me. is anybody contesting this part?
B/ in a sealed ear canal the low frequencies will be boosted compared to the same IEM not sealed.
again, this is very obvious to anyone using closed IEMs, losing the seal also means losing a lot of low frequencies.
there is also mention of phase shift, which is normal as far as I know in any analog change brought to the frequency response. be it a rolled off amp, an EQ or some acoustic tuning. if the signature changes, the phase will also be altered.
anybody has a problem with those ideas?
C/ the stapedius reflex uses a muscle and the hypothesis here is that a long use of that muscle could be a cause of listener's fatigue.
looks like a solid possibility to me, clearly not the only cause of perceived fatigue(pressure in the ear from the tip/shell, some nasty distortions, very spiky signatures, the lack of crossfeed...), but listening to loud sounds for a long period is certainly fatiguing, so be it that the stressed muscle is painful, or that when the muscle fails, we get fatigue from hurting the ear with too loud a sound, the result is the same. so I agree with the hypothesis here.
D/ the papers
suggest that a sealed ear canal
may be more likely to trigger the stapedius reflex(protection mechanism) than a vented IEM(or something with a flexible membrane for the ADEL or the inflatable thing). they also
suggest that the extra low frequencies
could be the trigger for the stapedius reflex to kick in sooner.
I'm guessing all those careful opinions exist because of all the variables that represent different IEMs with different signatures, and different individuals in different listening situations. overall I've seen no strange claims, the papers implies some possibilities(not all to my taste) but the claimed parts seem solid to a newbie like myself doing low-fi IEM measurements.
here is my personal problem with this D/ part. all the talk and measurements are done showing the same given sound source with and without a seal. but as perfectly shown in the papers, one of the very obvious impact will be a strong change in frequency response. that in itself will have enough psycho acoustic repercussions for an estimated loudness or fatigue to mean close to nothing at all. that brings up an obvious question, what about a sealed IEM in sealed conditions, that gives about the same frequency response as a vented one in vented conditions? have any perceived loudness tests been done for that?
