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Old 29th May 2011, 06:02 AM   #1
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Default SPD - Subliminally Perceived Distortion

This is an open letter for those who insist on pushing the "Measurements only" arguments into every thread on this site, claiming it's only about THD or TIM or (name your favorite here______).

Ummm.... at the risk incurring your wrath, it looks like there's a lot more to it. Turns out the subjectivists may win some portions of this argument after all. And we can prove at least some of it. Scientifically. With info that has been peer reviewed and then published in highly respected Journals.

OK, take deep a breath and read on. You're not going to like this.

Here goes:

Along with measuring HD and THD and TIM, there are almost surely other forms of distortion which we have not yet found ways to define or measure in the reproduction chain. Earl Geddes' HOM for example, or some of the spatial imaging/size/localization distortions.

While there are audible events which are consciously noticed as pleasant or unpleasant, there are others that create subliminal physiological responses... even if "un-detected" on a conscious level.
You see, there's a LOT of signal information that we react to sub-consciously, in ways that are physiologically MEASURABLE....with no conscious recognition of what is happening. Such as HF content beyond 20KHz...and other as-of-yet un-named forms of distortion.

OK, so here's some science that supports this notion; please read the following paper about "super HF" audibility and then let's discuss the conclusions that can inferred:

Inaudible High-Frequency Sounds Affect Brain Activity: Hypersonic Effect

In the experiments described, test subjects were asked to identify if a new Pioneer super-tweeter with super steep cutoff slopes, reproducing from 26KHz and up, was audible. They used EEG's on the test subjects, looking for changes in alpha wave production. (Increases in Alpha waves have been shown to be a strong indicator of better health, deeper relaxation, higher creativity, etc. as well as pleasure.)

- The Pioneer tests showed the test subjects had a notable long-term increase of alpha-wave activity when the super-tweeter was playing, even when not consciously detected.

- It ALSO showed a long-term DECREASE in alpha waves when system bandwidth was restricted by removing the super-tweeter. (Listening fatigue?)

- And these differences showed even when the test subjects were unaware the super-tweeter was playing.

Something notable was that some of the subjects strongly defended the notion that they were NOT hearing any difference, even though their EEG's clearly showed otherwise!

Gee, does anyone here think just maybe... if an EEG shows conclusively that people DO react to frequencies in the 20KHz to 100KHz range, (even when they don't take conscious notice)...
Could it then be that an EEG might also show a difference in response when subjects are comparing between cables or amplifiers?

If an EEG or other physiological measurement could show consistent differences in physiological response.... would you still want to categorically assert that it cannot possibly make a difference what cables or what amplifier you use?

How's this for an interesting perspective: double-blind tests are all looking to see if we can CONSCIOUSLY detect the difference... oh-oh...what about the subliminal?

Ladies and Gentlemen: usual double-blind audio testing does not measure any part of the SUBLIMINAL response. Anyone see a flaw in this?

Some would infer that without testing for subliminal response, double-blind testing is USELESS. Yep, or at least pretty flawed.


Now this: we may not be hearing only with our ears !! One of the study's conclusions: "Therefore participation of non-auditory sensory systems such as somatosensory perception also needs to be considered in further investigations."

So if we want to determine which amplifier or cable designs are better, it might be time to start measuring EEG response (and other physiological indicators such as GSR - Galvanometric Skin Resistance - which correlates closely with EEG results) and see how well they correlate with existing amplifier measurements.

When there is the temptation to state something is "inaudible", (such as cables, capacitors, resistors, etc.) it may be wise to re-read the above study and be reminded that even when we are not "consciously noticing" something in the music, we may in fact still be perceiving and subliminally registering the difference in ways that are both physiologically measurable and meaningful.
Who knows? We may in fact be responding to small differences in our local electromagnetic field!

BTW, my background is in EE, and like many, I wanted to believe that what I had learned in school was sufficient, and good enough to explain the world around me. Well, it wasn't.

After a few years studying this issue, I am convinced that if we really want to get a handle on what makes for great sound, we will need to find ways of studying the subliminal response as well as the conscious one. The next frontier in audio is measuring our subliminals. I've been doing some of this with my speakers at HolisticAudio.com, using GSR to see how time/spatial information affects the body, and the results are quite amazing. Turns out that accurate time-response helps create much greater relaxation response, even though it is not "usually noticed" consciously.

Let's coin a new acronym: ===> S.P.D. ===> Subliminally Perceived Distortion

Hmm...what you don't know may actually hurt you!
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Old 29th May 2011, 11:11 AM   #2
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The Oohashi paper is very old news and has been beaten to death here. There were curious contradictions in their data. Two different groups have tried to replicate this work and were unable to do so. 'Nuff said.
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Old 30th May 2011, 10:16 PM   #3
DF96 is offline DF96  England
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Quote:
Ladies and Gentlemen: usual double-blind audio testing does not measure any part of the SUBLIMINAL response. Anyone see a flaw in this?
DBT does not block subliminal responses to the sound, but it does block subliminal responses to cost, make, designer, circuit topology, external appearence, expectations etc. DBT therefore ought to enhance subliminal responses - if something is more pleasant to listen to then this ought to be reflected in the scores even if the listeners are not consciously aware of the difference. For true subjectivists DBT is your friend. You could gather some real evidence. DBT does not block alpha waves, but it does block the placebo effect and may reduce the herd effect.

Let us assume for a moment that it can be shown that, say, 25-30kHz components can improve sound (for at least some listeners). So what? The current 20kHz limit is not a fundamental property of the universe, but the result of tests on people. An objectivist who clings to 20kHz as a hard limit is just as foolish as a subjectivist who insists on 50kHz as the norm. It would still be true that for most people most of the time 20kHz is a reasonable boundary for enjoying music (as opposed to listening to equipment), as many can't even hear 15kHz and maybe some can perceive 25kHz. It would still be true that the RF properties of cables were irrelevant to audio, except perhaps for EMC purposes.
 
Old 30th May 2011, 10:28 PM   #4
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Sub-sonic frequencies aren't audible either, but are documented to be very unpleasant to be around. Those are the "undefinable" things that end up destroying an otherwise good work environment. Employees feel uncomfortable, develop headaches, etc. Same thing. Different end of the frequency band.

~Tom
 
Old 30th May 2011, 10:40 PM   #5
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Loud and deep enough and it's Brown 25 time.
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Old 30th May 2011, 10:45 PM   #6
tomchr is offline tomchr  United States
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No kidding!
 
Old 31st May 2011, 01:37 AM   #7
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Jack, this is a great idea. It looks crazy at the first read, but not after thinking of it. Evaluating directly the correctness of a device through the measurable reactions of a listener, or to be more accurate, his measurable emotional level, finally the most reliable sensor, is logically correct.

Long time ago when I was student I’ve been collaborating in a study about sleep phases, EEG, variation of IQ and so and on. I can say to those that are not familiar with these fields that this is not paranormal activity but real world science.
Now, the application is maybe not straightforward, because first, interpretating an EEG is not that easy, and second, what is the kind of wave that has to be visualized ? Alpha ? Theta ? There is a lot a individual variations (just following the age of the subject, for example), and detractors of the method could objective then that a good system is the one that keeps the auditory asleep.

As Jack says, it’s better to measure the skin conductivity : easier, faster, cheaper and only one parameter to be considered. For the sceptics, this conductivity shows very fast variations following the emotional state. The big job will be to transcript the data in something usable and correlated to any audio quality.

About the relevance of extended bandwith over the 50 Khz, I dunno, but a thing is sure : the low frequency EEG waves can be entrained by low frequency visual or audio stimuli and can produce a trance like state on the subject , under some conditions. We can falll asleep when driving on highways (visual entrainment) , or fall asleep near a fountain. This explains also why the Catholics where using organs, gregorian songs, and of course the “Oouuhhm” of the Tibetan monks (but not the HOM of dr Geddes !). There’s a redundancy of examples of this.
As tomcr said, some noises are very negative (supermarket or factory noise), but it’s not the same music.

Good luck Jack for this little revolution.
 
Old 31st May 2011, 10:58 PM   #8
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Quote:
Originally Posted by Radugazon
As Jack says, it’s better to measure the skin conductivity : easier, faster, cheaper and only one parameter to be considered. For the sceptics, this conductivity shows very fast variations following the emotional state. The big job will be to transcript the data in something usable and correlated to any audio quality.
There is a danger here of subjectivists outdoing objectivists: "we know you say it sounds worse, but your physiological responses tell us that you are enjoying it more, therefore it must be better." Are we expected to believe that people who don't believe in DBT because of the 'stress' it induces would be quite happy to do listening tests hooked up to a lie detector and an EEG while lying in a scanner?
 
Old 31st May 2011, 11:01 PM   #9
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DBTs apparently do not induce stress when the variables are level, EQ, distortion, data compression, or dynamic range compression. It's an interesting phenomenon- what it it about those variables that relaxes the poor nervous listeners? Perhaps some kind person with a Hubbard Electrometer can shed light on this.
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Old 31st May 2011, 11:17 PM   #10
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Let's face it Jack, you are a salesman. Selling $36k9 speakers makes you a player, not a disinterested party. You are about as out of place amongst DIY enthusiasts as a pool shark in a small town trying to hustle the locals for a few bucks.

The study you quote has the following at the bottom 'The article must therefore be hereby marked “advertisement” '. It's a commercial. It's like the research about tobacco and health funded by the tobacco industry.

Research my shiny metal 4ss.

w
 

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