Creating a Audio Dartboard

[tonmeister2008]

Then again, there are always some intangibles that we can't measure that relate to success.

So what intangibles are we missing in testing and evaluating loudspeakers, for example?

If I brought in 500 listeners, ran them through a double-blind test, and 85% preferred the same speaker, and that outcome could be predicted with over 86% accuracy based on objective measurements, it suggests we at least have most of the important "intangibles" accounted for.

 

[amirm]

I guess what I'm saying is that we can't accept anything blindly (NPI).

I am certainly not asking anyone to take anything blindly. The first thing I ever do regarding a dbt is to scrutinize its assumptions. 9 out of 10 times I find something less than ideal with it. And often, I dismiss the entire test as not being useful (the ones examining jitter audibility often fall in this category for example).

That said, I do learn things from them when done right as was the case with Sean's recent test results posted here.

I am hoping that we get people who are dismissing the entire methodology to accept its usefulness to some extent. That would be useful progress I would think .

 

[tonmeister2008]

Hi Sean,

As a long time Proceed and Mark Levinson owner, having gone through Series 2, 3, and 4 as well as owning Revel F30s in the past, I am very glad to get a chance to communicate with you.

I am doubly glad that I get to keep my left nut! I hope to learn even more from you in times to come!

Jack

Pleased to meet you Jack, and thanks for keeping me employed. I hope to keep both of my nuts, but joining this group, one can't be too sure

 

[MylesBAstor]

So what intangibles are we missing in testing and evaluating loudspeakers, for example?

If I brought in 500 listeners, ran them through a double-blind test, and 85% preferred the same speaker, and that outcome could be predicted with over 86% accuracy based on objective measurements, it suggests we at least have most of the important "intangibles" accounted for.

I think that you can get the results that you want. You've already indicated that with the CODEC work.

Listening to music is much different than evaluating some sounds.

 

[JackD201]

Hi Frantz,

I'm not discounting science at all. I just think that there is an appropriate method for everything. I'm just saying that as a consumer, DBTs are not practical for me. It doesn't mean that it can't be for someone else, like Amir for example. In fact if you go back and read all of my posts on the subject I've given my opinion on where DBTs are very useful indeed. As Dr. Olive pointed out, they use many other methods aside from DBTs depending on what exactly they are investigating. So it is definitely a part of the whole but that's just it, a part. It isn't the end all and be all that many suggest it is.

I think this is what folks who are likeminded as myself are trying to say. For tightly focused personal evaluations for purchase or for members of the press, review, DBTs by itself are insufficient in completing the undertaking.

As for the people that can not hear the difference and fail DBTs even within the realm of chance, I have a word to describe them..........LUCKY! I'm sure they can afford better vacations than I can!

Peace.

Jack

 

[Ron Party]

I made no such insinuation Ron. I take exception to that.

Geez, what part of "Perhaps I'm mistaken" didn't you understand? While I read your statement in the manner I've described, if you intended no such insinuation, then 'nuff said. No need to personalize this.

I had intended to log back into the forum this morning and address the balance of your post - you will recall I stated it was late and I was getting tired - but in the intermin I see that others, including Dr. Olive, have addressed many of all of your concerns (and thanks to those that did), including the benefit of using trained listeners, save these two:

1) I do not question DBTs per se. I question its utility from a consumer stand point.

2) By the way, I answered you r question as best I could. It seems you have forgotten to answer mine. Amir did. You don't have to but it would help me see better where you are coming from.

"Given there is no perfect component out there, why did any of you choose what you have now? Did any of us blind fold ourselves in the dealer's shop? More importantly, should we? How important is actively participating in a DBT shoot out to you when you select a component for your own use?"

In reverse order, I have participated a blind testing of interconnects and power cables. Brands included Nordost, Transparent, NBS, Blue Jeans and 1 other *high end* brand, the name of which escapes me right now. Heard no difference. I now purchase all of my interconnects from Blue Jeans and I use the stock power cord that comes with any new piece of equipment I acquire.

I hope to purchase new speakers before year's end. I did not ABC/HR them, but I have heard them, read some user accounts, seen multiple measurements, talked with the person who designed and makes them, and, in light of my budget constraints and personal goal in audio reproduction, which is to avoid as much coloration as possible, these speakers fit the bill more so than any other speakers.

As to how blind testing is of benefit to you as a consumer, well it may or may not be. How's that for a self-evident truth! Seriously, consumers make decisions for any number of reasons. Whatever floats your boat, so to speak.

As an audio consumer, it still is the case of whatever floats your boat. Our founding father, Steve Williams, loves to quote me as saying much of audio reproduction comes down to a flavor choice. There is no right or wrong, there is only taste.

Now let's take the following example in our recent history. Recall the recent spectacle with the ~$3K Lexicon *rebadging* of the ~$500 Oppo blu-ray player. At least on-line there was a lot of speculation that Lexicon did nothing to the Oppo other than literally drop it inside of a new case, and I believe it was Audioholics that took the case off the Lexicon, photographed it, measured it and compared the measurements with an Oppo, and posted everything for the world to see.

There is a bit of dispute as to whether that is all Lexicon did. (It certainly wouldn't be the first time such a thing has occurred.) But for sake of argument, let's assume it is true. Now based on brand name, price, and aesthetics, it is easy to believe a consumer undertaking a non-blind comparison of the two products would find the Lexicon delivered a more satisfying picture, with deeper blacks and truer colors. In fact, there was one reviewer who stated as much, and he was raked through the proverbial coals in several internet fora.

What do we make of this? Well, on the one hand, if that consumer walks into a high end B&M store, and the saleperson sells him/her that Lexicon, it could be stated that consumer got exactly what he/she wanted for a myriad of reasons. Other consumers might be mad as hell had they found out they could have bought the same player and saved ~$2500 in the process. $2500 buys a lot of albums or concert tickets, after all.

The same applies to Amir's previous example of the exact same cable, but with either a red or blue covering, particularly if one of those cables is sold at a steep multiple of a price over the other.

So can blind testing help a consumer? The answer is a resounding, unequivocal yes. If the question is will blind testing help you (or any one person) in particular, the answer is maybe.

 

[audioguy]

In reverse order, I have participated a blind testing of interconnects and power cables. Brands included Nordost, Transparent, NBS, Blue Jeans and 1 other *high end* brand, the name of which escapes me right now. Heard no difference. I now purchase all of my interconnects from Blue Jeans and I use the stock power cord that comes with any new piece of equipment I acquire.

I, too, am a Blue Jeans user. I have failed every blind test I've taken on IC's, speaker wire and power cords. So if there is a difference, it clearly isn't important enough for me to spend the money. And for those that are thinking of asking, these were both short term and long term comparisons in my room with all components I was familiar with other than the object under test (if it happened to be in the system at the time).

By the way, if anyone is interested in some nice power cords, let me know

 

[The Smokester]

We probably all have anecdotal experiences which "color" our view of DBT. I have several and here is one.

When I was entering "the high end" I took my Sony SCA555? SACD player over to the Wadia dealer, plugged it and a Wadia player into a highly-resolving system and carefully equalized the sound pressure. Then, I sat there for a few hours challenging whoever came along to identify the Wadia. I sat there flipping the switch back and forth between players at the victim's (I mean listener/test subject's) request but they could have no idea which player they were listening to. The results were purely random. The store owner guessed? wrong and he was greatly distressed.

Then, a professional classical musician (cellist) whom I knew and respected came along and I asked him to try the test. He listened carefully for a short while, then confidently and correctly identified the Wadia. He also provided a detailed accounting of what his clues were and convincingly described the difference in details that he heard.

I know that there are many untested explanations for this result (since it was really not a very controlled situation), but I can't help believing that the capabilities of the listener are very, and perhaps overridingly, important. It also biases me to think that, when someone assumes Gaussian statistics to analyze one of these experiments, that they may be on the wrong track.

 

[JackD201]

Hi Ron,

The qualifier didn't quite make up for what I took for an accusation. It's just that attacking people is not in my nature so naturally if I feel I am accused of doing so, my feathers are perhaps way too easily ruffled. Anyway, that's cleared up. Let bygones be bygones?

So in the case of the Oppo, how exactly do you surmise a blind test would have helped the consumer? I mean if we go through the motions, the buyer would have had to ask, what BD players the store had, asked the sales person to line them up behind a blanket or something, ask the same sales person to switch the players around. Lexicon and the Oppo would have to have been, by sheer luck, been in the line-up. Being blind and thus inoculated from visually induced biases, the buyer would also have been able to discern that there was no difference between not just the two units but also the units against themselves.

All this is definitely within the realm of possibility but a bit of a stretch when it comes to probability don't you think? If the Audioholics allegations are true, then it was simply a case of good investigative journalism. If false then a classic case of irresponsible journalism. If true, I think that helped more consumers in less time than advocating that every consumer go through a similar procedure as outlined above. If false, it hurt both the consumers and HSG because as you said, consumers make decisions for any number of reasons, one of these has got to be looks.

As for the red and the blue cable, yes I heartily agree. It would apply to a fat as a constrictor cable vs one that looks like a reject from radio shack. It can go the other way too with the ultry skinny cables from say Audience and 47 Labs whose skinniness is part of their visual appeal. People CAN be influenced by what they see. I know I can and have been in the past when I practically lived on the merry-go-round. I did manage to get off the merry-go-round eventually when I learned what to listen for and had a much clearer idea of what I was shooting for. Incidentally that would be not a search for perfection but rather the elimination of distractions that disrupt sustainable periods of suspended disbelief by deviating from, to borrow from Stevie, my flavor of choice. That would be full bandwidth, high dynamic range, neutral but with a touch of forgiving sweetness up top so I can still enjoy mediocre recordings of performances I really like. In any case it was this combination of professional training and self education that brought me down to earth, cured my audiophilia nervosa and also saved me a lot of money. Because I know what types of distortions or frequency deviations bother me most, I know what to avoid when I hear it. The cable can be red, blue or purple, pedestrian looking or fancy. If I hear something I don't like about them from the get go, be they reasonable priced or stratospherically priced, out they go. If they seem okay, then I go for an extended evaluation where the component must run the gauntlet of my music collection. The higher the price, the higher the standards I apply. Thank goodness I'm surrounded by excellent, and patient dealers.

Now here's where I make a U-turn. After finishing the last paragraph, I just realized that not everybody gets the luxury of extended home trials like I do. So I have been unfair. Perhaps in a store setting, a blind shoot out, sans blanket, just might be the most ideal if it were possible to have all the candidates on one's shortlist available. If the results were inconclusive, heck go for the one with the best value all other things considered. If it was conclusive, go for the best one you can afford. So I concede that point to you Sir. I just hope that the buyer can get past the looks too. He's still got to look at the darned thing

Jack

 

[Ron Party]

When I was entering "the high end" I took my Sony SCA555? SACD player over to the Wadia dealer, plugged it and a Wadia player into a highly-resolving system and carefully equalized the sound pressure. Then, I sat there for a few hours challenging whoever came along to identify the Wadia. I sat there flipping the switch back and forth between players at the victim's (I mean listener/test subject's) request but they could have no idea which player they were listening to. The results were purely random. The store owner guessed? wrong and he was greatly distressed.

Then, a professional classical musician (cellist) whom I knew and respected came along and I asked him to try the test. He listened carefully for a short while, then confidently and correctly identified the Wadia. He also provided a detailed accounting of what his clues were and convincingly described the difference in details that he heard.

I know that there are many untested explanations for this result (since it was really not a very controlled situation), but I can't help believing that the capabilities of the listener are very, and perhaps overridingly, important. It also biases me to think that, when someone assumes Gaussian statistics to analyze one of these experiments, that they may be on the wrong track.

I don't think the explanation is properly characterized as untested. Instead, I think you answered your own question, i.e. it was not properly controlled.

I think you already know this, but it is worth stating. To begin with, what you're describing was not a DBT. It may have been somewhat blind to the testee, but generally speaking such tests are highly unreliable. Questions about your test would include, without limitation: what do you mean when you wrote "equalizing the sound pressure" and how did you go about doing so, where were you standing, what did you have to do to switch the players, did you say anything to the testee during the test, what order did you play the two players, did you ever play the same player 2 times is a row without telling the testee, was there anything audible when switching between the two players, how many trials were there, how many times did the testee correctly identify one player or the other.

The subject of using trained listeners has been covered. Generally speaking they do better. The subject of using professional musicians also has been covered. They do not.

 

[Ron Party]

As for the red and the blue cable, yes I heartily agree. It would apply to a fat as a constrictor cable vs one that looks like a reject from radio shack. It can go the other way too with the ultry skinny cables from say Audience and 47 Labs whose skinniness is part of their visual appeal. People CAN be influenced by what they see. I know I can and have been in the past when I practically lived on the merry-go-round. I did manage to get off the merry-go-round eventually when I learned what to listen for and had a much clearer idea of what I was shooting for. Incidentally that would be not a search for perfection but rather the elimination of distractions that disrupt sustainable periods of suspended disbelief by deviating from, to borrow from Stevie, my flavor of choice. That would be full bandwidth, high dynamic range, neutral but with a touch of forgiving sweetness up top so I can still enjoy mediocre recordings of performances I really like. In any case it was this combination of professional training and self education that brought me down to earth, cured my audiophilia nervosa and also saved me a lot of money. Because I know what types of distortions or frequency deviations bother me most, I know what to avoid when I hear it. The cable can be red, blue or purple, pedestrian looking or fancy. If I hear something I don't like about them from the get go, be they reasonable priced or stratospherically priced, out they go. If they seem okay, then I go for an extended evaluation where the component must run the gauntlet of my music collection. The higher the price, the higher the standards I apply. Thank goodness I'm surrounded by excellent, and patient dealers.

Let's keep the conversation going, since we're now focusing on consumers.

And let's keep the discussion going as it applies to the red and blue cables. (Why do I feel were about to go Matrix here?)

Your stated your own particular flavor of choice as "full bandwidth, high dynamic range, neutral but with a touch of forgiving sweetness up top so I can still enjoy mediocre recordings of performances I really like".

So I have to ask: why must this be a sighted test?

In your litmus test I don't see anything about aesthetics. Let's assume that subconsciously you believe the red cable matches, and the blue cable clashes, with the decor in your room. Therefore you find the blue cable does not pass the test.

Now you may say, nonsense. I'm a trained listener. I would never make this kind of decision.

But, as we've already covered, no one is immune from bias, that includes both trained and untrained consumers. And our ears (or more correctly, the brain to which they are connected) are notoriously good at "hearing" differences where none exist. There exists lots of nice science to show the huge difference between what people think they hear and what they actually hear.

The human ear is pretty good at figuring out certain kinds of signals. The human brain is even better at making things up. Give the brain some subconscious bias, and it will want to believe it hears a difference where there is none. Try finding references to various fMRI studies on how the brain processes audio. Maybe Dr. Olive can chime in here.

 

[JackD201]

Well to me a long term evaluation is sighted because I know it is there and that it is what's playing or being played through. I'm not comparing the piece under consideration to anything else, rather I undergo the process of familiarizing myself with what that piece brings to the table within my system's context. Here I try to find both strengths and weaknesses. Since component selection is always a matter of trade offs, I want to know exactly what I'm getting and what I'm giving up. At least that's the idea.

That's why I mentioned the piece has got to run through the gauntlet of my collection. The method I choose may not be perfect but at the very least it protects my wallet from the infatuation associated by simply having something new or just plain pretty. This is important to me because when something new comes in and at first listen produces sounds that are better in some ways than that which came before it, experience has taught me that this difference has often come with downturns that eventually bothered me over time. You are right in that this "new gear infatuation" can make ones judgement blurred or skewed in the component's initial favor by masking the said unit's trade offs.

So since I am evaluating the unit for its own attributes and contributions to the overall presentation of my system I see no reason to blind test it against something else. I do this type of due diligence because I have to be prudent when it comes to my disposable income. I've wasted quite a bit of money in the past so I have become more critical and even skeptical of likely candidates, particularly those with reviews that glow too much.

Every once in a while though, I get hit by a lightning bolt like when I first tried Mullard CV2492s on my amplifiers. Telefunken Highs, Mullard Mids and Siemens CCa Bass. It becomes difficult to resist the infatuation but time is really the only way to know if it's really love and not love at first sight. Six months of listening and I pulled the trigger and hoarded the darned things. If any of you guys are on the hunt for these, I am heartily sorry

Now there was a time when two very similarly priced preamps passed my personal evaluations with flying colors out of the 5 I was able to try out. I guess you can say that I had already been biased for these two pieces having chosen them as finalists. That is when I shot them out with each other to be absolutely sure. I eventually went with the one that fit my flavor more closely albeit at the expense of the other's advantage in ergonomics, enhanced functionality and visual aesthetics . I figured getting up to adjust the volume was at least good exercise. I would have been happy with either but I could only choose one.

 

[MylesBAstor]

Well to me a long term evaluation is sighted because I know it is there and that it is what's playing or being played through. I'm not comparing the piece under consideration to anything else, rather I undergo the process of familiarizing myself with what that piece brings to the table within my system's context. Here I try to find both strengths and weaknesses. Since component selection is always a matter of trade offs, I want to know exactly what I'm getting and what I'm giving up. At least that's the idea.

That's why I mentioned the piece has got to run through the gauntlet of my collection. The method I choose may not be perfect but at the very least it protects my wallet from the infatuation associated by simply having something new or just plain pretty. This is important to me because when something new comes in and at first listen produces sounds that are better in some ways than that which came before it, experience has taught me that this difference has often come with downturns that eventually bothered me over time. You are right in that this "new gear infatuation" can make ones judgement blurred or skewed in the component's initial favor by masking the said unit's trade offs.

So since I am evaluating the unit for its own attributes and contributions to the overall presentation of my system I see no reason to blind test it against something else. I do this type of due diligence because I have to be prudent when it comes to my disposable income. I've wasted quite a bit of money in the past so I have become more critical and even skeptical of likely candidates, particularly those with reviews that glow too much.

Every once in a while though, I get hit by a lightning bolt like when I first tried Mullard CV2492s on my amplifiers. Telefunken Highs, Mullard Mids and Siemens CCa Bass. It becomes difficult to resist the infatuation but time is really the only way to know if it's really love and not love at first sight. Six months of listening and I pulled the trigger and hoarded the darned things. If any of you guys are on the hunt for these, I am heartily sorry

Now there was a time when two very similarly priced preamps passed my personal evaluations with flying colors out of the 5 I was able to try out. I guess you can say that I had already been biased for these two pieces having chosen them as finalists. That is when I shot them out with each other to be absolutely sure. I eventually went with the one that fit my flavor more closely albeit at the expense of the other's advantage in ergonomics, enhanced functionality and visual aesthetics . I figured getting up to adjust the volume was at least good exercise. I would have been happy with either but I could only choose one.

Better increase your compound's security then

 

[MylesBAstor]

So what intangibles are we missing in testing and evaluating loudspeakers, for example?

If I brought in 500 listeners, ran them through a double-blind test, and 85% preferred the same speaker, and that outcome could be predicted with over 86% accuracy based on objective measurements, it suggests we at least have most of the important "intangibles" accounted for.

Before we get to intangibles, let's ezxplore some testing basics-esp. the neglect for the organism being tested.

The book "Talent is Overrated" is a good place to begin.

Then I'm not quite sure how you do your "speaker shuffle?" Does each speaker go to the same spot or do you predetermine the correct room placement first for each speaker first? And do you use ML electronics for all your tests? If so, then I might point out that one can be developing a speaker that will only work with one amplifier/electronics chain. (this is not a trivial matter since I once ran into the case where a amplifier designer used a single speaker to design/voice his electronics. Turned out that the amplifier only ended up sounding good on that one speaker (and at least four, quite dissimilar speakers were tried with the amplifier.) And I'm not quite clear how you prevent the listener from identifying the speaker they're listening to?

Two, how do you account for the learning process? We know it takes say 10,000 attempts to automate a learning process. At first, we use say 1000X times more neurons in the brain and those neurons tend to be located superficially in the brain. As we learn and the process becomes automated, the brain is able to reduce the number of neurons to complete the task and those neurons are located deeper in the brain.

How do you control for adaptation of the organism to the stress?

Finally, how do you control for effects of the actual testing upon central nervous system arousal (that inverted U) and its effect upon perception? For instance with an Olympic Weightlifter who has only one task to complete, central nervous system arousal should be maximal since perception and the taking in of the external environment is not necessary. But then again in the case of pianist, something that you can relate to, ones central nervous system arousal needs to be as low as possible since the musician needs as much perceptual ability as possible.

Then while I think your trying to "teach" novices about listening, in the end what you're testing is their ability to learn what you taught them, not necessarily what constitutes music.

Now I understand what you're trying to accomplish and that is laudable, but one can't just accept everything at face value and not think about the test methodology.

 

[FrantzM]

Myles

In what ways blind protocols neglect the organism under test?
Let's suppose that the organism has indeed special abilities. Why is that these abilities disappear once some KNOWLEDGE of what is being tested is removed? Why is it do difficult to accept the consistently provable and proven fact that what we see has an influence on or recollection of perceptions?

I will turn the table on you .. The same can be said about a test in which the person conduction the test has full knowledge of the component ( I am focusing on cables , the most difficult components to accurately and consistently discern under knowledge-removal tests).. . I know the component (cable), I know what it is purported to do .. I even (too often) now of its reputation and /or price ... I also know how unreliable auditory memory is (although I can invoke it to disprove other methodologies) .. This is a VERY faulty methodology wouldn't you say ? More so than the other one .. Which would you rather take at face value?
By the way I proclaim it again I don't choose my components in DBT .. I have however failed in BT with cables that I knew very well .. I have moved toward a non-believer when it comes to (electrically adequate) cables and have come to reluctantly accept DBT as a very useful tool ... YMMV but so far attempts to prove that DBT is more flawed than sighted protocols have not been very convincing at least in this forum.

Frantz

 

[MylesBAstor]

Myles

In what ways blind protocols neglect the organism under test?
Let's suppose that the organism has indeed special abilities. Why is that these abilities disappear once some KNOWLEDGE of what is being tested is removed? Why is it do difficult to accept the consistently provable and proven fact that what we see has an influence on or recollection of perceptions?

I will turn the table on you .. The same can be said about a test in which the person conduction the test has full knowledge of the component ( I am focusing on cables , the most difficult components to accurately and consistently discern under knowledge-removal tests).. . I know the component (cable), I know what it is purported to do .. I even (too often) now of its reputation and /or price ... I also know how unreliable auditory memory is (although I can invoke it to disprove other methodologies) .. This is a VERY faulty methodology wouldn't you say ? More so than the other one .. Which would you rather take at face value?
By the way I proclaim it again I don't choose my components in DBT .. I have however failed in BT with cables that I knew very well .. I have moved toward a non-believer when it comes to (electrically adequate) cables and have come to reluctantly accept DBT as a very useful tool ... YMMV but so far attempts to prove that DBT is more flawed than sighted protocols have not been very convincing at least in this forum.

Frantz

The process of adaptation to stress - the testing process itself and the bodies changes in response to sound which is another stressor. We certainly know the biologically certain frequencies can have deleterious effects even.

 

[FrantzM]

The process of adaptation to stress - the testing process itself and the bodies changes in response to sound which is another stressor. We certainly know the biologically certain frequencies can have deleterious effects even.

Let's call this fishing for proofs.. The simple fact is that the single most important parameter is the Knowledge and what psychological response it induces. Most advertising is based on that well known, proven and repeatable fact.
I can understand the reluctance in the end ... if it pleases you and you prefer to use a given product go ahead .. but don't claim it makes a vast difference when not knowing it's there or not makes the "vast differences" much less certain or even make them disappear" ...

Frantz

 

[amirm]

Frantz makes a good point. To the extent differences cannot be shown in DBT and/or measurements, it is kind of hard to characterize them as "huge/night-and-day," etc. Use of such terms definitely inflames the level of argument.

After all, if the difference is huge, then people should be able to detect them even with all the flaws of DBT.

In my own testing, the differences found are always small. Those small differences may mean a lot to someone in the form of increased sense of space, clarity, etc. but objectively, the difference is small.

 

[MylesBAstor]

Let's call this fishing for proofs.. The simple fact is that the single most important parameter is the Knowledge and what psychological response it induces. Most advertising is based on that well known, proven and repeatable fact.
I can understand the reluctance in the end ... if it pleases you and you prefer to use a given product go ahead .. but don't claim it makes a vast difference when not knowing it's there or not makes the "vast differences" much less certain or even make them disappear" ...

Frantz

Sorry Frantz but it's not fishing for proofs. This is hard factual research going on since the '40s and is typified in motor learning and teaching.

Stress related protein synthesis (such as heat shock proteins or molecular chaperones) is a huge area in cancer research and many other medical areas. Stress in the body leads to illness through effects on our hypothalmus-pituatary-adrenal axis. There are hormones secreted by our adrenals that control our immune system.

 

[FrantzM]

Sorry Frantz but it's not fishing for proofs. This is hard factual research going on since the '40s and is typified in motor learning and teaching.

Stress related protein synthesis (such as heat shock proteins or molecular chaperones) is a huge area in cancer research and many other medical areas. Stress in the body leads to illness through effects on our hypothalmus-pituatary-adrenal axis. There are hormones secreted by our adrenals that control our immune system.

Myles

This doesn't address the issue at hand: The change in perception descriptions when the knowledge is removed. We can accept stress when the subject knows he or she is under stress but this is often not the case sighted and knowing which is which a quick determination is often arrived at ... Whwn knowledge is removed not so ...
The point you mention are well taken ... They don't tell anyone much about the non-value of a test in which scored rather in other areas of Audio reproduction namely speakers and in the case of trained listeners electronics ... Why not with others? the stress would have been a constant ...
So it is going very far, to get to a basic point that while there are differences between some of our dear components, the differences are so small as to be imperceptible in the vast majority of cases, especially when basic and known physics would tell us that they were ..well ... imperceptible or there couldn't be any effect.. One of these lifting the cable from the floor among many others ... I'll stop there ...

Frantz

P.S. I am quickly adding that to me Electronics sound different and so do speakers, transducers in general .. Blind or not ..