The 2011 Richard C. Heyser Memorial Lecture: "Where Did the Negative Frequencies Go?" Nothing is Real

Nothing Is Real
It is a common put-down of audiophiles: "You're imagining things." But is this a meaningful criticism? Is there a real difference between "reality" and "illusion"? Or was Professor Dumbledore on to something?

I have been interested in human perception almost as long as I have been working in magazines. This sound is something with which everyone in this room will be familiar: a 1kHz tone at –20dBFS.

[Play 1kHz, –20dBFS sinewave tone]

What I'd like you to do now is to imagine the same tone for 10 seconds.

I believe a scan of your brain would show the same activity in both situations: with a "real" sound and with an "imaginary" sound. We can't directly experience reality; instead, our brain uses the input of our senses to construct an internal model that reflects that external reality, to a greater or lesser degree. So what is reality, what is the illusion? Internally, they are the same thing. That's why hallucinations are so unsettling—there is no way of knowing without further investigation that they don't correspond to anything in the outside world.

I am sure that some are shifting a little in their chairs, so I will demonstrate this conjecture with some music. A couple of years after the Abbey Road sessions I mentioned earlier, the band got back together to record an album for DJM Records. Here's a picture of us in 1974: three sharp-dressed men.


The Obie Clayton Band (L–R): John Atkinson, Michael Cox, Alan Eden

Baggies and platform shoes were mandatory in 1974, otherwise Mark Knopfler wouldn't have had anything to rail against in Dire Straits' "Sultans of Swing." Here's a needle-drop of a track from our LP, which was released in 1975, engineered by Jerry Boys (of subsequent Buena Vista Social Club fame), produced by Tony Cox at Sawmills Studio, and mastered by George Peckham. (Yes, it was a "Porky Prime Cut.") I am playing bass guitar, I'm one of the backing vocalists, and I supply the choir of clarinets in the bridge.

[Play Obie Clayton Band: "Blues for Beginners," needle drop from Obie Clayton LP, DJM DJLPS 458 (1975)]

Think about what you've just heard. I mentioned bass guitar, vocals, and clarinets. There is also a lead singer, a piano, guitars, drums, a harmonica. What's so unusual about that?

What is unusual is that none of this is real. There are no individual sounds of instruments being reproduced by the loudspeakers. Even though you readily hear them, there is no bass guitar, there are no drums, there is no lead vocalist. The external reality is that there are two channels of complex audio-bandwidth voltage information that cause two pressure waves to emanate from the loudspeakers. Everything you hear is an internal construct based on your culture and experience. The impression you get at 2:51 that someone is striking a match to light a cigarette at the right of the stage is something that exists only in your head, your brain back-interpolating from the twin pressure waves striking your ears that that must have been what happened at the original event.

I first heard this phenomenon described in a talk given by Meridian's Bob Stuart a quarter century ago, and it was discussed at length in Edmund Blair Bolles's A Second Way of Knowing: The Riddle of Human Perception (Prentice Hall Press, 1991). Your brain creates "acoustic models" as a result of the acoustic information reaching your ears. We do this so naturally—after all, it's what we do when our ears pick up real sounds—that it doesn't strike us as incongruous that the illusion of the sounds and spatial aspects of a symphony orchestra can be reproduced by a pair of speakers in a living room.

As with our experience of liquid water, the familiarity and apparent simplicity of perception hides depths of complexity. We just do it. Yet there is as of yet no measurement or set of measurements that can be performed on those twin channels of information to identify the sounds I have just described, and what you perceived with no apparent effort when you listened to that recording of my band.

So if the brain creates internal models to deal with what is happening in the "real" world, let's examine how those models work.


Live from the 131st AES Convention: JA throws a baseball for Stephen Mejias to catch.

I was at a Mets game a few years ago, thinking how difficult it is for an outfielder to catch a pop-up, given that when the ball leaves the bat, the fielder has almost no data with which to calculate where the ball will land. I was reminded of something Barry Blesser wrote in the October 2001 issue of The Journal of the AES (p.886). "The auditory system . . ." Blesser wrote, "attempts to build an internal model of the external world with partial input. The perceptual system is designed to work with grossly insufficient data."

Catching a ball illustrates Blesser's point, not just about the auditory system's but also the visual system's ability to use incomplete information. At first the fielder has very little info on which to create a model of the ball's trajectory. Certainly there is not enough information to program a robot to catch the ball (footnote 1). The robot needs to use math. By contrast, the fielder's brain continually updates the model with new information—a process of successive approximation, if you will—until, plop, the ball lands in his glove.

This internal modeling of reality is quirky. First, with visual stimuli, there is a latency of around 100 milliseconds while the brain processes new data. Visually, we experience the world as it existed a tenth of a second in the past. It has been proposed that we have evolved mechanisms to cope with that neural lag; in effect, our internal models predict what will occur one-tenth of a second in the future, which allows us to react to events in the present—such as catching a fly ball, or maneuvering smoothly through a crowd (footnote 2).

But certain situations can unmask that lag. Something that we must all have experienced is when we have glanced at a clock with a second hand or with a numeric seconds display: The first tick appears to take longer than subsequent ticks. But this isn't an illusion: the first tick does take longer—at least in your reality, as opposed to the clock's—because of the time required for the brain to accommodate new data into its model.

I remember discussing perception with Bob Berkovitz when I visited him at Acoustic Research in Boston, in the early 1980s. The conversation stuck in my mind because Bob, who was working with Ron Genereux on digital signal processing to correct room acoustic problems, defined audio as being "one of the few areas in which an engineer can work without the end product being used to kill people."

During that visit, Bob subjected me to a perceptual test. I sat in a darkened room with a red light flashing in the left of my visual field. At some point, Bob switched off the light on the left and turned on a similarly flashing red light on the right. The question is: What did I see?

The answer is not "A red light flashing on the left, then a red light flashing on the right."

What I saw was a flashing red light on the left that then slowly moved across my field of vision until it was on the right!

It was another moment of satori. The conflict between "reality" and what I perceived seemed to demonstrate that, once the brain has constructed an internal model, it is slow to change that model when new sensory data are received. The brain's latency in processing aural data is shorter than it is with visual data, but it still exists. Otherwise there wouldn't be the phenomenon of "backward masking," where a loud sound literally prevents you from hearing a quiet sound that preceded it.

Here's an audio example analogous to the clock's slower first tick with which everyone will be familiar. When you hook up a new component but with the channels reversed, at first, all you're aware of is that something is not quite right. The orchestral violins are on the left, as they should be, but their image wobbles, and is ambiguously positioned. You don't hear them on the right, where they now should be. Then, when you realize that Left=Right and vice versa, the imaging solidifies and is correctly heard as a channel-reversed image. The thought crystallizes the perception, not the other way around.

Although evolution has optimized the human brain to be an extremely efficient pattern-recognition engine that uses incomplete data to make internal acoustic models of the world, as this example suggests, that same evolutionary development has major implications when it comes to the thorny subject of sound quality.



Footnote 1: Following the lecture, I read in Steven Levy's 1984 book Hackers: Heroes of the Computer Revolution that students at MIT in the 1950s programmed a robot arm to catch a ball, but I don't have any further information on this. Also, on how a fielder manages to catch a ball, I am told that as part of the successive approximation process I describe, he adjusts his position to keep a constant angle between the ball and his eye.

Footnote 2: See, for example, the essay at www.luminous-landscape.com/tutorials/what_we_see.shtml.

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Comments
JohnnyR's picture
Misguided?

I haven't seen one iota of explanation from yourself yet as to why both of us and Harman Kardon and the other links George posted to are wrong. Still waiting ChrisSy.

ChrisS's picture
Georgie & JRusskie = Harman Kardon?

Has HK hired you guys as DBT consultants?

 

Hey JRusskie,

Can you answer this one?

If A=B and C=B, then A=?

If you pass the test, then perhaps someone will hire you... But you and Georgie might have to fight over the job.

JohnnyR's picture
Duhhhhhhhhhh........

"i think THESE are the sort of differences between individuals that make DBT difficult: everyone hears differently. there is no absolute sound."

The sole purpose of DBT is to see if the person listening can distinguish between A and B. If they can't then for all practical purposes there is no difference in the sound from A and B. You and ChrisSy seem to think it's all about what the person "likes". It's a straight forward test method and "likes" has nothing to do with it.

Please explain to us all how Harman Kardon manages to use DBT all the time and do it well? I will be awaiting your reply Ariel.

ChrisS's picture
Twas the night...

So every household has a Harman Kardon product? And you and Georgie have living rooms that look like anechoic chambers? No fireplaces, of course....

ChrisS's picture
And, and...

Hearing a difference between a Harman Kardon product and another product in a anechoic chamber means what to you, Georgie and JRusskie?

Do you know that Ford makes the best trucks in the world?

ChrisS's picture
That's the Pepsi....No, it's...

Are you sure I didn't say 'licks". You know maybe tasting an audio product will yield just as useful results in a DBT.

ChrisS's picture
It's So Easy, Even A 3 Year Old...

JRusskie,

Now run out to your nearest Boris' Convenience store and get yourself a can each of Pepsi (do you even have Pepsi in the Former-USSR?) and Coca-Cola and set up your own Pepsi (or whatever passes for cola in Russia) Challenge.

Wiki has a nice explanation of how to do a DBT...

Once you've done your very own Peps(k)i Challenge, please send us your conclusion. We're curious...

The next step now is to get everyone in your subsidized housing project to participate in your Pepski Challenge.

Gather up that data, compare it your own conclusion and let us know how useful that information is.

I'm sure you'll enjoy the challenge of your doing your very own DBT's! (You won't even have to ask Harman Kardon to use their anechoic chamber!)

John Atkinson's picture
Some knowledge of statistics required

JohnnyR wrote:
The sole purpose of DBT is to see if the person listening can distinguish between A and B. If they can't then for all practical purposes there is no difference in the sound from A and B.

And that's the problem with these tests. If a formal blind test gives results that are indistinguishable from what would be given by chance, formal statistical analysis tells us that this result does _not_ "prove" there was no difference in the stimulus being tested, only that if there _was_ a difference, it was _not_ detectable under the conditions of the test. No more general conclusion can be drawn from the results. And as I have said, it is very difficult to arrange so that those conditions don't themselves become interfering variables. Even the fact that it is a test at all can be an interfering variable, as I explain in this lecture preprint.

JohnnyR wrote:
Please explain to us all how Harman Kardon manages to use DBT all the time and do it well?

I have visited Harman's facility in Northridge and their blind testing set-up is impressive. They have worked hard to eliminate interfering variables and their testing is time- and resource-consuming and painstaking. Even so, they have to make compromises. Blind testing of loudspeakers, for example, is almots always performed in mono. And despite the rigor of their testing, you still have anomalous results, like the Mark Levinson No.53 amplifier, which was designed with such testing but fared poorly in the Stereophile review.

While formal blind tests are prone to false negative results - not detecting a difference when one exists - sighted listening is prone to false positives, ie, it detects a difference when none exists or perhaps exaggerates the degree of difference. As neither methodology is perfect, we go with the one that is manageable with our resources. We therefore offer our opinions for readers to reject or accept in the context of their own experience and I believe Stereophile does  a better job of that than any other review magazine or webzine.

If you are uncomfortable with that policy, then you should not read the magazine. And if I remember correctly, JohnnyR, you admitted in earlier discussions on this sute that you neither subscribe to Stereophile, nor do you buy the magazine on the newsstand. So why should anyone pay attention to your opinions on how the magazine conducts itself?

John Atkinson

Editor, Stereophile

JohnnyR's picture
Silly Boy

So you are saying that if in a DBT the listeners could NOT tell a difference between two amps using music of their own choice then that doesn't prove the amps sound alike?  Funny stuff there Atkinson. For one who thinks you should trust your ears to evaluate components you just bashed the ONE single TRUE way to test by USING YOUR OWN EARS in a DBT.

"And that's the problem with these tests. If a formal blind test gives results that are indistinguishable from what would be given by chance, formal statistical analysis tells us that this result does _not_ "prove" there was no difference in the stimulus being tested, only that if there _was_ a difference, it was _not_ detectable under the conditions of the test."

Your own words are saying that "if there was a difference it was not detectable under the conditions of the test"........oh you mean like letting the listener use the music of their own choice and switch back and forth endless times between two amps and then guess wrongly enough times so that they can't tell which one was which? LMAO if that's not proof that both amps sound alike then what sort of test WOULD prove that they do?  Come on Atkinson you just don't like DBTs because they would show up so many components that people think sound "oh so better than the rest"

Opinions from you and your reviewers are the Gospel now folks. No need to test anything really just trust good ol'JA and his flunkies. Yay.

"If you are uncomfortable with that policy, then you should not read the magazine. And if I remember correctly, JohnnyR, you admitted in earlier discussions on this sute that you neither subscribe to Stereophile, nor do you buy the magazine on the newsstand. So why should anyone pay attention to your opinions on how the magazine conducts itself?"

Oh just maybe because  a lot of people care for this little thing called the TRUTH? When magazines like your's take liberties with the truth by having shoddy reviews instead of in depth testing, then it's everyone's and anyone's responsibility to speak up when crappy falsehoods are published and the readers are supposed to take it all on faith. That's why. I for one do not take your opinions on anything audio related as worthwhile at all for the simple reasons that you show so much promise when you measure speakers but fail to even bother with the snakeoli products that you let slide under the radar yet let your reviewers give them glowing reviews sans any testing what so ever. Maybe that's the sighted listening bias you just spoke about yet you fail to even try with those type of products to get to the real TRUTH.

ChrisS's picture
Inconclusive?

JRusskie,

If you like Harman Kardon marketing, but you're not sure if Ford makes the best trucks in the world, then get yourself an F-150 and whatever truck you used to rumble across Afghanistan with, do your DBT (just like  the Pepski Challenge) and let us know what you come up with...

You are marketing TRUTH now? How pure is it?

I know some construction workers who might be interested...

ChrisS's picture
A War In Your Head...

JRusskie, Just looking at your response to John's post and comparing word-for-word what John wrote and what you think he says, there's such a huge world of difference!! There's a war in your head!

[Flame deleted by John Atkinson].

GeorgeHolland's picture
"Even so, they have to make

"Even so, they have to make compromises. Blind testing of loudspeakers, for example, is almots always performed in mono."

Well Mr Atkinson the reasoning behind testing speakers in mono is to eliminate the dreaded comb filter affect that would otherwise show up if a stereo pair were auditioned and the listener moved their head even a couple of inces. I'm surprised you didn't mention that fact but then again you think DBTs are hard to do, so if you don't know how to do them then indeed they are hard to do. *Chuckle*  Any DBT done should be auditoned is such a manner. The rest of your "excuses" for not doing them is the same old same old from you, nothing surprising there.

ChrisS's picture
"Kiss the girls..."

So Georgie Porgie,

Let's say JRusskie is DBT'ing a $1500 speaker and a $500 speaker and can't hear a difference, and you are DBT'ing a $4500 speaker and a $4000 speaker and you happen to have enough working neurons to hear a difference... Which set of speakers should the ex-shepherd construction worker buy?

John Atkinson's picture
Mono vs Stereo testing

GeorgeHolland wrote:
John Atkinson wrote:
Even so, they have to make compromises. Blind testing of loudspeakers, for example, is almost always performed in mono.

Well Mr Atkinson the reasoning behind testing speakers in mono is to eliminate the dreaded comb filter affect that would otherwise show up if a stereo pair were auditioned and the listener moved their head even a couple of [inches].

That is a consideration, of course, but in my opinion a minor one. As I had understood from Floyd Toole back in the day, the additional complexity required  of  Harman's physical speaker shuffling apparatus to do blind speaker testing in stereo was not justified by the results, ie, they felt that the stereo performance could be predicted from the mono results.

I don't agree with that, but more importantly, this illustrates the thesis offered in my lecture, that when you move the testing situation a step away from how the product is going to be used, you can't be sure that the assumptions you make haven't invalidated the test. As I write in the abstract to the lecture, "perhaps some of things we discard as audio engineers bear further examination when it comes to the perception of music."

BTW, I am still waiting for you to acknowledge that the criticism you made of my lecture, that it was not about Richard Heyser, was incorrect.

John Atkinson

Editor, Stereophile

GeorgeHolland's picture
More excuses?  I see what

More excuses?  I see what Johnny meant. You are never wrong. I am pretty sure Haram Kardon knows what they are doing. Please address any criticisms to them not me.

I am afraid that comb filtering IS a big deal. That would explain why cables "sound" different. It's not the cable but the listener changing where their head is between "testing"

You will be waiting a long time for any ackowledgement about your "lecture". Stop being the primadonna already.

Regadude's picture
Prima donna supreme

Georgie wrote:

"Stop being the primadonna already."

Look in the mirror and repeat those words!!!! laugh

ChrisS's picture
Oops! My head moved...

So how does one differentiate speakers that sound differently, amplifiers that sound differently, pre-amps, turntables, tonearms, cartridges, DAC's, etc., if a turn of one's head makes that much difference?

Where's your reliability, Georgie? Doesn't science depend on reliability?

JohnnyR's picture
For The Lazy and Mentaly Deficient.......

I can see what George is up against in here with Tweedle Dum and Tweedle Dee tag teaming and showing their ignorance.

http://www.ethanwiner.com/believe.html

Golly look what he meant.I think Ethan was banned from here ages ago for showing up Fearless Leader and his cronies and out right showing how REAL science works. BWAHAHAHAHAHAH loser boys.

Regadude's picture
For Johnny, about Johnny...
John Atkinson's picture
Ain't that the truth

Just bookmarking the link for future reference.

John Atkinson

Editor, Stereophile

JohnnyR's picture
Atkinson..........

......when you start doing a single DBT or even a SBT then you can talk about the "truth". Have you EVER designed and built your own speakers? Nahhhhhhhh you are too lazy or too "busy". Still finding plenty of time though to post online all the time though strangely enough.cheekyTill then you aren't an engineer so take your own advice and don't comment on speaker design anymore.

If you are going to save the link then please also save this link where discussion about it unfolded.

http://forums.audioholics.com/forums/loudspeakers/83412-diy-loudspeakers...

As you can see the original post was just one of many OPINIONS about the topic that is if you bother to read it at all. There are various OPINIONS about the topic and notice just how many of the so called "hobbyists" ended up being professional speaker builders. If you just pick and choose certain OPINIONS from the thread then you are guilty of leaving out facts.

For starters read the sixth post down by Jinjuku regarding Jeff's post that pretty much sums up where DIY has progressed.

ChrisS's picture
You think, therefore it's true...

Not real science either...

GeorgeHolland's picture
Frick and Frack strike again.

Frick and Frack strike again. Regadude and ChrisS always come up with strawman replies and ignore the links posted."Not real science "? How pompus can you get? Mr Winer measured the effects of comb filtering, what did you measure ChrisS the length of your nose when you typed that reply? You dismiss anything people link to yet show us nothing in return. Regadude, posting opinions isn't real science just so you both understand. Now run along lil boys and study real hard, maybe in another 20 years you might be able to hold your own in a discussion.

ChrisS's picture
Georgie thinks....

Has Winer's results been verified?

Did you know that Harman Kardon makes the best audio products in the world? And Ford makes the best trucks, right?

JohnnyR's picture
Do Some Testing Yourself Genius

Or is that above your abilities like thinking?

Go ahead, put on a pink or white noise source and move your head about and tell me the sound doesn't change. You won't bother so forget it ChrisSy.laugh

ChrisS's picture
ADHD

When moving a microphone while recording a person's voice, the sound changes. Did the voice change?

GeorgeHolland's picture
You never answer a question ,

You never answer a question , you just put forth silly questions of your own. That's what people do when they don't know or are scared to try.

Moving a microphone while recording a person's voice? If that's how you do things then no wonder you don't know what Johnny was talking about. Yes the sound changes as recorded by the microphone so what?  Genius.angle

ChrisS's picture
Dear Georgie...

I'll answer you this one... You and JRusskie always answer your own questions that you pose to everyone in these discussions. There's no need to provide any answer to you. As well, your attitudes and limited knowledge of the application of research methodology make civil and thoughtful discourse impossible.

So my questions to you and JRusskie are formed to reveal how each of you think whenever you provide a response.

You provide enough information for me to say that I find the "best" use of my time in these discussions is to make fun of you and JRusskie.

Ariel Bitran's picture
And Chrissy

makes some sense of the whole darn thing.

Regadude's picture
Tweedle dee and tweedle dum...

The only duo that strikes here George, is you and Johnny. You both STRIKE OUT!

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