Differences in how we hear..its in the brain

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Arj
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#1 erstellt: 09. Mai 2006, 20:56

An article quoted from another forum.. very interesting read about how different peaople "process" sound differently in their brain .

We shouldn’t fight about taste? Day in, day out, millions of hi-fi fans demonstrate the opposite. The discussion about the right sound regularly results in heated emotions. For example, horn loudspeakers divide the audiophile community into two camps. One side says that horn speakers falsify the sound. The other side isn’t bothered by this at all and enthuses about the precision and speed of the reproduction. The only thing they have in common is the uncomprehending head shaking of one about the other. But why is there such a splendid fight about audio qualities? How and why do we decide whether a sound does or doesn’t please us? Is it habit? Accident? Or is there more behind it?

Amazing hearing test

In the basement of the Neurology Department of the Heidelberg University Clinic a big step nearer the answer has been taken. Deep under the Clinic itself, in order not to disturb the sensitive hospital equipment, Dr. Peter Schneider and his colleagues of the Biomagnetic section have only recently discovered something sensational. “People actually hear differently”, is the enthusiastic summary of physicist Schneider of his results. Together with researchers from Southampton and Liverpool, the researchers have found evidence that people perceive and process pitch quite differently – something that present expert opinion completely discounts.

In another cellar room, in the AUDIO hearing room, the editorial staff sits with a very special hearing test. From the speakers are emitted sequentially short peeps and after each pair the hearers cross the appropriate square, indicating whether the following tone rises or falls. Eager scratching of pencils on the distributed questionnaire can be heard. After hardly a minute it’s over. Distinct whispers run through the seat rows. Irritated glances at the neighbour’s paper. How could the colleague have possibly crossed “descending”? That tone sequence was clearly ascending! Peter Schneider collects the questionnaires in no way astonished over the different answers to his gearing test. “You have here in the editorial staff a mixture of fundamental and overtone hearers,” he explained, “you all hear the same tone, but you don’t hear them all the same way. You don’t hear better or worse, just quite simply differently.”

A suspicion…

Fundamental hearers and overtone hearers, that’s the new invisible border, which divides mankind into two camps. Independently of age, gender, profession and musicality, it defines how the brain perceives the pitch of sound. Each natural sound consists of a basic frequency, the fundamental, and the multiples of this frequency, the overtones. The number and strength of these overtones, the overtone spectrum, causes the character of voices, noises and instruments.

In order to determine pitch, the brain looks for the fundamental in the mixture of frequencies. Even should this frequency be missing, because it wasn’t transmitted by the loudspeaker, our hearing always produces the missing fundamental from the available overtones. At least, that’s what was thought. Until now.

The suspicion that tones are perceived very subjectively, was expressed as long ago as the 19th century by German scientist Hermann von Helmholtz. He differentiated so-called “synthetic hearing” by which the overtone groups were merged to a type of sound mass, from “analytical hearing”, by which the single tones were perceived consciously.

Schneider and his colleagues wanted to put things on a firm basis and developed a special tone hearing test; the fundamental was removed from complex tones whose overtones represented whole number multiples of the fundamental. There was now played a sequence of tones that in fundamental frequency and number of harmonics (the whole number multiples) differed. Some people assessed the tone succession as descending, others as ascending. 334 professional musicians, 75 amateur musicians and 54 non-musicians were tested in this manner.

…is confirmed

With an amazing result. The test subjects were clearly split into two groups, fundamental hearers and overtone hearers. While the fundamental hearers, as previously expected, assembled the missing fundamental frequency from the available overtones and thus determined the pitch, the brain of the overtone hearers adapted the pitch from the available overtone spectrum. The chasm thus originating between the perceived pitches can be up to 4 octaves. Thus, when you hear the B above middle C played in a string concerto, the person sitting beside you may perceive the F two-and-a-half octaves higher. “It’s as if the test subject saw a blue banana instead of a yellow one,” was how Peter Schneider explained the enormous difference. “And the statistical distribution indicates that there are more extreme fundamental hearers or overtone hearers than there are “centrist” hearers who find them in balance.” In other words, there are more people who see a blue banana rather than a yellow one – the results of the studies up to now show that the frequency of the extremes is slightly higher. It is therefore possible to imagine a world with many, many blue bananas, which should be yellow for everyone. Why should this be?

It is exactly this question that is occupying the Heidelberg researchers. With the knowledge that the brain assembles the tones and therefore also the pitch in several different ways, the scientists detected an amazing connection. By means of magnetic resonance imaging, the brains of 87 test subjects were anatomically recorded, and while they were listening, their brain electrical impulses were measured using magnetoencephalography.

The result is amazing. The people characterised as fundamental hearers were shown to have, in the lateral region of the Heschl Gyrus (a part of the hearing cortex), an appreciably greater volume of grey matter in the left side than in the right, the overtone hearers a correspondingly greater volume in the right. Furthermore, in the case of fundamental hearers, the left side of the Heschl Gyrus reacts more strongly and distinctively to sound than does the right side, and the other way round for the overtone hearers. In the case of professional musicians, the absolute volume of grey matter in the hearing cortex is much bigger, but the relative sizes of the grey matter in the left and right sides is that same as for non-musicians. This therefore means that, for every person, independent of age, musicality or gender, one side or the other side responds more strongly to music and tones. The other half certainly doesn’t remain inactive during hearing, but from birth one of the sides dominates our perception of sounds. And this has consequences.

Left the drummer, right the singer…

“Many other studies have shown that the left and right sides of the hearing cortex have different functions,” explains Peter Schneider about the function separation in the brain’s hearing centre. The left hand side is particularly sensitive to short, quick impulses, for all sounds that last no longer than 50 milliseconds. The right-hand side reacts sensitively to longer tones and is responsible for the spectral manipulation of the perceived sound. “A relationship between the different hearer types and the special characteristics of the sides is only logical”.

Special characteristics – that is certainly what separates fundamental and overtone hearers. Not only are the pitches differently interpreted, but also the instructions as to how sensitively a hearer will react to any given sound appear to be stored in the two halves of the hearing cortex. Quick, short, sharp impulses and virtuoso finger exercises – the left side and the fundamental hearer respond to them. Long stately melodies and the processing of sound colours – that is balm for the right side and soothes the overtone hearer.

It is therefore no accident that the choice of instrument of fundamental hearers is predominantly percussion, guitar, piano and high solo instruments such as trumpet and transverse flute. On the other hand, overtone hearers choose instruments that produce long sustained tones with characteristic sound colours or formants in the spectrum – strings, lower brass or woodwind, organ and voice. Differences are apparent in the way of playing. fundamental hearers like it rhythmic or virtuosic, overtone hearers prefer long melody bridges and are especially interested in sound colours and harmony. “Interestingly enough, the arrangement of preferred instruments according to fundamental and overtone hearers corresponds with the seating arrangement of a modern symphony orchestra,” said Schneider. It’s hardly a surprise that the difference between the hearer types occurs mainly in what is for mankind the most important frequency range, 1500Hz and below.

It is only a short step from musical instruments to music. How does it work out in live music? Or in the mixing of a CD? When the recording engineer is a fundamental hearer and gives more value to rhythm than to tone colour, does the result then sound less good to overtone hearers? Do we find such recordings more or less pleasing? Do some musical styles therefore appeal more to us than others? Do overtone hearers prefer symphonic music, while fundamental hearers prefer a jazz concert?

These are also burning questions among scientists. “For example, it is very interesting that some hi-fi set-ups have hardly any measurable differences, but are judged to sound very different,” says Dr.André Rupp, leader of the Biomagnetics Section, “is there perhaps a relationship?”

AUDIO has also posed this burning question. Are we finally on the trail of the puzzle as to why some components, be they horn speakers or flat speakers, polarise the hi-fi world so much? Base tone hearers pay more attention to timing and precision. If these criteria are fulfilled, fundamental hearers perceive tonal colouring even if these have been neglected.

Overtone hearers again are inclined to forgive weaknesses in rhythm rather than tolerate sound colouring. If a rather extreme overtone hearer encounters a speaker designed and tuned by a fundamental hearer, the verdict will hardly be good. Might it be, perhaps, that here lies the secret as to why some names on the hi-fi scene are celebrated by some and demonised by others?

AUDIO researches further

The possibility that our completely individual biases are already genetically programmed is also probable [yes, it really does say that!]. It is important that one should know one’s own personal hearer-type. However, one thing is certain; without further intensive research will the questions remain unanswered.

viren
Stammgast

#2 erstellt: 10. Mai 2006, 03:27

Hello Arj,

A fascinating, if ongoing, study. Can't neglect subjective perceptions, can we!

However, things usually don't work out to be "black and white". It's the nature of the scientific method to try and come up with absolutely conclusive results. The human psyche often doesn't oblige.

Could we possibly react differently to the types of music we hear - become overtone hearers when listening to classical music, and become more of fundamental hearers when listening to jazz? Does mood influence a bias towards either of these perceptions?

Perhaps we should just avoid the analysis and accept differences amongst us - and enjoy the moment for what it is!

Viren.

deaf
Stammgast

#3 erstellt: 10. Mai 2006, 03:54

Dear Arj,
A cracker topic,but too hairy to deal with.Even racial differences decide how a particular sound is deciphered by which part of the brain.As Viren says enjoy the moment and the music,and audio too.
Regards Deaf.

Arj
Inventar

#4 erstellt: 10. Mai 2006, 07:26

Viren,
but it is an interesting perspective to look at.
my take is a "Single theory" view on anything leads to biases. But if one is able to look at the same aspect from different perpectives we only come out richer.

In the past 1 year I have been able to understand that we can look at the perspective of spound via so many factors like understanding

Specs and graphs
design
acoustics
memories (eg those who grew up listening to LPs love it more)
Type of music
cultural heritage (British colonies like British components eg Singapore, french cloloies like taiwan prefer french etc etc)
Perception ie what do we want to hear (Brands/blind testing)
The Ears respose ie fletcher-Munson curves
And now even depending how even ones brains acoustic centers works.

Personally I find it a rather fascinating study of sound and how we like to hear it

square_wave
Inventar

#5 erstellt: 10. Mai 2006, 11:22

This is very interesting from an “academic perspective” . It helps us understand why there is so much divide among audiophiles on the idea of the “perfect system” or “perfect reproduced sound”.
I guess Viren was trying to gauge its relevance to a typical audiophile/music lover when it comes to enjoying music either reproduced or live. I agree with him. We just have to accept the fact that people are different and like to hear “different” depending on ones taste and perception. I always believe that any audiophile would have made his greatest discovery when he actually discovers which “ CAMP” he belongs to. It is only from that point he will start making worthwhile investments in audio equipment which will serve him better. For this anyone would have to listen to hundreds of configurations and decide for himself. There is no alternative to first hand experience.

viren
Stammgast

#6 erstellt: 10. Mai 2006, 13:30

Hi Arj,

I'm all for understanding more as to how we humans react to stimuli. And appreciate the work done by these researchers in exploring such complex relationships.

But I retain a bit of scepticism as to the conclusions drawn from such work. By necessity, such research has to be conducted within very defined boundaries - some of those boundaries are artificial. In a different environment, what's to say that other parts of the brain are not interacting and influencing our perceptions.

Viren.

Arj
Inventar

#7 erstellt: 10. Mai 2006, 14:04

square_wave schrieb:

We just have to accept the fact that people are different and like to hear “different” depending on ones taste and perception.

Well.. that is one way of looking at it.. another is to try to understand why there is. maybe you will end up and understand only 25% of it or even less, but to me personally it is the process of discovery which is fascinating hence try to put such gems in the forum.

people like fletcher Munson and then Robinson and Dadson were able to explain Why people hear differently only since they tried to understand.. if they just left it at that, we would have not understood that each persons hearing can be scientifically be proven to be different and this changes as per the frequency.

I feel the easiest approach one can take is to say people are different and leave it like that. but it is people like the above researchers (again maybe this guy is on the wrong path)who actually make a difference in the way people look at things.

I feel strongly on this (As is apparent:D ) as that is what makes the difference between assuming desease is a wrath of god and finding a medicine to cure it !

Arj
Inventar

#8 erstellt: 10. Mai 2006, 14:16

Adding to the above, if you want to test out your own hearing and have your curve, try the below link.
if you try that with a friend and both hear the same piece of music differently, it might help you understand as the some of the reason Why you hear different things

http://www.phys.unsw.edu.au/~jw/hearing.html

square_wave
Inventar

#9 erstellt: 10. Mai 2006, 14:27

Arj schrieb:

square_wave schrieb:

We just have to accept the fact that people are different and like to hear “different” depending on ones taste and perception.

I surely appreciate such people's work. And I appreciate your effort in getting such gems to the forum so that we all benefit. I was just looking at it from an audiophile’s point of view and trying gauge its relevance to a typical audiophile/music lover when it comes to enjoying music either reproduced or live. Basically looking at it from a different angle. That’s all

Arj
Inventar

#10 erstellt: 10. Mai 2006, 15:11

No issues..

there is a very nice saying by a german philosopher called Arthur Schopenhauer

"All truth passes through three stages. First, it is ridiculed. Second, it is violently opposed. Third, it is accepted as being self-evident."

-

Krish
Stammgast

#11 erstellt: 11. Mai 2006, 04:37

viren schrieb:

Hi Viren,

This is interesting, because it is analogous to all the work being done in the area of trying to understand human conciousness.An area that till recently was the exclusive preserve of philosophers.

The problems in studying either are quite similar.While both phenomenons are universal, the way that they are experienced are distinctly individual.

I think Arj has summed it up quite nicely with that quote from Schopenhauer.These are early days and the skepticism is understandable.

Personally,I am always amazed at how far we have been able to further our understanding of how the brain creates the mind.Do we know all there is to be known ? far from it.But what we know today, is so much more than what we knew in the past and that is what is facinating.

Meanwhile it's all about the music, ofcourse.

Cheers

Amp_Nut
Inventar

#12 erstellt: 11. Mai 2006, 09:09

Hi Arj,

Just read the long post. ( I had been putting it off till I had time on my hands )

AWESOME !

Thanks

Arj
Inventar

#13 erstellt: 13. Mai 2006, 23:12

Actually found a test for this

1. Download this audio file (FLAC format)

http://stud4.tuwien....o.de_-_overtone.flac

2. Download this plugin for your Windows media player

http://www.illiminable.com/ogg/oggcodecs_0.71.0946.exe

After you install the above then you should be able to play The file.

There is a total of 12 pairs. A German-speaking voice introduces each iteration and every pair is repeated once. For each sequence jot down, whether you thought the frequency to be increasing or decreasing.

Afterwards compare your results with this table:

--Inc_Dec
1 --------x
2 --------x
3 --x
4 --x
5 --x
6 --x
7 --------x
8 --------x
9 --x
10 --------x
11 --------x
12 --x

The more your results agree with this list, the more you are a fundamental tone hearer. If your result is the exact inverse of the above, you are a pure overtone hearer.

[Beitrag von Arj am 13. Mai 2006, 23:17 bearbeitet]

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