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maestro@ultrapiano.com
science forum Guru Wannabe
Joined: 23 Oct 2005
Posts: 145
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 Posted: Sun Oct 23, 2005 6:20 am Post subject:
how your ears work
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Inside the cochlea of a human ear are hundreds of thin cilia. Rather
like an insect's eye, which is made up of hundreds of very primitive
eyes, each cilium responds individually to the pressure variations in
the cochlear fluid caused by sounds, contributing its own primitive
interpretation of the sound to the overall picture. Each cilium
responds to pressure by firing a synapse and sending a bio-electrical
signal along the aural nerve into the inner brain, the journey along
the aural nerve taking about a 25th of a second. While a 25th of a
second's worth of pressure variation information is on the aural nerve,
the brain attempts to match its auditory memory with features in the
pressure variation information. Neural pathways into the brain's
memory of pressure variation patterns are strengthened during this
process, resulting in the brain deciding on what the sound 'is'. |
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bgranat
science forum beginner
Joined: 23 Oct 2005
Posts: 1
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| Posted: Sun Oct 23, 2005 9:25 am Post subject:
Re: how your ears work
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Sounds good to me.... |
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cvandall
science forum beginner
Joined: 23 Oct 2005
Posts: 1
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| Posted: Sun Oct 23, 2005 1:29 pm Post subject:
Re: how your ears work
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I gave this much thought and I can find no fault with it.
"maestro@ultrapiano.com" <StpNrrs@aol.com> wrote in message
news:1130048430.296561.135220@g14g2000cwa.googlegroups.com...
| Quote: | Inside the cochlea of a human ear are hundreds of thin cilia. Rather
like an insect's eye, which is made up of hundreds of very primitive
eyes, each cilium responds individually to the pressure variations in
the cochlear fluid caused by sounds, contributing its own primitive
interpretation of the sound to the overall picture. Each cilium
responds to pressure by firing a synapse and sending a bio-electrical
signal along the aural nerve into the inner brain, the journey along
the aural nerve taking about a 25th of a second. While a 25th of a
second's worth of pressure variation information is on the aural nerve,
the brain attempts to match its auditory memory with features in the
pressure variation information. Neural pathways into the brain's
memory of pressure variation patterns are strengthened during this
process, resulting in the brain deciding on what the sound 'is'.
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stickyfox@gmail.com
science forum beginner
Joined: 23 Oct 2005
Posts: 10
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S.O.D.D.I.
science forum beginner
Joined: 19 Aug 2005
Posts: 6
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| Posted: Sun Oct 23, 2005 8:19 pm Post subject:
Re: how your ears work
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The best current book on this subject is "Music, The Brain and Ecstacy:
How Music Captures Our Imagination" by Robert Jourdain (Morrow, 1997).
(No, not the drug ecstacy, you silly youts.)
Jourdain follows the theme from anatomy to neurophysiology and brain
structure to psychology and musical learning.
It's a real good book, dense but well worth the effort.
My only problem is that Jourdain is a DWEM supremacist and that colors
his science writing just a bit.... but the only way to see what I'm
talking about is to read his arguments on tone perception.
Good resource for synthesists. |
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p1an0@aol.com
science forum beginner
Joined: 26 Oct 2005
Posts: 9
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| Posted: Wed Oct 26, 2005 12:35 am Post subject:
Re: how your ears work
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so what 'is' a sound?
maestro@ultrapiano.com wrote:
| Quote: | Inside the cochlea of a human ear are hundreds of thin cilia. Rather
like an insect's eye, which is made up of hundreds of very primitive
eyes, each cilium responds individually to the pressure variations in
the cochlear fluid caused by sounds, contributing its own primitive
interpretation of the sound to the overall picture. Each cilium
responds to pressure by firing a synapse and sending a bio-electrical
signal along the aural nerve into the inner brain, the journey along
the aural nerve taking about a 25th of a second. While a 25th of a
second's worth of pressure variation information is on the aural nerve,
the brain attempts to match its auditory memory with features in the
pressure variation information. Neural pathways into the brain's
memory of pressure variation patterns are strengthened during this
process, resulting in the brain deciding on what the sound 'is'. |
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maestro@ultrapiano.com
science forum Guru Wannabe
Joined: 23 Oct 2005
Posts: 145
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| Posted: Wed Oct 26, 2005 1:38 am Post subject:
Re: how your ears work
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p...@aol.com wrote:
so what 'is' a sound?
maes...@ultrapiano.com wrote:
| Quote: | Inside the cochlea of a human ear are hundreds of thin cilia. Rather
like an insect's eye, which is made up of hundreds of very primitive
eyes, each cilium responds individually to the pressure variations in
the cochlear fluid caused by sounds, contributing its own primitive
interpretation of the sound to the overall picture. Each cilium
responds to pressure by firing a synapse and sending a bio-electrical
signal along the aural nerve into the inner brain, the journey along
the aural nerve taking about a 25th of a second. While a 25th of a
second's worth of pressure variation information is on the aural nerve,
the brain attempts to match its auditory memory with features in the
pressure variation information. Neural pathways into the brain's
memory of pressure variation patterns are strengthened during this
process, resulting in the brain deciding on what the sound 'is'.
From the brain's point of view a sound 'is' approaching from the left,
for example, or a sound 'is' running water, or 'is' frightening, or |
pleasant. The brain can detect such qualities without thought, because
of automatic biologically evolved processes occuring within it, such as
comparison of remembered pressure variation patterns with those in the
sound.
Sound can be described mathematically as consisting of sinewaves at
different frequencies and amplitudes, or as the numbers in a .wav or
..mp3 file, but the information on the aural nerve is none of these.
Each cilia fires when sufficient pressure above the ambient has been
applied, and then takes about a 10th of a second to recover so that it
is ready to fire again (by which time the internal pressure in the
cochlea will usually have decreased to below the ambient for a short
while). Some cilia are less responsive than others and take more time
to recover, but each cilium individually behaves like a very primitive
ear, which becomes dormant for a short while whenever it has been
squashed by the pressure in the ear sufficiently for its synapse to
fire.
The hundreds of cilia individually send their primitive information
along the aural nerve to the inner brain, and the brain can interpret
the total of the sound information corresponding to a 25th of a second
while it is on the aural nerve. A loud sudden sound would probably
cause a lot of cilia to fire simultaneously, along with low-level
echoes, and the brain can detect that pattern of information as it
travels along the nerve fibres. High frequency sound might result in
the frequent occurrence of large numbers of cilia firing in a short
period of time, corresponding to a short length of the aural nerve on
which the pattern is occurring.
The often-repeated belief (sometimes called the travelling wave theory)
that the ear itself hears sound mechanically (rather than the brain
doing the hearing and deciding on what a sound 'is'), with each cilium
tuned by nature to respond to a specific sinewave frequency, and
vibrating sympathetically to 'sound waves' of that frequency because of
resonance effects in the cochlear fluid, and the basilar membrane
detecting the strength of the vibration (rather like the base of a
cat's whisker) to give the amplitude of a frequency, is basically quite
ridiculous and should be abandoned. |
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stickyfox@gmail.com
science forum beginner
Joined: 23 Oct 2005
Posts: 10
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| Posted: Wed Oct 26, 2005 11:33 am Post subject:
Re: how your ears work
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Is there a better theory? I think pretty much all of the physiology of
hearing is based on this "oft-repeated belief."
What exactly do you find wrong with it? |
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Matthew Fields
science forum Guru Wannabe
Joined: 26 Oct 2005
Posts: 200
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| Posted: Wed Oct 26, 2005 12:35 pm Post subject:
Re: how your ears work
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In article <1130326395.896226.112020@g47g2000cwa.googlegroups.com>,
stickyfox@gmail.com <stickyfox@gmail.com> wrote:
| Quote: | Is there a better theory? I think pretty much all of the physiology of
hearing is based on this "oft-repeated belief."
|
The oft-repeated-belief that each hair cell resonates a particular
frequency and that it interprets sound mechanically, rather than
sound being interpreted by the brain, leads to very definite predictions
about how each should behave under experimental conditions.
| Quote: | What exactly do you find wrong with it?
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Since it leads to predictions, it's fine as a historical scientific
hypothesis. Since those predictions have repeatedly, consistently turned
out to be wrong, it's not a hypothesis worthy of any further serious
consideration. As a scientific theory, it has failed, gloriously. Science
moves on.
--
Matthew H. Fields http://www.umich.edu/~fields
Music: Splendor in Sound
To be great, do better and better. Don't wait for talent: no such thing.
Brights have a naturalistic world-view. http://www.the-brights.net/ |
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stickyfox@gmail.com
science forum beginner
Joined: 23 Oct 2005
Posts: 10
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| Posted: Wed Oct 26, 2005 1:37 pm Post subject:
Re: how your ears work
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Wow, now there are two of you; this is interesting.
So what you're saying is that, according to the popular opinion, each
frequency component stimulates certain hair cells, and those cells in
turn interpret the sound and identify it to the brain? I have never
heard of this theory before.
It was my impression that each cell responds to a particular frequency
component and relays the presence or absence of that component to the
brain, and that the brain interprets the whole set of sensations. This
seems to be the jist of the few anatomy diagrams and articles I found
in a brief internet search. It also agrees with high school physics.
What predictions and studies are you referring to? |
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Matthew Fields
science forum Guru Wannabe
Joined: 26 Oct 2005
Posts: 200
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| Posted: Wed Oct 26, 2005 2:45 pm Post subject:
Re: how your ears work
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In article <1130333836.082466.134930@g44g2000cwa.googlegroups.com>,
stickyfox@gmail.com <stickyfox@gmail.com> wrote:
| Quote: | Wow, now there are two of you; this is interesting.
So what you're saying is that, according to the popular opinion, each
frequency component stimulates certain hair cells, and those cells in
turn interpret the sound and identify it to the brain? I have never
heard of this theory before.
It was my impression that each cell responds to a particular frequency
component and relays the presence or absence of that component to the
brain,
|
Bingo, same thing as we were just saying, and dead wrong.
| Quote: | and that the brain interprets the whole set of sensations. This
seems to be the jist of the few anatomy diagrams and articles I found
in a brief internet search. It also agrees with high school physics.
|
High school physics barely prepares you for real acoustics much less
cellular dynamics.
| Quote: | What predictions and studies are you referring to?
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That the loss of a specific cell or neighborhood of cells can be
mapped to deafness at a specific frequency but not around it, for instance.
Doesn't work.
--
Matthew H. Fields http://www.umich.edu/~fields
Music: Splendor in Sound
To be great, do better and better. Don't wait for talent: no such thing.
Brights have a naturalistic world-view. http://www.the-brights.net/ |
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Chel van Gennip
science forum beginner
Joined: 26 Oct 2005
Posts: 2
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| Posted: Wed Oct 26, 2005 2:53 pm Post subject:
Re: how your ears work
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On Wed, 26 Oct 2005 14:35:34 +0200, Matthew Fields wrote:
| Quote: | In article <1130326395.896226.112020@g47g2000cwa.googlegroups.com>,
stickyfox@gmail.com <stickyfox@gmail.com> wrote:
Is there a better theory? I think pretty much all of the physiology of
hearing is based on this "oft-repeated belief."
The oft-repeated-belief that each hair cell resonates a particular
frequency and that it interprets sound mechanically, rather than sound
being interpreted by the brain, leads to very definite predictions about
how each should behave under experimental conditions.
|
Let's put the question a bit more abstract. Does the spectrum of incoming
sound define which nerves are activated (no presure detector, brain
working on frequencies much lower than the soundwaves), or does the
presure of the sound define which nerves are activated (presure detector,
brain works at the frequencies of the sound waves)
If you propose the second, is there any proof of any activity in the
brain at the required speed level (about 25us or less)
--
Chel van Gennip
Visit Serg van Gennip's site http://www.serg.vangennip.com
NEW: Recording of Ludwig van Beethoven, Sonata Tempest
http://www.serg.vangennip.com/musichigh/N-Beethoven-Storm-20051023.mp3 |
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Matthew Fields
science forum Guru Wannabe
Joined: 26 Oct 2005
Posts: 200
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| Posted: Wed Oct 26, 2005 3:01 pm Post subject:
Re: how your ears work
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In article <3s9jjgFmsaelU1@individual.net>,
Chel van Gennip <chel@vangennip.nl> wrote:
| Quote: | On Wed, 26 Oct 2005 14:35:34 +0200, Matthew Fields wrote:
In article <1130326395.896226.112020@g47g2000cwa.googlegroups.com>,
stickyfox@gmail.com <stickyfox@gmail.com> wrote:
Is there a better theory? I think pretty much all of the physiology of
hearing is based on this "oft-repeated belief."
The oft-repeated-belief that each hair cell resonates a particular
frequency and that it interprets sound mechanically, rather than sound
being interpreted by the brain, leads to very definite predictions about
how each should behave under experimental conditions.
Let's put the question a bit more abstract. Does the spectrum of incoming
sound define which nerves are activated (no presure detector, brain
working on frequencies much lower than the soundwaves), or does the
presure of the sound define which nerves are activated (presure detector,
brain works at the frequencies of the sound waves)
If you propose the second, is there any proof of any activity in the
brain at the required speed level (about 25us or less)
|
Based on the actual physics and neuroscience I've seen, I wouldn't
propose any of the above, and I'd refuse to be constrained to a bifurcation.
Last I heard, there are areas of the brain analogous to the spectrum, but
not individual sensors analogous to the spectrum. There's an interpretation
of periodicity-related information by all the hair cells, and a
reinterpretation into spectral data in the brain, and a large range of
opportunity for error or illusion in between--which accounts for things
like our perceptions of the "fundamental" frequencies of carillon bells,
a pitch NOT corresponding with anything in the spectrum.
--
Matthew H. Fields http://www.umich.edu/~fields
Music: Splendor in Sound
To be great, do better and better. Don't wait for talent: no such thing.
Brights have a naturalistic world-view. http://www.the-brights.net/ |
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Chel van Gennip
science forum beginner
Joined: 26 Oct 2005
Posts: 2
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| Posted: Wed Oct 26, 2005 3:42 pm Post subject:
Re: how your ears work
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On Wed, 26 Oct 2005 17:01:01 +0200, Matthew Fields wrote:
| Quote: | In article <3s9jjgFmsaelU1@individual.net>, Chel van Gennip
chel@vangennip.nl> wrote:
On Wed, 26 Oct 2005 14:35:34 +0200, Matthew Fields wrote:
In article <1130326395.896226.112020@g47g2000cwa.googlegroups.com>,
stickyfox@gmail.com <stickyfox@gmail.com> wrote:
Is there a better theory? I think pretty much all of the physiology of
hearing is based on this "oft-repeated belief."
The oft-repeated-belief that each hair cell resonates a particular
frequency and that it interprets sound mechanically, rather than sound
being interpreted by the brain, leads to very definite predictions
about how each should behave under experimental conditions.
Let's put the question a bit more abstract. Does the spectrum of
incoming sound define which nerves are activated (no presure detector,
brain working on frequencies much lower than the soundwaves), or does
the presure of the sound define which nerves are activated (presure
detector, brain works at the frequencies of the sound waves)
If you propose the second, is there any proof of any activity in the
brain at the required speed level (about 25us or less)
Based on the actual physics and neuroscience I've seen, I wouldn't
propose any of the above, and I'd refuse to be constrained to a
bifurcation. Last I heard, there are areas of the brain analogous to the
spectrum, but not individual sensors analogous to the spectrum. There's
an interpretation of periodicity-related information by all the hair
cells, and a reinterpretation into spectral data in the brain, and a
large range of opportunity for error or illusion in between--which
accounts for things like our perceptions of the "fundamental"
frequencies of carillon bells, a pitch NOT corresponding with anything
in the spectrum.
|
Well, I think we can be sure the brain is not interpreting signals at a
25us level. So there must be at least one, maybe more mappings from sound
patterns before perception. The first mapping has to be at the mechanical
level, as the speed of nerve cells is not in the us range.
There are some indications that one of the mappings is frequency related:
e.g. the sensitivity band of the ear and the changes when people get
older, and the existence of "band deafness".
It is likely the mapping(s) is (are) more complex. The ear comes early in
the evolution. Hearing was not related to music or even communication. I
think it was primarely food related: "Is there food or am I food?"
Important information that had to be processed fast by primitive brains.
--
Chel van Gennip
Visit Serg van Gennip's site http://www.serg.vangennip.com
NEW: Recording of Ludwig van Beethoven, Sonata Tempest
http://www.serg.vangennip.com/musichigh/N-Beethoven-Storm-20051023.mp3 |
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Matthew Fields
science forum Guru Wannabe
Joined: 26 Oct 2005
Posts: 200
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| Posted: Wed Oct 26, 2005 4:55 pm Post subject:
Re: how your ears work
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In article <3s9mfhFn5craU1@individual.net>,
Chel van Gennip <chel@vangennip.nl> wrote:
| Quote: | It is likely the mapping(s) is (are) more complex. The ear comes early in
the evolution. Hearing was not related to music or even communication. I
think it was primarely food related: "Is there food or am I food?"
Important information that had to be processed fast by primitive brains.
|
Could equally be related to avoiding predation or finding a mate.
--
Matthew H. Fields http://www.umich.edu/~fields
Music: Splendor in Sound
To be great, do better and better. Don't wait for talent: no such thing.
Brights have a naturalistic world-view. http://www.the-brights.net/ |
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