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Angelo Campanella
science forum Guru Wannabe
Joined: 08 May 2005
Posts: 226
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 Posted: Mon Dec 26, 2005 6:03 pm Post subject:
Re: how your ears work
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HellPope Huey wrote:
| Quote: | Count your blessings, o ye with decent hearing and cool toys.
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Which brings up another (old) subject; the mechanism of hearing damage
via loud noises (NIPTS), especially why nerve damage damage always
starts in the 4k-6k region regardless of the spectrum of the incoming noise.
Is it a quantum effect? My first guess a few decades ago was that it
was a resonance effect where the ear canal and middle ear were resonant,
hence amplified slightly. Later on, another "explanation" appeared; that
the hair cells sensing high frequencies are near and just behind the
oval window, and hence experiences the most intense noise level.
[Also, I now believe that it is the sweeping action resulting from the
acoustic velocity of the inner ear liquid within the cochlea that
produces the physical damage, and not primarily the acoustic pressure
there. This liquid velocity would be greater in certain parts of the
cochlear spiral, and less in others especially for mid and low sound
frequencies.]
Another aspect I have learned is that the damage starts, or is most
likely to begin, around 5,600 Hz. Modern hearing testing (not the
Bekesey method) simply looks at the discrete frequencies of 3k, 4k, 6k,
8k, and of those, the 4k is the most common indicator (likely because 6k
is skipped, and 8k taken instead). But the measured 4k hearing loss is
hardly accurate in the sense of mapping primary damage. It is only handy
in that everyone makes a 4k measurement, hence it has become the de
facto harbinger of NIPTS.
So, any good explanation of why primary hearing damage starts in 4k-6k
region?
Angelo Campanella |
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Matthew Fields
science forum Guru Wannabe
Joined: 26 Oct 2005
Posts: 200
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| Posted: Mon Dec 26, 2005 7:37 pm Post subject:
Re: how your ears work
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In article <6gWrf.357336$zb5.175661@bgtnsc04-news.ops.worldnet.att.net>,
Angelo Campanella <a.campanella@att.net> wrote:
| Quote: | HellPope Huey wrote:
Count your blessings, o ye with decent hearing and cool toys.
Which brings up another (old) subject; the mechanism of hearing damage
via loud noises (NIPTS), especially why nerve damage damage always
starts in the 4k-6k region regardless of the spectrum of the incoming noise.
Is it a quantum effect? My first guess a few decades ago was that it
was a resonance effect where the ear canal and middle ear were resonant,
hence amplified slightly. Later on, another "explanation" appeared; that
the hair cells sensing high frequencies are near and just behind the
oval window, and hence experiences the most intense noise level.
[Also, I now believe that it is the sweeping action resulting from the
acoustic velocity of the inner ear liquid within the cochlea that
produces the physical damage, and not primarily the acoustic pressure
there. This liquid velocity would be greater in certain parts of the
cochlear spiral, and less in others especially for mid and low sound
frequencies.]
Another aspect I have learned is that the damage starts, or is most
likely to begin, around 5,600 Hz. Modern hearing testing (not the
Bekesey method) simply looks at the discrete frequencies of 3k, 4k, 6k,
8k, and of those, the 4k is the most common indicator (likely because 6k
is skipped, and 8k taken instead). But the measured 4k hearing loss is
hardly accurate in the sense of mapping primary damage. It is only handy
in that everyone makes a 4k measurement, hence it has become the de
facto harbinger of NIPTS.
So, any good explanation of why primary hearing damage starts in 4k-6k
region?
Angelo Campanella
|
If indeed it really does. There's a critical band that's essential to
understanding speech where a little hearing loss does more to affect
speech comprehension than other bands. I'd go with explanations
supported by solid otology and neurology, myself, if indeed there is
such an effect. Peeking online, I see articles on the topic in
pubmed.gov (Medical research abstracts), www-nehc.navy.mil (Navy
environmental health center), and other reputable sources, as well
as a variety of unvetted and other sources.
--
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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J Ketutsalo
science forum beginner
Joined: 26 Oct 2005
Posts: 6
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| Posted: Mon Dec 26, 2005 10:45 pm Post subject:
Re: how your ears work
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Angelo Campanella wrote:
| Quote: |
Which brings up another (old) subject; the mechanism of hearing
damage via loud noises (NIPTS), especially why nerve damage damage
always starts in the 4k-6k region regardless of the spectrum of the
incoming noise.
|
Because at around 4k the transmission through the outer and middle ear
is most efficient, largely due to a quarter wavelength resonance of the
ear canal. At those frequencies you simply get more energy to the inner
ear to do the damage. |
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The Ghost
science forum Guru Wannabe
Joined: 24 Mar 2005
Posts: 115
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| Posted: Tue Dec 27, 2005 2:13 am Post subject:
Re: how your ears work
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Angelo Campanella <a.campanella@att.net> wrote in
news:6gWrf.357336$zb5.175661@bgtnsc04-news.ops.worldnet.att.net:
snip....snip
| Quote: | So, any good explanation of why primary hearing damage starts in
4k-6k region?
Angelo Campanella
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http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_u
ids=1880280&dopt=Citation |
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Angelo Campanella
science forum Guru Wannabe
Joined: 08 May 2005
Posts: 226
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| Posted: Tue Dec 27, 2005 3:22 am Post subject:
Re: how your ears work
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Matthew Fields wrote:
| Quote: | Angelo Campanella <a.campanella@att.net> wrote:
So, any good explanation of why primary hearing damage starts in 4k-6k
region?
If indeed it really does.
|
Essentially all the audiograms I have inspected in relation to hearing
loss due to occupational noise have that area severely affected (much loss).
| Quote: | There's a critical band that's essential to
understanding speech where a little hearing loss does more to affect
speech comprehension than other bands.
|
In the few kHz region for sure, speech comprehension is severely
affected. But my question has to do with the etiology of the dominance
of the loss in the 4 kHz area. The 5.6 kHz phenomenon I reference is an
area of severe loss, a narrow notch that may be the earliest effect. I
venture to say that everyone has a notch there. It might be
"antiresonance" in the ear canal, but I have seen no recent elaboration
on it. But is it such, or really a sensoneural loss?
| Quote: | Peeking online, I see articles on the topic in
pubmed.gov (Medical research abstracts), www-nehc.navy.mil (Navy
environmental health center), and other reputable sources, as well
as a variety of unvetted and other sources.
|
I think I have seen many of them...
I'm just trying to get up-to-date without a lot of effort....
Ang. C. |
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Matthew Fields
science forum Guru Wannabe
Joined: 26 Oct 2005
Posts: 200
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| Posted: Tue Dec 27, 2005 4:08 am Post subject:
Re: how your ears work
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In article <Pr2sf.359675$zb5.37163@bgtnsc04-news.ops.worldnet.att.net>,
Angelo Campanella <a.campanella@att.net> wrote:
| Quote: | Matthew Fields wrote:
Angelo Campanella <a.campanella@att.net> wrote:
So, any good explanation of why primary hearing damage starts in 4k-6k
region?
If indeed it really does.
Essentially all the audiograms I have inspected in relation to hearing
loss due to occupational noise have that area severely affected (much loss).
There's a critical band that's essential to
understanding speech where a little hearing loss does more to affect
speech comprehension than other bands.
In the few kHz region for sure, speech comprehension is severely
affected. But my question has to do with the etiology of the dominance
of the loss in the 4 kHz area. The 5.6 kHz phenomenon I reference is an
area of severe loss, a narrow notch that may be the earliest effect. I
venture to say that everyone has a notch there. It might be
"antiresonance" in the ear canal, but I have seen no recent elaboration
on it. But is it such, or really a sensoneural loss?
Peeking online, I see articles on the topic in
pubmed.gov (Medical research abstracts), www-nehc.navy.mil (Navy
environmental health center), and other reputable sources, as well
as a variety of unvetted and other sources.
I think I have seen many of them...
I'm just trying to get up-to-date without a lot of effort....
Ang. C.
|
I looked at the list of newsgroups you posted to, didn't see sci.med or
anything specifically related to otorhinolaryngiology there, would tend
to ask active researchers in that field.
Here's a link I'd try, just because I've heard of some of these folks's
work.
http://www.khri.med.umich.edu/
They're making pretty amazing strides in understanding hearing all the
way from the ear canal to conciousness and perception, at levels
electrical, cellular, mechanical, molecular, genetic... quite a range
of stuff.
--
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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Angelo Campanella
science forum Guru Wannabe
Joined: 08 May 2005
Posts: 226
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| Posted: Tue Dec 27, 2005 2:33 pm Post subject:
Re: how your ears work
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Matthew Fields wrote:
It looks like they are set up with labs that might make progress in
understanding the noise frequency (non) selectivity in causing hearing
loss. But that page does not indicate activity in that regard.
| Quote: | They're making pretty amazing strides in understanding hearing all the
way from the ear canal to conciousness and perception, at levels
electrical, cellular, mechanical, molecular, genetic... quite a range
of stuff.
|
That range is apparently what the researchers are interested in, rather
than always the problems that need to solved. They must have some
well-heeled sponsors.... I should not be so crass.. Thanks for the leads..
Sincerely,
Angelo Campanella. |
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TheGhost
science forum addict
Joined: 09 Aug 2005
Posts: 85
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| Posted: Tue Dec 27, 2005 8:57 pm Post subject:
Re: how your ears work
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Angelo Campanella <a.campanella@att.net> wrote in
news:Agcsf.196950$qk4.107303@bgtnsc05-news.ops.worldnet.att.net:
| Quote: | Matthew Fields wrote:
Here's a link I'd try, just because I've heard of some of these
folks's work.
http://www.khri.med.umich.edu/
It looks like they are set up with labs that might make progress
in
understanding the noise frequency (non) selectivity in causing hearing
loss. But that page does not indicate activity in that regard.
They're making pretty amazing strides in understanding hearing all
the way from the ear canal to conciousness and perception, at levels
electrical, cellular, mechanical, molecular, genetic... quite a range
of stuff.
That range is apparently what the researchers are interested in,
rather
than always the problems that need to solved. They must have some
well-heeled sponsors.... I should not be so crass.. Thanks for the
leads..
Sincerely,
Angelo Campanella.
|
In the event that you and others are interesed in the opinion of one of the
top researchers in the field on this matter, you will find it an article by
JJ Rosowski which was published in J Acoust Soc Am. 1991 Jul;90(1):124-35.
Abstract:
A model of external- and middle-ear function is described that uses
existing data to quantify the flow of sound power from the environment to
the cochlea of humans, cats, and chinchillas. This model estimates the
sound power produced at the entrance of the cochlea by an environmental
sound stimulus, and can be used to predict the shape of the auditory
threshold function and the relative potency of various traumatic acoustic
stimuli. The shapes of the predicted and measured threshold functions in
the three species are similar in best frequency, bandwidth, and low-
frequency slope, and the model accurately predicts the hypersensitivity of
the middle-frequency regions of the cochlea to acoustic trauma. The model
assumes that the mechanics of the middle-ear system are linear even at high
stimulus levels and does not include the effects of either middle-ear or
cochlear efferent loops. The effects of these simplifications on the model
are discussed as are the implications of the model results for hearing
protection and damage |
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Angelo Campanella
science forum Guru Wannabe
Joined: 08 May 2005
Posts: 226
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| Posted: Wed Dec 28, 2005 1:06 am Post subject:
Re: how your ears work
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The Ghost wrote:
| Quote: | In the event that you and others are interesed in the opinion of one of the
top researchers in the field on this matter, you will find it an article by
JJ Rosowski which was published in J Acoust Soc Am. 1991 Jul;90(1):124-35.
|
That article goes a long way toward establishing the primary parameters
needed to model acoustic energy transfer through the outer-middle-inner
chain. Very interesting in the parallels between cat, chinchilla and
human ears (cats win).
The high frequency vulnerability is cited as being around 3 kHz, and
attributed to resonance. The same family of resonances has an
antiresonance notch around 6 kHz for cats, so the human antiresonance
notch may be near 6kHz.
| Quote: | The effects of these simplifications on the model
are discussed as are the implications of the model results for hearing
protection and damage.
|
The tendency to experience hearing damage at frequencies higher than
the exciting frequency is also noted, declared to be inconsistent with
their existing model, and simply called an anomaly, with no subsequent
modeling provided at that time (1991). Nor was any numerical data on
these super-frequency anomalies provided. The experimenters that
gathered such data published them in a laryngology journal and a 1982
book, making it difficult to study further. My oservations of the very
frequent noise damage (NIPTS) that appears early at 4 kHz still stand
not yet fully explained.
Angelo Campanella |
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TheGhost
science forum addict
Joined: 09 Aug 2005
Posts: 85
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| Posted: Wed Dec 28, 2005 1:53 am Post subject:
Re: how your ears work
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Angelo Campanella <a.campanella@att.net> wrote in
news:Mylsf.365138$zb5.356745@bgtnsc04-news.ops.worldnet.att.net:
snip.....snip
| Quote: | My oservations of the very
frequent noise damage (NIPTS) that appears early at 4 kHz still stand
not yet fully explained.
Angelo Campanella
|
Well, if you put it that way, then there are two separate issues. One has
to do with your knowledge. The other has to do with whether or not the
noise damage that appears early at 4KHz has been fully explained.
As of 8/31/2005, John Rosowski could be contacted via email at
<John_Rosowski@meei.harvard.edu>. I assume that he is still at the Mass.
Eye and Ear Infirmary and that this email address is still valid. I am
confident that he would welcome your inquiry and address any
questions/concerns that you may have, and that he would be able to provide
you with an up to date assessment regarding the status of research and
current thinking on this issue. |
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Angelo Campanella
science forum Guru Wannabe
Joined: 08 May 2005
Posts: 226
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| Posted: Fri Dec 30, 2005 10:36 pm Post subject:
Re: how your ears work
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The Ghost wrote:
| Quote: | As of 8/31/2005, John Rosowski could be contacted via email at
John_Rosowski@meei.harvard.edu>. I assume that he is still at the Mass.
Eye and Ear Infirmary and that this email address is still valid. I am
confident that he would welcome your inquiry and address any
questions/concerns that you may have,
|
I just sent him a message asking same.
Thanks,
Ang. C. |
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TheGhost
science forum addict
Joined: 09 Aug 2005
Posts: 85
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| Posted: Sat Dec 31, 2005 1:33 am Post subject:
Re: how your ears work
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Angelo Campanella <a.campanella@att.net> wrote in
news:KDitf.207565$qk4.155545@bgtnsc05-news.ops.worldnet.att.net:
| Quote: |
The Ghost wrote:
As of 8/31/2005, John Rosowski could be contacted via email at
John_Rosowski@meei.harvard.edu>. I assume that he is still at the
Mass. Eye and Ear Infirmary and that this email address is still
valid. I am confident that he would welcome your inquiry and address
any questions/concerns that you may have,
I just sent him a message asking same.
Thanks,
Ang. C.
|
I have a further update on this which may be of interest to you.
According to my sources, the so-called notch at 4KHz does not mean that
maximum initial hearing loss occurs at exactly at 4KHz. For example,
maximum initial loss could be at 3.7KHz or 4.3KHz, but that would not be
revealed on a standard audiogram because thresholds at 3.7KHz and 4.3KHz
are not measured in a standard audiologic test.
With regard to the issue of source/cause of the 4KHz notch, there are two
very compelling pieces of evidence that locate it peripherally within the
cochlea. One piece of evidence is that the so-called 4KHz notch is present
in evoked response audiometry, which reflects the strength of frequency-
slective synchronous discharges of auditory nerve fibers. The other piece
of evidence is that 4KHz notch is associated with abnormal otoacoustic
emissions at 4KHz which are believed to be indicative of damage to the
cilia of outer hair cells. |
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Bob Stephens
science forum beginner
Joined: 05 Jan 2006
Posts: 2
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| Posted: Thu Jan 05, 2006 6:21 pm Post subject:
Re: how your ears work
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On Thu, 5 Jan 2006 17:46:29 +0000 (UTC), Didier A. Depireux wrote:
| Quote: | we loose about
1Hz/day for the highest frequency we can hear)
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I doubt that very much.
N.B. 20,000 / 365 = 54.79, so by your theory by the time you reach 55 years
of age your ears' frequency response has decreased from 20 Khz to DC...
Bob |
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Didier A. Depireux
science forum beginner
Joined: 13 Sep 2005
Posts: 7
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| Posted: Thu Jan 05, 2006 8:20 pm Post subject:
Re: how your ears work
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In alt.sci.physics.acoustics J Ketutsalo <ei.kiitos@spammia.fi> wrote:
| Quote: | Angelo Campanella wrote:
Which brings up another (old) subject; the mechanism of hearing
damage via loud noises (NIPTS), especially why nerve damage damage
always starts in the 4k-6k region regardless of the spectrum of the
incoming noise.
Because at around 4k the transmission through the outer and middle ear
is most efficient, largely due to a quarter wavelength resonance of the
ear canal. At those frequencies you simply get more energy to the inner
ear to do the damage.
|
You probably know the standard shape of the human audiogram, as shown in
http://swfsc.nmfs.noaa.gov/prd/dsweb/tm-256/fig2.gif
At -5dB (the average threhold of hearing of a 17yo male at 4kHz) for a
passive cochlea, the corresponding vibrations of the fluid in your ear
correspond to rms displacement that are less than the mean displacement from
Brownian motion. In other words, if it were not for active amplification
from outer hair cells, you would not hear anything. The counterpart is that
it doesn't take much to mess up your threholds at 4kHz, unlike say at 200Hz
where it takes a lot of energy to get any activation in the cochlea.
OTOH, your high frequency hearing might be the first to go (we loose about
1Hz/day for the highest frequency we can hear) because all vibrations in the
endolymph have to "pass by" the high frequency region of cochlea. So if you
hear a very loud, low frequency, sound, it causes large oscillations in the
endolymph that have to travel from the base of the cochlea (high-frequency
region) to the apex (low-frequency). The shearing effect of this traveling
wave might cause damage to the whole cochlea, even the parts that are not
tuned to low frequencies. Combine that with high sensitivity to 4-7kHz...
Didier
--
Didier A Depireux ddepi001@umaryland.edu didier@isr.umd.edu
20 Penn Str - S218E http://neurobiology.umaryland.edu/depireux.htm
Anatomy and Neurobiology Phone: 410-706-1272 (lab)
University of Maryland -1273 (off)
Baltimore MD 21201 USA Fax: 1-410-706-2512 |
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TheGhost
science forum addict
Joined: 09 Aug 2005
Posts: 85
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| Posted: Thu Jan 05, 2006 9:24 pm Post subject:
Re: how your ears work
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"Didier A. Depireux" <didier@umd.edu> wrote in
news:dpjm1l$q21$1@grapevine.wam.umd.edu:
| Quote: | In alt.sci.physics.acoustics J Ketutsalo <ei.kiitos@spammia.fi> wrote:
Angelo Campanella wrote:
Which brings up another (old) subject; the mechanism of hearing
damage via loud noises (NIPTS), especially why nerve damage damage
always starts in the 4k-6k region regardless of the spectrum of the
incoming noise.
Because at around 4k the transmission through the outer and middle
ear is most efficient, largely due to a quarter wavelength resonance
of the ear canal. At those frequencies you simply get more energy to
the inner ear to do the damage.
You probably know the standard shape of the human audiogram, as shown
in http://swfsc.nmfs.noaa.gov/prd/dsweb/tm-256/fig2.gif
At -5dB (the average threhold of hearing of a 17yo male at 4kHz) for a
passive cochlea, the corresponding vibrations of the fluid in your ear
correspond to rms displacement that are less than the mean
displacement from Brownian motion. In other words, if it were not for
active amplification from outer hair cells, you would not hear
anything. The counterpart is that it doesn't take much to mess up your
threholds at 4kHz, unlike say at 200Hz where it takes a lot of energy
to get any activation in the cochlea.
OTOH, your high frequency hearing might be the first to go (we loose
about 1Hz/day for the highest frequency we can hear) because all
vibrations in the endolymph have to "pass by" the high frequency
region of cochlea. So if you hear a very loud, low frequency, sound,
it causes large oscillations in the endolymph that have to travel from
the base of the cochlea (high-frequency region) to the apex
(low-frequency). The shearing effect of this traveling wave might
cause damage to the whole cochlea, even the parts that are not tuned
to low frequencies. Combine that with high sensitivity to 4-7kHz...
Didier
|
The implication that loud low-frequency sound creates large motion at the
base of the cochlea is misleading and incorrect. At low frequencies (below
a few hundred Hz) the pressure at the base of the cochlear does not follow
the pressure at the earcrum, but rather decreases with decreasing frequency
at an assymtotic rate of -12dB/octave. Furthermore, the motion of the
basilar membrane is not determined soly by intracochlear pressure, but by
both pressure and stiffness; and the siffness of the basilar membrane
decreases exponentially from base to apex. Consequently, because of the
relatively low pressure and high stiffness, both the gross motion and the
associated micromechnaical motion at the base of the cochlea are no where
near as large at low freqeuncies as you imply. |
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