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Old 10th August 2010, 10:09 PM   #31
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Extraordinarily so. The ear can detect a sound wave so small it moves the eardrum just one angstrom, 100 times less than the diameter of a hydrogen molecule.
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Originally Posted by SY View Post
As soon as you read that, you know you're dealing with garbage.

I'll leave the chalk calculation as an exercise for the reader. It is similarly garbage.
I saw something like that before. It might have been in a P. Chem. book.

You need to explain that to all the people posting this.
http://www.google.com/#hl=en&client=...31cdd35a4d476d

Last edited by 7n7is; 10th August 2010 at 10:11 PM.
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Old 10th August 2010, 11:11 PM   #32
sreten is offline sreten  United Kingdom
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Originally Posted by KSTR View Post
4dB lower than the established threshold of hearing, 0dB(SPL). Not too far out, I'd say. Bigger problem for a real chalk experiment might be HF absorbtion which is not modelled by the p~1/r relationship. Who's gonna take their subs down to Antarctica?

Hi, No, you do not seem understand the wiki reference you quoted regarding SPL, /Sreten.

Everyone seems to be trying hard to prove the OP is correct ... :wink:

Last edited by sreten; 10th August 2010 at 11:21 PM.
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Old 11th August 2010, 12:32 AM   #33
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Hi, No, you do not seem understand the wiki reference you quoted regarding SPL, /Sreten.

Everyone seems to be trying hard to prove the OP is correct ... :wink:
You're making a wrong assumption.
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Old 11th August 2010, 03:09 AM   #34
SY is offline SY  United States
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I saw something like that before. It might have been in a P. Chem. book.
If you have a P Chem book that says that a hydrogen molecule has a 100 A diameter, you need to get a new book. Hopkins Magazine needs to get better writers or hire a fact checker.

Just for giggles, I measured the SPL of chalk dropped on a tile floor from a meter away. 71dB peak. So we're down to -13dB ref 20 uPa.
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Old 11th August 2010, 11:31 AM   #35
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It said something about the softest sounds that can be heard cause motion of the eardrum in the angstrom range. Did you look at these links?
Google

10^-10 meters is a small distance. I wonder if there is any significant quantum mechanical effects with an eardrum moving a couple of angstroms.
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Old 11th August 2010, 12:27 PM   #36
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Originally Posted by wintermute View Post
A long while ago I read (or saw on a TV show) about how quiet it can be in Antarctica on a still day. Whilst no where near the claims of the chalk experiment, the person was relating how they could hear the shutter click of their colleagues camera who was over 1Km away.

Just a random anecdote no more

Tony.

WOW...I would imagine a fart would sound like a howitzer over there...
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Old 11th August 2010, 12:31 PM   #37
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Originally Posted by 7n7is View Post
Did you look at these links?
Yes. Very few were primary lit (mostly repeating one another), and the few primary sources didn't cite how that number was determined, it was incidental to the focus of the papers. Nice to see this forum hit the top of the Google list!

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WOW...I would imagine a fart would sound like a howitzer over there...
Thus the strict no-beans rule.
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Old 11th August 2010, 12:41 PM   #38
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Thus the strict no-beans rule.[/QUOTE]

That rules me out...we're talking Tchaikovsky's 1812 overture...on A-B repeat!
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Old 11th August 2010, 12:57 PM   #39
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These speculations on the ear resolving angstrom (or sub-angstrom) level displacements of the eardrum ignore several aspects related to internal signal to noise limitations. The eardrum, bone linkage and cochlear mechanism are embedded in your head, where the circulatory system pulsates to heart contractions that produce rhythmic tissue displacements (arterial response) of thousands of angstroms efficiently coupled through surrounding fluids. The nervous system that transmits signals resolved by the cochlea has a noise floor (as does every signal processing system) that provides a steady state lower limit to what can be heard.

Over 35 years ago as an engineering student in the auto industry (with 20 year old ears) I took the opportunity to spend over an hour in a state of the art anechoic chamber in the dark just for the experience. Once your ears recover from the background noise that usually assaults them you hear two things very distinctly. The throbbing of your pulse and a whine seemingly at maybe 1kHz which is the nervous system background noise. These are not at all subtle and would completely overwhelm any chalk dropping 16 km away.
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Old 11th August 2010, 01:44 PM   #40
sreten is offline sreten  United Kingdom
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Originally Posted by KSTR
4dB lower than the established threshold of hearing, 0dB(SPL).

Quote:
Originally Posted by sreten
Hi, No, you do not seem understand the wiki reference you quoted regarding SPL, /Sreten.

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Originally Posted by 7n7is View Post
You're making a wrong assumption.
Hi,

It appears I am, but checking my quick calculation I had screwed
it up, I cannot work out how now, the number -4dB is correct.
But that comes from a 1/Rsquared function for power and SPL.

Apologies for any misunderstandings.

/Sreten.

FWIW 0dB is not the threshold of hearing, it is near but is simply a reference level.
Those with normal hearing dip below 0dB for 0phons in the around 3KHz critical region.
(As 0phons is normalised to 0dB at 1kHz, all phon levels are normalised to dB at 1KHz.)
Those with very good hearing can hear - phon levels, bad hearing only higher levels.
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Last edited by sreten; 11th August 2010 at 02:13 PM.
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