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The ear can detect a sound wave so small it moves the eardrum just one angstrom...

post #1 of 23
Thread Starter 

I've been searching for this post for a while. The links make good food for thought.
 

Quote:
Originally Posted by digger945 View Post


I was reading this morning and came across this and posted it elsewhere in response to another member's question.

======================================================================================

 

DefaultPossibly the worst assumption in audio electronics

Wrong assumption -> people who study audio electronics know very little about human hearing, but assume they know more about it then they really do.

I guess I wrongly assumed most people knew this information, but then decided this must be one of the main reasons so many people have disagreements about audio electronics. Here's the great revelation. Human hearing is incredibly sensitive. Even though a lot of our hearing apparatus is mechanical it is far superior to most electronics on the market, ie. our hearing can detect more flaws in the electronics then those who parrot electronic theory realize. Its well known that real electronic components differ from theoretical electrical theory used to teach it. Of course, some people may have better hearing than other people. I read about these incredible numbers in the links below in reference to human hearing years ago.

There also seems to be a number prejudice, ie. when someone sees .1 % THD or even .01 or .001 % THD those that know nothing about human hearing assume that those numbers are so small they must be insignificant.

Read the great truths here about human hearing that most of you never knew.

Quote:
The human ear is one of the greatest marvels of nature: the inner ear or cochlea performs at least 1GFLOPS of real-time sensing, filtering, amplification, gain control, and data-compression computations in a tiny volume. The ear consumes about 14 μW of power while running on a 150mV battery; it could run on a pair of AA batteries for 15 years. The ear can sense 0.05 angstroms of eardrum motion at its best frequency and has an input dynamic range that spans 12 orders of magnitude in sound intensity. The ear operates over a frequency span of about 3 decades (10 octaves). Our ears report information with enough fidelity such that the auditory system can make a sound-location discrimination that corresponds to an inter aural time difference of a few microseconds even though the component parts of the system have 1-10 millisecond time constants. These impressive specifications were produced by at least 220 million years of evolution.
http://www.rle.mit.edu/avbs/document...NRFCOCHLEA.pdf

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Quote:
How sensitive is hearing?

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. Murray Sachs, director of biomedical engineering, likes to say that if there were nothing between you and the airport, 10 miles away, and if there were no other sounds, nothing for sound to reflect from--then theoretically, you could hear a piece of chalk drop at the airport.

Johns Hopkins Magazine - September 1996 Issue

There's more examples. Just use Google.

 

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I found it here....  http://www.diyaudio.com/forums/lounge/171623-possibly-worst-assumption-audio-electronics.html

 

 



 

post #2 of 23

Good info and makes perfect sense.  Most people can hear the faint ringing sounds of air molecules rubbing against their eardrums.  Hi-Fi has a long way to go until it can develop headphones with drivers that match the sensitivity and precision of our eardrums and inner ear.

 

One day we will be saying, "Magnets that moved a diaphragm? So primitive."

post #3 of 23


 

Quote:
Originally Posted by Currawong View Post

The ear can sense 0.05 angstroms of eardrum motion at its best frequency

This is what has always caught my eye....anyone care to venture a guess as to what frequency this is?


Anyway, a lot of this has been known for quite some time and human hearing, if properly trained, is an amazing thing. If you ever want to experience something very trippy, step inside an anechoic chamber and have them turn off the lights. I swear you will be able to hear your heart pumping and you will hear the blood going through your ears. It's a very eerie or should I say "ear-y" experience. You also become slight disoriented...at least I did. I had to sit down.

 

Cool post!

 

Warning: Spoiler! (Click to show)

On average, our most sensitive frequency is 3kHz or 3,000Hz.

 


Edited by LFF - 10/7/11 at 1:34pm
post #4 of 23

If the eardrum moves fast enough at 1 Angstrom, I wonder if it could produce radiation.

post #5 of 23
Enjoyable read, thanks for posting it. The human body is indeed an amazing machine. It's always good to remember that.
post #6 of 23
Quote:
Originally Posted by LFF View Post

Anyway, a lot of this has been known for quite some time and human hearing, if properly trained, is an amazing thing. If you ever want to experience something very trippy, step inside an anechoic chamber and have them turn off the lights. I swear you will be able to hear your heart pumping and you will hear the blood going through your ears. It's a very eerie or should I say "ear-y" experience. You also become slight disoriented...at least I did. I had to sit down.

 

And that's precisely what makes the post so misleading and ultimately rather pointless.

 

Yes, our ears are very sensitive and can detect sounds down to the thermal noise limit of the air itself.

 

But...

 

It can only do this under the right conditions, such as inside an anechoic chamber and after you've sat quietly and allowed your ears to acclimate.

 

In other words, you can't perceive air molecules banging against your eardrums while you're listening to music at 90+dB SPL. For that matter, you can't do it even while sitting in a quiet home out in the country. The ambient noise is simply too high.

 

se

 

post #7 of 23
Thread Starter 

That raises a very good point. Lately all my headphones have been models with very low isolation (or essentially zero in case of the Stax), so ideally I'll listen with my door and window shut and everything that makes even the slightest noise (such as external hard disk drives) switched off. I understand why people set up studios with considerable sound-deadening foam and the like.  It definitely raises many questions about our own hearing ability and how far we can take it as well as where we focus our priorities when buying equipment to improve our listening experience.

post #8 of 23

^ exactly.

 

like this part -

 

There also seems to be a number prejudice, ie. when someone sees .1 % THD or even .01 or .001 % THD those that know nothing about human hearing assume that those numbers are so small they must be insignificant.

 

I wish i could find that online test that shows you just how bad people are at detecting THD, and other common differences in sound.

post #9 of 23
Quote:
Originally Posted by Steve Eddy View Post

 

And that's precisely what makes the post so misleading and ultimately rather pointless.

 

Yes, our ears are very sensitive and can detect sounds down to the thermal noise limit of the air itself.

 

But...

 

It can only do this under the right conditions, such as inside an anechoic chamber and after you've sat quietly and allowed your ears to acclimate.

 

In other words, you can't perceive air molecules banging against your eardrums while you're listening to music at 90+dB SPL. For that matter, you can't do it even while sitting in a quiet home out in the country. The ambient noise is simply too high.

 

se

 


beerchug.gif

 

post #10 of 23

ph34r.gif

post #11 of 23
Quote:
Originally Posted by LFF View Post

 

This is what has always caught my eye....anyone care to venture a guess as to what frequency this is?

Anyway, a lot of this has been known for quite some time and human hearing, if properly trained, is an amazing thing. If you ever want to experience something very trippy, step inside an anechoic chamber and have them turn off the lights. I swear you will be able to hear your heart pumping and you will hear the blood going through your ears. It's a very eerie or should I say "ear-y" experience. You also become slight disoriented...at least I did. I had to sit down.

 

Cool post!

 

Warning: Spoiler! (Click to show)

On average, our most sensitive frequency is 3kHz or 3,000Hz.

 


I've done this! It was awesome being in there in the dark.. (tongue.gif) The sound engineering dpt at Virginia Tech students showed me their playrooms / systems and gigs!

 

post #12 of 23
Quote:
Originally Posted by Br777 View Post

^ exactly.

 

like this part -

 

There also seems to be a number prejudice, ie. when someone sees .1 % THD or even .01 or .001 % THD those that know nothing about human hearing assume that those numbers are so small they must be insignificant.

 

I wish i could find that online test that shows you just how bad people are at detecting THD, and other common differences in sound.


There is a blind test for THD online, however, I can't find it at the moment.

Just one thing, transducers that have less than 0.1% distortion, even only  in the frequency band we are most sensitive (3000 to 5000 Hz are exceedingly rare).

post #13 of 23

Good read. 

 

hahah.

"Loss of hair cells is permanent. ("You have all the hair cells you'll ever have at birth," says Young.) It mainly affects soft sounds and high frequencies, the range where women and children tend to speak."

 

 

However it has already been found that you can regenerate cochlear hair cells by deleting or inhibiting a certain gene, so there is hope for future old folk.  

 

But regardless you can't deny that aging degrades hearing (in addition to everything else that degrades with aging). 

 

Enjoying every second of my youthful hearing until that day comes (hopefully at which point something new will be around to fix it)! 

 

 

 

 

 

 

 

 

 

post #14 of 23
Quote:
Originally Posted by Currawong View Post

I've been searching for this post for a while. The links make good food for thought. 

 

How sensitive is hearing?

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. Murray Sachs, director of biomedical engineering, likes to say that if there were nothing between you and the airport, 10 miles away, and if there were no other sounds, nothing for sound to reflect from--then theoretically, you could hear a piece of chalk drop at the airport.

 


Key word there being "theoretical." All of this is just the same number-crunching hogwash that the post condemns audio electronics snobs for.

 

Can someone say "irony" and "double standards?"

 

 

You can't hear chalk drop in the next room, much less an airport many kilometers away. This is just theoretical mumbo jumbo that never happens in real day to day life.


Edited by Mochan - 10/11/11 at 7:19am
post #15 of 23

And let's just come out and admit it...

 

 it's pretty safe to say that even under the best circumstances, no one on this forum has any of these extreme abilities any more ;-)

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