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The Most Important Spec Sheet: The Human Ear - Page 5

post #61 of 86
Originally Posted by Grevlin View Post


I want to also add another little quirk - the 'ol noodle.


Besides the physical neurobiology, there is the perception of the sounds. I guess I would call it training the brain to recognize what it hears and be able to differentiate it and describe it.


There's already research in neuroscience on perceptual limitations based on physical structures in the brain. For instance, here's an interesting imaging study linking white matter concentration and pitch differentiation.

post #62 of 86

I printed that for a little light reading later.

post #63 of 86

You'll love the pretty pictures of voxel-based morphometry.


Speaking of pitch, thought I would bring up the spec of pitch discrimination. The most commonly cited just noticeable figure is 5 cents, or approximately .3 percent deviation from frequency, although this study suggests that professional musicians may do as well as 2 cents.

post #64 of 86
Thread Starter 

bumpity bump


Any more suggestions for additions for post 1 in this thread?


Format = spec + URL citation

post #65 of 86

Some blind tests demos that can be performed online related to the topic of this thread...




(find the smallest difference in sound levels you can reliably detect, in pitch, dynamic range, etc.)

post #66 of 86

I was trying to glance over this thread, but realized it was too technical and over my head at the moment.


So, apologies if this was already covered, but I have a question:

Do inaudible frequencies affect the way we perceive/hear audible frequencies?  


I read about masking, but that was comparing two audible sounds.



While typing this I came across this article on Wikipedia about the Hypersonic effect.




Why does everything in the audio world have to be so damn controversial?  But I digress; I find this topic extremely interesting and intriguing.  


I've always been fascinated by technical measurements vs subjective experiences.



For example, I'm a PC gamer and have been for a long time.  For the longest time in the PC gaming world, people have noticed a difference between single GPU's and multiple GPU's running together (SLI or Crossfire).  Some people have noticed a smoother gaming experience on a single GPU vs. multiple GPU's, if both systems were keeping frame-rates at or above their monitor's refresh rate.  Until just recently (recently, as in like this past year), we have only had one real way of measuring frames per second (FPS), the FRAPS method.  People with multiple GPU's, specifically rigs using Crossfire, noticed laggy gameplay with very high frames.  For years people have been stumped by this, and it has been a source of division/contention amongst gamers.  People would say Crossfire sucks, then other people would tell them they were stupid based upon technically phenominal statistics/measurements.  


Well, now there's a new method for measuring the performance of GPU's called "frame rating", which tells you both the FRAPS FPS, but also the observable FPS, and other details that were never present before, like frame time variance, ghosts, runts, etc.  All the people that vehemently defended AMD and Crossfire now look fairly dumb.  The thing is, they used the best/most sound testing experiments available to back up their claims, yet, in the end, they turned out to be wrong.



I guess what I'm trying to say is, graphs just do not tell the whole story, despite how scientific and mathematically sound they might be.  There's always something that we can't measure that does affect the way we perceive the world around us.  We shouldn't just dismiss people's claims as placebo, crazy, ignorant, or downright idiotic or whatever just because the scientific facts seem contrary to their beliefs.  One day those "dummies" might actually turn out to be right, and history has shown, time and time again, that some people dismissed as lunatics based upon their own beliefs that go against the status quo have, in time, been proven correct.   



Sorry if this post was all over the place.  I'm not really sure what I'm still doing awake...

Edited by Meremoth - 6/17/13 at 4:45am
post #67 of 86
Thread Starter 
Originally Posted by Meremoth View Post

Do inaudible frequencies affect the way we perceive/hear audible frequencies?


Under some circumstances, super audible frequencies in equipment not designed to deal with them can cause distortion down in the audible range. That's why DACs roll off all info above 21kHz or so.


Studies have shown that super audible frequencies can sometimes be perceived as sound pressure, but the presence or lack of super audible frequencies in music does not affect the perception of sound quality at all. In fact, you can roll off everything above 14kHz and sound will still sound good.


It's very useful to familiarize yourself with what various frequencies sound like by playing around with a good graphic equalizer. You'll quickly find exactly what frequencies matter and which ones don't. In music, the only sound above 12-14kHz is upper harmonics in cymbal crashes, and that it generally masked by much louder lower harmonics and the fundamental. Pretty much inaudible.


Basically, super audible frequencies can only hurt, they can't help. That's why they get rolled off in redbook. All this has been studied and figured out. No mystery here.


Edited by bigshot - 6/17/13 at 10:58am
post #68 of 86

Well, not the most knowledgeable person on the hypersonic effect.  I have read somewhere, which I wish I had links for, that told how frequencies up around 100 khz or so get into skull via the eye sockets.  They do perhaps effect our audio perceptions though the sound is inaudible through our normal hearing via the ear itself.  Rather it vibrates some nerves in the head.  


There is also the well known effect of radar signals of very high strength in the Ghz range that cause whistles to be heard.  The signal has to be very strong and was of course first experienced by radar operators.  Again it will cause the perception of a sound, though of course they aren't hearing via the ears, the brains nerves are being stimulated to create a synthetic perception of non-existent sound. 

post #69 of 86

When you high-pass filter some classical recordings at 21 kHz the remaining signal is usually ~70 dB down and most of it is static noise.

post #70 of 86
Thread Starter 
In the test I read on this, the group being tested were presented with three pieces of music... one with super audible frequencies, one with standard 20-20 and one that was 20-10kHz (the top octave rolled off). None of the listeners expressed any preference for the super audible or full frequency range. Most subjects didn't even think 20-10 sounded any worse than the others.

There's no indication at all that super audible frequencies add anything to sound quality in music.
post #71 of 86

Thanks for posting this! really cool. I was wondering whether or not a .25% THD was audible or not, and affecting my audio experience.
Glad that it's not. Now just to focus on fine tuning that sound signature...Almost perfect, almost

My wallet's really going to hate me

post #72 of 86

While measuring distortion is great for designing, manufacturing and maintaining amplifier circuits (both voltage & power) humans don't hear distortion in a way that can be related to a simple percentage number.


Some of Doc Geddes  papers on distortion:


'Sound Quality Perception'



post #73 of 86
Thread Starter 
that's a lot of stuff. would you mind summarizing and pointing us to the relevant parts?
Edited by bigshot - 6/23/13 at 12:08pm
post #74 of 86

The relevant part is: You can't say that this unit is better than that unit just because it has a lower THD percentage.


It's been a long time since I read any of those papers and some of his papers are not an easy read.


Maybe this PowerPoint


A 2007 ALMA China presentation on distortion perception is here.



Edited by Speedskater - 6/23/13 at 12:32pm
post #75 of 86
Thread Starter 
We're looking for a general threshold of audibility for non-linear distortion. Is there anything in there like that?
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