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Air band, where art thou?
Old 29th December 2002
  #1
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Air band, where art thou?

A post by e-cue has lodged itself in my brain, saying, I believe, that the air band is out of reach of 44.1 kHz, which would make it above 22.2 kHz.
Surely that's beyond human hearing?
What can we hear up to? Have higher sampling rates gotten us clearer? Whenever I've looked into this subject, albeit briefly, it always seems fraught with complexity and contradiction. Does any GS feel clear on the subject?

And where is the air band?
Old 29th December 2002
  #2
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Re: Air band, where art thou?

Quote:
Originally posted by Renie
A post by e-cue has lodged itself in my brain, saying, I believe, that the air band is out of reach of 44.1 kHz, which would make it above 22.2 kHz.
Surely that's beyond human hearing?
What can we hear up to? Have higher sampling rates gotten us clearer? Whenever I've looked into this subject, albeit briefly, it always seems fraught with complexity and contradiction. Does any GS feel clear on the subject?

And where is the air band?
Great thread.

Actually, the air band goes up to 40K. (other eq's go beyond 22K also, the avalon at 32K, etc) The nightpro unit is unique in that is doesn't phase shift the hell out of everything. Try EQ'ing a square wave with one... It boggles the mind.

Can you hear a 40K tone? No. Can you "sense" it? Totally.

Do this experiment. Play a 1K tone with a 30K,40K, and even higher frequency tone. Have someone else take the 40K tone out of the signal (so it's a blind taste test). You should be able to sense a difference. I'm not sure how scientifical this test is, but I've read enough aes journals to see it backed up.

It's not really a simple question as "What can we hear up to"... Frequencies mess with other frequencies in ways I'd have to study psychoacoustics all my life to truly understand
Old 29th December 2002
  #3
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Renie's Avatar
 

Liquid strat,

thanks for that link I will check it out.

e-cue,

I will try your test. Where does the air band really begin, is it about 18-19k? or does it start more like around 14k?

What do you mean by 'sense' rather than hear? you are talking about hearing right? are you saying the ear functions on a different level after a certain point?

Can you hear this (upto 40k) air band, if it's there, on vinyl?

Is there a way to trick the air into a 44.1 CD?

Do you record at higher rates with your digital work or do you work with tape and leave the chopping of air to the mastering house. If you know the air will have to go for the CD format do you pay much consideration to it in the mix?

thanks!!
Old 30th December 2002
  #4
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Re: Re: Air band, where art thou?

e-cue,

> Have someone else take the 40K tone out of the signal (so it's a blind taste test). You should be able to sense a difference. I'm not sure how scientifical this test is, but ... <

Right, it's not scientific because it doesn't account for why you (may) hear a difference. I've seen similar arguments for the audibility of content above 20 KHz., where someone says to play a 15 KHz. square wave and then switch it to a sine wave. They claim that the change in harmonics shouldn't be audible because all that changed was supersonic, thus proving the importance of supersonic content.

But both of these "tests" are invalid for the same reason: They don't take into account that the loudspeakers are nonlinear at those frequencies. So what you think is evidence that frequencies above 20 KHz. can be "sensed" if not heard, really just reveals nonlinearities that change what falls within in the audible spectrum.

> Frequencies mess with other frequencies in ways I'd have to study psychoacoustics all my life to truly understand <

Not at all! It's quite simple, and you can understand it quite readily. At high levels the ears become nonlinear, and so create sum and difference tones in response to supersonic (and not supersonic) frequencies. But this doesn't mean you're actually hearing those frequencies. Rather, your ears generate those frequencies when the source is loud enough.

I sometimes play percussion in a local symphony, and when I hit the orchestra bells very hard I can hear the low difference tones being produced inside my ears. But this happens only at very high volumes, and only when I'm standing right next to the bells. It is not part of the normal listening experience.

--Ethan
Old 30th December 2002
  #5
Gear Addict
 

Ethan, surely e-cue is just saying that these tones affect the listening experience and are therefore relevant to recording. The test he proposes is valid to prove that, isn't it? Whether we're really "hearing" these tones is a different question, more academic than practical.
Old 31st December 2002
  #6
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Re: Re: Re: Air band, where art thou?

Quote:
Originally posted by Ethan Winer
e-cue,

Right, it's not scientific because it doesn't account for why you (may) hear a difference.
--Ethan
Ethan,

I'm an engineer, not a scientist. I can hear, or sense, the air band on the NTI. If I didn't, I'll sell a box to funk logic called the "Airinizer" that was just a dummy knob. There was an article I read in an AES journal several years back that I tried like hell to find, but came up empty. A scientific test was done. In the test they had several test subjects, and I'll try to break it down factually as much as possible: Group A could hear 20hz to 22K roughly. (the females and children could hear slightly higher than the men test subjects) Group B consisted of people that couldn't hear about 10K. When a 1k tone was played, everyone could hear it. When a 15K tone was played, only group A could hear it. When a 1k and 15K tone was played together, group A could tell, but group B couldn't tell the difference between the 2 tones together and a simple 1K tone. HOWEVER, when they took the 15K tone out, group B could tell the difference. It went on further, and so forth

This is how I based my half-ass "test" I stated earlier. I'll try to find the article which actually explains it the tremendous detail.

Quote:
At high levels the ears become nonlinear, and so create sum and difference tones in response to supersonic (and not supersonic) frequencies
Huh? Supersonic and not supersonic? What do you mean by high levels? I wasn't blasting 30K tones in my ear, and the 2 tones I spoke of were summed to the same level. In db's, what do you consider high levels?

Furthermore, a lot of the songs I work on get airplay -no pun intended- in nightclubs at albeit not flat response speakers, but at what I would consider high volumes. So this information in the higher frequencies... what's a mixer to do?
Old 31st December 2002
  #7
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Ethan Winer's Avatar
 

Re: Re: Re: Re: Air band, where art thou?

e-cue and J,

> I'm an engineer, not a scientist. I can hear, or sense, the air band on the NTI. <

I'm sure you can, but [i]not[/i[ because supsersonic frequencies are audible! Rather, the Q of the filter is broad enough that even with a center frequency beyond the limits of hearing, frequencies within the audible band are affected too. That is what you are hearing.

> HOWEVER, when they took the 15K tone out, group B could tell the difference. It went on further, and so forth <

Did they say how loud the tones were played? Did they say if the tests were double-blind? Without having the research at hand to evaluate, we're both just guessing.

> What do you mean by high levels? I wasn't blasting 30K tones in my ear, and the 2 tones I spoke of were summed to the same level. In db's, what do you consider high levels? <

Beats me. But I know for a fact that when the level is high enough our ears become nonlinear and can generate the sum and difference tones. That's why I mentioned the orchestra bells.

I am certain this nonlinearity accounts for what many consider "proof" of the impact of supersonic content. Even if a test could be devised where supersonic content can be shown to be felt if not heard, I maintain it's more of a novelty and curiosity than legitimate evidence we need sample rates higher than 44.1 or 48 KHz for a satisfying musical experience.

--Ethan
Old 31st December 2002
  #8
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Re: Re: Re: Re: Re: Air band, where art thou?

Quote:
Originally posted by Ethan Winer
I maintain it's more of a novelty and curiosity than legitimate evidence we need sample rates higher than 44.1 or 48 KHz for a satisfying musical experience.

--Ethan
I can make a satisfying musical experience onto a cassette tape. I don't need higher sampling rates. I've mixed plenty of 'hits' (commercially sucessful) that I was happy with the sonic quality at sampling rates from 48K, 24-bit to 44.1K, 16-bit, to even lower considering the clock in some other older digital systems.

Have you used an NTI eq? I'd like to see on a graph the actual bell curve of the air band, but when I boost 40K, I see no change of frequencies below 22K on a spectral analyzer.

Out of curiousity, did you read the Neve transcript yet?
Old 1st January 2003
  #9
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Ethan Winer's Avatar
 

Re: Re: Re: Re: Re: Re: Air band, where art thou?

EC,

> I can make a satisfying musical experience onto a cassette tape. <

Yes, indeed!

> Have you used an NTI eq? I'd like to see on a graph the actual bell curve of the air band, but when I boost 40K, I see no change of frequencies below 22K on a spectral analyzer. <

I don't have one and I've never used one. But common sense dicates that if you move a knob and hear a change, then something within the audible spectrum was altered.

> did you read the Neve transcript yet? <

Yes. I saw some good stuff in there, and also a fair amount of misinformation. What specifically are you referring to?

--Ethan
Old 1st January 2003
  #10
Gear Addict
 

Quote:
. I saw some good stuff in there, and also a fair amount of misinformation. What specifically are you referring to?
I believe he was referring to the modules that Geoff Emerick knew sounded wrong despite anything in the "audible" range that could tell him they were.

I'd be amused to hear about the "misinformation".

Bear
Old 2nd January 2003
  #11
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e-cue's Avatar
 

Re: Re: Re: Re: Re: Re: Re: Air band, where art thou?

Quote:
Originally posted by Ethan Winer > Have you used an NTI eq? I'd like to see on a graph the actual bell curve of the air band, but when I boost 40K, I see no change of frequencies below 22K on a spectral analyzer. <

I don't have one and I've never used one. But common sense dicates that if you move a knob and hear a change, then something within the audible spectrum was altered.
Agreed. So, common sence also ditates that higher frequencies DO matter.

Quote:
> Have you used an NTI eq? I'd like to see on a graph the actual bell curve of the air band, but when I boost 40K, I see no change of frequencies below 22K on a spectral analyzer. <

I don't have one and I've never used one.
I'd suggest you check out a unit, otherwise you are just basically conjecturing what you think the unit is or is not doing.

Quote:
> did you read the Neve transcript yet? <

Yes. I saw some good stuff in there, and also a fair amount of misinformation. What specifically are you referring to?

--Ethan
The Geoff Emerick experence... What "mis information" did you notice? Rupert has said some outragious things, like stating that CD's are making the young restless and more violent prone.
Old 2nd January 2003
  #12
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Re: Re: Re: Re: Re: Re: Re: Re: Air band, where art thou?

e-cue and Fission,

> Agreed. So, common sence also ditates that higher frequencies DO matter. <

Not at all! Unless and until shown otherwise, I have to assume making a change in the "air band" is affecting something in the audible range. Anything else makes no sense. Either we can hear supersonic content or we can't. This has been measured time and again, and the conclusion is always the same: even the youngest and best ears can't hear much beyond 20 KHz. That's why it's called supersonic!

> The Geoff Emerick experence... What "mis information" did you notice? <

There are lots of reasons a transformer that's not wired correctly could affect material in the audio range. To draw the conclusion that this proves stuff happening at 54 KHz. matters is silly. Here's the real proof: What loudspeaker were they listening to that can reproduce 54 KHz?! Same for tweaking the "air band" in an EQ.

> Rupert has said some outragious things, like stating that CD's are making the young restless and more violent prone. <

Yes, that's another good example. Perhaps not from the transcript, but typical of what I've seen stated by him.

--Ethan
Old 2nd January 2003
  #13
Gear Addict
 

Ethan, how about this:

Devise me a system which can create clean tones at say 40 kHz. I'm going to have you listen to this system, and set up a galvanic skin response test and a small electro shocker set to go off 1 second after the tone. After conditioning, we are going to remove the shock and see what your reaction is to the tone. I'll bet you're skin crawls every time. If you don't have a reaction until 22 kHz or lower, well, I'll owe you a coke.

(A Cal Tech professor rigged a similar test to show that we have a subconcious sense of magnetic fields. We're generally unaware of it, but when zapping is involved, our sense of it is quite strong.)

Bear
Old 3rd January 2003
  #14
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Ethan Winer's Avatar
 

Bear,

> Devise me a system which can create clean tones at say 40 kHz. <

Again I ask: What loudspeaker do you expect to play it through? All this supersonic stuff presumes a speaker that can actually play back 40 KHz, or 54 KHz. for Rupert Neve. But how many speakers can reproduce that? I think there might be one new brand that claims this. None others can.

--Ethan
Old 3rd January 2003
  #15
Interesting...

I use 24bit 48k sessions but I use analog EQ's (often valve) to boost sub bass and HF frequencies - and I capture those results at 24bit 96k

Sometimes I wonder if I am synthesizing frequencies, harmonics and or overtones above or below the fixed range of my 48k / 24 bit DAW?

or not



(obviously rotten technical terminology I have used, but you get the idea)
Old 3rd January 2003
  #16
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Ethan Winer's Avatar
 

Jules,

> Sometimes I wonder if I am synthesizing frequencies, harmonics and or overtones above or below the fixed range of my 48k / 24 bit DAW? <

Well, if the original source material is sampled at 48 KHz. and you believe your processing is adding content appreciably higher than 20 KHz, you're either synthesizing new tones (unlikely unless you're intentionally adding distortion) or it just seems like you're adding supersonic content.

Again, the real issue is that loudspeakers don't reproduce that high. The second issue is we don't hear that high.

--Ethan
Old 3rd January 2003
  #17
urumita
 
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Real world: #1. when I was 12, I came back from a day on my 13' skiff and I had to clean it. I stayed out in the marsh to watch the sunset, so it was dark. I turned on a floodlight on top of the boat house, turned on the water and started to unravel the hose and suddenly the hair on the back of my neck got very tight, instinctively I spun around and saw the silohuette of something coming straight for me from the direction of the light. I was so scared that I shot it with the waterhose pistol and it fell to the ground and was writhing and jumping around, still being scared I covered it with a nearby garbage can and ran away. It was a bat, the next day my father brought it to the animal shelter and they tested it for rabies, positive. What freak is their sonar in?
#2. Staff engineer at a studio (me, 30) that for days complains that there's something wrong with the studio that causes headaches, because I get headaches when I'm in the CR for more than 15 min.. Finally the tech that I had to bribe to check the system finds a 26 kHz "ringing" in the nice PS for our NEVE 8036 that some how made its way into every module on the board. It didn't show on the meters so the level had to be low, not high.
Even when I powered down the loudspeakers I "felt" something was wrong, and the tech explained to me it was possible that it could have been also physically produced from the PS (maybe he was just trying to shut me up). But that's exactly how we found it, because we never shut down the console and I said there was still something wrong and it was the only thing in the room that was on. he checked it and found this problem, Which he explained was feedback, arsen.
In medical hearing tests, I register as normal with a slight deficiency at 4kHz.
What does this prove? That you can only hear bats with rabies?
It makes me believe that you hear also with something other than your ears, especially LF. Researchers are discovering that the senses really aren't seperate and that a relationship like that between smell and taste exists also between hearing and "touch" . This is the physical animal side to "air band"
Electric world: DX-7 FM synthesizer, modulating one freq. with another changes the sound of both freqs. from how they would be found seperately. Not a test just an example. This would occur in a speaker also, or a guitar string, a flute (which when I play I hear LF beating in my inner ears, another type of example;as it is above, so it is below), a membranofon. there's also resonance to consider.
Another point, I don't believe that the band limited vs. non band limited tests proved that the listeners heard the higher freqs., it stated that the listeners heard the difference and preferred the non band limited material.
Whether it's proved or not doesn't make any difference, changes made to complex wave music signals above the audible band effect those in the bands below it. It's just that it's difficult to explain how and why, and indeed it hasn't been proved. Who cares, I'm glad that certain manufs. have chosen to believe and that the choice is available.
I always end up mixing mostly on my panasonic ghettoblaster with a CD in at low levels alternately with the bass button in and out, ofcourse I check it on somthing better regularly, and I don't worry much about the air band and at times do quite agressive band limiting to various tracks, but never to my mix. Somehow, if I want something to sound airy, it sounds airy. It has more to do with the source and how I'll record it.
Old 4th January 2003
  #18
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Renie's Avatar
 

hey nice post batman!

I'm still digesting all this.
Old 4th January 2003
  #19
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Ethan Winer's Avatar
 

Rojo,

> What freak is their sonar in? <

Since it was flying toward you, you probably just heard its wings flapping.

> a 26 kHz "ringing" in the nice PS for our NEVE 8036 <

It may well be that a high frequency like that can give you a headache. I suppose it's possible.

> changes made to complex wave music signals above the audible band effect those in the bands below it. <

Sure, as long as you're playing through loudspeakers that can reproduce those frequencies. Which most cannot. And this is the real point, since "air band" stuff assumes playback through loudspeakers.

Your other examples are acoustic in nature, and there is no doubt that musical instruments (and dropping a circular saw blade on a cement floor, etc.) generate frequencies above 20 KHz. Years ago I jingled a set of keys in front of my Neumann U47 and watched the output on a spectrum analyzer - there was content all the way to 50 KHz.

--Ethan
Old 4th January 2003
  #20
Gear Addict
 

Cavity resonances help a person sense sub bass frequencies. A lot of people think headphones never sound right because you don't feel the bass in the same way. Why shouldn't cavity resonances in places like the sinuses allow perception of highs? It isn't all in the ears.

Bear
Old 5th January 2003
  #21
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LuvToLaf's Avatar
 

Jules said; "Sometimes I wonder if I am synthesizing frequencies, harmonics and or overtones above or below the fixed range of my 48k / 24 bit DAW?

or not"

That's my take, I believe the air band creates sub harmonics in the normal hearing range, and that this is one of many reasons why analog is so essential in the process of making music ready for digital. It can be tape, a console input, a piece of rack gear.

The test must include many sounds that create the beats in the lower ranges, where it shows up and how it compliments the music could be very hard to find. One test (idea), take 2 or more gens at 40khz and sweep one or two till you actually see (scope) or hear a beat form in the normal spectrum, once generated, it can then be passed on to digital safely with-in it's restrictions.

--LTL
Old 5th January 2003
  #22
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Ethan Winer's Avatar
 

LTL,

> I believe the air band creates sub harmonics in the normal hearing range <

There's no such thing as subharmonics, at least not in nature. There are audio devices that create "subharmonics," like those sub-octave synthesizers, but it is not a natural phenomenon.

The only time combining two frequencies creates sum and difference tones is when there is also nonlinearity - that is, distortion.

--Ethan
Old 6th January 2003
  #23
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Quote:
Originally posted by Ethan Winer
The only time combining two frequencies creates sum and difference tones is when there is also nonlinearity - that is, distortion.

--Ethan
:eek:
Then distortion is what I could very well mean. Perhaps this distortion is sensed by a listener in normal ranges.

A sound pressure still exists at 40khz, though our ears may not detect it as a sound, rather a sense, and depending on amplitude will compress.

I have a small Night Pro, when in analog the upper 40khz "air band" range is preferred, but the Q of the NP is rather wide, and lower frequencies are enjoying some boost at this range as well.

You are the Bottom Master (smoother shaker), and that stuff is far more critical and worthy of attention given the LF wave/room behavior & dispersion/absorbtion as opposed to the ultrasonic laser beam of 40khz.

--LTL
Old 6th January 2003
  #24
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beckertronix's Avatar
 

more fuel to the fire

Everyone always quotes Rupert on this subject, but there's alot more out there that goes beyond the anecdotal. This ones always fun reading:

http://www.svconline.com/ar/avinstall_life_beyond_khz/

Perhaps the important point thing here is not whether we can hear a 40kHz tone or not, but what effect supersonic content or lack thereof has on our 20-20k world. Regardless of what a speaker can reproduce, an oscillation at 50k can have serious effects on all of us, be it headaches, or a loss of power in the audible bandwidth. And the benefits of a wide bandwidth in equipment design, alll the way up to the 100's of kHz, on things like transient response and overall smoothness of sound, are well documented.
It's a fun intellectual game, but if you're hearing either the original supersonic frequency or a new, synthesized frequency, you're hearing something.
Don't get me wrong, this is a great topic and I love bouncing these things around
Old 6th January 2003
  #25
urumita
 
7rojo7's Avatar
 

I didn't expect a serious response to my experiences, I even changed my Avatar to coax a laugh out of a few grumpy guys.
However they are truthful stories.
To set things straight, I didn't write that I heard the bat, I wrote that the hair on the back of my neck became tight, (maybe it should be called the "hair band") and thus later I explained that researchers are now finding that the senses don't function exactly like we've always believed that they do.
Dr. Bong, my chinese doctor always says "you no notice? Whole body connected!".
Another pearl, "the lips of wisdom are open to ears that hear"

pay attention
Old 7th January 2003
  #26
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Ethan Winer's Avatar
 

L,

> Then distortion is what I could very well mean. <

You can't have it both ways. If folks choose to believe that sound has magical properties that elude scientific measurement, that's their choice. But you can't go back and forth from one unfounded theory to another, hoping to eventually hit on something relevant.

> stuff is far more critical and worthy of attention given the LF wave/room behavior & dispersion/absorbtion as opposed to the ultrasonic laser beam of 40khz. <

No fooling!

--Ethan
Old 7th January 2003
  #27
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Ethan Winer's Avatar
 

Re: more fuel to the fire

BT,

> ... avinstall_life_beyond_khz/

It's an interesting article, but I'm skeptical of authors that have a vested financial interest. If David heard a difference in tweeters that have a different response above 20 KHz., perhaps he should look more closely at how they're different below 20 KHz. too.

> Regardless of what a speaker can reproduce, an oscillation at 50k can have serious effects on all of us, be it headaches, or a loss of power in the audible bandwidth. <

Yes, an outright oscillation at 50 KHz. can certainly affect what's in the audible range. If it's loud enough it will overload a stage and cause distortion. But if it's just a slight ringing or low level oscillation, you'd still need speakers capable of reproducing that high in order to hear it.

> this is a great topic and I love bouncing these things around <

Me too.

--Ethan
Old 9th January 2003
  #28
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Quote:
Originally posted by Ethan Winer
LTL,

> I believe the air band creates sub harmonics in the normal hearing range <

There's no such thing as subharmonics, at least not in nature. There are audio devices that create "subharmonics," like those sub-octave synthesizers, but it is not a natural phenomenon.

--Ethan
Ok, synthesis means artificial electronic generated subharmonics, but these musicians produce subharmonics with their natural instruments. If they are produced in lower octaves, can it be possible to generate them from the ultrasonic octaves too?

Scroll to Mari Kimura article

http://www.swets.nl/jnmr/vol28_2.html

--LTL
Old 9th January 2003
  #29
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Ethan Winer's Avatar
 

LTL,

> Scroll to Mari Kimura article

As it happens I play the cello and am quite familiar with that article and the technique it describes. That has nothing to do with the concept of harmonics and subharmonics as we've been discussing. Rather, it describes a method of bowing that forces the string to vibrate in a non-standard way.

--Ethan
Old 10th January 2003
  #30
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LuvToLaf's Avatar
 

Quote:
Originally posted by Ethan Winer
LTL,

> Scroll to Mari Kimura article

That has nothing to do with the concept of harmonics and subharmonics as we've been discussing. Rather, it describes a method of bowing that forces the string to vibrate in a non-standard way.

--Ethan
Ohhh! Their just calling it a subharmonic but it really dosn't exist, unless synthesized. They are generated by technique but will not accure naturally, while eluding scientific measurement. Subharmonic is here now a distorted term. We should not use the term at all, after all we can't have it both ways.
All in fun,
--LTL
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