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Topic: Two Ultrasonic Frequencies Create an Audible Sound (Read 95991 times) previous topic - next topic
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Do Frequencies above 20khz really matter?

Reply #25 –
Quote
Maybe... just maybe... these unintended modulations could be a critical part of an ethreal quality for the recorded sound. If in an A/B test, the unfiltered version for whatever reason sounded better, you would keep it, yes?


If a standard Red Book CD does capture the lower frequency harmonics as part of the recording. Then wouldn't this "ethereal" quality have been recorded with it? And as we can't hear those 50khz sounds they don't matter?

Do Frequencies above 20khz really matter?

Reply #26 –
Edit: posted something wrong. Just edited my previous post which refers to the post above this here.

Edit 2: Let's also be careful about reffering to it as an ethereal quality - it could be, or it could be unpleasant, or useful, or not useful

Do Frequencies above 20khz really matter?

Reply #27 –
If a linear system does not respond to the 56 kHz and 57 kHz tones then there is no signal to modulate to produce beats. If the system is nonlinear then a 1kHz tone is likely to be generated but the mechanism is a nonlinear transfer function and not beats.

Do Frequencies above 20khz really matter?

Reply #28 –
Isn't the point of high fidelity recording to get a high quality reproduction of sound. So wouldn't it follow that we would want a recording with no artifacts in it?

Do Frequencies above 20khz really matter?

Reply #29 –
One thing that did occur to me when @playmusic says "ethereal". Maybe some high freqs could be sensed by the body. Much like when you listen to very low freq that you can't hear but can feel. But whether this can also apply to high freqs I don't know?

Do Frequencies above 20khz really matter?

Reply #30 –
Quote from: boomtopper on
One thing that did occur to me when @playmusic says "ethereal". Maybe some high freqs could be sensed by the body. Much like when you listen to very low freq that you can't hear but can feel. But whether this can also apply to high freqs I don't know?


The pinnae apparently does, but to what extent isn't clear. If at all. Like I say, there needs to be proper testing done.

Do Frequencies above 20khz really matter?

Reply #31 –
This testing has indeed been done since at least the 50's. The results are robust and well researched. For references see, for example, the citations on Wikipedia about the absolute threshold of hearing. We call those frequencies ultrasound, that are above all humans' upper limit of perception. You'll know that - but it is so thoroughly researched, what do you think has been missed?

There is the controversial claim of a hypersonic effect, but those studies have been heavily criticized for not including the physical intermodulations (within the audible range) for the negative test samples. This is what I called for when I wrote you must test B vs. low passed B and not A vs. B.

Do Frequencies above 20khz really matter?

Reply #32 –
Quote
If anyone had equipment good enough to playback these inaudible but somehow perceivable >20KHz frequencies, and trained enough ears, then it would have been this guy in this studio. And in turn, Rupert effing Neve agreed there was something different about these channels. And lo and behold, they found there actually were transformers incorrectly fitted. Assuming the story is true, (and remember Rupert Neve was a first hand witness to this, and Fletcher is as trusted as it comes), then this would be evidence that somehow, some people have perceived a difference when there was a +3db peak at 54KHz. I am not saying 'look, this is guarenteed proof of the concept', but it is a convincing demonstration of an effect we definitely do not know enough about.


No, it's not.  This is an argument from authority, and in this case the authorities are not experts in psychouacoustics or audiology, nor was the 'experiment' conducted well.
They are people who 'work with' sound, but that is not the same thing a someone who researches hearing rigorously.

So I frankly don't give a toss if it's Rupert Neve or Geoff Emerick or Fletcher -- I have seen far too many such pros on pro boards make factually incorrect claims about audio and digital audio in particular, to blindly grant them that authority.  I have seen some of  them promulgate some of the direst just-so stories of high end audio too.  (Neve in particular has previously reported badly controlled experiments that he claims shows proof of 'ultrasonic' hearing.)  Neve is an audio gear engineer, not a scientist.  Geoff Emerick is a mixing and mastering engineer, not a scientist.  They are great at what they do, but what they do well is not scientific research.  It is mainly to do with the practical manipulation of sound. They build or record things that 'sound good'.  Success at this need not involve any new science; there are an infinity of ways to manipulate sound and signals that really will make an audible difference, without having to invoke 56kHz signals. 

My personal hypothesis is that success at making things that 'sound good' gives some of them the false impression that anything they believe they hear, must be real -- that they are immune to the various psychological biases that are part of our makeup.


Anyway, when does this turn into a thread about the (still unreplicated AFAIK) Oohashi et al. 'hypersonic effect'?










Do Frequencies above 20khz really matter?

Reply #33 –
Quote from: PlayMusic on
Fletcher is a very trusted and respected individual in the pro echelons of modern recording culture


I love Fletcher to death, but I promise you he has only a minimal grasp of the science of audio. He knows gear models and brands, and he's an excellent recording engineer who can turn the knobs to make music sound good. But he doesn't know a standing wave from slew rate limiting.

One thing I didn't see mentioned here so far is that our ears distort, and that's a common source of IM beat tones. I sometimes play percussion in the local symphony, including glockenspiel (orchestra bells). If I play two adjacent high notes very loudly, I can clearly hear the low frequency beat tone that's generated inside my ears. I doubt anyone in the audience ever hears that because they're much farther away from the bells than I am. So the level of those notes is much lower inside their ears, and the generated IM products are much lower too.

--Ethan
I believe in Truth, Justice, and the Scientific Method

Do Frequencies above 20khz really matter?

Reply #34 –
Quote from: rpp3po on
This testing has indeed been done since at least the 50's. The results are robust and well researched. For references see, for example, the citations on Wikipedia about the absolute threshold of hearing. We call those frequencies ultrasound, that are above all humans' upper limit of perception. You'll know that - but it is so thoroughly researched, what do you think has been missed?


My point is that there is plenty more testing worth doing, to confirm or not whether there is more to the presence of ultrasonic frequencies. Are you aware of any testing on ultrasound and the emotional perception of a sound? Or whether it can improve presence of a recorded piece? Scientists would have to be creative with the studies they implement, but as I said a few times, my point is that people should be open to the idea that there could be interesting psychoacoustic effects yet to be found. This is as much to do with psychology and biology as it is audio science. I'm sure if anything new were found, we would all be quite interested.

And again, there could well be nothing to it. Till we know, let's not shun the topic as many have. We'll find out eventually.

Quote from: krabapple on
No, it's not.  This is an argument from authority, and in this case the authorities are not experts in psychouacoustics or audiology, nor was the 'experiment' conducted well.


Like I said in a sentence prior to the section you quoted, this 'experiment' was not on an academic, peer reviewed paper. But it is not some kid in their bedroom making claims they heard 54KHz, this is people who had the highest grade equipment in the world, and the maybe the most carefully trained hearing in their industry. The conditions this anecdote came from give it more credance than you're giving it.

Quote
They are people who 'work with' sound, but that is not the same thing a someone who researches hearing rigorously.


No, people who visit forums like this 'work with' sound, either casually or in a job in a studio, or similar. If you think Rupert Neve doesn't have a next-level understanding of hearing and how to control voltage specifically for use in audio, the entire science around it, and left a genuinely timeless legacy, you might be mistaken. The story is an anecdote, so none of us should assume it is a fact, but coming from him makes me pause for thought, and is worth our consideration.

Oh, you say it is not the same as someone who researches hearing rigourously. Would you trust someone who does? That is something I have done in a great academic institution, working hard to improve our understanding of psychoacoustics - something I studied extensivly, and a subject I have written entirely new theories on. Am I worthy of your audio forum X-factor contest?

Quote
Neve is an audio gear engineer, not a scientist. Geoff Emerick is a mixing and mastering engineer, not a scientist.  They are great at what they do, but what they do well is not scientific research.


I don't know what your engineering experience is, but in mine, it is a science. Do you think those two haven't  invented at least some of the scientific techniques recording engineers worldwide use on a daily basis?

Have you invented any?

Quote
Success at this need not involve any new science; there are an infinity of ways to manipulate sound and signals that really will make an audible difference, without having to invoke 56kHz signals.


That is true, but you wouldn't say something like 'computers work fine as they are. The internet is great. Let's put a bar up on any new research or technology, it's fine!' Progress is based on hit or miss research, and the hits keep adding up. No one has said introducing ultrasound will improve the audio, in fact in the anecdote given, they were unhappy with the +3db peak in that range. I have suggested that the field is worth further study - you know, 'just in case', and because we don't know everything there is to know about psychoacoustic effects.

Do Frequencies above 20khz really matter?

Reply #35 –
Quote from: Ethan Winer on
One thing I didn't see mentioned here so far is that our ears distort, and that's a common source of IM beat tones. I sometimes play percussion in the local symphony, including glockenspiel (orchestra bells). If I play two adjacent high notes very loudly, I can clearly hear the low frequency beat tone that's generated inside my ears. I doubt anyone in the audience ever hears that because they're much farther away from the bells than I am. So the level of those notes is much lower inside their ears, and the generated IM products are much lower too.

--Ethan


Hi Ethan, I actually did cover this in my large post on the first page, referring to the basilar membrane.

The audience won't hear your instrument because other tones in the symphony might be louder louder and mask them, but to you the tones must be loudest (and a similar/same amplitude, otherwise they would be masked anyway).

Thanks for your awesome acoustic research, made a huge difference to our acoustic design at the studio here!

Edit: In fact, the distortion in our ears on the basilar membrane is basically the entire subject of my research and testing into hyper-dissonance (gride) sounds, which I linked to on the first page - it's also on http://public.me.com/playmusic

Oh and regarding fletcher - his scientific knowledge is irrelevant to the anecdote from Rupert Neve, just that he is trusted enough to pass on a story without completely bullshitting (I think!)

Do Frequencies above 20khz really matter?

Reply #36 –
Quote
I don't know what your engineering experience is, but in mine, it is a science. Do you think those two haven't invented at least some of the scientific techniques recording engineers worldwide use on a daily basis?


I thought you did a BA? So that is not strictly true. I would have said you're more engineering. While you will have of knowledge in parts of this you by no means have a complete picture. And the same of course of myself that is why I question. Especially in the field of psychoacoustics.

Do Frequencies above 20khz really matter?

Reply #37 –
What is not strictly true? My engineering experience not being a science? I am referring to the studio craft of recording being science, in response to someone saying engineering is not a science. Much of it may be subjective, but it is mostly scientific methods and techniques which lead to the desired results. But I'm preaching to the converted now.

And Rich, I'm not claiming to be an authority on anything, this is a debate. I asked a lot of open questions in my first post on the first page.

Do Frequencies above 20khz really matter?

Reply #38 –
Quote from: PlayMusic on
What is not strictly true? My engineering experience not being a science? I am referring to the studio craft of recording being science, in response to someone saying engineering is not a science. Much of it may be subjective, but it is mostly scientific methods and techniques which lead to the desired results. But I'm preaching to the converted now.

And Rich, I'm not claiming to be an authority on anything, this is a debate. I asked a lot of open questions in my first post on the first page.


Opps I misread the manner of text, interepreting it like that my applogies . Of course your knowledge that you use in your everyday work is grounded in science and physics and helps you get the best results. But Next to say someone who specialises in the physics and science of sound they would mainly have a differant level of understanding. They might not know how to get the best mix or make a killer master but they would have a more comprehensive understanding of sound and frequencies and how our environment affects it.

I do appreciate your awesome work on your psychoacoustics based dissertation and can see how you would have more of an idea that a standard studio engineer it doesn't mean you know everything about that whole field. As at the same time I also did well with my Dissertation yet there are gaps in my knowledge that I need to fill.

Do Frequencies above 20khz really matter?

Reply #39 –
True, but the physics of sound has been nailed, and well documented, so really any of us can go and be as well informed as them. This debate really relates to psychoacoustics more (edit:) which is often an open topic.

Do Frequencies above 20khz really matter?

Reply #40 –
Quote from: PlayMusic on
True, but the physics of sound has been nailed, and well documented, so really any of us can go and be as well informed as them.


Perhaps most aspects of physical hearing have "been nailed", but maybe not all of them?

Quote
Since it seems unlikely that the basic place theory for pitch perception can explain the extraordinary pitch resolution of the human ear, some sharpening mechanism must be operating.
  ~ Place Theory
Quis custodiet ipsos custodes?  ;~)

Do Frequencies above 20khz really matter?

Reply #41 –
Quote from: 2tec on
Quote from: PlayMusic on
True, but the physics of sound has been nailed, and well documented, so really any of us can go and be as well informed as them.


Perhaps most aspects of physical hearing have "been nailed", but maybe not all of them?



No, I was saying that the physics of sound and how it acts is nailed (in response to someone reffering to "someone who specialises in the physics and science of sound"), but you are right in a sense, because you may also be thinking of psychoacoustics, which as I keep saying is not fully researched, by a long shot

Do Frequencies above 20khz really matter?

Reply #42 –
Just looked at that place theory page, which demonstrates my point that psychoacoustics is not fully researched.

Do Frequencies above 20khz really matter?

Reply #43 –
Going back to the idea of beats.When 2 pure tones are played at the same frequency the human ear percieves this as a "fused" tone. For the human ear to perceive beats, the 2 tones that are playing usually have to have a frequency difference of 12.5hz. The sound that we percieved is still of a "fused" tone which sounds "rougher" when the frequency differance is increased beyond 15hz. As this difference is increased further there is a point where the fused tone gives way to 2 seperate tones but still with a "rough" sound. If we go on even further the "smooth" sperate 2 tones are perceived while it is still in the human frequency range.

The frequency of the beats that are heard are at (F2 - F1) or (F1 - F2).

In the case of 56k and 57k the difference is large. So therefore beats are not percived by the ear, instead they are perceived as indvidual tones. The other way in which the 1k harmonic could be heard is if it is a Non-Linear system such as Amplitude Modulation or a Distortion as mentioned above. This is because of Intermodulation Distortion

PS feel free to nit pick through this if there are errors

Do Frequencies above 20khz really matter?

Reply #44 –
It is certainly possible to produce audible frequencies by heterodyning two ultrasonic ones, and this was discussed in at least one popular science or audio magazine a couple of years back.  New Scientist was one if my memory serves me.  There are advantages, but also disadvantages, such as high distortion and poor LF.  It was, I believe, considered as a technique for steering audio to individuals in a crowd.

A quick google search gives this url: http://bcwildfire.ca/hprScripts/WildfireNe...Fire.asp?ID=339

And there is a web site selling such a product at: http://www.atcsd.com/site/content/view/13/104/

However what this has to do with high end audio escapes me...
Ed Seedhouse
VA7SDH

Do Frequencies above 20khz really matter?

Reply #45 –
Quote from: boomtopper on
In the case of 56k and 57k the difference is large. So therefore beats are not percived by the ear, instead they are perceived as indvidual tones. The other way in which the 1k harmonic could be heard is if it is a Non-Linear system such as Amplitude Modulation or a Distortion as mentioned above. This is because of Intermodulation Distortion


And one other problem I found with this and of course the most obvious. Is that those frequencies mentioned are way out of our hearing range . So that puts out the idea that beats being caused by our perception of the 2 sounds.

Do Frequencies above 20khz really matter?

Reply #46 –
Quote from: PlayMusic on
No, I was saying that the physics of sound ...

Indeed, I was referring specifically to the physics of sound, rather than the psycho-acoustics of human hearing. Psyche, of course, in this case refers to mind, of which the ear is not generally considered to be a part of. Place theory, from what I understand, relates to how pitch is sensed by the inner ear. Psychoacoustics, of course, is the study of the psychological correlates of the physical parameters of acoustics.
Quis custodiet ipsos custodes?  ;~)

Do Frequencies above 20khz really matter?

Reply #47 –
Quote from: PlayMusic on
Oh, please say whether you read all that or not.

I read it until I started seeing namedrops, then I stopped reading. It was interesting up to that point, however.

Do Frequencies above 20khz really matter?

Reply #48 –
Quote from: PlayMusic on
True, but the physics of sound has been nailed, and well documented, so really any of us can go and be as well informed as them. This debate really relates to psychoacoustics more (edit:) which is often an open topic.


What it bottles down to is that the harmonic that is generated is not a product of psychoacoustics but rather from the systems that the signal has passed through. This then leads back to the point mde by rpp3po made saying that this is an Unwanted Artifact

Do Frequencies above 20khz really matter?

Reply #49 –
And here is more proof that our ears do not repond to frequencies beyond 20k.