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Cochlear nonlinearities

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With respect to the question of whether audio frequencies >20 kHz might have an effect on audio perception, it has been often assumed that:

 

1) assume cochlea acts linearly

2) assume basilar membrane does not vibrate >20 kHz due to the anatomy of the cochlea

 

The question really comes down to whether the cochlea acts linearly because if not, then just as high frequency electrical components can cause intermodulation distortion (IMD) so might ultrasonic frequencies affect audio perception.

 

[1] This paper discusses: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6366996/#R30 -- in  particular look at figure 6 -- the thick black line shows response at 22 kHz and presumably greater frequencies!

 

[2] This paper discusses the mechanics of basilar membrane vibration in detail: https://pdfs.semanticscholar.org/6f0a/46befffa8710ebb606ed3dec06d7be317be1.pdf?_ga=2.6977266.115791992.1562285968-561089348.1562285968

 

There are, of course many other scientific papers which bring the notion of cochlear nonlinearities into discussion, and provide mechanisms for ultrasonic effects but these two might give folks a start.

 

The folks who assume there is some absolute law of biophysics that allows the cochlea to be modelled linearly might want to read and understand these in detail --- the situation to me is not so perfectly clear.

 

Feel free to post other scientific studies which either support or refute these ideas (there are many many)

 


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[3] https://www.ncbi.nlm.nih.gov/pubmed/15106276

[4] https://www.ncbi.nlm.nih.gov/pubmed/17691656

[5] https://www.ncbi.nlm.nih.gov/pubmed/9035671

[6] https://www.ncbi.nlm.nih.gov/pubmed/15925206

 

[7] and [8] and for @alfe, an indication that your parent's do in fact  affect your own hearing: https://www.ncbi.nlm.nih.gov/pubmed/29716248https://www.ncbi.nlm.nih.gov/pubmed/30188326

😂

 

(the salient finding of the above studies is that ultrasonics might benefit tinnitus in some cases -- if so, then this is direct evidence that ultrasonics modulate the auditory system)


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9 hours ago, jabbr said:

[3] https://www.ncbi.nlm.nih.gov/pubmed/15106276

[4] https://www.ncbi.nlm.nih.gov/pubmed/17691656

[5] https://www.ncbi.nlm.nih.gov/pubmed/9035671

[6] https://www.ncbi.nlm.nih.gov/pubmed/15925206

 

[7] and [8] and for @alfe, an indication that your parent's do in fact  affect your own hearing: https://www.ncbi.nlm.nih.gov/pubmed/29716248https://www.ncbi.nlm.nih.gov/pubmed/30188326

😂

 

(the salient finding of the above studies is that ultrasonics might benefit tinnitus in some cases -- if so, then this is direct evidence that ultrasonics modulate the auditory system)

Just have to wait to be 80 years old and ultrasound will have no secret for me🤫


 


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It is undeniable that intermodulation effects [somewhere] can create audible artefacts from inaudible sounds. The issue is whether intermodulation in the ear can do so. Consider the paper referenced here

 

www.davidgriesinger.com/intermod.ppt

inaudible harmonics were audible with a speaker which intermodulated but disappeared when the intermodulation was removed. I don't think that vaguely referring to nonlinearties in the ear is good enough. Where is the evidence that nonlinearities exsit in the ear which may make hypersonic material in music audible.

We all know that teenagers can set ringtones which are inaudible to teachers. IIRC pitch discrimination in the top octave is not huge, plus the ampitude of hypersound in music is not great. Is it likely that minor nonlinearties inth ear would product audible artefacts?

I'm not sure that tinnitus studies have much to do with this.


You are not a sound quality measurement device

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4 hours ago, alfe said:

Just have to wait to be 80 years old and ultrasound will have no secret for me🤫

 

I'm not sure that ultrasound will improve the fuzzy connections between your neurons, but regular exercise and the proper power supply no doubt are important ;)

 

 


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46 minutes ago, adamdea said:

I'm not sure that tinnitus studies have much to do with this.

 

If indeed ultrasonics modulate tinnitus in a human, then this indicates two things:

 

1) ultrasonics are sensed in some way

2) ultrasonics modulate the auditory system.

 

Hard to deny.


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1 hour ago, adamdea said:

I don't think that vaguely referring to nonlinearties in the ear is good enough. Where is the evidence that nonlinearities exsit in the ear which may make hypersonic material in music audible.

 

There are 1098 papers searching for "cochlear nonlinearites" ... this isn't a vague, unsupported concept. Read for yourself:: https://www.ncbi.nlm.nih.gov/pmc/?term=cochlear+nonlinearity 

 

Some of the papers are actually written in a more accessible fashion that might be easier to understand.

 

The technical point is that a Fourier space analysis. e.g. sampling theorem depends on the system being linear -- what I mean when I say this is that each frequency can be considered and treated independently. If the cochlea were liinear that would mean that if there is no response to an isolated tone at 26 kHz, that means that 26 kHz information does not affect the system. Intermodulation distortion is but one type of nonlinearity that is known to affect audio electronics but the cochlea is not a transistor or a microphone or a speaker.

 

Again, the entire analysis that supposedly "proves" that sonic information > 20 kHz can have no affect on audio reproduction because the cochlea does not respond to isolated tones > 20 kHz entirely depends on the assumption that the cochlea behaves linearly. Given the relatively vast amount of research that the cochlea is not linear, I throw out this assumption. Again I am not saying that ultrasonics have been demonstrated to affect music reproduction, nor am I saying that ultrasonics have been proven not to affect music reproduction.

 

In any case the evidence that nonlinearities exist in the ear is contained in those 1098 papers (and elsewhere). Once you accept that there are nonlinearities, you need to throw out your linear assumptions. A wavelet analysis, for example might be more appropriate way to model the cochlea. One example: https://mathematical-neuroscience.springeropen.com/articles/10.1186/2190-8567-1-5


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An interesting perspective from a musical perspective:

 

David Trippett, Music and the Transhuman Ear: Ultrasonics, Material Bodies, and the Limits of Sensation, The Musical Quarterly, Volume 100, Issue 2, Summer 2017, Pages 199–261, https://doi.org/10.1093/musqtl/gdy001

https://academic.oup.com/mq/article/100/2/199/4951391


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2 hours ago, jabbr said:

 

I'm not sure that ultrasound will improve the fuzzy connections between your neurons, but regular exercise and the proper power supply no doubt are important ;)

 

 

 

but is a linear PS ok if non-linear effects are present in the ear?


"The overwhelming majority [of audiophiles] have very little knowledge, if any, about the most basic principles and operating characteristics of audio equipment. They often base their purchasing decisions on hearsay, and the preaching of media sages. Unfortunately, because of commercial considerations, much information is rooted in increasing revenue, not in assisting the audiophile. It seems as if the only requirements for becoming an "authority" in the world of audio is a keyboard."

-- Bruce Rozenblit of Transcendent Sound

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2 hours ago, jabbr said:

Again I am not saying that ultrasonics have been demonstrated to affect music reproduction, nor am I saying that ultrasonics have been proven not to affect music reproduction.

 

Good but at the listening position does it matter to a significant part of the market? I've been to four T.H.E. Show times and I'm starting  to doubt attendees can tell even simple things like which speaker is playing in a room. And recent visit to a well attended local show in Scottsdale added even more doubt to whether this is an issue for audiophiles. 

 

To repeat "You will find high resolution a very hard sell." I wish you luck but I'm pretty busy talking true believers off ledges.

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17 minutes ago, Rt66indierock said:

 

Good but at the listening position does it matter to a significant part of the market?

 

The vast majority of the market could care less and is happy with AAC or MP3 or whatever happens to be on Youtube

 

Quote

To repeat "You will find high resolution a very hard sell." I wish you luck but I'm pretty busy talking true believers off ledges.

 

I am not selling anything, rather having a hopefully rational discussion.

 

My goal ultimately is to have a more realistic hallucination of a live acoustic performance. I'd also like to improve some live amplified performances. When I say "goal" its not my daily business, rather drives my curiosity.


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6 minutes ago, jabbr said:

 

The vast majority of the market could care less and is happy with AAC or MP3 or whatever happens to be on Youtube

 

 

I am not selling anything, rather having a hopefully rational discussion.

 

My goal ultimately is to have a more realistic hallucination of a live acoustic performance. I'd also like to improve some live amplified performances.

 

Get me to 1% of the market for anything above CD quality because I can't get there.

 

I can't help you personally with your goal. For a non musician my brain is very close to a musician's. I can easily put myself in Lisner Auditorium when I listen to Waiting for Columbus.  

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1 hour ago, Rt66indierock said:

 

Get me to 1% of the market for anything above CD quality because I can't get there.

 

I can't help you personally with your goal. For a non musician my brain is very close to a musician's. I can easily put myself in Lisner Auditorium when I listen to Waiting for Columbus.  

 

That's what "audiophile" is all about, almost by definition. Very true that musicians will listen to performances, even tryouts, on no more than a laptop. In any case I  listen to Spotify all the time on my iPhone when I'm on the go and its quite enjoyable. I also use a FirstWatt J2 amp as a headphone amplifier which has to be waay  << 1% so its fun to push the envelope.

 

I believe there's room to do some really creative things with deconvolutions and wavelet transforms etc, just as movies are becoming more immersive/VR etc so we shall see what the future brings.


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5 hours ago, Rt66indierock said:

 

Get me to 1% of the market for anything above CD quality because I can't get there.

 

I can't help you personally with your goal. For a non musician my brain is very close to a musician's. I can easily put myself in Lisner Auditorium when I listen to Waiting for Columbus.  

Love that album.  Saw Little Feat twice in concert just after they finished recording for that album.  Not in those venues, but that album does a good job of what it was like to hear them live at the time. 

 

MMMMmmmmmmm?  Is it available on MQA?  Hahahahahahaha?  Really need that super debluring for that album. 


To paraphrase Rick James, "sighted listening is a helluva drug".

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1 hour ago, wgscott said:

Outstanding album. (Much better than the studio stuff.)  I would have liked to have seen them live.

First time was 10th night of a 17 consecutive date stretch.  You wouldn't have known it.  They played 89 US dates and 6 Japanese dates that year.  I saw them 6 months later, and still just as good.  


To paraphrase Rick James, "sighted listening is a helluva drug".

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17 hours ago, jabbr said:

 

There are 1098 papers searching for "cochlear nonlinearites" ... this isn't a vague, unsupported concept. Read for yourself...

 

I am confident that Adam did not mean that the notion of non-linearity in the auditory system itself is vague or unproven. I think that many of us, Adam included, know very well that there are, very obviously, a number of non-linear mechanisms at play, both mechanically and neurophysiologically.

 

It is just that to put all of these mechanisms together in a bucket, then pointing to that bucket as a clear source of the audibility of ultrasonics, that this is a bit vague.

 

Example: it you press an ultrasonic exciter to your skull (have fun), your will hear something. Does this demonstrate ultrasonic audibility (or rather detectability)? Yes, in a way. Does this rely on intermodulation? Yes, most likely. Is this relevant for audio reproduction in the context we are interested in? No, probably not remotely.

 

 


perception = controlled hallucination, hallucination = uncontrolled perception

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The fact (it is a fact) that ultrasonics can produce audible effects indirectly (even by some nonlinear effects in the human hearing apparatus itself), my guess is that the levels where the ultrasonics can produce much of a change are not created by the typical signal levels of >20kHz material on most normal recordings (outside of a lab or inside of studio.)

 

Just looked at the above 20kHz on a DolbyA encoded selection from a full 192k/24bit copy of Simon & Garfunkel '1966 Parsley' album.  On a spectogram with a 100dB range on Audacity, there were two tones - a very visible one at 28kHz and a weaker one just above 43kHz.  All of the 'splats' (musical or distortion created) start from below 20kHz.  A few of the splats maintain significant strength all the way up to the 43+kHz range, which also seems to be the final rolloff of the hiss.  (This would correlate with the DolbyA HW.)

 

Interesting observation --  the level of each splat at 20kHz seems to be less than the level of the tone at 28.8kHz.

About the 'splats' -- from what I see, the fact that they extend WAY beyond 20kHz, all the way up to 43kHz seems that it is likely to be electronically generated.  Most microphones from early '60s are more than just a few dB down above 20kHz, and ribbons can be -10dB or more at 20kHz.  Even condensers of the timeframe were sometimes not very flat to 20kHz -- looking at a U47 freq response graph - the one that I saw stops at 15kHz, and was on its way down.  Even if fully excited, I doubt that microphones like that could maintain an output representing the input much beyond the middle 20kHz range, even with decades of attenuation.  The more up-to-date U87Ai is -6dB to -10dB at 20kHz.  There is not going to be much at 30kHz at all.

 

Since the music material comes from microphones, and the typical microphone of the '60s age is a condenser likely -10 to -20dB just above 20kHz, unless it is a ribbon where it is likely down a lot more -- those splats don't appear to be generated by the microphone, unless it is the microphone itself distorting because of a huge impulse.  The splats appear to be electronic from somewhere, some place in time.  Physically complex mechanical devices seem to rolloff pretty quickly above a certain point -- but SOMETIMES might peak at a weird resonance frequency very decoupled from the normal frequency repsonse.

 

Now, I am not claiming that all apparent splats are just distortion, and sometimes there IS linear, sonically produced energy up there, but must be of a very very high level to hear (even for the magical ones who can hear 21kHz), or to directly detect distortion effects.  Of course, analog electronics especially can change behavior below 20kHz, when there is strong material above 20kHz applied to it.  Very strong signals in the distortion region above 20kHz can even shift the bias of some circuits (it is actually the result of severe IMD.)  The levels on the recording appear to be FAR FAR below what people can hear at 20kHz (or even 18kHz.) 

 

Effects from true ultrasonics (those in the air, not electronically) being audible are not quite the same as being necessary to produce any music effects (unless those effects might be to physically damage someone, for example.)

 

John

 

 

.

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John

 The attached is from Barry Diament's new Kay Sa album. This is genuine music content to >50kHz

Alex

02.Bye- Ya (Bolero) .jpg


"If you can't hear the difference between an original CD and a copy of your CD,

you might as well give up your career as a tester. The difference between a reconstituted FLAC and full size WAV is much less than that, but it does exist. - Cookie Marenco"

 

PROFILE UPDATED 18-06-2019

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26 minutes ago, sandyk said:

John

 The attached is from Barry Diament's new Kay Sa album. This is genuine music content to >50kHz

Alex

02.Bye- Ya (Bolero) .jpg

 

If the material above 15k is less than -40dB (or even greater), you aren't going to hear anything except distortion effects.  Energy outside of the audible range (which requires very high level at 20kHz, even for people who can hear it) is more of a burden than anything else.

The existance of non-audible high frequency energy is meaningless when it isn't harmful, and can be a burden.

 

Think about this -- marginally audible sounds at 20kHz (for the fortunate few) are going to produce more distortion effects than anything else for us 'normals'.

 

John

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18 minutes ago, sandyk said:

John

 Many of us don't give a damn about the theoretical side , we just prefer 24/192 or more recently DSD.

I shouldn't even be able to hear clear differences between even 128kbps .aac and , 16/44.1 and 24 /192 due to my age and hearing damage,  but I  can, and I can demonstrate this under non sighted conditions.

 I think that you  also know that by now too. Have my reports to you about the material you have provided been far off the mark so far ?

It's now up to the Scientists to find out why humans are able to hear these differences.

 

Kind Regards

Alex

I never argue about what people prefer, I  argue about what can be heard.

John

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