How well High-Fidelity audio aligns with human perception?

[Heinrich]

and do you agree with him or have you done scientific studies in neurobiology and discarded everything?
If I remember correctly, there is a neurobiologist designer who makes loudspeakers. Have you ever listened to them? Have you ever made comparisons? Or do you just write that we have to demonstrate our ignorant intuitions to you?

My authority in asking for prove depends on how far I'm into doing "scientific studies in neurobiology"? And again some "neurobiologist designer who makes loudspeakers. Have you ever listened to them?" is an argument towards me being an ignorant?

What we have is a settled case of whether phase distortion is objectional when listening to random program material. You know perfectly, what the results are. Still you reiterate decade old suspicions, using that neurobiology as an anchor point, but, there is no logical chain of conclusions that I can follow. And look, my "stereo" argument, questioning phase relations, mirrored at the HRTF, differing between real listening and stereo imagination (not illusion aka virtual reality). Putting together some random, singled out pieces from "neuro", picked up by a person not too deeply involved in the field, doesn't make a theory. Let alone that obviously the production process making a recording is a blind spot, apperently. This is laisure hifi talk, spiced-up with scientific literature, which, for honest (!) understanding even for the expert would need days of study.

Neurobiology doesn't lead hifi, it is rather what Dr Toole says (with all due respectful criticism): do people like what they hear? If you don't like your music, it's up to you, don't ask others for action.

 

[Suono]

La mia autorità nel chiedere prove dipende da quanto sono avanti con gli "studi scientifici in neurobiologia"? E ancora, un "neurobiologo progettista che costruisce altoparlanti. Li hai mai ascoltati?" è un argomento a mio dire che sono ignorante?

Quello che abbiamo è un caso consolidato sul fatto che la distorsione di fase sia discutibile quando si ascolta materiale audio casuale. Sai perfettamente quali sono i risultati. Continui a ribadire sospetti vecchi di decenni, usando quella neurobiologia come punto di ancoraggio, ma non c'è una catena logica di conclusioni che io possa seguire. E guarda, la mia argomentazione "stereo", che mette in discussione le relazioni di fase, rispecchiata all'HRTF, distingue tra ascolto reale e immaginazione stereo (non illusione, ovvero realtà virtuale). Mettere insieme alcuni brani casuali, selezionati da una persona non troppo coinvolta nel settore, non costituisce una teoria. Per non parlare del fatto che ovviamente il processo di produzione di una registrazione è un punto cieco, a quanto pare. Questo è un discorso hi-fi disinvolto, condito con letteratura scientifica, che, per una comprensione onesta (!) anche per l'esperto, richiederebbe giorni di studio.

Non è la neurobiologia a guidare l'hi-fi, è piuttosto ciò che dice il Dott. Toole (con tutte le dovute critiche): alla gente piace quello che sente? Se non ti piace la tua musica, la decisione spetta a te, non chiedere agli altri di

My authority in asking for prove depends on how far I'm into doing "scientific studies in neurobiology"? And again some "neurobiologist designer who makes loudspeakers. Have you ever listened to them?" is an argument towards me being an ignorant?

What we have is a settled case of whether phase distortion is objectional when listening to random program material. You know perfectly, what the results are. Still you reiterate decade old suspicions, using that neurobiology as an anchor point, but, there is no logical chain of conclusions that I can follow. And look, my "stereo" argument, questioning phase relations, mirrored at the HRTF, differing between real listening and stereo imagination (not illusion aka virtual reality). Putting together some random, singled out pieces from "neuro", picked up by a person not too deeply involved in the field, doesn't make a theory. Let alone that obviously the production process making a recording is a blind spot, apperently. This is laisure hifi talk, spiced-up with scientific literature, which, for honest (!) understanding even for the expert would need days of study.

Neurobiology doesn't lead hifi, it is rather what Dr Toole says (with all due respectful criticism): do people like what they hear? If you don't like your music, it's up to you, don't ask others for action.

the author of the discussion asked himself questions, we answer later on with our experiences highlighting the same doubts. if you want answer, otherwise....
Neurobiology does not and cannot follow hi fi. Those who design speakers instead, should follow mathematics, physics, music, neurobiology..

 

[Heinrich]

the author of the discussion asked himself questions, we answer later on with our experiences highlighting the same doubts. if you want answer, otherwise....
Neurobiology does not and cannot follow hi fi. Those who design speakers instead, should follow mathematics, physics, music, neurobiology..

I see, translating (sort of) English to X, then to Y, back to English may be a problem.

So, very concrete:
- the overtones are phase correlated to the base tone
- in an accord of base tones, the listener can associate the overtones to their respective basetones by individual phase relation
- especially if the accord is intonated by different instruments

Hence the phase relation between basetone and overtones shall be maintained during recording/playback

Does it sound new to you, or does it reflect the discussion correctly to some sensible degree?

In case, the hypothesis is easily tested at home, with amateurish tools. If we were that much into the topic we should be able to generate an accord (today even using AI, it does, I tried, but needs tight monitoring for validity, of course), with shifting phase, detecting a threshold of an effect. That's what I asked from the proponents of a re-newed discussion on "phase". Neurobiology is very far, by lengths too far fetched.

 

[Suono]

in an accord of base tones, the listener can associate the overtones to their respective basetones by individual phase relation

in practice, even if you don't know the subject, it could be fine.

 

[tengiz]

In case, the hypothesis is easily tested at home, with amateurish tools. If we were that much into the topic we should be able to generate an accord (today even using AI, it does, I tried, but needs tight monitoring for validity, of course), with shifting phase, detecting a threshold of an effect.

Yes, it's straightforward - I ran a crude test using a synthesized note with an attack/decay envelope, a fundamental, and a few harmonics, then varied the phases in different ways. Exactly as expected, changing the harmonic phases alters the waveform - and to a lesser extent, the envelope - and if the change is large enough, it becomes audible.

Whether to call it sensitivity to the “signal envelope” or to “relative harmonic phase,” it’s effectively the same phenomenon from a signal processing standpoint.

However, when the internal phase structure of each note is preserved and only the relative phases between notes in a chord are shifted, I found no audible difference.

differing between real listening and stereo imagination (not illusion aka virtual reality).

Oh, come on — and you're saying you’re not being pedantic?

Yes, the “imaginary illusion” is a co-creation of the "hi-fi stereo" and speakers in a room - plus whatever your brain (and/or soul) hallucinates on top. But do we really need to keep stating the obvious with disclaimers? I thought that was a given.

Sure, I get it: someone "not deeply involved in the field" - and I’ve more than once readily admitted that applies to me with audio - might say something that, taken literally, makes no sense or sounds heretical. But I’d like to think it’s still possible to use our brain (and/or soul) to make an effort to extract - however unlikely - the essence from a distorted or ill-formed signal. After all, this is just “leisure talk,” right?

 

[Heinrich]

Yes, it's straightforward - I ran a crude test using a synthesized note with an attack/decay envelope, a fundamental, and a few harmonics, then varied the phases in different ways. Exactly as expected, changing the harmonic phases alters the waveform - and to a lesser extent, the envelope - and if the change is large enough, it becomes audible.

Now we are talking! Really, I appreciate anecdotal experiments, a logical concept behind the talks. Some may call it unscientific, but when it comes to me, hey, how did Mr Volta find electricity?

However, when the internal phase structure of each note is preserved and only the relative phases between notes in a chord are shifted, I found no audible difference.

Could you exemplify on the 'internal phase structure'?

Oh, come on — and you're saying you’re not being pedantic?

Yes, the “imaginary illusion” is a co-creation of the "hi-fi stereo" ... After all, this is just “leisure talk,” right?

I'm not actually. And right, it's for leisure which contradicts pedantism? Regarding illusion versus imagination, I stated my stance before. I would prefer the latter term every other day. Stereo, to me at least, is an effort to be taken, making up a mental image of the scenery. I cannot walk around it, I must not turn my head, all those techniques to gather more information isn't available. In that sense stereo cannot be virtual reality, is no illusion, but a subjective experience. I almost always dismiss it in my daily consumption of audio content.

 

[Suono]

and if the change is large enough, it becomes audible.

and when it becomes audible, that is, you can actually feel it, the damage in our brain has started much earlier

 

[kemmler3D]

My understanding of the example is that the phase relationship between different sounds — like notes in a piano chord — is basically random. It's impossible to strike keys with perfect timing, so the frequency components from different notes don’t have any consistent phase relationship. And since we don’t hear a noticeable difference when the same chord is played again, it seems like faithfully reproducing that randomness isn’t critical.

But it’s a different story for each individual piano key. The harmonics within a single note start out with a well-defined phase relationship. That can drift over time — due to slight detuning or string dispersion — but the initial alignment is always there. If a playback system disrupts that, it might change how the note sounds.

Of course, practical playback systems can’t tell whether frequencies belong to the same sound or not. If they alter phase in a frequency-dependent way, they affect everything. But that doesn’t change the basic idea.

The phase relationship between each note in the chord is random but the phase between the harmonics in each individual note are NOT random at all... If you play with the additive synth Harmor you can see this, there's a knob that lets you randomize the phase of each harmonic in each note. It often changes the character of the sound a good bit, but not entirely. It's not all or nothing ... You may find it interesting to mess with. You can resynthesize real samples with it too, so you can see how it works with an actual piano sound...

 

[tengiz]

Could you exemplify on the 'internal phase structure'?

I didn’t vary the phase between the fundamental and harmonics within each note across the test samples for chords.

That said, I’ll admit that when you actually strike a piano string or pluck a harp, you get a very specific magnitude and phase structure - determined by the shape of the string when the hammer bounces off or it’s released. This simulation didn’t attempt to capture that; modeling it properly would take a lot more care and detail - I’d need to brush up on my Mathematical Physics/Applied PDEs.

So yeah, it’s entirely possible that an artificial harmonic structure is much less forgiving when you mess with phase than a real physical string. I wouldn’t be surprised if, with a more realistic simulation, those phase changes turned out to be inaudible altogether.

I'm not actually. And right, it's for leisure which contradicts pedantism? Regarding illusion versus imagination, I stated my stance before. I would prefer the latter term every other day. Stereo, to me at least, is an effort to be taken, making up a mental image of the scenery. I cannot walk around it, I must not turn my head, all those techniques to gather more information isn't available. In that sense stereo cannot be virtual reality, is no illusion, but a subjective experience. I almost always dismiss it in my daily consumption of audio content.

Fair enough. But - and this is me being pedantic - I’d argue that you can take this idea to its logical conclusion and apply it to all sensory input: the only way our perception works is through the brain (or mind) interpreting it. There’s nothing else there.

 

[tengiz]

The phase relationship between each note in the chord is random but the phase between the harmonics in each individual note are NOT random at all...

Right, isn't that what I've said in the second paragraph?

But it’s a different story for each individual piano key. The harmonics within a single note start out with a well-defined phase relationship. That can drift over time — due to slight detuning or string dispersion — but the initial alignment is always there. If a playback system disrupts that, it might change how the note sounds.

 

[beagleman]

I am into classical music. Get to go to a handful of concerts every year.

Even the mediocre "halls" just sound so much bigger and fuller than my decent system at home.
I think the room is more the bottle neck with classical.

My system will play louder than the real life music, but it never even begins to sound as "Big" and spacious and full.

 

[kemmler3D]

Right, isn't that what I've said in the second paragraph?

Yes, but you might be surprised how much inter-harmonic phase distortion is needed to really alter the character of the sound, it's worth messing with.

 

[tengiz]

Yes, but you might be surprised how much inter-harmonic phase distortion is needed to really alter the character of the sound, it's worth messing with.

Oh, yes.

 

[tengiz]

I am into classical music. Get to go to a handful of concerts every year.

Even the mediocre "halls" just sound so much bigger and fuller than my decent system at home.
I think the room is more the bottle neck with classical.

My system will play louder than the real life music, but it never even begins to sound as "Big" and spacious and full.

I can totally relate to that.

But after spending a lot of time and effort making my room matter less, I’m at the point where I still really appreciate the “real thing” and still go to live concerts - but now I’m more mindful about which seats to get. For piano or piano + orchestra, for example, it’s a much better experience in certain parts of the hall. With just orchestral music, it’s more forgiving - the area where it still sounds good is wider and deeper. And I mean it: it’s genuinely harder to hear, say, individual piano notes clearly when you’re in a spot where the sound gets noteceably smeared by reverb, reflections, and so on.

At home, I don’t have to deal with that. With good recordings, it feels like I don’t have to compromise anymore. When I go to concerts with my family, they like box seats - which, honestly, are usually far from ideal if you actually want to listen seriously.

 

[BenB]

Whether to call it sensitivity to the “signal envelope” or to “relative harmonic phase,” it’s effectively the same phenomenon from a signal processing standpoint.

That's not exactly true. If you are sensitive to the relative harmonic phase, you'll hear differences even in the steady-state (consider a string instrument being slowly bowed rather than plucked, or a woodwind or brass instrument playing steadily... basically driven harmonic oscillation).

If you are sensitive to the envelope, then you'll hear the difference where the magnitude goes through changes.

I suggest you try varying your envelope significantly too see how it impacts your perception. There's more than one way to make a musical note (or chord).

 

[tengiz]

That's not exactly true. If you are sensitive to the relative harmonic phase, you'll hear differences even in the steady-state (consider a string instrument being slowly bowed rather than plucked, or a woodwind or brass instrument playing steadily... basically driven harmonic oscillation).

If you are sensitive to the envelope, then you'll hear the difference where the magnitude goes through changes.

I suggest you try varying your envelope significantly too see how it impacts your perception. There's more than one way to make a musical note (or chord).

I appreciate the clarification. Perhaps I didn’t use the term envelope in the way it’s typically used in the field. If it usually refers to the attack/sustain/decay sequence, then that’s not exclusively what I meant. Phase variation affects the shape of the waveform, and if the harmonic structure is complex enough, it can also affect the overall amplitude contour over timespans much longer than a single cycle in sustained cases as well.

 

[Heinrich]

... take a lot more care and detail - I’d need to brush up on my Mathematical Physics/Applied PDEs.

Do you play an instrument yourself? (Electric) Bass guitarists are in parts very deep into magical thinking. The pianists I know not so much ... . Back to the bassists they claim, that a so called 'long scale' model will sound richer in the overtones etc bla bla, than a 'short scale'. Thing is, due to scaling effects in the mechanics the short is less prone to buzzing the string to the neck, while the long scale does it all the time. It enriches the sound for sure, but it is decidedly not harmonic - the guitarists don't get that.

So much on harmonics: even for musicians even its spectral content is not that important, let alone the phase of the chaotic elements.

A wind instrument won't be that exact in regard to phase, especially when the note starts. Again, the mechanics of the instrument prevents that. The strict relation develops within a few cycles, but isn't established at once, like it is with strings. While for strings the overtones depend strongly on where the string is excited, including irregularities that sustain with a violin, but not with a guitar. Consider that for a sustained note the player has to drive the damped oscillator continuously, which may have an impact on how the harmonics are excited, and hence the phase. Chaos is a crucial part of an instrument's sound, and the artists seek out for a personal signature originating in that.

All in all the overtones typically are not static; with my guitar I observe an exchange of energy between the harmonics, one going down while the other comes up, and back again. Asking for shape of wave? This effect depends on the model, not only on type of instrument. Percussion is a different field alltogether.

This, at least combined, is another counterargument against a need for strict phase fidelity. Would you mind to present your experiment with a little bit more detail, some numbers?

What do we have? Some quite speculative assumptions picked as isolated, not to the point results from neurobiology, applied to a very much simplified and widely generalized model of mechanical instruments, and a king size gap in between.

 

[BenB]

I appreciate the clarification. Perhaps I didn’t use the term envelope in the way it’s typically used in the field. If it usually refers to the attack/sustain/decay sequence, then that’s not exclusively what I meant. Phase variation affects the shape of the waveform, and if the harmonic structure is complex enough, it can also affect the overall amplitude contour over timespans much longer than a single cycle in sustained cases as well.

My apologies. You're right that the envelope isn't simply the onset and offset behavior. It's everything you'll get when you plot the abs(hilbert(x)). However, there are many different signals that can create the same envelope, and those signals will sound different from each other. It seems to me that it's the underlying signals that matters to our hearing, and that the envelope is a useful engineering concept that has no direct bearing on auditory perception. I think I erroneously connected implications to your statement that were never intended.

 

[BenB]

Do you play an instrument yourself? (Electric) Bass guitarists are in parts very deep into magical thinking. The pianists I know not so much ... . Back to the bassists they claim, that a so called 'long scale' model will sound richer in the overtones etc bla bla, than a 'short scale'. Thing is, due to scaling effects in the mechanics the short is less prone to buzzing the string to the neck, while the long scale does it all the time. It enriches the sound for sure, but it is decidedly not harmonic - the guitarists don't get that.

So much on harmonics: even for musicians even its spectral content is not that important, let alone the phase of the chaotic elements.

A wind instrument won't be that exact in regard to phase, especially when the note starts. Again, the mechanics of the instrument prevents that. The strict relation develops within a few cycles, but isn't established at once, like it is with strings. While for strings the overtones depend strongly on where the string is excited, including irregularities that sustain with a violin, but not with a guitar. Consider that for a sustained note the player has to drive the damped oscillator continuously, which may have an impact on how the harmonics are excited, and hence the phase. Chaos is a crucial part of an instrument's sound, and the artists seek out for a personal signature originating in that.

All in all the overtones typically are not static; with my guitar I observe an exchange of energy between the harmonics, one going down while the other comes up, and back again. Asking for shape of wave? This effect depends on the model, not only on type of instrument. Percussion is a different field alltogether.

This, at least combined, is another counterargument against a need for strict phase fidelity. Would you mind to present your experiment with a little bit more detail, some numbers?

What do we have? Some quite speculative assumptions picked as isolated, not to the point results from neurobiology, applied to a very much simplified and widely generalized model of mechanical instruments, and a king size gap in between.

Thanks for posting this. I've been meaning to write something about how harmonic phases from real instruments aren't locked to the phase of the fundamental in the way that most people might anticipate. The phases vary, and we don't really pick up on it (because we aren't that sensitive to it).
It's long been known that with synthetic waveforms we can demonstrate an audible difference by massively varying the phase of harmonics. Generating an audible difference with the type of phase distortion associated with actual speakers is much more difficult, even with synthetic data.
It's all really much ado about nothing, and I would prefer this thread not get sidetracked into another phase distortion discussion. Perhaps we ought to have a stickied thread to address phase distortion, and keep it out of other threads.

 

[Multicore]

The playback chain should be concerned with reproducing the content as accurately as possible.

I agree but it appears there is not consensus. The central operative word in Stereophile's definitions of its Class A, B, C and D grading system of components is how musical they are. This can only make sense to me if components can add or remove music from the signal. I don't see how to reconcile the goal of maximizing musical content with maximizing accuracy.