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Does Phase Distortion/Shift Matter in Audio? (no*)

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Did you do the test on speakers or headphones?
Initially headphones, just tested with speakers and also got 10/10 correct (I do have a 2.1 system with the sub pretty close to my seating position, maybe that's a relevant factor). So this issue is not only detectable with headphones as is often claimed.
 
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Because the hair cells in the ear is sensitive only to half of the waveform. An asymmetric signal change in timbre when flipped.
Source? I have found some physiological evidence of mechanisms in the ear that are sensitive to absolute polarity. From that journal article:
The stereociliary staircase is associated with a functional polarization such that (positive) deflections of the bundle towards its taller edge are excitatory and cause MET channels to open, whereas (negative) deflections towards its shorter edge cause MET channels to close. All hair bundles are oriented in precisely the same abneural direction to confer a common response polarity during basilar membrane motion.
But this is not phenomenological evidence that or why polarity inversion is associated with a change in perceived 'timbre'.
 

KSTR

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See for example http://www.davidgriesinger.com/intermod.ppt, slides 48ff.

Assume you have a fundamental and a 2nd harmonic as shown in post #38, but inverted so that whe wobble from the 2nd is in the lower half. Simplified, the ear basically ignores the lower half, therefore wobble from the 2nd doesn't cut through. OTOH, when the wobble is in the upper half, the 2nd comes through to full extent. That causes the timbre changes from polarity flip or phase shift. This "deafness" can also be shown with a spike riding on a waveform, when the spike is in the negative half of the waveform it less audible and has a different timbre. Or just listen to a pink or brown pulse (highpassed step function), it sounds very different depending on polarity.
 

Francis Vaughan

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To be clear about polarity inversion and phase shift.

Everyone is taking the logic of what I wrote and working backwards, which isn't a valid reading of what I intended.
I noted that polarity inversion is often called a phase inversion because sin(x + 180º) = - sin(x). I railed against polarity inversion being called phase inversion because it causes confusion. Now everybody is confused.

Confused because they think I said that messing about inverting the phase of components of a signal is inaudible, or meaningless.
I said: polarity inversion is often called phase inversion, and I think this is a bad thing as it it causes confusion, especially as polarity inversion is generally inaudible. This is especially so in conversations about phase in general.

Some posers think I said, inverting the phase of a component of the signal is inaudible. I didn't.

If you invert the phase of a component of the signal you did not invert the polarity of the signal.

All evidence seems to show that unless you reach the point of asymmetric non-linearities in your audio chain, absolute polarity is inaudible. Get loud enough and you will eventually start to distort the air, and air is not symmetrical. Loud bass can reach the point where the air in loudspeakers is ceasing to be linear, and causing distortion. It is important to distinguish between non-linearities in the reproduction chain changing the sound from absolute phase itself.

Also, if your signal cannot be decomposed with a Fourier transform it isn't periodic. If it isn't periodic the word phase is not defined. You might be talking about moving the shape of the signal about in some sense, maybe with timing offsets but unless you have a decomposition into periodic components the word phase has no meaning. We can argue about whether your signal has a Fourier transform, but be clear, the definition requires it to be periodic. (To be really pendantic, a Fourier Transform does not require that the basis functions be sin and cos. They do need to be periodic.)
 

KSTR

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All evidence seems to show that unless you reach the point of asymmetric non-linearities in your audio chain, absolute polarity is inaudible.
Sorry, Sir, you are not up do date and obviously you've never tried. This is one of the best examples where everbody can do (and almost certainly succeed in) their own ABX test as it is so extraordinarily simple to set up.
The polarity test is actually my go-to test that I always do before more complicated tests. On some days I'm not mentally or physically fit enough and then I also fail and know I don't need to do any further listening when I can't make it in that simple test. It is really simple and the differences are large enough, I basically recommend the polarity test (with headphones) for people that are new to ABX or other blind testing as they will have a positive result almost for certain.
 

Francis Vaughan

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you are not up do date
Do you have a modern citation? Genuinely interested. Peer reviewed modern research. And, no I'm afraid a personal anecdote doesn't count.
It has been a while since I looked into this, and if there is more modern work showing this I'd be interested.
 
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To be clear about polarity inversion and phase shift.

Everyone is taking the logic of what I wrote and working backwards, which isn't a valid reading of what I intended.
I noted that polarity inversion is often called a phase inversion because sin(x + 180º) = - sin(x). I railed against polarity inversion being called phase inversion because it causes confusion. Now everybody is confused.

Confused because they think I said that messing about inverting the phase of components of a signal is inaudible, or meaningless.
I said: polarity inversion is often called phase inversion, and I think this is a bad thing as it it causes confusion, especially as polarity inversion is generally inaudible. This is especially so in conversations about phase in general.

Some posers think I said, inverting the phase of a component of the signal is inaudible. I didn't.

If you invert the phase of a component of the signal you did not invert the polarity of the signal.

All evidence seems to show that unless you reach the point of asymmetric non-linearities in your audio chain, absolute polarity is inaudible. Get loud enough and you will eventually start to distort the air, and air is not symmetrical. Loud bass can reach the point where the air in loudspeakers is ceasing to be linear, and causing distortion. It is important to distinguish between non-linearities in the reproduction chain changing the sound from absolute phase itself.

Also, if your signal cannot be decomposed with a Fourier transform it isn't periodic. If it isn't periodic the word phase is not defined. You might be talking about moving the shape of the signal about in some sense, maybe with timing offsets but unless you have a decomposition into periodic components the word phase has no meaning. We can argue about whether your signal has a Fourier transform, but be clear, the definition requires it to be periodic. (To be really pendantic, a Fourier Transform does not require that the basis functions be sin and cos. They do need to be periodic.)
To be fair, you clearly confused a bunch of readers by stating in a post, you have now edited, that a polarity inversion was "absolutely" a 180 degree phase shift or words to that effect. I was going to correct you at the time, but figured someone else would do it.
 

Francis Vaughan

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To be fair, you clearly confused a bunch of readers by stating in a post, you have now edited,
If it was edited in the first little while after I wrote it then I realised I had badly worded it. So I would have corrected it or improved the clarity. I can hardly be blamed for doing that. But that was ages ago, and people are quoting it now. Not then.
 
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I really don't know why people don't discuss polarity more in HiFi. Every reviewer worth their salt always presented either an impulse oscillogram and/or comments on absolute polarity for digital products reviewed.

All processors, be they analogue or digital, should be examined for polarity, again, using an impulse or assymetrically clipped sine.

With people using multiple amplifiers, processors and distributed subwoofers, biamping, DSP etc, it's rather important.
 

BlackH20

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Paul has zero education in audio ( I mean that sincerely) and I am not sure he has an advanced degree in anything but has had the silver tongue of an audio salesman selling a lot of crap with PS Audio. Now I have to make my donation Amrin, not sure if I want a "former donor" under my name, looks like I may have sold a kidney.
 
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Not at all obvious to me - I got 6/10 with IEMs.
Don't be afraid to do more than 10 trials, you may have gotten better over time (I'd say up to around 16 trials in a session before fatigue might set in). You need to be at a decently high (but comfortable) volume too. You can also try EQing up the bass first to make the difference more obvious, then gradually decrease this until the EQ is off. (The results of mine I posted were without EQ, just subsequently noticed it's easier with the bass boosted.)
 
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Do you have a modern citation? Genuinely interested. Peer reviewed modern research. And, no I'm afraid a personal anecdote doesn't count.
It has been a while since I looked into this, and if there is more modern work showing this I'd be interested.
The successful blind ABX test results of mine I posted are valid data in contradiction to your claim, not mere personal anecdote. Please just try the test - there's nothing like hearing and confirming an audible difference with a blind ABX for yourself.
 

Francis Vaughan

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The successful blind ABX test results of mine I posted are valid data in contradiction to your claim, not mere personal anecdote. Please just try the test - there's nothing like hearing and confirming an audible difference with a blind ABX for yourself.
I will. However the problem is that you are not necessarily validating proof of audibility of absolute phase. You may be validating that your reproduction chain has an asymmetric transfer function. Lots of speakers and headphones can. You need to show that whatever distortion your system has it is not overly asymmetric in nature. Even harmonic distortion is a good start to such behaviour.
This is why I prefer a peer reviewed study. Whist your double blind trial is good, unless you validate your test system, it remains anecdotal.
 

restorer-john

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They also comment on pace rhythm and timing. Reviewers have a habit of bulking out their reviews with whatever stuff makes them sound learned.
Absolute polarity tests have been a feature of CD player reviews since day dot. PRaT is just a strawman.

I have no idea why you appear to be railing against maintaning absolute polarity in a reproduction system. We know asymmetric waveforms are captured. We know plenty of recordings have asymmetric content, be it deliberately or accidentally.
 

dc655321

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Don't be afraid to do more than 10 trials, you may have gotten better over time (I'd say up to around 16 trials in a session before fatigue might set in). You need to be at a decently high (but comfortable) volume too. You can also try EQing up the bass first to make the difference more obvious, then gradually decrease this until the EQ is off. (The results of mine I posted were without EQ, just subsequently noticed it's easier with the bass boosted.)
Thanks for the tips! I may try again...
Though, I will say again that "obvious" seems like a hyperbolic description, imo.
The test felt like another one of those, "if you have to squint to see it" effects...
 
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