Absolute Polarity?

[awkwardbydesign]

"Just as likely, IMO, is that some people just cannot bear to accept that others can hear things they can't.
Regards,
Andy"

Oh yes!

[bauzace50]

@ awkwardbydesign,

there are things that one hears but others do not! My listening arrangement is in the near field, where the speakers and I form an equilateral triangle about 3'x3'x3' (or less). and that triangle is near the rear of the room, where the rear walls are close by. This creates certain reflections so that I actually hear phantom rear channels, quite especially in movies (my system has 2-channel DVD video fed through my analog 2-channel system).

It is rather mindblowing that I hear the intended rear sounds of movies appearing to come from the rear( while I have ONLY two front speakers). Really! But it all comes down to the phase relationships created ACCIDENTALLY in that specific configuration. (I do NOT use my Dynaquad 4-speaker surround because of this happy accident). It would take lots of energy to decide to move to some other location.

So, yes, there are things one hears that others may not. And there are explanations in plain physics.

Regards,
bauzace50

[charlieblue]

Here's a link for all to test their audibility on absolute polarity:
http://www.audiocheck.net/blindtests_abspolarity.php
All you need is a pair of headphones and your PC!
I scored average, by the way, so I guess I am not sensitive to absolute polarity . Or, my Senheisers are playing games to me, or my on-board pc audio card is crappy or, well, I'm running out of excuses here !

However, on their speaker-phase-polarity page the difference between right and wrong is only too obvious :
http://www.audiocheck.net/audiotests_polaritycheck.php

Best,

Charlie

[Ldg]

To seperate phantom perception from 'sensitivity' seems a sensible first step.

To be rigorous, trust no-one, and try to forget everything that anyone speculated on the topic.

Take a well recorded audio track in a lossless format. Invert it, in a reputable audio editor. Transfer both tracks to CD, play back tracks at random, and guess which track is playing. History says you won't pass the test.

I venture that 'some can distinguish' is mythical, and yet another artifact of phantom perception, expectation bias, WHY. The bane of proper progress and development of good sounding playback, IMO. Because such things are a distraction from the things that do make a transferable, repeatable difference. But are otherwise a healthy debating practice sport

[bauzace50]

Hi,

the links referred by charlieblue are rather interesting. I will test these out later on. And the caveats by ld are pertinent.

Thanks,
b50

[Logan]

Let's try to forget about the stereo equipment for a moment.

I go to a concert and sit in a particular seat. The trombones play a particular note. It reaches my ears as a compression wave, having a particular wavelength. If I then move to another seat one half wavelength further back in the hall so that I hear this note as rarefactions, am I going to hear anything different?

And if three trombonists are playing the note in unison, how do I know that compressions and rarefactions as the sound waves exit from their instruments are aligned with each other? They're not all exactly the same distance from my ears when they play. And what about twenty first violinists in a symphony orchestra? Or is the Berlin Philharmonic better than the Burkino Faso State Symphony Orchestra because the former plays in absolute phase and the latter doesn't? Does the conductor of the orchestra, who is ultimately responsible for how it sounds, hear the same phase that I'm experiencing?

If "absolute phase" is in no way absolute in a concert hall or a recording studio, why should it be of so much importance when we ponder whether our speaker drivers are moving towards or away from us? I can indeed hear minor changes when I alter the position of my listening chair relative to my speakers but I ascribe this to room acoustics effects rather than the influence of compressions and rarefactions.

I'd be pleased if the Absolute Phase brigade could answer these questions or at least attempt to clear up any misconceptions I may have.

I once allowed a VTA fanatic to fiddle with my tonearm to set optimal VTA by ear. He moved what he thought was the arm height adjuster hither and yon until he proclaimed that perfect VTA had been achieved, and left, apparently satisfied with himself and his expertise. I was rather bewildered by all this because I had heard no change in the sound whatsoever while he worked. So I checked and found that the "adjuster ring" he'd been mistakenly fiddling with had not altered the arm height one iota during the exercise. I did the job properly myself and found the best setting with no difficulty. Are we dealing with the same phenomenon with regard to "absolute phase" - a profusion of delusion?

[Ldg]

..the links referred by charlieblue are rather interesting. I will test these out later on.

I applaud the spirit, but I just scored 8/10 without even listening, just guessing.

But hey, they call me Lucky

So I wouldn't attach much value to the result in this test. Rigor is everything in such things.

[Hanuman]

Let's try to forget about the stereo equipment for a moment.

I go to a concert and sit in a particular seat. The trombones play a particular note. It reaches my ears as a compression wave, having a particular wavelength. If I then move to another seat one half wavelength further back in the hall so that I hear this note as rarefactions, am I going to hear anything different?

I can see the point you're trying to make (and I personally don't obsess over absolute phase) but I don't think your example holds water. The sound pressure wave will arrive at the second position (one half-wavelength back) later in time relative to the first and will still be "in phase", relatively, at the moment it hits the ear.

[bauzace50]

Hi,
so, absolute polarity is controversial, at best, and I am not sensitive to it. Thanks for the comments!

One obvious curiosity is Doppler Frequency Shift. Remember a constant sine wave sound emitted by a travelling vehicle (such as an ambulance sounding its siren). The pitch goes up as the source approaches, and then goes down as the source goes away.

Wonder why modern "sirens" are designed with all sorts of hiccups and crazy yelping? Would it be to make them intelligible in the cacophony of city environments?

These are the modern embodiment of the ancient historical bells of ships and temples.

Regards,
b50

PS: see:
http://en.wikipedia.org/wiki/Doppler_effect

http://en.wikipedia.org/wiki/Bell_(instrument)

http://en.wikipedia.org/wiki/Siren_(noisemaker)

[Hanuman]

This is quite an interesting subject when you have a closer look at it. I googled "effect of sound wave phase in human auditory system" and the reality was stark, obvious and basic: Our auditory system knows all about phase differences at tiny levels - we rely on this to locate the direction of sounds (an understanding of this makes the idea of successful stereo replay from two speakers even more miraculous!). If people are insensitive to the absolute phase of sound waves coming at them from loudspeakers I posit that the reason is that the brain just doesn't care about absolute phase (there seems little doubt that the physical and neurological system would be sensitive enough to detect it). The brain just makes sense of the data that's coming, either way. There's probably a degree of adaptation and self-correction, too. I know that this is absolutely the case for the visual system. In this sense @Logan is on the money - the brain works it out based partly on expectation and experience. If I'm right about this (fat chance!) then those who claim to be sensitive to absolute phase are actually demonstrating a deficiency of some kind - the correction mechanism is not working properly.

Of course, we're all making a bit of an assumption, here, that the inner workings of the cochlear react differently to compressions versus rarefactions. Is there anyone on the forum qualified to verify or invalidate that?

[Ldg]

I agree, Hanuman, we are accutely sensitive to timing differences between ears, and construct images of location based on it. But apparently not the absolute phase of the audio compression wave. For sure, the sensation of location doesn't change when absolute phase is A/B inverted, for example. This has to be a big clue. AFAIK, cochlea works by moving tiny hairs in a tuned spiral tube, perhaps the same neurons simply fire no matter which way the hair moves ?

But what evidence (rather than testimony) is there that anybody is sensitive to absolute phase ? Rather than phantom perception. AFAIK, there is none.

Before attempting to explain why some people might or might not be sensitive, it's necessary to establish, with fair rigor, whether that is actually true.

[andyr]

Before attempting to explain why some people might or might not be sensitive, it's necessary to establish, with fair rigor, whether that is actually true.

And here we have the classic "audio debate" territory.

Your posit puts you in the "engineer/objective" camp, which loves meaurements and DBTs before they will believe anything. I myself am in the "other" (non-measurement/non DBT/non-engineer/subjective? camp!

If someone claims they can hear when absolute polarity is reversed, as I keep an open mind, I'm happy to believe them ... and will also be interested in conducting experiments to see whether I can, too. Morever, in case I am one who is relatively insensitive to absolute polarity, I will take care to ensure my system is in the best possible situation to allow me to hear this effect, when I play the Cardas Test Record - so electrical phase is set correctly in all my components (by having the power tranfsormer connected optimally to 'active' & 'neutral') and I have speakers which don't have 1 driver reversed. To this end, I will shortly be changing the active XOs in my Maggies to all 6dB (to match the latest Maggies), to see whether that helps. If it doesn't then I will conclude that I am one of the "lucky" majority that aren't sensitive to this phenonmenon ... but I won't diss people who say they are!

Whereas the objective camp won't lift a finger until someone "proves" to them that it's worth their while to do so.

Regards,

Andy

[aardvarkash10]

wrong andy. LD has posted the result of his random entry into a test sequence. Sure its anecdote as well, but then the only opposing anecdote is yours. (by way of light relief, I did the same test as LD, also just random entry. I scored 2/10!)

Am I rushing out to test the hypothesis of audible absolute polarity? Nope. No real driver to do so - people with far more experience than I have already done so and have settled on a position that, while particular instruments (sax) can be detected as being different in sound between phases, no-one can identify which is "correct" or even better. Moreover, they find that once the instrument is in a mix of other sounds, the effect is no longer detectable.

Even yourself, supporting at least at an intellectual level the possibility, found that you can only detect the effect in a highly controlled and very limited circumstance.

So, chase smoke, or do something useful...? Easy call really.

[Ldg]

......If someone claims they can hear when absolute polarity is reversed(..), I'm happy to believe them ...

Trouble is the very fertile possibility of phantom perception and expectation bias makes it near impossible to know if any such effect is real. No matter whether one is objectivist or subjectivist in outlook, discussion of the topic needs to begin with understanding this point. There's a genuine prospect it's not a real effect. Failing blind tests, for example.

Personally, I'm fascinated by phantom perception, as part of the human condition. I also see it as a bane of progress and development of things that really can make an improvement. And I think perception of absolute phase is yet another obvious candidate here.