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An interesting paper on jitter audibility - Page 7

post #91 of 112
12/24/06 at 5:48pm
Quote:
Originally Posted by regal View Post
Ever notice the ones objecting the most are selling things that this scientific study basically claims are useless. The spam on this forum is getting out of hand.
The above sounds a lot like libel to me. If you believe my products are so useless, then dont buy them....I dont think I want your business anyway.

Steve N.
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post #92 of 112
12/25/06 at 2:28am
Quote:
Originally Posted by audioengr View Post
The above sounds a lot like libel to me.
Nah . . . , just stupid -- for whole lot of reasons.
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post #93 of 112
12/25/06 at 4:29am
Quote:
Originally Posted by audioengr View Post
The above sounds a lot like libel to me. If you believe my products are so useless, then dont buy them....I dont think I want your business anyway.

Steve N.
I, for one, appreciate your input here and can find no commercial motivation underlying your posts, even in my most paranoid moments, which like my dementia, have become increasingly frequent.

Thanks again for your input.
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post #94 of 112
12/25/06 at 12:16pm
Thread Starter 

More data from ASHIHARA Kaoru

Some more details that the author sent me
-----------------------------------------

Hello Jim,

Additional comments came from my co-worker, Dr. Kiryu.
Prior to the second experiment, we had sent the materials with time jitter
of several amounts to some of the participants. They could, therefore, train
themselves with the materials. In fact, one listener told us that he could
detect time jitter of several ns. However, in the experiment that was a
strict double-blind test, his score was much worse as written in the paper.
Recently, the materials were sent to Dr. Kiryu’s friend who is an
audiophile. This man said that the sufficient training made it possible to
detect time jitter of 150 ns.

I want to add some more.
We had considered about the maximum permissible jitter in audio package
media. When random time jitter does not cause any distortions larger than
1/2 LSB (Least Significant Bit), it does not degrade the quality of sounds
because the distortions in this case are smaller than the quantization noise
level. When there is time jitter, the maximum distortion occurs where the
slope of the waveform is its maximum. The size of distortion can be obtained
by multiping the slope by jitter size. Does it make sense to you? My English
may be awkward sometimes. Please make it up for with your imagination.
Anyway, if you can find the maximum slope (inclination?) in the waveforms of
the sound materials, you can estimate the maximum permissible jitter size.
We estimated the maximum permissible jitter size by checking the maximum
slope in the music waveforms in many CDs. The values varied considerably
between 182 ps and 2567 ps. This means that in certain materials, time
jitter has to be smaller than 182 ps to guarantee a 16-bit resolution.

In our research, the material that was most susceptible to jitter was a
music played by a music box and it contained a lot of high-frequency
components. One hundred eighty-two ps correspond to the maximum permissible
jitter in a pure tone of about 13.3 kHz. If a 20 kHz pure tone has to be
reproduced with a resolution of 16 bit, the maximum permissible jitter size
is about 121 ps. By the way, I do not know any loudspeakers or headphones
that have linearity corresponds to a 16 bit resolution. After all, I won’t
believe someone who says that he can detect time jitter of 100 ps or less in
CDs.

I visited the site of Headfi.org and found your heated discussion on this
topic.

Keep going!

-----------------------------------------
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post #95 of 112
12/25/06 at 1:49pm
How much time was a subject allowed to evaluate two sources to say which sounded best?

Give me a week of comparison of two programs, and I bet I could do well - the one I said was better would have less jitter to a statistically significant degree. Each trial of two programs would take one week, so 10 weeks would be needed to conduct 10 trials, 20 weeks for 20 trials, and so on.

Brief AB comparisons are unreliable due to perceptual confusion which we remain unaware of.

Sometimes two CD sources (same make and model) will sound identical in such brief AB testing but prolonged listening to both can make one realize something is wrong with one of the two, even though you can't say what it is. Here you wil prefer one over the other without really knowing why.

Experimental conditions can induce some anxiety that diminishes perceptual discriminations, and brief AB testing can induce perceptual confusion that we are unaware of but which impede/mask discriminations.
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post #96 of 112
12/25/06 at 4:38pm
Thread Starter 
Quote:
Originally Posted by drarthurwells View Post
How much time was a subject allowed to evaluate two sources to say which sounded best?
This s not about preference and has never been about preference it is about discerning an audible difference between jitter-free and jittered sources and that is all.

There is no point debating preference if there is no difference and detection of difference according to the paper is at a very high level of jitter, you couldnt but a source that has such high jitter.
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post #97 of 112
12/25/06 at 5:30pm
AudioEngr

Just wondering if you are maintaining phase correctly across all those combinations so that the music is actually the same. Some things are so easily manipulated as to almost magic in who it can be done.

Do you write detailed procedures so that this type of experimentation can be repeated? You really can't use the same interconnects since some of the devices handled different signal types. Are you using the same power supplies for each type when you are testing them? Such as a regenerator? If you are not using a regenerator for power then as power changes over the day the supply may effect the devices being tested. Are all the devices similarly isolated across all tests setups? Do you ensure that the CDs are operating at the proper speed? A little change can make a big difference. How sensitive are you sound level settings when doing these tests? My last of many other types of test issues that could be raised is how long do your test subjects get to lesson to the various setups to learn what each really does sound like. This last one goes to the issue raised above concerning educated ears.

Quote:
Originally Posted by audioengr View Post
The jitter demonstrations that I have done compared the following in chronological steps:

1) Stock CD Transport playing a commercial CD track into modded P-3A DAC using S/PDIF
2) Stock CD Transport playing low-jitter copy of same track into modded P-3A DAC using S/PDIF
3) Modded CD Transport (same model) playing low-jitter copy of same track into modded P-3A DAC using S/PDIF
4) Computer playing same ripped track using Off-Ramp USB converter and S/PDIF to modded P-3A DAC
5) Computer playing same ripped track using Off-Ramp USB converter and I2S to modded P-3A DAC

DAC was the same one used for all experiments, same preamp, same amps, same speakers. The jitter was reduced (more precise and clear imaging) in each step. The listeners are all in front of the equipment, so they cannot see what I am doing. The playback equipment is changed back and forth using A/B teminology, changing which ones is A and B at random etc.. Much like what you get when you are being fitted for glasses.

The vast majority of listeners were able to hear an improvement in each of the 5 steps. A few had limited HF hearing, so they didn't. The only difference was the jitter in the digital signal(s). Measurements were not taken, but I had previously looked for the difference in jitter between the S/PDIF and the I2S from the Off-Ramps and I cannot see it on my 2nsec resolution scope. If it was a 500psec difference, I would have seen it.

You must understand that my CES setups are some of the most resolving that you will find at CES. It is essentially my same reference system that I use for the business. I have complete control over all components, speakers and cables. I dont share with any other vendors. Everything in the system is built by me or modded by me.

Steve N.
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post #98 of 112
12/25/06 at 7:02pm
Quote:
Originally Posted by drarthurwells View Post
How much time was a subject allowed to evaluate two sources to say which sounded best?

Give me a week of comparison of two programs, and I bet I could do well - the one I said was better would have less jitter to a statistically significant degree. Each trial of two programs would take one week, so 10 weeks would be needed to conduct 10 trials, 20 weeks for 20 trials, and so on.

Brief AB comparisons are unreliable due to perceptual confusion which we remain unaware of.

Sometimes two CD sources (same make and model) will sound identical in such brief AB testing but prolonged listening to both can make one realize something is wrong with one of the two, even though you can't say what it is. Here you wil prefer one over the other without really knowing why.

Experimental conditions can induce some anxiety that diminishes perceptual discriminations, and brief AB testing can induce perceptual confusion that we are unaware of but which impede/mask discriminations.
Sorry, I just cannot read and comprehend your words with that monkey picture staring at me. I just cannot stop giggling.....
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post #99 of 112
12/25/06 at 7:03pm
Quote:
Originally Posted by hciman77 View Post
This s not about preference and has never been about preference it is about discerning an audible difference between jitter-free and jittered sources and that is all.

There is no point debating preference if there is no difference and detection of difference according to the paper is at a very high level of jitter, you couldnt but a source that has such high jitter.
Jim - The low-jitter disk is ready to ship, and I included a little Christmas surprise while I was at it, knowing that you prefer Classical.

Steve N.
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post #100 of 112
12/25/06 at 7:11pm
SLWISER - a lot of questions, but here goes:

Do you write detailed procedures so that this type of experimentation can be repeated?

I never bothered.

You really can't use the same interconnects since some of the devices handled different signal types. Are you using the same power supplies for each type when you are testing them?

For the two transports I did use the same digital IC.

Such as a regenerator? If you are not using a regenerator for power then as power changes over the day the supply may effect the devices being tested. Are all the devices similarly isolated across all tests setups?

Changes over the day are not relevant. I do the test over a short period and have repeated it several times at different times of the day. Always the same result. The devices are all plugged into the same extension box. no power conditioning.

Do you ensure that the CDs are operating at the proper speed?

Speed? These are crystal controlled. Speed variations are minimal from one unit to the next. Certainly not enough to be aubible, say from transport to computer.

A little change can make a big difference. How sensitive are you sound level settings when doing these tests?

Levels are identical. The preamp is not adjusted during the test. The DAC output is identical level with all sources.

Steve N.
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post #101 of 112
12/25/06 at 7:36pm
Steve

Thanks for providing these answers to my various questions.

Steve

Quote:
Originally Posted by audioengr View Post
SLWISER - a lot of questions, but here goes:

Do you write detailed procedures so that this type of experimentation can be repeated?

I never bothered.

You really can't use the same interconnects since some of the devices handled different signal types. Are you using the same power supplies for each type when you are testing them?

For the two transports I did use the same digital IC.

Such as a regenerator? If you are not using a regenerator for power then as power changes over the day the supply may effect the devices being tested. Are all the devices similarly isolated across all tests setups?

Changes over the day are not relevant. I do the test over a short period and have repeated it several times at different times of the day. Always the same result. The devices are all plugged into the same extension box. no power conditioning.

Do you ensure that the CDs are operating at the proper speed?

Speed? These are crystal controlled. Speed variations are minimal from one unit to the next. Certainly not enough to be aubible, say from transport to computer.

A little change can make a big difference. How sensitive are you sound level settings when doing these tests?

Levels are identical. The preamp is not adjusted during the test. The DAC output is identical level with all sources.

Steve N.
Reply
post #102 of 112
12/25/06 at 7:55pm
Quote:
Originally Posted by drarthurwells View Post
Give me a week of comparison of two programs, and I bet I could do well - the one I said was better would have less jitter to a statistically significant degree.
Then just do it.

Quote:
Originally Posted by drarthurwells View Post
Experimental conditions can induce some anxiety that diminishes perceptual discriminations, and brief AB testing can induce perceptual confusion that we are unaware of but which impede/mask discriminations.
Why not. You seem to know awfully lot about experimental design and the pitfalls of various conditions. Instead of armchair criticism of those who at least tried to make a piece of solid research, why don't you design and conduct a better test?


Regards,

L.
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post #103 of 112
12/25/06 at 11:58pm
Thread Starter 
Quote:
Originally Posted by audioengr View Post
Jim - The low-jitter disk is ready to ship, and I included a little Christmas surprise while I was at it, knowing that you prefer Classical.

Steve N.
Many thanks - I look forward to this test.

Cheers

Jim
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post #104 of 112
12/28/06 at 4:32am
Quote:
Originally Posted by drarthurwells View Post
One other factor is amplification of error effects in a source. A very small error (in reading a CD) goes through many steps of processing and amplification before it even reaches a speaker or headphone. A small reading error can then emerge as much larger an error before reaching a speaker or headphone. Related to large scale chaos eventually emerging from an insignificant small beginning.
Any kindergartener who ever played the 'telephone' game can tell me that any message that goes through multiple carriers/iterations can end up much different from its origins.

If you're going to throw around a term like 'chaos theory' I expect a much more rigid scientific analysis. Otherwise you're just spouting off what you heard in some sci-fi movie, which is exactly why ezkcdude made the Jeff Goldblum reference.
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post #105 of 112
12/28/06 at 12:29pm
Originally Posted by drarthurwells:
One other factor is amplification of error effects in a source. A very small error (in reading a CD) goes through many steps of processing and amplification before it even reaches a speaker or headphone. A small reading error can then emerge as much larger an error before reaching a speaker or headphone. Related to large scale chaos eventually emerging from an insignificant small beginning.

Quote:
Originally Posted by Toe View Post
Any kindergartener who ever played the 'telephone' game can tell me that any message that goes through multiple carriers/iterations can end up much different from its origins.

If you're going to throw around a term like 'chaos theory' I expect a much more rigid scientific analysis. Otherwise you're just spouting off what you heard in some sci-fi movie, which is exactly why ezkcdude made the Jeff Goldblum reference.

Art: It's like making a copy from a copy, then a third copy from the second copy, then a fourth copy from the third copy, and so on.

The last copy is very different from the original - adulterated in many ways. The very small effects of jitter are magnified and distorted along the signal path, which is analogous to making copies along the way.

The basic premise of Chaos theory is that initial minor changes in a system can lead to cataclysmic or large changes down the road. I think this is analogous to the jitter situation where very small and insignificant phase errors can result in audible effects.

As far as experimental testing of such effects using brief AB test comparisons - unreliable. Give me a week with A and a week with B, alternating over six weeks, and then I could detect a small jitter difference and could reliably tell you if A or B were playing - could not do this in a few 5 minute trials of AB.

So, skeptics will ask why if it takes such experience to hear a problem that is not more readily discernible, then why is it a problem?

The answer is that we listen over extended periods and learn to hear the good things and the bad things over time, and then get dissatisfied with problems we learn to detect with much experience.

A CD player with high jitter will sound good at first, but over months will become unsatisfactory. Most AB testing is "at first" - like meet sampling - and should be over months to really be discriminating.
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