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Audibility of Jitter, Proposing a series of tests
Arnold B. Kruege...
post May 27 2010, 22:12
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QUOTE (udauda @ May 27 2010, 09:00) *
QUOTE (Arnold B. Krueger @ May 27 2010, 03:48) *
How many of the references that went into this page meet TOS 8?
2?




QUOTE
[1] yes- and it is quite well-known.

OK

QUOTE
[2] yes- done by Dolby.

OK

QUOTE
[3] objective measurements only- no need to meet TOS 8.

IOW, it sheds no light on audibility

QUOTE
[4] yes- and we have discussed it on this thread. Also there is an addendum from the authors.

The first link is broken, the second link's contents sheds no light on audibility

QUOTE
[5] not referenced above- no need to meet TOS 8.

IOW, it sheds no light on audibility

QUOTE
[6] no- written in 1970, well before David Clark's test in 1982.


IOW, it sheds no light on audibility.
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Soap
post May 28 2010, 00:06
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QUOTE (Arnold B. Krueger @ May 27 2010, 03:48) *
QUOTE
[4] yes- and we have discussed it on this thread. Also there is an addendum from the authors.

The first link is broken, the second link's contents sheds no light on audibility

Works here.


--------------------
Creature of habit.
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udauda
post May 28 2010, 00:11
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If you just stop being Asianophobic.. nah I'm just kidding. I totally understand your concern. Most of the listening test-related studies from asia do not really follow the proper DBT(BS.1116-1) procedure, thus end up being null.

[3] The paper merely discusses that jitter components in high-end systems are usually less than 1ns. Again, no need to shed light on audiblity.
[4] The Link works fine- an addendum from the authors works too. Another Link FYI.
[5] Again, not even mentioned in the presentation itself. Not sure if it meets the TOS 8. (wish I could obtain a copy)
[6] Certainly outdated. As you've said, does not meet TOS 8.

Except with [6], I still see the excerption as a good outline.

This post has been edited by udauda: May 28 2010, 00:14
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Arnold B. Kruege...
post May 28 2010, 00:31
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QUOTE (Soap @ May 27 2010, 19:06) *
QUOTE (Arnold B. Krueger @ May 27 2010, 03:48) *
QUOTE
[4] yes- and we have discussed it on this thread. Also there is an addendum from the authors.

The first link is broken, the second link's contents sheds no light on audibility

Works here.


Works here, now. I haven't changed anything.
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Arnold B. Kruege...
post Oct 11 2012, 17:00
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QUOTE (udauda @ May 27 2010, 09:00) *
QUOTE (Arnold B. Krueger @ May 27 2010, 03:48) *
How many of the references that went into this page meet TOS 8?
2?


No need for sarcasm. smile.gif

[1] yes- and it is quite well-known.


I have the paper right here before me, and it says quite clearly that the thresholds of audibility that it plots out were "calculated"

QUOTE
[2] yes- done by Dolby.
[3] objective measurements only- no need to meet TOS 8.
[4] yes- and we have discussed it on this thread. Also there is an addendum from the authors.
[5] not referenced above- no need to meet TOS 8.
[6] no- written in 1970, well before David Clark's test in 1982.


That makes the count of TOS8-compliant papers exactly 2, no?

(no sarcasm intended) ;-)
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punkrockdude
post Oct 11 2012, 21:01
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I have not read everything but here is a test I did with my Focusrite ISA828 unit with ADC, RME Multiface II and a Black Lion Audio microclock mkII.

The FLAC files are here and just line them up in a sequencer application and/or just listen.

http://www.interfearingsounds.com/blandat/..._comparison.zip
http://www.interfearingsounds.com/blandat/..._comparison.zip

For the lazy ones, here are the files phase flipped so that you can hear what's been nulled and not:

http://www.interfearingsounds.com/blandat/...se_flipped.flac
http://www.interfearingsounds.com/blandat/...se_flipped.flac

This has all been taken from my old topic over at TapeOP messageboard. http://messageboard.tapeop.com/viewtopic.php?t=70170
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punkrockdude
post Oct 14 2012, 13:38
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What's your opinion on the difference in audible difference in my last post? What makes the behaviour? Regards.
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Arnold B. Kruege...
post Oct 15 2012, 14:48
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QUOTE (punkrockdude @ Oct 14 2012, 08:38) *
What's your opinion on the difference in audible difference in my last post? What makes the behaviour? Regards.


Any possible audible differences are effectively masked by a gratuitous warbled tone.
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punkrockdude
post Oct 22 2012, 19:49
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QUOTE (Arnold B. Krueger @ Oct 15 2012, 15:48) *
QUOTE (punkrockdude @ Oct 14 2012, 08:38) *
What's your opinion on the difference in audible difference in my last post? What makes the behaviour? Regards.


Any possible audible differences are effectively masked by a gratuitous warbled tone.

Are you serious?
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Arnold B. Kruege...
post Oct 22 2012, 20:34
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QUOTE (punkrockdude @ Oct 22 2012, 14:49) *
QUOTE (Arnold B. Krueger @ Oct 15 2012, 15:48) *
QUOTE (punkrockdude @ Oct 14 2012, 08:38) *
What's your opinion on the difference in audible difference in my last post? What makes the behaviour? Regards.


Any possible audible differences are effectively masked by a gratuitous warbled tone.

Are you serious?


If *you* are serious, you'll post a log of your ABX tests based on these files, perhaps using FOOBAR2000 as your comparison software. ;-)
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punkrockdude
post Oct 22 2012, 21:40
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QUOTE (Arnold B. Krueger @ Oct 22 2012, 21:34) *
QUOTE (punkrockdude @ Oct 22 2012, 14:49) *
QUOTE (Arnold B. Krueger @ Oct 15 2012, 15:48) *
QUOTE (punkrockdude @ Oct 14 2012, 08:38) *
What's your opinion on the difference in audible difference in my last post? What makes the behaviour? Regards.


Any possible audible differences are effectively masked by a gratuitous warbled tone.

Are you serious?


If *you* are serious, you'll post a log of your ABX tests based on these files, perhaps using FOOBAR2000 as your comparison software. ;-)

Why I wrote the last sentence is because of "A gratuitous warbled tone" and "POSSIBLE audible difference" (capitalized two words), like if you didn't really care that much.
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2Bdecided
post Oct 23 2012, 11:14
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QUOTE (punkrockdude @ Oct 14 2012, 13:38) *
What's your opinion on the difference in audible difference in my last post? What makes the behaviour? Regards.
Your 05 file is a fraction of a sample earlier than your 04 file - i.e. they are not perfectly in sync. Hence they won't null out. It's somewhat difficult to correct for sub-sample delays - you'd have to add a sub-sample delay to file 05 to make it null properly. However, adding that sub-sample delay will typically change the audio a little, so it's tricky to rely on null tests in this case. It could be done, with the caveat that you'd have to ignore any differences that were due to the sub-sample delay, and hope no actual differences were hidden by this. It would be hard to convince people of the validity of a positive or negative result - especially in comparison with the convincing -100dB result you posted.

But there is some good news - the sync is good enough to run an ABX test, especially on any ABX test tool that doesn't try to implement (or lets you disable) perfect seamless switching.

Without trying an ABX test of the two files and posting your results, you have not demonstrated an audible difference. Expectation bias is too powerful a thing for anyone on this board to believe anyone who says "I hear a difference" without a passed ABX test to prove the fact.

Cheers,
David.
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punkrockdude
post Oct 23 2012, 12:26
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2Bdecided: Interesting about subsamples. So there is actually space that is smaller than the audio file's actual time limit (sample rate)?
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dhromed
post Oct 23 2012, 13:25
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File 2 and 3 null out almost perfectly. Amplification of that difference by 50 and then another 20 dB* produces a beautiful example of a quiet muffled song, drowning in a thick ocean of noise. Can we reject any chance of audible difference here right off the bat?

Also, I'm not sure why there are 4 files on offer, but only 2 inverted files. I didn't use the inverted ones. Was I supposed to compare 2/3 and 4/5?

4 and 5 have a tiny subsample difference, so the diff is a complete piece of music, but without the bass. I don't have the qualifications to explain why the bass region vanishes.

QUOTE
like if you didn't really care that much.


The warbled tone extends rather far into the sample, and I suppose it was a basis for Arnold to dismiss the samples immediately. I couldn't ABX any of it, in any case.

QUOTE
Your 05 file is a fraction of a sample earlier than your 04 file


How did you know 5 is earlier than 4? Better tools? smile.gif


*) Audacity apparently doesn't allow more than 50dB amplification in a single step.
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Arnold B. Kruege...
post Oct 23 2012, 13:32
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QUOTE (punkrockdude @ Oct 23 2012, 07:26) *
2Bdecided: Interesting about subsamples. So there is actually space that is smaller than the audio file's actual time limit (sample rate)?


There always is. Samples are always separated by a finite amount of time, and anything that is finite can be made smaller.

Adjusting files in increments of less than a sample can be done. What you do is upsample the file to a sample rate by an amount that is as high as you need to make it, or at least is as high as you can practically make it, do the adjustment on the upsampled file, and then downsample the file back to the original sample rate.

This will scare the %$#!! out of some people, but if you have good resampling software, it can have useful results.
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Arnold B. Kruege...
post Oct 23 2012, 13:41
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QUOTE (2Bdecided @ Oct 23 2012, 06:14) *
QUOTE (punkrockdude @ Oct 14 2012, 13:38) *
What's your opinion on the difference in audible difference in my last post? What makes the behaviour? Regards.
Your 05 file is a fraction of a sample earlier than your 04 file - i.e. they are not perfectly in sync. Hence they won't null out. It's somewhat difficult to correct for sub-sample delays - you'd have to add a sub-sample delay to file 05 to make it null properly. However, adding that sub-sample delay will typically change the audio a little, so it's tricky to rely on null tests in this case. It could be done, with the caveat that you'd have to ignore any differences that were due to the sub-sample delay, and hope no actual differences were hidden by this. It would be hard to convince people of the validity of a positive or negative result - especially in comparison with the convincing -100dB result you posted.

But there is some good news - the sync is good enough to run an ABX test, especially on any ABX test tool that doesn't try to implement (or lets you disable) perfect seamless switching.


Agreed. File synch is generally good enough if its within 1/100th of a second.

QUOTE
Without trying an ABX test of the two files and posting your results, you have not demonstrated an audible difference.


I don't think the OP did this consciously, but by not first doing his own test, he's effectively telling us that he doesn't have time to do things right, but figures that we have nothing better to do than to spend the necessary time doing his homework for him.

QUOTE
Expectation bias is too powerful a thing for anyone on this board to believe anyone who says "I hear a difference" without a passed ABX test to prove the fact.


I don't think he actually claimed an audible difference, thereby escaping the TOS 8 issue.

At any rate I fell for his ruse, tried to ABX the files and found the problem that I identified, which he now seems to want to pick a fight with me about. ;-)

He is either very ignorant or very arrogant. ;-)

I'm about ready to do the good old plonk thing. Should I spend the time to see where his IP address leads? ;-)

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pdq
post Oct 23 2012, 16:16
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QUOTE (dhromed @ Oct 23 2012, 08:25) *
4 and 5 have a tiny subsample difference, so the diff is a complete piece of music, but without the bass. I don't have the qualifications to explain why the bass region vanishes.

Taking the delta between samples a fixed time interval apart acts as a low-pass filter with a 6 dB roll off, until the period approaches the time delta. It then acts as a notch filter when the period and the time delta are equal.
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2Bdecided
post Oct 23 2012, 17:21
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QUOTE (punkrockdude @ Oct 23 2012, 12:26) *
2Bdecided: Interesting about subsamples. So there is actually space that is smaller than the audio file's actual time limit (sample rate)?
The sample rate sets a frequency limit, not a time limit. The waveform at times "between" sample points is very well defined. However, frequency components at or above half the sample rate can't exist in a baseband sampled system.

Cheers,
David.
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2Bdecided
post Oct 23 2012, 17:22
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QUOTE (Arnold B. Krueger @ Oct 23 2012, 13:41) *
At any rate I fell for his ruse, tried to ABX the files and found the problem that I identified, which he now seems to want to pick a fight with me about. ;-)

He is either very ignorant or very arrogant. ;-)
He might be confused. I couldn't follow your argument at all.
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2Bdecided
post Oct 23 2012, 17:30
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QUOTE (pdq @ Oct 23 2012, 16:16) *
QUOTE (dhromed @ Oct 23 2012, 08:25) *
4 and 5 have a tiny subsample difference, so the diff is a complete piece of music, but without the bass. I don't have the qualifications to explain why the bass region vanishes.

Taking the delta between samples a fixed time interval apart acts as a low-pass filter with a 6 dB roll off, until the period approaches the time delta. It then acts as a notch filter when the period and the time delta are equal.
Is this right? You're describing the comb filter you get when you add suitably delayed signals together. However, when you subtract delayed signals, I think the basic response is a high pass filter - and if the delay is increased to give a comb filter effect, the lowest frequencies are always attenuated - i.e. DC is always in a notch filter.

(don't take my word for this - far too sleep deprived to be 100% sure of anything today wink.gif )

Cheers,
David.
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Kees de Visser
post Oct 23 2012, 18:21
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To illustrate the importance of sub-sample accuracy in null-tests I made a new version with an 80 millisample delay manually switching in and out. It makes it easy to hear how much better the null is with the delay. I still can't get it as good as the RME though. It would be interesting to do some lab measurements with the device running on internal and external clock.
null-test flac
null-test wav
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pdq
post Oct 23 2012, 18:53
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QUOTE (2Bdecided @ Oct 23 2012, 12:30) *
QUOTE (pdq @ Oct 23 2012, 16:16) *
QUOTE (dhromed @ Oct 23 2012, 08:25) *
4 and 5 have a tiny subsample difference, so the diff is a complete piece of music, but without the bass. I don't have the qualifications to explain why the bass region vanishes.

Taking the delta between samples a fixed time interval apart acts as a low-pass filter with a 6 dB roll off, until the period approaches the time delta. It then acts as a notch filter when the period and the time delta are equal.
Is this right? You're describing the comb filter you get when you add suitably delayed signals together. However, when you subtract delayed signals, I think the basic response is a high pass filter - and if the delay is increased to give a comb filter effect, the lowest frequencies are always attenuated - i.e. DC is always in a notch filter.

(don't take my word for this - far too sleep deprived to be 100% sure of anything today wink.gif )

Cheers,
David.

Oops...I meant high pass. crying.gif

BTW, if the period is twice the delay then the signal is amplified 6 dB.
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Arnold B. Kruege...
post Oct 23 2012, 20:12
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QUOTE (2Bdecided @ Oct 23 2012, 12:22) *
QUOTE (Arnold B. Krueger @ Oct 23 2012, 13:41) *
At any rate I fell for his ruse, tried to ABX the files and found the problem that I identified, which he now seems to want to pick a fight with me about. ;-)

He is either very ignorant or very arrogant. ;-)
He might be confused. I couldn't follow your argument at all.


Even after listening to his samples?
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2Bdecided
post Oct 24 2012, 10:02
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QUOTE (Arnold B. Krueger @ Oct 23 2012, 20:12) *
QUOTE (2Bdecided @ Oct 23 2012, 12:22) *
QUOTE (Arnold B. Krueger @ Oct 23 2012, 13:41) *
At any rate I fell for his ruse, tried to ABX the files and found the problem that I identified, which he now seems to want to pick a fight with me about. ;-)

He is either very ignorant or very arrogant. ;-)
He might be confused. I couldn't follow your argument at all.


Even after listening to his samples?
Yes. They consist of a bell, then a guitar, and a bloke singing. Fine for the purposes of investigating the audibility of jitter or any other DAC error in a signal consisting of a bell, then a guitar, and a bloke singing wink.gif

Of course I agree about the necessity of ABXing, and the fact it's a possible audible problem.

Cheers,
David.
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krabapple
post Sep 24 2013, 17:52
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FWIW, here's a good faith attempt to supply examples of audible jitter


http://www.cranesong.com/jitter_1.html
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