An interesting paper on jitter audibility - Page 3

I wasnt referring to this test. I mean in general.

Don't try to Jeff Goldblum me, buddy! I know what chaos theory is, and it doesn't say anything about jitter. This is a fancy marketing technique that is used all the time in audio. Tell me, how exactly does chaos theory govern jitter? I'd really like to know.

Yep, folks, this is another classic argument that shows up again and again. It smacks of truthiness. It seems like it could true, yet somehow, there is absolutely no evidence of this effect.

More of the same.

Jitter is no different than other aspects of high-end audio. If your system is not set-up well acoustically with superb resolving components and cables, then you probably cannot hear half of what we are talking about, whether its detail, imaging or jitter..... This is why drawing any conclusions from this study is tenouous at best. The systems used have questionable quality. Every system is at some level of perfection, there is just no way of telling where these were, at the bottom or the top. More likely in the middle IMO.

I suppose if you said you had a Bose system in your whole house and you could not tell the difference in jitter, then that would be a data point. For those that have Bose whole-house systems, you will probably not hear even high levels of jitter.

Steve N.

Originally Posted by drarthurwells:
Chaos theory at work. An extremely small (or minor) event can have catastrophic effects down the chain-of-causality road - a very small amount of jitter can go a long way in later effects on the sound.


ezkcdude: Don't try to Jeff Goldblum me, buddy! I know what chaos theory is, and it doesn't say anything about jitter. This is a fancy marketing technique that is used all the time in audio. Tell me, how exactly does chaos theory govern jitter? I'd really like to know.

Art: If you knew anything at all about Chaos theory you would know it is about events in general and is not restricted to a particular event. So it can apply to the case where any slight change can eventuate in large scale changes. Jitter is slight change that can lead to problems in sound quality at a large level of change.

Art: Repeated trials over many days of listening to more-jittered and less-jittered music will eventually bring this initial vague peception into full focus as we later realize the jittered music is really bad. Human perception can be very unreliable - any listening tests that don't allow much listening experience to both A (very slightly more jitter) and B (very slightly less jitter) may not show discrimination abilities between the two.

ezkcdude: Yep, folks, this is another classic argument that shows up again and again. It smacks of truthiness. It seems like it could true, yet somehow, there is absolutely no evidence of this effect.

Art: Twenty five years ago I bought a top Sony ES model CD for my system. A friend, who also had high end equipment, participated in some tests. First I cued up a CD on my Sony CDP with the exact CD being played on a nearby FM classical station, which I had tuned to with my high end FM tuner. I blindfolded my friend who tried to pick the better CDP sound from the same CD on FM, as I switched back and forth at the same volume.

He could not tell which was which in AB testing. Then I did the same with a tape made of a CD with the same CD being played in synch on the CDP I used to make the tape with. Again he could not reliably tell which was which in AB switching.

Then he listended repeatedly to a short passage from the CDP. He knew it was the CDP. Then we did the same with the tape. Then we repeated this AB where both A and B involved repeated listening to one before switching to the other. This allowed him to learn the sound. He then was able to state that the CDP had the better sound, but more importantly, was now able to reliably tell which of the two was playing while listening to the AB switching blindfolded.

AB only works when both A and B are for extended periods to allow adequate perceptual learning. Eyewitnesses to crime often make the wrong ID of suspects but are 100% accurate if they know the criminal before the crime. A long period of perceptual experience is best for perceptual learning to yield valid perceptual discriminations (visual or auditory).

And BTW, what does it mean when you say I "Jeff Goldblum you"?

Is that something you can tell me in public?

an excerpt from the Audio Precision Application Note 5: Measurement Techniques for Digital Audio


[Jitter] Audibility considerations

It is one thing to be able to identify and measure sampling jitter. But how can we tell if there is too much?
A recent paper by Eric Benjamin and Benjamin Gannon describes practical research that found the lowest jitter level at which the jitter made a noticeable difference was about 10 ns rms. This was with a high level test sine tone at 17 kHz. With music, none of the subjects found jitter below 20 ns rms to be audible.

This author has developed a model for jitter audibility based on worst case audio single tone signals including the effects of masking.
This concluded:
“Masking theory suggests that the maximum amount of jitter that will not produce an audible effect is dependent on the jitter spectrum. At low frequencies this level is greater than 100 ns, with a sharp cut-off above 100 Hz to a lower limit of approximately 1 ns (peak) at 500 Hz, falling above this frequency at 6 dB per octave to approximately 10 ps (peak) at 24 kHz, for systems where the audio signal is 120 dB above the threshold of hearing.”

In the view of the more recent research, this may be considered to be overcautious. However, the consideration that sampling jitter below 100 Hz will probably be less audible by a factor of more than 40 dB when compared with jitter above 500 Hz is useful when determining the likely relative significance of low- and high-frequency sampling jitter.

Have you ever seen Jurassic Park? If not, rent it.

drarthurwells: Just a heads up, in that long reply to ezkcdude you seem to have completely forgotten to provide any actual evidence, or even a coherent hypothesis, of how chaos theory applies to jitter being something that's audible, or to cite a source that does.

Well he doesn't really have to. One of the tenets of chaos theory is that in chains of correlated events a small change early on in the chain can have much larger consequences farther down the chain. This is related to the problem of statistical error propagation. The question then becomes, is a chain of audio components long enough for significant error propagation effects to be detected? Discuss ...

hciman,

Thanks, for posting this. It is very enlightening. It shows two very important things: 1) Jitter is detectable, but only at much higher levels than you would guess from these forums and 2) The evidence from the second paper is even more striking because it does show that trained professionals, whose living is based on their ears to a large extent, do appear to be better at detecting jitter. This second point is interesting, because it is often claimed by jitter-busters, and now we can at least have some evidence for that. However, if one wants to cite this aspect of these Japanese researcher's work, then one must also acknowledge that, in absolute terms, jitter should not be audible in the amounts that exist in our stereo systems (unless it is artificially generated). I would suggest that whatever changes people hear when they measurably improve jitter in their systems are not due to the jitter itself, but rather to other changes in the signal chain. Chaos? I don't think so.

Don't mean to be rude but I find the above statement very odd coming from someone who is (or claim to be) an audio engineer.

An audiophile can self-proclaim to have golden ears and defy all logic (I can hear the difference because I believe there is a difference, despite all measurements indicate otherwise.) But an engineer, being a man of science, should correlate his/her observations with the measurements before coming to a conclusion.

To say that measurements do not reflect what's audible is saying audio engineering is black magic; and black magic is not engineering because it's not based in science. Now it's possible the measurements (good or bad) do not correspond to what you hear, simply because the instrument is not made to measure the particular aspect of the audio spectrum of your interest, but that is not an excuse to ignore measurements in its entirety and its implications.