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Misleading Measurements


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19 minutes ago, The Computer Audiophile said:

Hi Paul, thanks for the thoughtful comments. 

 

As you can imagine, I see this differently, not with respect to your opinions of course, but with the efficacy of some measurements in light of the objectivist party line that berates audiophiles for talking about stuff that they believe can't be heard. I just don't see how objective leaning people can have it both ways, with a straight face. 

 

Objectivists often hate discussions of things like USB cables, claiming there are no measurements that can show a difference between them. The discussion often includes that these cables are bad for the industry, scare people away and mislead people into purchasing stuff they don't need. 

 

I see the discussion of inaudible measurements as being the other side of that coin. A DAC that measures -130 dB is worse than a DAC that measures at -131 dB. The better measuring DAC will be put on a pedestal and listed at the #1 DAC. This will no doubt cause people to purchase the DAC over others that may measure at -129 dB, -128 dB etc... It's human nature and there's no getting around it. 

 

Personally I don't mind the measurements and think adults can make up their own minds and purchase what they want. It just irks me that objectivists, who have goals other than looking at graphs to satisfy themselves, eschew one thing they claim is inaudible but consider the other inaudible items laudable. 

 

If we are solely talking about engineering feats of something like the lowest noise floor, then by all means show the measurements. But, that reminds me of the car audio competitions for the loudest sounds within the cabin of the car. What's the point. I suppose some people could purchase equipment for reasons other than listening and that's OK, but

 

Surely the audibility of jitter is something that objectivists can agree on. There must be a generally accepted number, below which is inaudible. Take that number and go lower by 10%. All jitter measurements below that shouldn't matter and can only serve to mislead people, if the accepted party line of objectivists is true and inaudible stuff doesn't matter. Thus, showing a pass fail for jitter should be the prudent way to display this info. 

 

Note: I'm not arguing for this position. I'm only pointing out what I see as a double standard and I'm seeking to understand why it's pushed so hard.

 

Well, audibility thresholds are not some voodoo magic, they are not a new concept. These can be (and have been) studied. I myself invested a lot of time and effort to create tools to aid in such studies. I wouldn't waste my time if I believed that everything is known and there's nothing new to learn in this space.

 

24 minutes ago, The Computer Audiophile said:

It just irks me that objectivists, who have goals other than looking at graphs to satisfy themselves, eschew one thing they claim is inaudible but consider the other inaudible items laudable. 

 

There's no accounting for tastes or preferences. A "true objectivist", if such a thing exists, would question any claims of audibility/inaudibility and look for real evidence to demonstrate that there is a correlation between some measurement and audibility, as well as measurements and preferences. Many of the papers I cite on the BIAS in Testing thread are designed to study exactly this.

 

33 minutes ago, The Computer Audiophile said:

if the reason for components is to listen, then it makes zero sense to care about that which is inaudible

 

Agreed!

 

 

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27 minutes ago, Currawong said:

I think that much of the problem with noisy, online "objectivist" talk is that it is based on a lack of genuine knowledge of what measurements show. I've noticed a recent trend for hyped Chinese DACs to show their low SINAD numbers, yet avoid showing the measurements of their leaky filters. The problem with both is that neither have their relation, if any, to what we actually hear explained. 

 

For example, how often do you read about the effect of digital filters on our perception of soundstage?  The claims regarding the effects of distortion down to -200dB were specifically related to this.  While running a file-based blind test to determine blatant audibility is interesting, basing it on comments/claims which are related to specific hardware is not the same thing.

 

What is more, I think the contradiction between "objectivists" seeming to claim distortion differences are inaudible one minute, and the next minute complaining about inaudible side-bands on SINAD tests, comes down to a significant number of them wanting to be part of the bandwagon, and blindly following whatever their at-the-moment chosen leader is saying, without having any actual knowledge themselves, let alone a desire to consider the blatant contradictions in their their beliefs. 

 

A major issue, which I have given an example above in my wording in the paragraph above, and I think which Chris' original post is also a good example of, is attachment to the same, repeated, simplistic ideas about both audio science and people, starting with the idea of anything, whether it be a measurement artefact or changing a physical product, being straight-up audible or inaudible, as with the huge variety of electronics and music we have available to us, as well as the complexity of it, these things clearly cannot be declared as absolutes using numbers.


Could you conceive that there are some objectivists that actually understand measurements, SINAD, jitter, filters, clocks, phase noise, etc, or are they all just ignorant? This being an objective forum, I’d like to see some objective evidence for your statement.

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2 minutes ago, The Computer Audiophile said:

 Paul says it has existed for quite a while. 

 

I'm losing track of what we are talking about. What data? Audibility thresholds? Of course this exists.

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1 hour ago, yamamoto2002 said:

 

You may be relieved to hear there is only Do, Do♯, Re and Re♯ between 16kHz to 20kHz

 

14,080Hz A    La
14,917Hz B(A♯)  La♯
15,804Hz H    Si
16,744Hz C    Do
17,739Hz C♯  Do♯
18,794Hz D    Re
19,912Hz D♯  Re♯
21,096Hz E    Mi
22,350Hz F    Fa
23,679Hz F♯  Fa♯
25,087Hz G    Sol
26,579Hz G♯   Sol♯
28,160Hz A     La

 

That's good news! 

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49 minutes ago, John Dyson said:

I have been thinking (honestly) about the matter of comparing sample rates, and how people DO sometimes hear differences.  Was thinking about errors in the experiments, and one error that seems to be very easy to make -- using not-linear phase filters in the conversions.  Let me explain:

 

The difference between say, minimum phase and linear phase isn't the wiggles that move around on square waves, but more the delay at low frequencies is very different than high frequencies on a minimum (or intermediate) phase filter.  This means that significant timing differences encroach into the audible spectrum.   The ONLY kind of filter where the delays are constant and the signal will remain maximally unmodified is a constant delay filter.  That means, 'linear phase'.

 

I haven't looked at any experiment in detail, because there are usually far more details missing than let any real evaluation be done.   As soon as 'software in a box' is used, I am not 100% sure that I trust its technical accuracy.   Anyway -- that is off topic,  it seems like there is a common 'tone control' (:-)) used by some audio people, choosing between linear phase, minimum phase and intermediate phase filter regimes.

 

An experiment about sample rates cannot be very consistent without using constant delay filters.   That doesn't mean, when all is said and done, the 'filter of choice' wont be used after the experiment.  But as soon as the delays are variable, then the results are in question when comparing the audibility of sample rates.   Again, after the experiment, use the filter choices that 'sound good' -- but the only way to do the experiments with not-linear-phase filters is to make sure that the delays are consistent between filter choices.

 

John

 

I didn't score well on the HD-Audio Challenge by Mark Waldrep, as an example. But I know a few others who scored perfectly, so there's something related to hi-res encoding or its playback that can possibly make these audible. I doubt that it has anything to do with the frequency response caused by the increased sampling rate between 44.1kHz and 96kHz. But then, the question is what is it? Is it the filter? The resampling in the DAC or the reconstruction filter? IMD with higher-frequency signals? Or are some ears just more sensitive to it than mine (I've no doubt that's true)? The reports of someone having useful hearing at 23kHz as an adult are possible, but very unlikely.

 

Here is a study result based on 384 test subjects of various ages. You'll note that the level of sound at 20kHz needs to be over 90dB to be detectable for age group 22-35 (and no, I'm not even remotely close to that age group!) The error bands go down to about 85dB level, so not much variation. I don't think I'd ever want to listen to a recording that had 90dB content above 20kHz:

image.png.252771ed6e2bbb1ecd9068eddb871d28.png

 

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3 minutes ago, ray-dude said:

 

I suspect it is differing levels of phase/timing sensitivity.  I'm definitely a phase/point source guy (on steroids) and have optimized my system around same. I've noted that when folks come over, some people are definitely more WOW for phase-related optimizations, and others barely hear them at all.  The later group seems to be more power/amplitude focused.  Some folks fall somewhere in between.

 

I guess the question is what phase differences are we talking about? A linear filter, by definition, will only introduce a constant delay. That same delay will be in both stereo channels, so the effect is inaudible while the music is playing. Unless you need to sync playback to video or to other devices that have a different delay, a linear filter shouldn't cause any phase issues. Of course, a filter could be poorly implemented, or some devices may use non-linear filters. In those case, I think it'll be worth testing for the audibility of the phase differences.

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1 hour ago, ray-dude said:

As a practical matter, in my room, ~1mm changes in speaker position is audible for me in this (very) artificial scenario (and since this is an objective forum, distance from my listening position to the same position on speaker drivers confirmed to be identical to within the ~2mm resolution of my laser measure

 

You do realize that you'll need to keep your head to ~1mm exact position in order to keep this precise phase alignment? Do you use a head vise? 😎

 

1 hour ago, ray-dude said:

If we were to naively translate that to frequency, at the speed of sound that implies ~340kHz hearing resolution.  My 53 year old ears tap out around 15kHz and clearly can not hear >300kHz tones.  However, I can hear phase timing differences with that level of signal timing resolution, in this (very) artificial scenario.  With a better treated room, I'm sure things would be much better still.

 

Actually, timing resolution has little to do with sampling frequency. A 44.1kHz/16bit redbook CD standard is fully capable of resolving timing differences well below 1µs, and higher resolution has more to do with the number of bits than the sampling frequency. Meanwhile, the lowest audible interaural time difference (ITD) reported in literature is 10µs, in other words, well within the capabilities of the redbook standard.

 

1 hour ago, ray-dude said:

For me, higher resolution sources (whether natively recorded or reconstructed with a sinc reconstruction function) has been about phase timing accuracy, not audibility of the ultra high frequencies.  Depending on the recording chain and performance of the components, that phase resolution may or may not matter obviously.

 

I understand your preference for hi-res, but I'm afraid it's not needed for higher phase resolution. 

 

 

 

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Just now, fas42 said:

 

That's the book learnin' explanation - but is not the reality. Anyone who has managed to evolve audio playback to the necessary quality knows what happens - it's quite trivial for an immensely complex soundscape to be perceived as being truly believable, at this standard of SQ.

 

Sorry, Frank, but that's false. Not just from books, but from my own experience. If you've not heard a properly instrumented 3-D audio with HRTF adjustment and head tracking, you should try it. There's no comparison to your "imagined" soundscape.

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44 minutes ago, fas42 said:

 

Don't you appreciate that there are multiple ways "for the mind to be tricked"? It can be done with the deliberately manipulated process you mentioned - or by having the clues available by a very high standard of playback. The soundscapes "inside the skull" are the same - if your mind decides that what you hear is the "real thing" then it hangs on to the illusion; and won't give it up readily ... you see, everything is "imagined" - our minds, internally, don't put instances "created by science" on a pedestal.

 

I do, and I also know that each mind and ear combination is different. When you claim you hear "realistic" soundscape it means absolutely nothing to me, since I don't know what it takes to trick your mind into believing something like this. Maybe your imagination is much better than mine. Or maybe your definition of realistic is not the same as mine. Or maybe your brain never adjusted to use your HRTF for sound location and compensated by using some other method, maybe ITD/ILD only. Or...? I can't see (or hear) into your mind Frank, so I can't tell what you can hear and what is enough to fool you.

 

With my system, I hear a very good approximation to a soundstage with very good tonal reproduction, with excellent dynamics. I hear depth and position of instruments, and I enjoy it immensely,  and have for about 20 years with only minor changes. And yet, it's not producing a real soundscape. I only occasionally (and mostly on binaural content) hear voices and noises that startle me, surprise me to the point of thinking it's coming from inside the house rather than from the audio system. I almost never hear the sound coming from my speakers, unless the sound is panned to be exactly at the speaker position. Most of the left-to-right sounds come from in between, with some coming outside the speakers. The soundstage depth is amazing on some content, and goes a bit in front of the speakers on other. But sounds never get close to me. They never envelope me to the degree that I can move my head around and feel like I'm there. That's what proper 3-D soundscape reconstruction does. It's the difference between a very good 2-D photograph and the 3-D world. At least to me.

 

 

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10 minutes ago, fas42 said:

Other people around me have appreciated the difference it made - which confirmed that I was not alone in hearing this ... people who couldn't give a damn about audiophile concerns just enjoyed listening to it; it "ticked the boxes".

 

I've had plenty of people say they love my system over the years. A few actually became audiophiles after listening to it, so you could say that it ticked at least some of the boxes. I'm not sure that proves anything 🤷‍♂️ 

 

I see that Alex is getting upset that we are veering off topic, so I'll stop here ;)

 

 

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16 minutes ago, The Computer Audiophile said:

I hear what you're saying, but a DAC that measures below the threshold of human hearing must also be in that "should just work" category correct?

 

Correct. But there are many more opportunities to mess up a DAC than a USB cable.

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3 hours ago, Audiophile Neuroscience said:

 

Hold the phone, is not the number of opportunities to mess up irrelevant? If in fact the DUT measures below the threshold of human hearing it "should just work" in that range below the threshold of human hearing, isn't that the assertion? So why report it is the question being asked. Things like price, aesthetics, build quality, and performance in the audible range are independent factors that people can use to guide purchase.


Already answered all of that.

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