|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
76.28.27.191
In Reply to: RE: Digital -still improving posted by Thorsten on April 06, 2016 at 08:33:59
>"no noise is audible"...
Well, if it's not noise, what else is it ??!!
Follow Ups:
Hi,
> Well, if it's not noise, what else is it ??!!
Here is the crux of the matter. Actually, head over to Audiostream.com, it has a good article by Jason Stoddart (from that company with a name I will not take into my mouth) on this whole subjectivist/objectivist kerfuffle.
What I'd like to add, is that common audio measurements have never been shown to have any positive correlation with perceived audio quality, as long as certain minimum performance levels are met.
Indeed, there is no single instance where we have a formal test that produces single number performance indicators that - if made better - reliably produce better sound.
It is my experience that it is fairly trivial to design audio gear where the frequency response is adequately flat to leave the room as biggest problem, with noise that is so low, even super quiet acoustically treated and isolated rooms have more and HD that is reliably lower than the Quad ESL63, which at least in the mid-range is probably still the lowest distortion loudspeaker bar non.
I am also quite aware of the limitations of the human auditory system. It is so much not like a microphone or speaker, what is amazing that we can even get any credible illusion of listening to music from the current mechanisms (including recording).
It is actually a learned process, I remember reading a story where a TV crew filmed the Bushmen in Namibia. When they tried to show them the recordings on the TV monitors the Bushmen could not see the images, all they saw were colored dots. You might say they could not see the picture for the pixels. Of the story may be apocryphal.
Anyway, unlike the "everything sounds the same" brigade I however am not deluded enough to think just because Frequency response, noise and distortion are below anything that can be heard/perceived in normal or even extreme systems we have eliminated all audible differences.
Let me take an example that is brutal. If you have a 120dB/20Hz tone, you are unlikely to be able to hear around 10 - 20% 2nd harmonics, but you likely will be able to hear 0.0001% if the 100th harmonic. Now no-one measures this high harmonics and in a single number like THD the high harmonics are usually totally swamped by lower order HD.
There are many facets in audio performance which are currently not covered by generally agreed, standardised measurements.
As I said before, in my experience such aspects as the precise noise-shaping algorithms in Delta Sigma system (which in theory at least are all supra-sonic in nature), Dither noise (possibly shaped), digital filter algorithms, the precise nature and spectrum of harmonic distortion (actually the intermodulation distortion products generally are more pernicious in terms of audibility), general time-domain performance (something most "flat response"speakers totally mangle) etc. all impact more than the difference between -110dB SNR and -140dB SNR (in isolation) or the difference between 0.005% THD and 0.0025% THD.
Ciao T
At 20 bits, you are on the verge of dynamic range covering fly-farts-at-20-feet to untolerable pain. Really, what more could we need?
"What I'd like to add, is that common audio measurements have never been shown to have any positive correlation with perceived audio quality, as long as certain minimum performance levels are met."
Thorsten: Can you suggest what those minima might be in re (1) stereo separation, and (2) permissible phase shift from either phono cartridge or tape head though to speaker input? I ask because I'd claim to have heard too little of the former and/or too much of the latter more than once, reliably (subsequently confirmed by measurement). There must have been some standards suggested by Bell labs or some such, decades ago, but if so, their importance seems to have been somewhat forgotten.
Jeremy
Well, I don't know how much dither-noise we can hear, in a playback device. But you could be right. Filter algorithms seem almost impossible to hear.But -I'm glad you said 'audio tests are limited'. This, because they want them to be -or the equipment isn't there (yet), to dig deep into the human auditory-system.
It was said at a presentation at RMAF (show) last year, that measurements were created for 3 things: design criteria, production consistency and to sell audio products.
You're right-in-line with these statements...
Edits: 04/06/16 04/06/16 04/06/16 04/06/16
Hi,
> Well, I don't know how much dither-noise we can hear,
If we are talking 16 Bit Data and we use dither only in the LSB (which may not be enough to be effective) we are in effect down to 81dB "analogue audio equivalent" SNR, which is marginally better than dual half track master Tape at 15IPS, or not...
I use "analogue audio equivalent" here to indicate a measurement and calculation process that is equal to an analogue device, like say a Studer Professional Tape master machine.
I would certainly class broadband noise at -81dB down from maximum as audible in the right circumstances.
My old Sony Boodokahn Walkman (my several Pro ones too) managed noise better than -60dB with Dolby (and had 12dB headroom - so in modern parlance that would count as -72dB) and that noise was extremely intrusive on headphones - but in the analogue days that is what you got, live with it.
> Filter algorithms seem almost impossible to hear.
As I have designed no commercial digital device ever that did not offer alternative filter options, you might want to seek them out for a listen and try for yourself. I find the differences between "FIR Brickwall" and "Slow "Rolloff Apodising" gross and I have a firm favorite too (hint, neither of the above).
> It was said at a presentation at RMAF (show) last year, that
> measurements were created for 3 things: design criteria,
> production consistency and to sell audio products.
>
> You're right-in-line with these statements...
And I totally agree with the last two.
The first, I strongly disagree. If we want evidence based design goals it is useless.
If you let incomplete measurements that carry no proof whatsoever of correlating with valid design goals dictate your design - you belong into a loonie bin.
That is not engineering, that is not science. That is not even rank empiricism (which is unjustly denigrated these days).
It is what Richard Feynman called "cargo cult science".
Except the guys who practiced cargo cults (or those who read the future out the entrails, coffee ground or stars) can be excused on the principle they had no way of knowing better...
With what we now call the scientific method dating back to ancient Greece and most people these days being not only literate (it helps) but also schooled in the scientific method and critical thinking (Southern USA excluded), never mind people with higher education, there is no more justification of the worship of the "THD Meter Needle" (or "SNR meter Needle", AP2, Prism D-Scope etc. et al.) than there is for caring about the "E-Meter needle" (SciTo).
Or possibly much less.
The E-Meter is a primitive lie detector that reacts reliably to skin resistance which together with the so-called "Audit Process" is in fact a pretty reliable detector if you are getting close to stuff that matters to the subject, unless (s)he is a pathological liar.
That does not make SciTo good science (on the contrary), but it does put THD Meter Needle worshippers (and their related ilk) into a place where even the E-Meter readers go - ROTFLMFAO...
A "measurement" gives a precise answer to the precise question. In fact, the more precise your question is, the more useful the resulting measurement (that is paraphrasing Shannon/Weaver's definition of information).
Precision is of course limited by the test gear. Sometimes even a 15K AP2 is "not good enough", some times a top of the line LeCroy 5GHz Analyser (think a nice house in a nice 'hood, like Kensington) is not good enough.
But if you formulate the question right, the answer will precise within the limitations of the test gear. And the answer will make sense. If you get it wrong, the answer will still be entierly accurate, but it will make no sense whatsoever.
It matter Jack how precise or true the answer is, it is not even the wrong answer, it is what your teacher would mark your essay as "failed, missed topic", unless you got the rights question first.
Now if you are like, totally out of the ballpark, totally off the reservation, way beyond the pale... Should you use THAT as the basis of setting design goals?
Elsewhere (PM me - I'll send you the link) I expounded my time meeting a senior designer of DAC and ADC chips for one of the market leaders. We met in the queue at the immigration in Peking in 2008. He was even a bit (not much) of an audiophile...
But when we talked business we were in different galaxies.
He described how he would get his bonus if he designed a chip that measured slightly better than the competition and cost slightly less (I like a fat Bonus, share options etc as much as the next guy).
At the time he was really happy, because his company's product (and his design) had been chose by Apple to replace British Wolfson Micro in all Apple products. we are talking about a huge sale.
When I asked him (as a semi audiophile with a fairly serious system and even a degree of love for music) if he ever evaluated his ADC/DAC chips by listening - I got an even blanker stare than I got from that working girl in Amsterdam when I asked her if hopping on the good foot and doing the bad thing did anything for her...
So, bottom line. Failed.
An "AA+"for effort, a "FF-"for achievement.
Me? I don't give a pair of fetid dingo kidneys about measurements, except as a way to confirm that things work the way I intended them too, but I'd never use them as predictor of quality.
Ciao T
At 20 bits, you are on the verge of dynamic range covering fly-farts-at-20-feet to untolerable pain. Really, what more could we need?
nt
I meant noise generated (by) the algorithms...In any case, the person who broke-down what measurement/specs are good for works for a co. that makes the highest-precision audio analyzers in the industry.
Edits: 04/06/16 04/06/16
.
Post a Followup:
FAQ |
Post a Message! |
Forgot Password? |
|
||||||||||||||
|
This post is made possible by the generous support of people like you and our sponsors: