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Topic: AES 2009 Audio Myths Workshop (Read 171377 times) previous topic - next topic
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AES 2009 Audio Myths Workshop

Reply #350 –
Quote from: 2Bdecided on
I mean, you're not seriously saying people can't ABX tape, are you?


We *know* that people can ABX tape:

A friend of mine ABXs analog tape and wins. Really pretty good analog tape!

The point is that unlike some people, other people have done their homework. I'll bet money that so far, Dwoz and 2Bdecided have *not* actually ABXed Ethan's files.

AES 2009 Audio Myths Workshop

Reply #351 –
Quote from: Ethan Winer on
If the response is flat within 0.1 dB and the sum of all noise and artifacts is -100 dB, I'm confident calling a device transparent regardless of the nature of the artifacts.


I'll meet your 100 and  0.1, and bid 80 and 0.2. ;-)

If I get to be picky about  some things, even 70 and 3 can work.

You know vinyl generally measures just horrible, and can sound almost OK. Not that it can pass ABX.

That's because people had a century or so to hide a lot of the decay well below the "gum line".

AES 2009 Audio Myths Workshop

Reply #352 –
Quote from: googlebot on
As 2bdecided said, exact masking thresholds wouldn't be needed. Digital audio has become so good, that quite hefty safety margins could probably be tolerated without necessarily excluding too much gear. So why not just start and juggle some numbers? 2bdecided started with -120dB, Ethan could live with -100dB. What would be (not the maximum possible but just) a safe translation to FR, THD, IMD, IR, etc.?


Here are some reasonable assumptions:

(1) Clipping and broken or otherwise pathological equipent and other situations are avoided.

(2) Equipment tends to slide into the mud, not drop off a cliff. You rarely find 0.01 THD at 1 KHz and 10% THD at 1,001 Hz, all other things being equal, especially if you avoid clipping.

(3) Linear distoriton and nonlinear distortion tends to be worse at the frequency extremes, where fortunately, the ear tends to be a lot less sensitive.

(4) We are actually listening to music for enjoyment, not trying to collect pathological musical selections to make a point.

(5) People tend to operate equipment well below maximum power and SPL capabilties, and in rooms with some background noise and suboptimal acoustics.

Then, relaxed specs like 80 dB dynamic range and +/- 1 to 3 dB frequency response can be sonically transparent.

BTW 80 dB DR inherently presumes that all IM and THD are 80 dB down or better.

AES 2009 Audio Myths Workshop

Reply #353 –
Quote from: John Eppstein on
It is my contention that the state of the art of audio measurement and the state of the science of human audio perception at tis time are not accurate enough really adequately quantify what we're discussing.


John, it is easy to show that your ideas about state of the art of audio measurement and the state of the science of human audio perception  are from the stone age.


Quote
I'm not saying that the electronic measurement equipment isn't good enough - I'm sure it can measure the signal quite well.


And in ways that it is quite clear you have no working knowlege of. At least you've done a good job of hiding it and ignoring it when pointed out to you.

Quote
The problem is that we don't know how to interpret the measurements properly and in some cases we may not understand what needs measuring.


Again John, at your apparent hihgly limited level of understanding, that might be true.

There seem to be a lot of misapprehensions about what we don't know about these things - apparently even from people who should know better, as in they earned PhDs in related areas.

Quote
In terms of audio perception some aspects are fairly well understood, but other aspects - specifically how the brain handles perceptual information and how the perceptual systems encode information for transmission from the primary sensory organs to the brain are currently the subject of some very interesting research.


Research is ongoing, but a lot is already known. If we wait for the research to stop as you seem to be advising, we'll die without doing good things we can do now.

Quote
I think that in some ways we're attempting to do the equivalent of brain surgery with a dull pocketknife.


Yes, there are a lot of people massively pontificating here who are the equivalent of dull knives.

Quote
When people using a conventional testing methodology such as ABX say that they can find no perceptual difference between an inexpensive consumer quality converter and a $10,000 mastering converter but an overwhelming majority of professional engineers can pick out work done with each (and unanimously prefer the professional unit) that tells me that there's something wrong with the testing methodology. (I'm not saying that ABX is an invalid or unuseful tool, I'm just saying that it has limitations.)


John, you are picking your pros from a nest of bozos. There are pros who follow ABX very carefully. They just don't necessarily post a lot at places like gearslutz and the womb.  Places like the womb very obviously want to keep inconveneient truths away from its inmates.  They ban people who tell inconvenient truths. Sometimes after only 2 posts.

Quote
Science is supposed to be based on observation. We observe the world around us. We study our observations. We construct hypotheses explaining our observations and compare them to the behavior of the world; when they appear to fit they become standard (more or less) theory. We conduct tests of the theory and, as our technology progresses enough to provide sufficiently accurate tests, we prove the theory and it becomes law, or, unproven, it remains theory until a better explanation comes along.


Right, which was the thinking behind the development of ABX.

Quote
We do not throw out observation simply because it doesn't agree with conventional wisdom, especially when conventional wisdom is to a large degree based on simplification. The Catholic Church tried that with Galileo.


The guys who are still worshipping the $100,000 Studers  and banning people who tell inconvenient truths are the modern day equivalent of the 15th century pope.

Quote
A real scientist tries to find out those things that he doesn't know. He doesn't simply point to the establish body of knowledge and treat it like scripture. That type of person is a pedant, not a scientist.


Even worse are the people who don't know what the body of knowlege is, and treat their ignornace like scripture. Welcome to the audiopile and pro audio forums that either ban discussion of ABX or redicule it incessantly when it is mentioned.

Quote
(Please note that I am not endorsing ghosties, faeries, wizards, or  expensive sculptures that make your dentist's stereo sound better......)


No, we're talking about expensive sculptures that make some recording engineers LPs sound better...

You know there is a school of thought that says that Studer puts rediculous prices on some pieces of audio sculpture that people demand they make, simply because they want to stop the madness, and they *are* a business.

AES 2009 Audio Myths Workshop

Reply #354 –
Quote from: Ethan Winer on
Quote from: Arnold B. Krueger on
Schoepenhauers list: 38 ways to  win arguments by cheating. This list is over 100 years old!

Here's one strategy that's glaringly missing from the list:

When you are unable to defend your position, say "Go read a book, I don't have time to teach you the basics."



Missing?

Maybe not said explicitly, but there by implication.

14 Try to bluff your opponent.

15 If you wish to advance a proposition that is difficult to prove, put it aside for the moment.

18 If your opponent has taken up a line of argument that will end in your defeat, you must not allow him to carry it to its conclusion.

25 If your opponent is making a generalization, find an instance to the contrary.

28 When the audience consists of individuals (or a person) who is not an expert on a subject, you make an invalid objection to your opponent who seems to be defeated in the eyes of the audience.

29 If you find that you are being beaten, you can create a diversion--that is, you can suddenly begin to talk of something else, as though it had a bearing on the matter in dispute.

30 Make an appeal to authority rather than reason.













AES 2009 Audio Myths Workshop

Reply #355 –
Quote from: John Eppstein on
Quote from: Arnold B. Krueger on
Quote from: John Eppstein on
BTW, did you recap the power supply and do the bias adjustment on the Threshold? Because if you didn't you didn't give the amp a fair evaluation.


That would probably be a TOS 8 violation.


Why would applying proper maintainance to the amplifier be a TOS 8 violation?



Lack of substantiation of a claim of improved sound quality.

Quote
Do you understand what "adjusting the bias" means?


LOL! I was adjusting bias in 1960. I built the amp from scratch from my own design. You really don't know who you are talking to, do you? ;-)

Have you ever done sensitivity tests on bias adjustments. IOW adjusted and misadjusted bias to see what effect it had on audible and measurable perforamnce?

I have done this, of course.

Believe it or not, changing the oil does not make a difference in how a car runs, if the oil is still OK.

Quote
Do you understand why replacing electrolytic capacitors is necessary every few years to retain performance?


That is a patently false claim. 

I have equipment with electrolytics that is > 20 years old that meets and even exceeds origional spec. Sounds good, too. 

However, on a few rare occasions I've also had to recap equipment that grotesquely failed to meet spec after 2 years, and sounded pretty bad. The bad sound put the gear on the test bench and the test bench told all. The caps were at 10% of less of marked capacitance.

Quote
Do you really think that comparing a high quality device that is old, needs repair, and is operating out of spec to a new, cheaply build device that is virtually brand new is a fair test?


Of course not. That is both insulting and also an excluded-middle argument.

Quote
A new Camry will beat a Ferrari if the Ferrari hasn't had a tune up or oil change in 10 years. In fact, the Ferrari probably won't even start.


If you store a car properly, the oil will be just fine after a decade or more. The most common reason why cars don't start easily after long periods of storage is that the fuel drains or evaporates from places like the carb.

AES 2009 Audio Myths Workshop

Reply #356 –
Quote from: Canar on
Quote from: Notat on
The next question is which would they label high-fidelity? For me "high-fidelity" brings to mind my grandfather's open reel tube rig. That's the sound and era I associate with "high-fidelity".

Why not be more explicit and ask which has more "accurate reproduction"?
Because high fidelity means accurate reproduction.
Exactly.

Whereas Notat seems to be looking for an audio processor that makes things sound like a respected 1960s audio system. That processor could in fact be a respected 1960s audio system

Point is (and it's been made 20 times already) that's outside the scope of this discussion. We're discussing things that (hopefully!) don't change the sound, not things that do.

If you're claiming your 1960s audio system more accurately reproduces the sound at its input than a digital recorder and solid state amplifier, then that's within this discussion. We should be able to test both, and see whether none, one, or both of them are "transparent". If one or both are transparent, we've answered the question.  In the case that neither are transparent, we may be able to say which is "least bad".

If you're claiming you 1960s audio system sounds nicer to you than a digital recorder and solid state amplifier, then that's outside the discussion.

It's not irrelevant - obviously when you are choosing your home stereo, it's probably highly relevant.

But for sanity, we have (IMO!) to determine whether things change the sound, or not. Then you can pick any sound changing things you like - and when you have the sound you want, you can add other non-sound-changing things without losing the sound you want.

Cheers,
David.

AES 2009 Audio Myths Workshop

Reply #357 –
Quote from: John Eppstein on
Let's see - a few posts back you said the Delta card had noise 90dB down below 2K. So let's take 20 iterations of that.
90,87,84,81,78
75,72,69,66,63 (oops, worse than the Studer already)
60,57,54,51,48
45,42,39,36,33
30,27,24,21,18

That's right, after 20 iterations the noise floor of your Delta card is 18dB down below 2kHz. I'd say that's pretty significant, wouldn't you? In fact, I'd say that performance is pretty poor - far from "transparent".


I take it that you still haven't done any ABX listening tests of Ethan's files. Doing file based ABX on a computer is relatively easy. People who avoid it tell us implicilty about their real-world technical compentence and intellectual curiousity. Anybody can pick numbers off of a plot.


 

AES 2009 Audio Myths Workshop

Reply #358 –
Quote from: John Eppstein on
Let's see - a few posts back you said the Delta card had noise 90dB down below 2K. So let's take 20 iterations of that.
90,87,84,81,78
75,72,69,66,63 (oops, worse than the Studer already)
60,57,54,51,48
45,42,39,36,33
30,27,24,21,18

That's right, after 20 iterations the noise floor of your Delta card is 18dB down below 2kHz. I'd say that's pretty significant, wouldn't you? In fact, I'd say that performance is pretty poor - far from "transparent".
Noise doesn't add like that.

If you want to learn how it really works, that's good. I'm sure someone can explain it (and the real-world test itself is pretty trivial, even if you don't want to work through the maths).

If you don't want it understand it properly - i.e. if you want to maintain your current level of ignorance and argue from that position - then you'll disqualify yourself from this discussion.

Cheers,
David.

AES 2009 Audio Myths Workshop

Reply #359 –
Quote from: John Eppstein on
<snip soundblaster plots>

Which is supposed to prove exactly what?

What do sine waves have to do with real world audio signals?

And frankly, I'm glad to put up with a little bit of noise if the recorded audio sounds better.
You can't find something to record which that doesn't introduce noise or doesn't wreck the signal? How sad.

Maybe it sounds better to you because you like noise?

Quote
That's one of the problems with defining THD as a component of S/N, BTW. The S/N spec doesn't actually tell you anything at all about how it SOUNDS.

Measurements are meaningless if you don't know how to interpret them.
If there's an aspect of the sound blaster's performance that causes it to be ABXable, then this will show up in appropriate measurements.

FWIW to get these "decent" results, you have to use the right sound blaster card (quite an early one IIRC), in the right PC set-up, with the right drivers and software, at the "right" sample rate, and still keep away from 0dB FS.

If anyone thinks these measurements suggest that all cards from the Creative Sound Blaster range, in all circumstances, will measure and/or sound this good, they're totally wrong.

Cheers,
David.

AES 2009 Audio Myths Workshop

Reply #360 –
Quote from: Arnold B. Krueger on
What are the results of applying what you know about masking and the variable sensitivity of the ear with frequency to the rightmark curves you made? Presume that FS = 90 dB.
I didn't make them. I wouldn't asses audio codecs in this way. And now you're making me part of the measuring equipment! How on earth can that work?!


Anyway, I won't duck your question: Looking at the curves, my experience tells me (even without the labels) that it's gone through an MPEG-like filterbank and/or psychocoustic model based noise addition process. Hence my experience tells me that sine wave tests are pretty much irrelevant in this context (they won't reveal the faults of the codec), therefore these graphs are pretty much irrelevant, and whether the codec under test is any good will have to be determined using another method altogether.


Anyway, googlebot keeps explaining the point very patiently and compactly, so I don't think I need to repeat it.


Some numbers have emerged in this thread. That's a good start.

So let's be more rigorous: what is the test signal, how is it analysed.

Cheers,
David.

AES 2009 Audio Myths Workshop

Reply #361 –
Quote from: 2Bdecided on
Quote from: John Eppstein on
Let's see - a few posts back you said the Delta card had noise 90dB down below 2K. So let's take 20 iterations of that.
90,87,84,81,78
75,72,69,66,63 (oops, worse than the Studer already)
60,57,54,51,48
45,42,39,36,33
30,27,24,21,18

That's right, after 20 iterations the noise floor of your Delta card is 18dB down below 2kHz. I'd say that's pretty significant, wouldn't you? In fact, I'd say that performance is pretty poor - far from "transparent".


Noise doesn't add like that.

If you want to learn how it really works, that's good. I'm sure someone can explain it (and the real-world test itself is pretty trivial, even if you don't want to work through the maths).

If you don't want it understand it properly - i.e. if you want to maintain your current level of ignorance and argue from that position - then you'll disqualify yourself from this discussion.



Good point, David. I thought that he had picked those numbers off of some plot someplace. It appears that John picked those numbers from of where the sun shines not. ;-)

The larger point is important. Noise doesn't drop 3 dB every iteration because after a few iterations the noise sources are no way equal. The 3 dB rule only works for equal intensity noise sources.

For example, when the noise sources differ by 10 dB, the sum drops only a few tenths below the larger noise.

Here's the sequence from my noise sums spreadseet, starting at 90 dB:

1 -86.990  (3.01 dB drop)
-85.229
-83.979
-83.010
-82.218
-81.549
-80.969
-80.458
-80.000
-79.586
-79.208
-78.861
-78.539
-78.239
-77.959
-77.696
-77.447
-77.212
-76.990
20 -76.778 dB  (ca. 13 dB drop total, but only .322 dB drop for the iteration.

AES 2009 Audio Myths Workshop

Reply #362 –
Quote from: Arnold B. Krueger on
Quote from: 2Bdecided on
Quote from: John Eppstein on
Let's see - a few posts back you said the Delta card had noise 90dB down below 2K. So let's take 20 iterations of that.
90,87,84,81,78
75,72,69,66,63 (oops, worse than the Studer already)
60,57,54,51,48
45,42,39,36,33
30,27,24,21,18

That's right, after 20 iterations the noise floor of your Delta card is 18dB down below 2kHz. I'd say that's pretty significant, wouldn't you? In fact, I'd say that performance is pretty poor - far from "transparent".


Noise doesn't add like that.

If you want to learn how it really works, that's good. I'm sure someone can explain it (and the real-world test itself is pretty trivial, even if you don't want to work through the maths).

If you don't want it understand it properly - i.e. if you want to maintain your current level of ignorance and argue from that position - then you'll disqualify yourself from this discussion.



Good point, David. I thought that he had picked those numbers off of some plot someplace. It appears that John picked those numbers from of where the sun shines not. ;-)

The larger point is important. Noise doesn't drop 3 dB every iteration because after a few iterations the noise sources are no way equal. The 3 dB rule only works for equal intensity noise sources.

For example, when the noise sources differ by 10 dB, the sum drops only a few tenths below the larger noise.

Here's the sequence from my noise sums spreadseet, starting at 90 dB:

1 -86.990  (3.01 dB drop)
-85.229
-83.979
-83.010
-82.218
-81.549
-80.969
-80.458
-80.000
-79.586
-79.208
-78.861
-78.539
-78.239
-77.959
-77.696
-77.447
-77.212
-76.990
20 -76.778 dB  (ca. 13 dB drop total, but only .322 dB drop for the iteration.


OK, my bad. It's 4AM here and I have insomnia........ not thinking as clearly as I should be.

That Delta still has an awful lot of noise for an allegedly "perfect", "transparent", etc, device.

However, you guys seem to be missing at least one part of the equation - a good part of audibility has to do with the relative frequencies of the spurious products relative to the signal and how they relate harmonically. The less harmonically related they are, the more audible they become. So the actual "noise floor" (including THD as part of S/N) can be a very misleading figure.

AES 2009 Audio Myths Workshop

Reply #363 –
Quote from: John Eppstein on
However, you guys seem to be missing at least one part of the equation - a good part of audibility has to do with the relative frequencies of the spurious products relative to the signal and how they relate harmonically.


Now I didn't get a PhD flogging masking curves, but all of my readings of them say that harmonic relationships don't matter.

I think the reason for much of what we observe is that most musical sounds generate a lot of maskers, and they are often (but not allways harmonically related.

Therefore music generates a lot of maskers for distortion that is harmonically related, and not so much for dstortion that is inharmonic.

And that would be one reason why I keep harping on IM - because IM generates a mix of distortion products that are both harmonic and inharmonic.

Quote
The less harmonically related they are, the more audible they become. So the actual "noise floor" (including THD as part of S/N) can be a very misleading figure.


Actually, we rarely depend on noise to mask harmonics. The most common masker of harmonics created by equipment faults is harmonics in the music. Remember that many instruments generate more harmonics than the fundamental!

AES 2009 Audio Myths Workshop

Reply #364 –
Quote from: Arnold B. Krueger on
Now I didn't get a PhD flogging masking curves, but all of my readings of them say that harmonic relationships don't matter.
Actually, if you get raw data on individuals for tone-on-tone masking, there's some really strange stuff there - dips and peaks. It's probably not "harmonic" in the context of this discussion. It's probably beat frequencies vs in-ear distortion products vs critical bandwidth.

Cheers,
David.

AES 2009 Audio Myths Workshop

Reply #365 –
Quote from: dwoz on
Quote
Because high fidelity means accurate reproduction.
Soundblaster is therefore the "tiger woods" of the audio chain.
Sarcasm really has no place in this discussion. The argument doesn't centre around whether Sound Blaster is high-fidelity, it centres around whether Sound Blaster is high-fidelity enough. If we're looking for a good benchmark on what I consider high-fidelity, I would say something built around a Texas Instruments PCM1794A: http://focus.ti.com/docs/prod/folders/print/pcm1794a.html

However, I am hardly a professional electrical engineer and there may be higher-fidelity solutions out there. This is just the best solution that I've been able to find so far in my never-ending quest for audio knowledge.

On a moderation note: If there are specific instances where you think posters are in breach of the terms of service, please use the Report button. It's not always easy for us to discern which violations that you users have identified in the thread, and it helps us sort out public opinion. I am not particularly happy with all the ad hominem in this thread, but it is being employed by users that I tend to have a degree of respect for on an intellectual level, so my own approach is to wait for the flames to die down as they usually do.

AES 2009 Audio Myths Workshop

Reply #366 –
Quote from: Canar on
Quote from: dwoz on
Quote
Because high fidelity means accurate reproduction.
Soundblaster is therefore the "tiger woods" of the audio chain.
Sarcasm really has no place in this discussion. The argument doesn't centre around whether Sound Blaster is high-fidelity, it centres around whether Sound Blaster is high-fidelity enough. If we're looking for a good benchmark on what I consider high-fidelity, I would say something built around a Texas Instruments PCM1794A: http://focus.ti.com/docs/prod/folders/print/pcm1794a.html


At this point it appears that the disagreement would be over word forms. The PCM1794 is probably the *highest* fidelity chip around or close to it. So you're not asking for high fidelity, you are asking for highest fidelity.

Based on its low-volume asking price of about $16, it would appear to be a likely candidate for a 2-channel computer audio interface in the $500 range.

I'm sure you know that as a device for listening to commercial recordings, it is a study in the futility of overkill.  It might have a logical place in some higher end lab gear.  For general istening, everything after 100 dB is vanity. This one can be peaked up to 130-ish dB.

Also, the usual audiophool pubs will go on and on about how it has "chocolate-like" highs.

The nature of things is that in 3-5 years (if not today) the piece price will go down to something like $5 or less, and now it will show up in stuff in the under-$200 range.  A while after that a commodity verison of the same technology will be sold in large volumes for a buck or less.

Too bad you'd be forced to use this thing with grossly inferior audio gear such as your ears! ;-)


AES 2009 Audio Myths Workshop

Reply #367 –
I've split off some of the ad hominem back-and-forth into the Recycle Bin.

I'm not going to tolerate any of it in this thread from here on. Any post that even makes me think it could be taken personally will be binned with no consideration to its technical value.

C'mon guys, we can do better than this.

AES 2009 Audio Myths Workshop

Reply #368 –
Quote from: Arnold B. Krueger on
(4) We are actually listening to music for enjoyment, not trying to collect pathological musical selections to make a point.

(5) People tend to operate equipment well below maximum power and SPL capabilties, and in rooms with some background noise and suboptimal acoustics.

Then, relaxed specs like 80 dB dynamic range and +/- 1 to 3 dB frequency response can be sonically transparent.


I agree with all points except those two. We live in times where >100 dB dynamic range begins to come free with entry level mainboards. So it has become just unnecessary to constrain a black box specification to (what you call) "usual" use cases. The whole intention of the "black box proposal", as I understand it, is that a component could be called "transparent" with a "end of discussion" surety. Not limited to "usual" music, not limited to >30 dB listening environments. Transparent should mean transparent, wether you are a guy in your mansion's basement with a favor for academic, contemporary sound composition on $50000 speakers  or a regular guy enjoying country music in his living room. Allowing such may have been a constraint in the past, because it would have meant that only (severely over-engineered) high-end gear would have passed the test, but I think the world has moved on since then. Calling anything in the 80 dB region already transparent just opens the door for elitists calling it a poor man's spec sufficient for mass media consumption. But nowadays a poor man with good advice can buy gear, that could be called transparent by much higher standards than that.

AES 2009 Audio Myths Workshop

Reply #369 –
Quote from: googlebot on
Quote from: Arnold B. Krueger on
(4) We are actually listening to music for enjoyment, not trying to collect pathological musical selections to make a point.

(5) People tend to operate equipment well below maximum power and SPL capabilties, and in rooms with some background noise and suboptimal acoustics.

Then, relaxed specs like 80 dB dynamic range and +/- 1 to 3 dB frequency response can be sonically transparent.


I agree with all points except those two. We live in times where >100 dB dynamic range begins to come free with entry level mainboards. So it has become just unnecessary to constrain a black box specification to (what you call) "usual" use cases. The whole intention of the "black box proposal", as I understand it, is that a component could be called "transparent" with a "end of discussion" surety. Not limited to "usual" music, not limited to >30 dB listening environments. Transparent should mean transparent, wether you are a guy in your mansion's basement with a favor for academic, contemporary sound composition on $50000 speakers  or a regular guy enjoying country music in his living room. Allowing such may have been a constraint in the past, because it would have meant that only (severely over-engineered) high-end gear would have passed the test, but I think the world has moved on since then. Calling anything in the 80 dB region already transparent just opens the door for elitists calling it a poor man's spec sufficient for mass media consumption. But nowadays a poor man with good advice can buy gear, that could be called transparent by much higher standards than that.

But psychoacoustics have to come into it. EG if distortion below a certain level is inaudible a piece of gear with distortion below that threshold is transaparent as far as that parameter goes. Another piece of gear with more zeros in front of it in the spec isn't any more transparent.

AES 2009 Audio Myths Workshop

Reply #370 –
Quote from: botface on
But psychoacoustics have to come into it. EG if distortion below a certain level is inaudible a piece of gear with distortion below that threshold is transaparent as far as that parameter goes. Another piece of gear with more zeros in front of it in the spec isn't any more transparent.


I haven't said that. What's your point?

Going for only 80 dB is just so close to the absolute thresholds of human hearing, that it wouldn't take much effort to produce a positive ABX result for any device incapable of delivering more than that. Since the call was for a black box to determine transparency and not a question about what's sufficient for great music listening pleasure, I just found 80 dB to be not enough. Especially when taking into consideration how much more even budget gear is able to deliver nowadays.

AES 2009 Audio Myths Workshop

Reply #371 –
Quote from: John Eppstein on
What do sine waves have to do with real world audio signals?

Everything. Unless of course you think Fourier was wrong. Hint: He wasn't.

--Ethan
I believe in Truth, Justice, and the Scientific Method

AES 2009 Audio Myths Workshop

Reply #372 –
Quote from: Woodinville on
Ethan, you need much longer analysis windows on your spectrum plots, especially those at low frequencies. Also, for higher frequencies you might use uniform frequency scales to make looking for harmonics easier.

I'm pretty much a beginner with FFT. Several people at Gearslutz told me that Sound Forge's FFT has fatal flaws, so I have since downloaded the latest Rightmark analyzer. I did indeed notice that the skirts are much steeper when viewing those same Wave files. I just wish the Rightmark analyzer would let me play with the parameters without having to close the Wave file and start all over again each time.

I'd like to learn more about FFTs. I'm not a math guy, so I imagine I'll never fully understand all the nuances. But I'd like to try anyway. Should I start a thread asking for advice here, or in the Scientific Discussion section? If you or others can direct me to a site that has a clear explanation using English descriptions more than math, that'd be most excellent. This page loses me on the very first sentence:

http://en.wikipedia.org/wiki/Fast_Fourier_transform

--Ethan
I believe in Truth, Justice, and the Scientific Method

AES 2009 Audio Myths Workshop

Reply #373 –
Quote from: Arnold B. Krueger on
Here's the sequence from my noise sums spreadseet, starting at 90 dB:

1 -86.990  (3.01 dB drop)
-85.229
-83.979
    .
    .
    .
--76.990
20 -76.778 dB  (ca. 13 dB drop total, but only .322 dB drop for the iteration.

There's actually a much quicker way to calculate it. If you combine the same level of noise (uncorrelated of course) 21 times then the final noise level is square root of 21 greater. The square root of 21 is 4.58, which is 13.22 dB, so the final SNR is 90 - 13.22 = 76.78.

AES 2009 Audio Myths Workshop

Reply #374 –
Quote from: Ethan Winer on
Should I start a thread asking for advice here, or in the Scientific Discussion section?
Scientific Discussion would be a great place for such a thread.