Computer Audio Asylum: RE: Better duck under that desk; by Ryelands Music servers and other computer based digital audio technologies.

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Posted by Ryelands (A ) on August 1, 2009 at 04:35:48

In Reply to: RE: Better duck under that desk; posted by Werner on July 31, 2009 at 22:46:23:

Kristan wrote:

Problem is that the only accepted and allowable viewpoint is subjectivism; objectivism and scientific method is, perversely, ironically, treated as junk science . . .

The audio world is a bit like the “environmental” milieu except that the latter not only endorses “junk science” but lobbies politically on its behalf.

Common to both is that many who aggressively extol the supremacy of “scientific method” prove unable to subject their science to the most rudimentary scrutiny. They prefer to cherrypick papers on the basis of lightweight press reports and use them as intellectual cudgels.

I am wondering if this is the case with some posts in this thread.

deskducker wrote:

[Their] findings are quite different than the musings here.

I’ll reply, if I may, to Werner's points later but I’d like first to look at the Meyer & Moran paper as people are suggesting it refutes Kuchner’s work. (Werner reports that it has already been criticised by “objectivists” - whatever they are - but I haven’t seen that so apologies if I go over old ground.)

Sadly, (a) some of those who cite the paper appear not to have read it and (b) while it is on a related topic, it is nevertheless on a different one. Point (a) may explain why (b) gets missed.

The link that deskducker and Phelonious Ponk give is not to a journal paper but to a note on a blog about tests by “two veteran audio journalists who aren’t professional engineers” written by a third audio journalist, The Audio Critic editor, Peter Aczel.

As polemics go, it’s harmless, knockabout stuff but it tells you little about what the paper says and less about how to get hold of it.

Deskducker’s question, “Have any of you read the Audio Critic Double/Blind study?” is thus confusing: the answer can only be “No” because there isn't a pertinent study by The Audio Critic .

What there is is a September 2007 article in the Journal of the Audio Engineering Society written by AES members E Brad Meyer and David R Moran under the auspices of the Boston Audio Society (BAS) of which they are members and former officers. I eventually found their paper at:

http://drewdaniels.com/audible.pdf

The BAS has a follow-up note describing the test equipment used at:

http://www.bostonaudiosociety.org/explanation.htm

Kuchner’s papers report a five-year experimental program assessing “the human discriminability of temporal convolution” with tests that “employed either lowpass filtering or delays due to spatial misalignment” using “special ultrahigh-fidelity equipment” and showing “discernment at a ~ 5 microsecond timescale” which proved to be “much shorter than found previously”. (Editors demand this turgid stuff.)

Moran and Meyer, on the other hand, report “a series of double-blind tests comparing the analog output of high-resolution players playing high-resolution recordings with the same signal passed through a 16-bit/44.1-kHz ‘bottleneck’. [snip] The test results show that the CD-quality A/D/A loop was undetectable at normal-to-loud listening levels, by any of the subjects, on any of the playback systems.”

In short, their subjects were unable to distinguish the sound of SACDs played on a range of more or less high-end audio setups with the sound of the same SACDs after converting their output to 44.1 KHz using a “well-regarded professional CD recorder”.

However, unless I’ve missed something, their experimental procedure was so casual as to undermine the reliability of their results. That doesn’t, of course, mean that they were wrong, only that you can’t tell either way from their study.

Note that the paper was asking if SACDs sounded better than CDs, not whether 44.1 KHz recording could capture the finest nuances of “temporal convolution”. If it was, it would have had to demonstrate (as Kuchner did with his) that their apparatus was capable of reproducing such detail. It didn't do that.

1. In all, 554 trials were conducted but it is not reported how many subjects were used or how many trials each performed. Sixty were members of the Boston Audio Society but what proportion of the total they comprised is not known. They are likely to have known the authors. If the tests were non-judgmental and the subjects unaware of their purpose, this might be acceptable but neither condition is reported as being met.

It is the ABC of psychological experiment that subjects tend to provide “good” results and subject selection and procedure design must allow for that. This was not done.

2. The trials were conducted at four sites with different audio setups though most were done at the first, a moderately high-end domestic setup. Unfortunately, the first “well-regarded professional CD recorder” used proved to be faulty and the second, for whatever reason, unsuitable:

The first of these trials was done with the Pioneer player, and the fadeup of the room tone at the beginning of the Hartke disc revealed a slight but audible nonlinearity in its left channel decoder. We did some tests with the Sony, which sounded clean at any gain setting, and then switched to the Yamaha DVD-S1500, which was used for the remainder of the tests at this site.

The text implies (it’s not clear) that the Pioneer was used for three months. It is not reported that results obtained with the faulty device were discarded or what proportion of the total they represented.

Details of the second site seem to have been lost:

I do not currently have a detailed equipment list for this venue, but the speakers were very large and capable high-end monitors, approximately 7 feet tall, and the power amps were sufficient to drive the speakers to very high levels without audible distortion.

3. It is not clear that the test discs used actually reproduced the quality claimed for SACD (though the recordings were reported as musically very fine).

. . . we did a trial using the only disc we came across with an acoustic/electronic noise floor lower than our CD link [snip]. We advanced the gain beyond our nominal setting by 20 dB and used the player’s A-B repeat to loop through a short segment containing only room tone and a couple of extremely quiet musical notes. The noise of the CD loop was easily audible at the listening chair.

4. Over twenty SACDs were used for the trials (some but not all are listed). Subjects could choose which tracks to listen to but the choices are not recorded.

Although the authors note that “The two variables that determine whether differences would emerge, in our experience, were the source material (of which very little is quiet enough) and the system gain”, there is not only no record of who listened to what or when but subjects were allowed to alter gain settings in ways that are not recorded.

5. Some trials were sighted, some unsighted but the procedure used is not recorded. There was no control set.

All of these are serious omissions but the last lot are showstoppers. At the end of his or her first year, a psychology student making such howlers might be asked tersely by their tutor, “Have you considered Media Studies at all?”

In summary:

1. The Meyer and Moran paper reports very sloppy experiments. It doesn’t follow that their thesis is wrong but only a lay reader would claim that they provide competent proof either way.

2. Even if they were robust, the results are irrelevant to an assessment of Kunchar’s work and most certainly do not refute it.

3. The point most at issue in this thread is whether Kunchar's results mean that 44.1 KHz recordings are (or are not) “perfect sound forever”. That is a proper debate to hold but Meyer and Moran’s paper has no more part to play in it than cheap abuse about dog dirt posturing as scientific insight. Let’s move on.

Dave

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