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AES conference London: High Resolution perception, paper about listening test
Kees de Visser
post Jul 5 2007, 11:25
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Unfortunately I wasn't able to visit the june 2007 AES Conference in London about High Resolution Audio.
The paper/presentation about a high-res audio listening test seems interesting. I'm wondering if anyone on HA happens to have been there and can share some information.

preview of the paper session:
Monday, June 25 11:00 – 12:30
Paper Session 2 — Perception

2-1 Which of the Two Digital Audio Systems Meets Best with the Analog System?— Wieslaw Woszczyk,1 Jan Engel,2 John Usher,1 Ronald Aarts,3 Derk Reefman3
1McGill University, Montreal, Quebec, Canada
2Centre for Quantitative Methods CQM BV
3Philips Research, Eindhoven, The Netherlands

In this listening test, two digital audio systems (B and C), and one analog system (A) were tested by 10 test persons who listened to a surround sound scene “live” (without recording). The main question to be answered was: “Which of the two digital systems meets best with the analog system?” Both digital versions had 24-bit dynamic resolution but differed in sampling rate with which the analog signal was sampled. One version © was sampled with a CD rate of 44.1 kHz, the other (B) 8 times faster. There were also two test conditions, where in one condition there was a bandwidth cut off at 20 kHz instead of the 100 kHz that was possible with special 100 kHz microphones and added super-tweeters. For each subject, the experiment was replicated six times, in each of the two conditions. The outcome of each experiment was a 0 or 1, where the 1 means that the, technically best, digital system B has been chosen as meeting the analog quality. The paper describes the test and the outcome.

Without having read the paper, it's not clear to me whether the test was double-blind or not. Apparently it was not possible to replay sources, since the audio source was "live". How reliable would a test like this be ?
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post Dec 11 2007, 08:48
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QUOTE (Kees de Visser @ Dec 10 2007, 02:36) *
It's also important to know that only two sample rates were used: 44.1 and 352.8 kHz, derived from a 128xFs 5 bit delta-sigma modulator. It would have been interesting to know if popular standards like 96 and 192 kHz would behave differently. I can imagine however that time and budget were limited.

I found the choice of 352.8 kHz fairly interesting, but I suppose that deriving the signal from the same ADC with the same clock was the only way to keep the test fair. The paper is very light on the details of the design of the digital chain, which leads me to wonder what impact it could have had on the test results. DACs are known to change in performance (notably THD+N) with different sample rates (see the datasheets of most sigma-delta audio DACs for reference).
QUOTE (Kees de Visser @ Dec 10 2007, 02:36) *
Note also that only one brand of AD/DA converter has been used (Digital Audio Denmark). AFAIK it hasn't been tested if results remain identical with other brands.
Absolutely. The fact that the paper doesn't make strong conclusions about audibility, however, means that it's less important to reproduce the results of the trials to support the conclusions.

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