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  • KikeG
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Help! Sacd Good Or Bad?
Reply #75
I agree pretty much with Pio's explanations and Frank proposals.

However, about the first, I think you don't have to confuse linear response with impulse/causal response. IIR filters, which are causal, can perfectly be linear in its behaviour. Linear refers usually to amplitude linearity, whilst the difference between IIR and FIR is mostly on the phase/time response.

I think that our ear, as a mechanical semi-linear minimum phase (IIR-style) device, won't differ much in its response with transients or with continuous signals, but I don't know enough about this to talk with authority. That's why I set up the lowpass audibility blind tests with impulsive high-frecuency contents inside a musical signal: http://www.hydrogenaudio.org/forums/index....4894&hl=lowpass

About Frank proposal, I think that as a first test, 96/24 compared to 96/24 -> 44.1/16 -> 96/24 would be enough.
  • Last Edit: 04 March, 2003, 03:52:19 AM by KikeG

  • KikeG
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Reply #76
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... but I think it's unfair to say that we cannot feel at much higher frequencies. I believe Christian was fair with his tests and that it somehow proves that the frequency range is more complex that what we currently know.

That's why I set up a similar test, but with a digital lowpass and critical musical signals, at the link at my previous post. Only one person I know of has proved to hear the 20 KHz lowpass, none a 21 KHz lowpass.

  • ExUser
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Reply #77
This is completely off-topic, but I just wanted to say that I always feel enlightened when the major names around HA come out for a high-signal-to-noise discussion. This is one of those times. Thanks, guys.

  • robUx4
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Reply #78
I just wanted to add something to my paleonthological (?)/biological theory. We are mostly made of water, which conduct ultrasonic waves very well. So there is a chance that we would be responsive to these even though it doesn't come direcly from the ear. The same way as we "feel" a low bass sound instead of hearing it.

So that would mean a headphone is probably not enough to conduct this test.
  • Last Edit: 04 March, 2003, 04:47:35 AM by robUx4

  • Pio2001
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Reply #79
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The human animal evolved from others animal that used to live in water. And in water the sound you can "hear" is much higher in the frequency range. The same way as our brain have a reptilian part (this is the technical name), maybe our body have some reminiscents of our origins.


Easily cheched : just to compare the hearing ability of a fish with the human one. But whatever result is got, it won't make human hear above 20 kHz...

But you're right about ultrasounds in the body. According to this paper, the human body conducts ultrasounds better than air.

  • user
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Reply #80
interesting study and paper about difference between DSD & PCM 24 bit/176,4 kHz carried out scientifically with abx/double blind,

here the short English paper pdf :
http://www.hfm-detmold.de/eti/projekte/dip..._paper_6086.pdf

German complete websites with pics etc, partly English citings:
http://www.hfm-detmold.de/eti/projekte/dip...m/xdslindex.htm

German complete Theses as pdf, 99 pages:
http://www.hfm-detmold.de/eti/projekte/dip...rbeit%20neu.pdf

short German pdf with pics:
http://www.hfm-detmold.de/eti/projekte/dip...vergleich_d.pdf

I hope, it wasn't posted before.

145 test subjects, all trained listeners in various ways, could not abx at all, they felt very frustrated finding no differences. Counting all samples, it was ca. 1450 vs. 1450, so pure guessing which sample was dsd and which was pcm 24/176,4

Only 4 guys could find difference under headphone conditions with guessing probability less than 5%.
at stereo mode, nothing at surround.


Find more studies or papers at http://www.hfm-detmold.de/eti/ , select German or English version http://www.hfm-detmold.de/eti/indexen.html and look under Theses.
  • Last Edit: 24 March, 2006, 10:00:32 AM by user
www.High-Quality.ch.vu -- High Quality Audio Archiving Tutorials

  • Pio2001
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Reply #81
I remember having read this. It must have been discussed somewhere already.

Their statistical model is flawed.

The statement that 2.76% of the completed tests yelded results within the range of "critical probability" (i.e. less than 5% probability of guesswork) is very funny.

If things went completely according to chance, 5% of the completed tests should have yelded results within the range of critical probability, since by definition, critical probability is 5% !

They give detailed information about the results they got. We should be able to see if some results are really significant. But we need to define what is a success and what is a failure.
Implicitly, their definition of a success is "one test at least got a result equal or better than a given score".
We must then specify a probability threshold according to the tested hypothesis. For example, if the possibility that there is an audible difference between DSD and PCM is high, we can use p<0.05. But if we consider this hypothesis as very unlikely, we have to demand a much lower p, so that the tested hypothesis, though unlikely, is still much more probable than chance.
Then we need to compute the minimum individual score s, so that the probability, for random guessing, that at least one people get a score superior or equal to s is inferior or equal to p.

I did not do this, but one of the 145 tests at least was significant, the one who scored 20/20.
They explain that a small click at the beginning of the playback might explain this success, though this click was not conciously audible.

  • SebastianG
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Reply #82
I wonder why they have chosen 176,4 kHz at 24 bits and not something that has a similar data rate like 16 bits. Garf once linked an interesting paper that compared DSD to PCM 176,4 kHz at 8 bits. The PCM thing still seemed to be superior in terms of SNR and linearity.

Sebi

edit: wording
  • Last Edit: 24 March, 2006, 11:04:28 AM by SebastianG

  • Pio2001
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Reply #83
Probably to stay close to real-world applications.