Audibility of "typical" Digital Filters in a Hi-Fi Playback
Reply #820 – 2014-12-01 19:23:37
If one is of the mind that, "People will be under tremendous, undo stress having to juggle three distinct sounds in their heads to determine which is which" [I'm not one of those people, but Stuart seems to be... What explain this difficulty then? http://www.avsforum.com/forum/91-audio-the...ml#post26141122 My selections of A and B were done entirely by my hearing alone, of an extremely subtle difference that took me over an hour to pull off, but the important point is I had no outside assistance from dogs, analyzers, etc.. [Using such external tools as these would have been correctly deemed "cheating", since it is then no longer a test of human hearing at all.] If the difference was always there, why so much difficulty as to take an hour? In the parallel thread I post the results of a double blind test with this note from the tester: http://www.hydrogenaud.io/forums/index.php...st&p=883067 Clearly Stuart is right in the stress that triple stimulus creates when differences are small.Here's an example. In taking a test one is on their honor to not only not cheat, but also to honestly give it their focused attention and to do the best they can, rather than randomly selecting answers without giving it a good listen. Everyone with me so far? OK, say while taking a test, three quarters through, you notice your correct number of responses is exactly 50% of the number of trials taken so far, clearly implying no real ability to differentiate A from B. Tell me, can we REALLY expect such test subjects to continue with the remaining trials giving it their "very best" effort? I doubt it. Instead of hypotheticals let's look at real results of a real sample:foo_abx 1.3.4 report foobar2000 v1.3.2 2014/07/11 06:18:47 File A: C:\Users\Amir\Music\AIX AVS Test files\Mosaic_A2.wav File B: C:\Users\Amir\Music\AIX AVS Test files\Mosaic_B2.wav 06:18:47 : Test started. 06:19:38 : 00/01 100.0% 06:20:15 : 00/02 100.0% 06:20:47 : 01/03 87.5% 06:21:01 : 01/04 93.8% 06:21:20 : 02/05 81.3% 06:21:32 : 03/06 65.6% 06:21:48 : 04/07 50.0% 06:22:01 : 04/08 63.7% 06:22:15 : 05/09 50.0% 06:22:24 : 05/10 62.3%06:23:15 : 06/11 50.0% <---- difference found reliably. Note the 100% correct votes from here on. 06:23:27 : 07/12 38.7% 06:23:36 : 08/13 29.1% 06:23:49 : 09/14 21.2% 06:24:02 : 10/15 15.1% 06:24:10 : 11/16 10.5% 06:24:20 : 12/17 7.2% 06:24:27 : 13/18 4.8% 06:24:35 : 14/19 3.2% 06:24:40 : 15/20 2.1% 06:24:46 : 16/21 1.3% 06:24:56 : 17/22 0.8% 06:25:04 : 18/23 0.5% 06:25:13 : 19/24 0.3% 06:25:25 : 20/25 0.2% 06:25:32 : 21/26 0.1% 06:25:38 : 22/27 0.1%06:25:45 : 23/28 0.0% 06:25:51 : 24/29 0.0% 06:25:58 : 25/30 0.0% 06:26:24 : Test finished. ---------- Total: 25/30 (0.0%) Notice what the feedback loop of results allowed me to do. I was able to positively identify a revealing segment and complete the test successfully. Without that feedback I could not determine that and stay with that segment. Doing this in trial mode does not work because once you think you have found the difference, you have to go and run the test again and by then you may forget what you had heard. The newer foobar abx plug-in makes that near impossible anyway because there is no help with re-selection of the precise segment. Another variation is second guessing yourself which is a serious, serious problem. You identify a difference and you listen and get a bunch of trials right. Without feedback you may wonder, "what if I am getting this wrong?" That is all that is needed to change the perception you had of the difference. Placebo works both ways. It can easily erase differences or make them sound different. Without feedback you would then get a bunch of trials wrong. With feedback you would know that you got off track and get back on and see confirmation of that in correct answer after correct answer. Our goals in these tests must be to do everything in our power to discover differences. Not see how many ways we could encourage a negative outcome by handcuffing the listeners.Although it still exists in the training mode, mid-test feedback has been removed from the current foobar ABX v.2 testing, now in beta, and when I saw that I thought it was a good idea. Scolding or praising a test subject during a test ["You are doing great!" vs. "You can't hear a thing. You might as well be flipping a coin." will influence at least the mood and disposition of the test subject, even if it doesn't technically bias the test results in one specific way or another. Per above, it is only a "good idea" if you want to force more negative outcomes.