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What we measure is what we hear
Reply #75
Good work carried out by Toole and others aside:
Are there good measurement methods available that can prove that the spatial characteristics of two audio events will be indistinguishable in a blind test?

Read the last 10 posts or so again, and ask a different question! ;-)

All we can do in the blind test or any test is reject the hypothesis that there is an audible or other difference. We can't ever prove that any two sounds are absolutely indistinguishable.

The sensitivity of technical tests is such that we can always find a difference between two signals, particularly if they originate in acoustical events.

The sensitivity of really well-done DBTs is such that we can generally find a difference between two signals, particularly if they originate in different ways in an acoustical sense, even at the identical same event.  I haven't done any formal sensitivity studies, but I know that it is not always easy to find two microphones that match each other so well that they can't be distinguished by ear, even when they are as coincident as we can make them.

As has been pointed out by others, my experiences tell me that moving my head a foot, or changing its orientation by a dozen or two degrees makes things sound different. I know that if I'm doing a DBT involving small differences I have to hold my head in a consistent manner in order to obtain reliable detection near the threshold of audibility.

I think that measuring the behaviour of loudspeakers in a room (or microphones) in a perceptually meaningful manner is quite hard.

That depends on which perceptual meaning that you are investigating.

It is easy to find _some_ difference, it is hard to tag the relevant differences while discarding the irrelevant differences.

Obviously, the better job you do of reducing or eliminating the irrelevant differences, the easier it is to reliably detect the relevant ones. That's why the golden ears look so silly to people who have done a lot of good listening tests. Their so-called tests control so few things that their experiences are chock full of audible differences. Out of this thicket of audible differences they pick one subtle or non-existent thing such as the SQ of a DAC or amplifier, and write several pages of poetry about it.

People tends to move their heads, and HRTFs can vary quite a bit from person to person.

So when the golden ears fail to ever talk about the difficulties that are common in listening tests for these reasons, we have evidence about the reliablity of their conclusions.

Sticking a single omni B&K microphone at "sweet spot" does not tell us all there is to know about a loudspeaker/room system.

That would hardly be news!

Toole advocates empirical weighting of on-axis/off-axis loudspeaker measurements done in anechoic chambers, together with physical analysis of room geometry, but I dont think that approach is necessarily "perfect"?

You have not yet noticed that nothing in the real world is perfect or ever will be?

(Yoda-like laughter...)  ;-)

  • krabapple
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What we measure is what we hear
Reply #76
if perception really varied from moment to moment, we could as well argue that one day an individual could positively pass an ABX test and the other day fail

Which is exactly why a failed ABX test proves nothing.

By that token, a lone "successful" ABX  on Day 1 is not evidence enough to predict  that the subject would 'really' hear the difference again on Day 2.

Context matters.  Woodinville has outlined positive and negative controls that provide context for drawing more confident conclusions from an ABX text.

That said, when an 'audiophile' natters on about how exquisitely good their audio discrimination is, and then fails a simple ABX of the very abilities they claim to already have (e.g., "mp3s/standard resolution/mass market DACS/plain speaker cable sounds like crap to me.  I can tell every time.") ,  I don't worry too much about whether they were trained enough.  I just enjoy the show.
  • Last Edit: 03 January, 2013, 12:24:27 PM by krabapple