In article , Paul B
wrote:
Thus spake Jim Lesurf: snipped
If subjects can't hear fairly large differences in a calibration
cycle, I can envisage 2 explanations. Firstly, some/many/most
subjects are fairly insensitive to variations & by definition, would
be wasting money by buying expensive audio equipment for sonic
reasons alone.

That may be so. However, if so, we would then have to be cautious
about trying to draw specific/individual conclusions from the above as
it is a generalisation. So some people *might* be able to hear *some*
differences when others cannot.

A maddeningly large sample may be needed.

That would depend on two factors, currently undetermined.

1) How small the fraction of the general population may be that can
actually detect a given, small, change. The smaller the fraction, them more
people in general you would have to test to get some reliable idea of the
number of people involved.

2) The extent to which such people are 'self identifying'. If it were the
case that those who keep insisting they can hear differences which others
cannon *can* do this, then they have identified themselves from the general
population. Thus if they then demonstrated in a suitable test that they
*can* do what they assert, then we can know they exist - although that in
itself won't tell us what fraction of the general population they
represent.

The snag, though, is that the general result of tests indicates that people
can't hear the small differences that they claim. Hence at present the
evidence is that the fraction of the population involved is between 'small'
and 'nil' according to curcumstances. i.e. a value we can't reliably
distinguish from 'nil'.

[snip]

The advantage of some of the ABX forms of test is that the comparisons
can be done on all sorts of time scales - under the control of the
test subject. So they can switch quickly if worried about 'memory' or
drifts in their physiology, etc. For some kinds of difference this
seems IIRC to produce enhanced sensitivity. But for others it shows no
sign of the subjects being able to hear any difference, on any
timescales people have employed.

Months? I ask because I've either replaced or upgraded equipment,
listened & made a mental note that I could hear no differences then
forgotten about it. Months later, I've played a particular piece of
music to be struck by how different it sounds.

Indeed, that happens to me over timescales from hours to months, using the
same equipment and source material.

However some of the tests I recently read about in the JAES, Audio Amateur,
etc, involved loaning some people a 'black box' for some months, and
inviting them to decide on an 'AB' or 'ABX' basis what it contained. This
was in one case apparently done because those being tested insisted that a
'quick' test was not 'sensitive', but prolonged listening would enable them
to be more discriminating. The reported results showed no foundation for
their belief.

[snip]


But only if the tests are valid & don't end up perpetuating a
fallacy. If it meant going back to the drawing board, so be it.

The problem with *if* here is that it is a speculation. That has no
real use in the scientific method *unless* you can then propose a test
which would distinguish you hypothesis from the competing ones...

Thus a given test *might* not be 'valid'. But to decide this would
require a suitable test, ideally also a proposed 'mechanism' for the
cause of the lack of 'validity' which the new test would probe.

You make it seem that I advocate rolling dice Yes, of course it's
more satisfactory to forward a displacing theory rather than merely
suggesting the existing one is flawed but where would we be if someone
was to suggest that lead in cosmetics was dangerous & others said that
they would continue using it until the doubter came up with a
substitute. As for speculation Jim, much good science has come from it.

Without that, we have to work on the basis of using the hypotheses
that are consistent with the evidence we have, and trying to avoid
adding mechanisms which the evidence does not require, or ideas we
cannot test.

Many things *might* be the case. But that does not tell us they *are*
the case. For that we require relevant evidence. Alas, "the evidence
does not agree with my beliefs" is not actually evidence... :-)

Until someone comes up with a watertight explanation why DB is
infallible or near as dammit so, I'll reserve the right to be sceptical
in the same manner that I've been sceptical of my own hearing. To sum
up,

No test method or experiment is "infallible". I am afraid that science does
not work like that. What it does it gathers evidence so we can use that to
assess how reliable or useful a given idea may (or may not) be. If you wish
for "infallability" then I'm afraid you will have to ask a theologian, not
a scientist or an engineer. :-)

I'm not suggesting that DB testing is completely pointless but IMO,
can't be relied upon as the sole means of testing, especially when some
use it as a club to bash people with the idea that most equipment
sounds essentially identical. I feel more comfortable with folks being
cloth-eared than folks having so-called golden ears!

I agree - but only if the speculation is testable and some evidence to
support it can be gathered and assessed. So if we say a given product is
'dangerous' we migh then regard it with caution, but then expect some
evidence to back up the assertion. If no evidence can be provided, we can
decide to regard the assertion as having no reliable substance.

We may change our minds at a later point if evidence *does* appear. But the
change of understanding should be based on evidence.

Otherwise we would have to work on the basis of never doing anything at all
because it "might be dangerous".

Slainte,

Jim

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