In article , Alan Murphy
wrote:
"Jim Lesurf" wrote in message
[big snip]

So. Can you now say what practical test/experiment you can suggest
that would be useful to test your hypothesis that the failure is due
to 'masking' rather than 'removal' of the audible difference?

When I wrote the original post with the term 'masking' I was not aware
that it has a particular meaning and significance in audio science, not
being familiar with the literature. Having read some relevant papers I
now realise that I should have replaced 'masking' with 'the test is not
sufficiently sensitive to reveal differences which may be present when
using some other method'. My apologies for not being sufficiently clear.

Well, that moves the goal-posts a bit. :-) But I don't think that it deals
with the real issue I was asking about. I will try to clarify further using
your restatement as a basis.

Hypothesis 1: Once the levels are equalised the test is not sufficiently
sensitive to reveal differences which may be present when using some other
method.

Hypothesis 2: Once the levels are equalised there are no perceivable
differences.

What test would allow us to discriminate between these two hypotheses? In
one case you draw a conclusion about the test. In the other about
perception. For these to be distinct proposals we have to try and do an
experiment whose observed results could support one hypothesis and not the
other.

If we are unable to determine a real test that could distinguish between
them, then in what way are the two hypothesis different?


The test that I proposed above would indeed reveal whether the AB test
is insensitive and to what degree, concordant with the scientific
method.

Sorry, I'm afraid I am not sure which test you are referring to here. Nor
therefore how it shows that - for the situation with audio and equalised
levels - it allows you to state "the test is insensitive" as opposed to
"any other differences than level are imperceptable".

I do not have enough knowledge of the subject to propose a test
that would detect low jnd differences in complex scenarios.

This, of course, makes it difficult to test the distinction between
hypotheses (1) and (2). But then, we can proceed according to the
usual scientific method....

The problems here can be expressed in two ways.

One is the 'Spock rule'. A difference which makes no difference *is* no
difference. i.e. that if when we equalise the levels we can't percieve any
difference, then in practice there is no difference so far as human
perception is concerned.

The other is the normal scientific method of avoiding adding in mechanisms
which are not needed to explain the observations. This implies that if we
can't hear a difference, then we can conclude that any difference is so
small as to be imperceptable *unless* we can devise a test suitable for the
situation that might falsify this assumption. In essence, Occam's Razor.

So I'd still be interested in seeing what experiment would allow us to test
you (modified) hypothesis (1) against (2). If we can't, we can presumably
assume that a percieved difference that vanishes when the levels are
equalised was due simply due to the difference in levels, and avoid adding
in other mechanisms. As I understand it, this is the normal scientific
method.

Does the above not seem reasonable to you?


Incidentally during my "googling" I did notice some suggestion that when
different signals are presented simultaneously to seperate ears much
smaller differences can be detected than when these signals are
presented to both ears serially. Any ideas on this?

Afraid I don't know. Although I would guess that it may be because
symultaneous signals can be compared 'directly' by the brain whereas
when presented serially this has to be a comparison between a current
signal and a 'memory'. (Even if the memory is an effect at a physiological
level, or at least below conscious memory.)


I have read about various types of experiments that indicate our perception
of things like dissonance depends upon both signals being present in the
same ear (or not). I'd assume that in part these things are due to
indvidual nonlinearities in each ear, and in part due to the ways the
signals are combined in the brain to give us spatial perception. But apart
from these generalisations, I dunno. :-)

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

[huge snip of anal material]

Jim, you've got your head totally up your arse about equalistion.

This was a total red herring.

Alan.

"You're still my favourite contributor on any ng" :-)

In article , Alan Murphy
wrote:
[huge snip of anal material]

Jim, you've got your head totally up your arse about equalistion.

Actually, all I was trying to do was see if your views were of any
value, and hence worth taking seriously.


This was a total red herring.

From what you now write I take it the answer is, "No", and that you accept
that the ideas you were putting forwards are not really worth considering.

OK.

Alan.

"You're still my favourite contributor on any ng" :-)

Funny way of showing it. If you like someone I'd expect you to be polite
and considerate towards them. Not evade their questions and then
duck out with a "head up arse" comment.

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

"Stewart Pinkerton" wrote in message
...
On Fri, 17 Sep 2004 08:25:55 +0000 (UTC), "Alan Murphy"
wrote:

"Don Pearce" wrote in message
...
On Thu, 16 Sep 2004 08:48:58 +0000 (UTC), "Alan Murphy"
wrote:

Because the DAC is much quieter and I can identify it
every time :-)

Alan


What do you mean by quieter - less background noise or less volume? If
the volume is less, then in use you would compensate by turning the
wick up a bit and end up with the same volume again. So to compare
quality you would still need to equalise the sound levels.

d
Pearce Consulting
http://www.pearce.uk.com

Both, but I was just trying to make a point really, Don, about
the difficulty of establishing proper procedures when testing
sensory descrimination. In the visual field, with which I am
familiar, very slight alterations in test procedure, such as
seperating contiguous samples by a few mm or so can
decrease discrimination of colour difference by an order
of magnitude. Presenting the samples, in series, in A/B fashion,
further greatly decreases discrimination depending on the time
interval between viewings. The differences are still there of
course but are masked by the method of testing.
Resort to instrumentation is not helpful in judging differences
below about 5 - 10 jnd's, depending on position in colour
space, due to the acuity of the visual system. I suspect the
same holds true for auditory differences.

That is *precisely* why level-matched time-proximate ABX (and ABChr)
testing has proven over many decades to be the *most* sensitive test
for audible differences in sound quality. One cannot of course
discriminate well between two sound sources played simultaneously,
unlike a side by side visual presentation, plus of course it's true
that our visual sense has significantly more acuity than our aural
sense.

Given the above, I never fail to be amused by all those 'high enders'
who insist that ABX is insensitive, and the only *real* way to
discriminate subtle differences is by living with the sound for
sevberal days or weeks, changing over the cabling in a leisurely
fashion. As you correctly note, if you do that with say a couple of
colour prints, you'll completely fail to notice quite serious colour
casts. Look at those prints in quick succession in the same light, of
course..................
--

Stewart Pinkerton | Music is Art - Audio is Engineering

Why if the visual sense is more cute than the aural can we get away with
greater levels of video compression than Audio compression before we begin
to notice the quality suffering? Why is the eye so much easier to trick?

"Alan Murphy" wrote in message
...
"Jim Lesurf" wrote in message
...
In article , Alan Murphy
wrote:
"Jim Lesurf" wrote in message
[big snip to avoid repeating my sequence of questions]

I think it might be clearer, Jim, if I just outline my views on the
subject and hope that you find this acceptable.

I'm afraid that your mode of response does not actually seem 'clearer'
to
me as you have not dealt with the main issue I was specifically asking
you
about. (Please see below.)

I agree that, for the results to be meaningful in AB testing, levels
should be equalised and regret that my devious attempts to wind up
Stewart were misinterpreted.

OK.

I do feel however that AB testing is possibly not a suitable test for
revealing differences close to 1 jnd and is accurate to perhaps 5
jnd.

[snip]

I appreciate that you may "feel" something. I also appreciate that you
might be correct. However, since you seem to be arguing on the basis of
taking an academic approach founded upon applying the scientific method,
my
questions were to invite you to apply this to your own statements.

As for a test to determine whether AB testing is sufficiently
sensitive
to distinguish small audio differences I would propose the following:
It
should be possible to determine minimum audible differences of 1 jnd
over a discrete range of frequencies on a test setup, say from 1000 to
15000Hz at 2000 Hz intervals. A set of digital AB samples to Red Book
CD
standard at normal listening levels would then be prepared, one of
which
would be a pure tone at each of the frequencies and the other would be
the same tone corrupted at alternate values by positive then negative
random increments of digital noise varying from 0 to 5 jnd. My
prediction is that an AB test on these samples would not be able to
distinguish differences of less than 5 jnd. Over to you.

My series of questions was partly to establish if I had understood you
correctly. Partly to establish what test you had in mind that could be
carried out and whose results could distinguish between your hypothesis
that the failure was due to 'masking' and the alternative hypothesis
that
the failure was due to 'removal' of the actual differences.

Unfortunately, your reply does not deal with this point.

I carefully arranged my series of questions so that all but the last
could
be answered fairly quickly and simply with a 'yes' or a 'no'. I would
have
preferred this as it seems clearer to me that your restatement. However
the
key question was the last one (restated above) so I'd like to know your
answer to this. Or do you accept that when you argue that the failure is
due to 'masking' this is no more than a personal belief?

The outline you give from visual experiments is an analogy. This may or
may
not be an appropriate analogy. To test this we would require a response
to
the question which you did not deal with.

So. Can you now say what practical test/experiment you can suggest that
would be useful to test your hypothesis that the failure is due to
'masking' rather than 'removal' of the audible difference?

When I wrote the original post with the term 'masking'
I was not aware that it has a particular meaning and significance
in audio science, not being familiar with the literature. Having
read some relevant papers I now realise that I should have
replaced 'masking' with 'the test is not sufficiently sensitive to
reveal differences which may be present when using some other
method'. My apologies for not being sufficiently clear.

The test that I proposed above would indeed reveal whether the
AB test is insensitive and to what degree, concordant with the
scientific method. I do not have enough knowledge of the subject
to propose a test that would detect low jnd differences in complex
scenarios.

Incidentally during my "googling" I did notice some suggestion that
when different signals are presented simultaneously to seperate ears
much smaller differences can be detected than when these signals are
presented to both ears serially. Any ideas on this?

Alan.


One of the main functions of the hearing system is as a comparator, of
sorts, in order to judge the orientation of the source of sound. So I would
guess the system is particularly sensitive to any differences between
whatever is entering the ears at a given moment in time.

"The EggKing" wrote in message
...

"Stewart Pinkerton" wrote in message
...
On Fri, 17 Sep 2004 08:25:55 +0000 (UTC), "Alan Murphy"
wrote:

"Don Pearce" wrote in message
...
On Thu, 16 Sep 2004 08:48:58 +0000 (UTC), "Alan Murphy"
wrote:

Because the DAC is much quieter and I can identify it
every time :-)

Alan


What do you mean by quieter - less background noise or less volume? If
the volume is less, then in use you would compensate by turning the
wick up a bit and end up with the same volume again. So to compare
quality you would still need to equalise the sound levels.

d
Pearce Consulting
http://www.pearce.uk.com

Both, but I was just trying to make a point really, Don, about
the difficulty of establishing proper procedures when testing
sensory descrimination. In the visual field, with which I am
familiar, very slight alterations in test procedure, such as
seperating contiguous samples by a few mm or so can
decrease discrimination of colour difference by an order
of magnitude. Presenting the samples, in series, in A/B fashion,
further greatly decreases discrimination depending on the time
interval between viewings. The differences are still there of
course but are masked by the method of testing.
Resort to instrumentation is not helpful in judging differences
below about 5 - 10 jnd's, depending on position in colour
space, due to the acuity of the visual system. I suspect the
same holds true for auditory differences.

That is *precisely* why level-matched time-proximate ABX (and ABChr)
testing has proven over many decades to be the *most* sensitive test
for audible differences in sound quality. One cannot of course
discriminate well between two sound sources played simultaneously,
unlike a side by side visual presentation, plus of course it's true
that our visual sense has significantly more acuity than our aural
sense.

Given the above, I never fail to be amused by all those 'high enders'
who insist that ABX is insensitive, and the only *real* way to
discriminate subtle differences is by living with the sound for
sevberal days or weeks, changing over the cabling in a leisurely
fashion. As you correctly note, if you do that with say a couple of
colour prints, you'll completely fail to notice quite serious colour
casts. Look at those prints in quick succession in the same light, of
course..................
--

Stewart Pinkerton | Music is Art - Audio is Engineering

Why if the visual sense is more cute than the aural can we get away with
greater levels of video compression than Audio compression before we begin
to notice the quality suffering? Why is the eye so much easier to trick?



No idea - it's a big subject and I believe you can effect an acceptable
animation with as little as 3 frames a second, but what interests me is am I
the only one who is noticing the truly crap 'digital' colour in movies these
days? Recently viewed films like Master & Commander and Northfork have
absolutely *terrible* fake-looking colour whilst Black Narcissus (nearly 60
years old), which I watched a few evenings ago, is a visual feast, even with
its 'hand coloured Himalayas'!!

Seems to me, that movies (like music) have only got worse in the last so
many decades!! (Not to mention the 'cocoa powder' effect on a lot of digital
TV pictures also!!!)

Keith G wrote:

what interests me is am I
the only one who is noticing the truly crap 'digital' colour in movies these
days?

No idea if its anything digital or otherwise, but whatever they filmed
the matrix on was utter garbage - you could see the grain on the film
easily.

On Thu, 30 Sep 2004 22:26:21 +0100, Ian Molton wrote:

Keith G wrote:

what interests me is am I
the only one who is noticing the truly crap 'digital' colour in movies these
days?

No idea if its anything digital or otherwise, but whatever they filmed
the matrix on was utter garbage - you could see the grain on the film
easily.

Probably done on purpose, to give that 'film noir' look.
--

Stewart Pinkerton | Music is Art - Audio is Engineering

"Stewart Pinkerton" wrote in message
news
On Thu, 30 Sep 2004 22:26:21 +0100, Ian Molton wrote:

Keith G wrote:

what interests me is am I
the only one who is noticing the truly crap 'digital' colour in
movies these days?

No idea if its anything digital or otherwise, but whatever they
filmed the matrix on was utter garbage - you could see the grain on
the film easily.

Probably done on purpose, to give that 'film noir' look.

Agreed. Its not like they didn't have the money or technology for a clearer
picture.

"Arny Krueger" wrote in message
...
"Stewart Pinkerton" wrote in message
news
On Thu, 30 Sep 2004 22:26:21 +0100, Ian Molton wrote:

Keith G wrote:

what interests me is am I
the only one who is noticing the truly crap 'digital' colour in
movies these days?

No idea if its anything digital or otherwise, but whatever they
filmed the matrix on was utter garbage - you could see the grain on
the film easily.

Probably done on purpose, to give that 'film noir' look.

Agreed. Its not like they didn't have the money or technology for a
clearer picture.


I believe the Matrix films have a deliberate green tint to depict 'being
inside the Matrix' but, interestingly, filmed only on 35mm it would
appear....?? (Too much location work for 70mm I suppose?)

My problem is with the predominance of 'hazy blue, dim/dark, nearly
monochromatic' pix like:

Gothika
Northfork
Payback

....all of which we have watched lately, in that order. (There are a great
number of other flics that are much the same, but which do not come readily
to mind.)

While the deliberate 'downtoning' of Northfolk depicts well the 'bleakness'
of the situation (at the cost of some stunning views of the Montana
vastness*), it being sandwiched by the other two, simply simply invokes an
'oh gawd, not another bloody dim, Hollywood 'blue' movie here!

It would be easy to take a cheap shot here and suggest that the
hazy/grainy/'digitised' modern films (as opposed to the lurid, Technicolour
oldies) mirror the modern, mass tastes for digital/ss music over
analogue/valve, but I don't think it's as simple as that - I have no problem
with grain (or even 'noise') and certainly prefer the use of *good* CGI to
the 'wobbly models' we've seen in many older films, but I can't help feeling
that 'movie' standards are actually on the decline, like everything
else...??

Coming Soon (mebbe tonight) - Gone With The Wind! (Believe it or not I've
never seen it - it's going to be very interesting from a colour POV, if
nothing else!)

'Audio' relevance in this post? - Easy, the soundtrack in Northfork is quite
superb throughout and *must* be heard! :-)


*Seeing the bitter, bleak shots of Montana in Northfork prompts me to ask
'how can a nation that once had the utter *balls* to deal with
conditions/terrain like that evolve into the nation of loud-mouthed,
fat-arsed couch potatoes we see on the box today? (Or is it just 'poor
sampling' - I'd like to think so....)