"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?