Mark DeBellis wrote:
On 24 Jun 2005 01:09:45 GMT, Gary Eickmeier
wrote:


You can't do a "quick switch" test with two sources that run at
different speeds because you can't synchronize them, which would be a
dead giveaway in itself, so that is a bad example.

If you want to use that example, you will have to listen first to one,
then the other, in its entirety, then decide if the speed difference is
audible. If so, then do a blind series, listening to a known version,
then to a randomly chosen one, and decide whether it is the same or
different. In this manner you will eventually arrive at a number for a
speed differential that is at the audible threshold. That is the basic
idea of how audio research is done. You may find that speed differences
of 1.01 will be inaudible to most, but audible to some with perfect
pitch. If this is interesting enough a question for you, then do the
research and report it.


p.s. Suppose one carried out research such as this and found, for a
given one-minute-long excerpt, what is the audible threshold. So a
given subject could reliably discriminate between the excerpt and a
version that is 1.01 as fast (say). What theoretical reason would we
have to think that, if we did a quick switch test (see my previous
email for a suggestion about how to do it), the subject would be able
to tell the excerpts apart in that test?

Because the difference in pitch would be the way you'd be telling them
apart. (You certainly don't think you can tell the difference between a
passage that is 60 seconds long and a passage that is 60.6 seconds
long, do you?) And we know that differences in pitch are much easier to
detect when you can switch directly between the samples.

I don't understand the point about perfect pitch, because I am
supposing that one version is faster than the other, not that the
speed and pitch are both higher (as would be the case with analog
tape). Maybe I am not seeing your point though.

If one version is faster than the other, then the pitch will be higher,
whatever the medium. The only exception would be if you were to use
digital signal processing to correct for this. In that case, you
probably won't be able to tell them apart without a stopwatch unless
the difference is substantial. Our resident conductor would presumably
do somewhat better, because she is trained to be sensitive to subtle
differences in tempo. But even she would have her limits.

bob