Mark DeBellis wrote:

p.s. Again, what you say here blurs the distinction between (a) whether
the perceptual effects of two 5-minute stretches are the same, and (b)
whether the listener can reliably judge, after hearing the two
stretches in succession, that they are the same (or different).

That's because there is no distinction. And THAT'S because there is no
such thing as a "perceptual effect."

If you
want to *define* the term "audible difference" along the lines of (b),
then nothing stops you, but it's still possible for there to be a
relevant difference in perceptual effects, along the lines of (a),
without the *perception of a difference*. No "definition" will make
those things the same.

Again, there is no such thing as a perceptual effect, independent of
perception. The only possible evidence that two things are perceivably
different is that they are perceived differently.

You are merely playing at semantics here.

bob