Klarinet Archive - Posting 000624.txt from 2001/02

From: Tony@-----.uk (Tony Pay)
Subj: [kl] Explicitness
Date: Sat, 17 Feb 2001 06:58:34 -0500

On Fri, 16 Feb 2001 21:57:44 -0800 (PST), Bilwright@-----.net said:

> Tony Pay wrote:
>
> > That's nothing to do with the letters 'P' and 'Q' being interpreted
> > as independent recordings from different microphones, and then being
> > combined in order to make clearer what was said. That's quite
> > another idea.
>
> (Tony, my keyboard doesn't have a dot other than "." So my P.Q is
> intended to mean the same as your P.Q)

I never used (P.Q) except in referring to your use of (P.Q), and then
only to say "whatever (P.Q) might mean".

> Yes, there is a distinction based on whether the initial 'combining'
> of the two waveforms occurred inside a human ear or inside an
> electronic device. But in both cases, the two waveforms were
> combined in order to produce something that was in neither of the
> original sources alone.

It's a question of *which* 'two waveforms'. In my illustration, P and Q
are two *numbers*. In your illustration, they're two *signals*.

> The site of combination has changed, or more correctly it has been
> subdivided a bit; and yet the basic principle is unchanged. This
> makes the illustration more universal to me, not less --- especially
> since the illustration emphasizes the concept that something was
> manufactured that was not 'in the air' according to the data received
> by any one of the three microphones alone (none of the microphones
> heard or recorded the entire event), and yet the differing result of
> P.Q and P+Q combination was related in different but useful ways to
> what 'really' occurred at the source.

I know you're excited about the film, which might be said at least not
to contradict the idea that the nonlinear behaviour of the middle ear
(if and when it eventually gets an uncorrupted signal) enhances rather
than diminishes our ability to extract useful information from it.

But in fact, someone who is still puzzled by that idea -- and indeed
may not believe that sum and difference tones of pure sine waves only
get generated in the ear -- doesn't get any further specific
understanding of the matter from the film. We don't find out what's in
Hackman's black box -- some sort of aural image enhancer? -- and it's
almost certainly not something that simply generates combination tones
from two sine waves of frequencies P and Q. Its action would probably
be more analogous to the action of our neural processors than to the
action of our middle ear.

The details of how our neural processors use the precise type of
nonlinearity produced in the middle ear are still mysterious. (And
notice, that middle ear nonlinearity is available to Hackman even
without his black box.)

But my fundamental point was rather that it can only be confusing for
you to use the same letters P and Q that I used for two frequencies, to
refer to two different *recordings*. Then you used 'P+Q' to refer to
simple linear combination of P and Q, and had to invent the notation P.Q
to refer to the effect of Hackman's box, whatever it did.

Whereas P+Q in my post referred to the FREQUENCY of the sum tone
generated by the nonlinearity of the amplifier. And my analogy was
intended to clarify an already confusing discussion by taking it to
another area of experience (hi-fi amplifiers) which might be more
accessible and interesting to the general public.

Is it any wonder that people are confused by this sort of post? And
stop reading this sort of post?

> (sorry for the extra adjectives, but I wanted to be as explicit as
> possible)

99% of being explicit is successfully avoiding other people taking a
wrong turning. Using the same letters for completely different things,
in discussions about different topics in the same thread, doesn't help.

Tony
--
_________ Tony Pay
|ony:-) 79 Southmoor Rd Tony@-----.uk
| |ay Oxford OX2 6RE GMN artist: http://www.gmn.com
tel/fax 01865 553339

... He who hesitates is probably right.

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