Maybe that's what he meant. As you know, the Great Man had a mischievous mind
as well as well as a brilliant one. He certainly seems to have had more of a
sense of humour than most academics I worked with. Maybe he meant that we never
quite know all the theory. Maybe like you say he never said it...
From: Jim Brown <firstname.lastname@example.org>
Sent: 04 February 2009 21:06
To: AMPS <email@example.com>
Subject: Re: [Amps] power and db
On Wed, 4 Feb 2009 20:31:46 +0000 (GMT), DAVE WHITE wrote:
>However - in a quote I believe was atttributed to a certain Prof.
>A. Einstein - "In theory, theory and practice are the same thing.-
>In practice they're not."
I recently finished reading a bio of Einstein, and I doubt that he
would have said exactly that.
I have a different philosophy. The real world is complicated, and
real problems often consist of many elements. If you think there's a
difference between theory and practice, you don't know enough theory
to understand the many things that are actually going on. In other
words, you're looking at the elephant through too small a hole in the
>In practice I'm sure that the human ear can discern a couple of dB
>if the signal is marginal.-
Absolutely. The study of human perception of sound is called
psychoacoustics, and it has been a well developed science for much of
the last century. When the engineers at Bell Labs were inventing
stereo in the 1930's, they made use of psychoacoustic work that had
been published around 1850 by Joseph Henry (the same guy whose name
is on the unit of inductance, in tribute to his invention of some
motors and meters), and further study based on his work by
psychoacoustic people at Harvard around 1935! I'm told that Lord
Rayleigh, the great British scientist who was a contemporary of
Henry's also published work on psychoacoustics similar to Henry's,
but I haven't found it yet.
When two sounds are nearly equal in loudness, a change of only a dB
or two in one of them relative to the other makes a significant
difference in how we hear them. This is WELL KNOWN to those who have
bothered to learn the science. That's not a difference between theory
and practice, it's a difference between knowledge and ignorance of
well established science!
>In theory this would be nonsense but
>it seems to hold true for me particularly on 160m.
See my previous post in this thread.
Audio Systems Group, Inc.
Member Acoustical Society of America
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