[CAUT] Semantics

[David Love]

Which also reminds us that the real language of physics is math.  All other
descriptions are poetry.

 

David Love

www.davidlovepianos.com

 

From: caut-bounces at ptg.org [mailto:caut-bounces at ptg.org] On Behalf Of Delwin
D Fandrich
Sent: Wednesday, May 13, 2009 11:10 AM
To: caut at ptg.org
Subject: Re: [CAUT] Semantics

 


| To me, the transducer argument *de-couples* the strings and
| the soundboard--(by doing this "transducing," taking one
| thing and making it another).  That goes against everything
| I've read about piano acoustics.

This would rather depend on what you are reading.

To be sure, Wm Braid White wrote eloquently, if some what confusingly, about
the power of resonance, that mysterious property he found in certain
materials-namely spruce-to amplify the sonorous quality of the strings. Thus
he was able to state that "more resonating power is required for the
relatively weaker treble strings than for the relatively stronger bass
strings." In this way he was able to explain why piano builders had found it
necessary to make their soundboard panels thicker in the treble area and
thinner in the bass area. In 1909 White did not yet have to contend with the
so-called "Diaphragmatic" soundboard.

But that was then and this is now. So far as I know there is no modern
writer who speaks of the piano soundboard system as an amplifier. In the
Five Lectures series, Klaus Wogram writes, "The soundboard transforms the
mechanical vibrations into radiated sound." Benade (Fundamentals of Musical
Acoustics) discusses the soundboard as a "two-dimensional driven plate."
This plate, by means of forced vibration (the stored mechanical energy of
the strings) creates sound (acoustical energy) by means of the resulting
physical motion. For Fletcher & Rossing (The Physics of Musical Instruments)
it is described thus: "Acoustically, the soundboard is the main radiating
member in the instrument, transforming some of the mechanical energy of the
strings and bridges into acoustical energy."

It might be helpful to try a little experiment. Locate a thin piece of wood
several inches wide and a few inches long. Now locate a small hammer. With
the thin-and so far silent-wood panel in one hand tap its surface with the
hammer. Sound (acoustical energy) is created when the hammer strikes
(mechanical energy) the wood panel. It is an impulse sound, of course, and
it dies out very quickly but if you could make your hammer strikes fast
enough (vibrating mechanical energy) the resulting sound would become a tone
(continuous acoustical energy).

By striking the piece of wood with the hammer you created sound, or
acoustical energy. It wasn't free-you had to invest mechanical energy to get
it-but that acoustical energy was not amplified from anything. It was
created. Now picture the soundboard bridge being struck repeatedly and
rapidly by a series of tiny hammer blows (the vibrating string) and picture
the soundboard responding to those blows by slight movements. Because of its
large size the soundboard will create sound-acoustical energy. This is not
amplified sound; there was no original sound to be amplified, only the
mechanical energy stored in the vibrating string. (And let's not quibble
over the minute amount of sound created by the vibrating string(s). This is
completely overwhelmed by the wash of acoustical energy coming from the
soundboard.)

Semantically we could, I suppose, quibble over whether the piano soundboard
system should be called a transformer-".a thing which transforms
something"-or a transducer-"a device for converting variations in one
physical quantity, as pressure, brightness, etc., quantitatively into
variations in another, as voltage, position, etc." (Both from the OED) What
we cannot do, at least not if we want our language to meet even minimal
standards of technical accuracy, is call the piano soundboard system an
amplifier. Over the past century our understanding of how the piano works
has evolved considerably as has the language used to describe and discuss
it.

Words and their meanings in a technical community-and both CAUT and
PianoTech are technical communities-are important. They convey certain
defined technical meanings to the participants. These are not casual
discussions over the Sunday barbecue with Aunt Matilda. To misuse technical
words or to apply one's own meanings to them-even if that usage was in vogue
a hundred years ago-can only mislead and confuse the reader or participant.

ddf 

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