Music Trade Review

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TECHNICAL^SUPPIY DEPARTMENT
William
BraidWhiteXecfimcalEditor
Which Has the Greater Influence on
Tone—The Sound Board or the Strings ?
Some Reflections on One of the Great Controversial Questions in the Technology of
the Piano Construction—Possible Ways to Its Solution
I
N the technology of the pianoforte there
are certain questions which constantly re-
appear, no matter how often they may be
treated in the attempt to settle and dispose of
them. If one looks closely at the history of
pianoforte construction during the last century
one is almost compelled, willy-nilly, to con-
clude that most of these have been in their
very nature insoluble, at least in the absence
of those precise methods of inquiry which only
now are coming into a rather uncertain and
belated favor. Among them all no one has
been so thoroughly the subject of controversial
discussion as the question whether the sound
board or the strings have the greater influence
in tonal production. And since at the present
time there is every reason to feel that those
whose business it is to design and construct
pianofortes are more willing to undertake fun-
damental questionings than previously they
have ever been, some more words at this time
apropos this famous controversy may not be
entirely inappropriate.
In any technological field which has not had
the advantage of scientific foundations it is
almost certain that opinions on important ques-
tions will partake far too much of personal,
and far too little of detached and impersonal,
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coloration. It is quite usual to hear piano
makers of various degrees (and piano tuners,
too) talking in a vein of complete assurance
about matters which scientific men who have
attempted to analyze them would certainly treat
with much reserve. Piano makers who are thus
dogmatic have simply never understood the
data upon which they are so ready to pro-
nounce; have never, in point of fact, had those
data before them in anything like their com-
pleteness. If the data had been before those
confident gentlemen in all their completeness,
if in fact they had ever been able to know (in
the strict sense of the words) what they were
talking about, it is quite certain that they would
usually have been far less confident in the
expression of their opinions. Scientific knowledge
always makes one very humble and very chary
of expressing dogmatic opinions about anything.
It is precisely with these thoughts in mind
that I venture to discuss here, quite tentatively
and without any notion of definite pronounce-
ments, the vexed question of the relations
between sound board and strings. What is
written here takes shape largely as the result
of having been able to talk over with Vice-
President Taylor and Research Director Wood-
bury, of the Mason & Hamlin Co., some of
their recent work in tonal research and of
having at first hand examined their data and
their methods of handling them. But, of course,
the opinions expressed are my own, I am alone
responsible for them, and they will be found
not to disagree in principle, I think, with the
opinions I have been known to hold during
many years.
Sound Board Motions Established
As I have had occasion to say quite definitely
in some very recent articles, there is not the
slightest question as to the existence of definite
and perceptible surface motions in the sound
board, motions which correspond with the
original periodic motions imparted to the
strings by the blows of the hammers. If a
pianoforte be carefully damped so that the
sound board cannot impart its surface motions
to the air (as by covering both its surfaces
with,a' heavy, continuous sheet of thick damper
felt), we at once perceive that the sounds which
are now given out are both "metallic" (twangy)
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{Continued on page 30)
William Braid White
Associate, American Society of Mechanical
Engineers; Chairman, Wood Industries
Division, A. S. M. E.; Member, American
Physical Society; Member, National Piano
Technicians' Association.
Consulting Engineer to
the Piano Industry
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29
and leeble. What is more, they die away more
rapidly, or at least are heard by the ear for a
shorter length of time. If now we examine the
sounds thus produced by any visual means, we
find that they are exactly what we should have
expected from the knowledge we have of the
behavior of stretched pianoforte strings which
are struck by pianoforte hammers. In a word,
they present the expected combination of fun-
damental and partial vibration forms, expressed
in resultant curves of familiar shapes. On the
other hand, when we take away the damping
material and restore the sounds to their original
quantity and quality, we find two interesting
facts, which, however, are also what should
have been expected. We find that the amplitude
of the sound curves is throughout greater for
equivalent hammer velocities (i.e., equivalent
blows upon the keys), and at the same time
that, in general, the even numbered partials
(octaves, octave twelfths, etc.) are strengthened
at the expense of the others (twelfths, seven-
teenths, etc.). It is evident that the effect of
the sound board is twofold and that it both
amplifies and modifies.
Qualitative vs. Quantitative
I might as well say frankly that I am not
at this moment in possession of quantitative
measurements on this point, although these will
come in due course. I cannot at this moment
say exactly how far this property exerted by
the sound board may be said to extend for
each note of the scale. It is, in fact, extreme!}
probable that we shall find quantitative meas-
urement a process of considerable confusion,
which will require a very great deal of inter-
pretation, and that an element of uncertainty
will be injected into any opinions founded upon
it. On the other hand, qualitative interpretation
is much simpler. It is only necessary to ex-
amine visually the sound curve to see that what
I have already described does exist. On the
other hand, if each curve be photographed, it
may be placed, in turn, under the Henrici
harmonic analyzer, whereupon each of its com-
ponents may be discovered and its relative
amplitude set forth.
The Plausible Fallacy
The sound board, then, is amplifier and modi-
fier. Hut that is not at all the same as to
say that it is itself a prime vibrator. A great
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