Music Trade Review

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TECIMCAI/NDSUPPIY
DEPARTMENT
William BraidW\ute,TecA/ucalEditor
And with relation to the first point it seems
proper to say that the question of tension or
compression does not appear to have any bear-
ing at all. There does not seem to be any
reason to suppose that to arch the board or
System Accepted for the Past Forty Years Is Based Upon the Idea of Means of Put- bend it in any way into any sort of a curve
would have any effect at all in improving the
ting Wooden Fibres in Compression Before Amplifying Vibrations
vibratory qualities of the wood or its ability
to transmit vibrations. No matter how we
HE system of soundboard construction undulatory explanation. We must, in fact, so look at it, we must see that along the grain
which has been accepted for at least forty long as we hold to our present theory of sound of the wood vibratory motion will be rapid
years throughout the world is based upon production, presuppose in the case of the piano and across the grain slow. Now, since it is
the idea that some means must be adopted to sound board surface motions, and this, in turn, necessary to build up the spruce sheet from
put the wooden fibres into a state of compres- means that motions generating these must be strips of lumber not more than four inches
sion or of tension before they can be depended propagated from the strings through the wide, in order that some kind of uniformity
on adequately to transmit and amplify the vibra- bridges and to all parts of the wood structure. of grain structure may be preserved throughout,
tions from the strings. The proof of the pud-
These motions, moreover, must be either evidently there must be a favorable and an
ding is found in the eating thereof, and no one duplicates of or based upon the original mo- unfavorable direction of vibratory transmission.
can deny that the art of sound-board construc- tions of the strings. This being so, it follows If it were possible to build up the board of
tion, built up on this principle, has achieved very that the wood structure of the board must be strips of which the grain did not all run the
wonderful results. Nevertheless, it is apposite capable of undertaking very considerable and one way but which from time to time gave us
to ask whether this system does of itself rep- L-laborate periodic vibratory motions.
a cross grain running straight through the end
resent an inevitable and self-evident acoustical
wood, we might be able to obtain better trans-
The Trachcid Structure
principle, or whether it is incidental to some
mission of vibrations throughout the whole
Microscopic
examination
of
the
wood
from
other and non-acoustical requirement.
which sound boards are made tends to confirm structure from any originating point. Hut this
As all readers know, I have discussed the this conclusion. The tracheid cells of which would be very difficult, and the ribs or bars
sound board in all sorts of ways through these spruce wood is composed are themselves minia- which are glued to the board on the side re-
columns and have constantly tried to learn all ture vibrating disks, or at least their structure mote from the bridges are, or should be, placed
that can be learned as to its behavior in use. is such that vibratory motion must be very there partly because they can help to perform
I have, as readers also know, spoken of making simple and easy for them. They are micro- this very necessary task. In a word, the board
researches into the physical motions of the scopically small and there is little reason to might perfectly well be flat, from the point of
sound board, and am able to say now that, in doubt that the shocks imparted by the strings view merely of undertaking vibratory motion
due course, the results of these investigations through the bridges are strong enough to set as required, provided that it was furnished with
will be set forth. Their very nature, however, them into parallel and responsive vibratory bars or ribs for transmitting vibrations rapidly
prevents any attempt at obtaining rapid results, motions.
to all parts of the structure.
for not only are the dates very obscure, but
In
a
word,
it
seems
impossible
not
to
be-
Why then are the bars commonly planed
the task of controlling the experimental
processes is very difficult, so that any apparent lieve that the sound board is just as much to a slope on each side of their center points,
results obtained must be very carefully checked a vibrator as is the string. There is some so that when they are glued down onto the
and many times repeated before they can be ground for holding with Dr. Paul that the board the latter takes a curved shape? In
accepted. Without such care, which all takes sound board is even more than the string the reality this is only because the downward
a long time, one is certain to be deceived true tone-maker, and in my "Modern Piano pressure of the strings must be resisted and
and to be led to rash conclusions, which after- Tuning" I have set forth the strong points of the principle of the arch called into play. With
wards certainly will be disproved. Hence the this view. Whatever the facts may exactly the board arched the down pressure of the
delay, which indeed is likely to continue for turn out to be, meanwhile, it is in my opinion strings can be better resisted, and, moreover,
quite safe to assume that the sound board the constant rising and falling of the bridges,
some time yet.
does take up and repeat in some definite way, which to some extent is always going on owing
Meanwhile, however, I am attempting to in- throughout the whole of its volume, the to the absorption and evaporation of moisture
troduce to readers every possible rational view vibratory motions of the strings.
by the board, is reduced to a minimum. The
of the subject, not being at all afraid to say
ribs thus are not only transmitting bars, but
If
this
be
true,
then,
of
course,
we
have
to
one thing one week and something that may
girders, of very flat curvature. Their curvature
ask
ourselves
what
kind
or
type
of
construction
sound contradictory the week after. All this
(Continued on page 40)
simply means, of course, that the very data will best enable the sheet of spruce to perform
such
motions.
There
are
two
sides
to
the
on which any discussion must be based are
extremely uncertain, so that the interpretation question. On the one hand there is the bare
of them may be found, with equal plausibility, question of the physical properties of the wood,
as it stands by itself, and, secondly, there is
on opposite sides alternately.
the question how far the connection of the
Associate, American Society of Mechanical
board with the strings and the constructions,
Surface Motions Certain
Engineers; Chairman, Wood Industries
thereupon
dependent
and
thereby
necessitated,
On several recent occasions in these columns
Division, A. S. M. E.; Member, American
influence
its
physical
behavior.
I have tried to analyze the physical behavior
Physical Society; Member, National Piano
Technicians' Association.
of the sound board under use and have come
to the conclusion that we cannot be content Easy to Repair DAMAGED FINISHES
Consulting Engineer to
with any hypothesis of merely molecular mo-
CAMPBELL'S Stick Shellac
lion. That is to say, despite the high authority
Permanent repairs are easily and
the Piano Industry
quickly made. No use to cut prices
of Hansing, it seems to me impossible to be-
or incur expense of reflnishlng.
Tonally
and Mechanically Correct Scales
lieve that the sound board can produce the
Campell's stick Shellac easily re-
Tonal and Technical Surreys of Product
stores scarred and scratched finishes
audible results with which we are familiar
to perfect condition. Melted into
Tonal Betterment Work la Factories
unless it partakes of some surface motion, for
hole, dent, scratch, then rubbed down
and
polished.
An
ideal
way
to
eco-
not otherwise can we conceive its amplificatory
nomically repair finishes.
Reference* to manufacturers of unquestioned
A color card of Campbell's Stick Shellac will
powers being applied; unless indeed we invent
position la Industry
be
sent
free
to
anyone
upon
request.
Shows
a brand new theory of sound to account for
actual samples and the range of 54 colors.
Write for one todav.
them; and this would be even more illogical
For particulmrt, mddrttt
THE M. L. CAMPBELL COMPANY
in the circumstances, since there is no reason
209 South State Street, CHICAGO
otherwise existing for discarding the present 1008 West Eighth Street
Kansas City, Mo.
The Basic Elements in the Construction
of the Sound Board in the Pianoforte
T
William Braid White
Punchings
Washers
Bridle Straps
5814.37th Ave.
George W. BraunsdorS, Inc.
Direct Manufacturer* n{
TUNERS' TRADE SOLICITED
Piano Tuners
Also— Felt* and
Cloths, Furnished
In Any Quantity
Wood.ide, L. I., N. Y.
39
and Technicians
are In demand. The trade needa tunera, rem-
latora and repairmen. Practical Shop School.
Send for Catalog M
Y. M. C. A. Piano Technicians School
1421 Arch St.
Philadelphia, Pa.