Music Trade Review

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WmBraid White
Technical Editor
Important Scientific Experiments
Relating to the Piano Soundboard
T AST month in this department I ventured
to speak rather definitely about the attitude
that the engineers and the physicists are taking
in the realm of music. I spoke of a very in-
genious instrument designed by Messrs. Lesti
and Tiedemann, which makes use of the photo-
electric principle, and which is intended to pro-
duce sounds of the most varied qualities at
will, without the intervention of string or pipe.
Some of the advantages, and some also of the
disadvantages, inherent in such an instrument
I undertook to point out.
In the course of the observations which I
made on this matter I spoke of the backward
state of the piano industry in respect to re-
search. Meanwhile, some matters have been
in hand in our laboratory which bear strongly
on this very point, so strongly in fact that I
think it proper to speak of them in some little
detail.
We have been investigating the several ele-
ments or departments of the tonal apparatus
DISTINCTIVE
TONE QUALITY
For generations Poehlmann Music
Wire and Fly Brand Tuning Pins
have made many pianos famous for
their renowned tonal qualities.
The continued prestige of Fly Ttrand Pins and
Poehlmann Wire is due solely to quality. Every
detail is watched minutely. Made from special
drawn wire by men who have done nothing else
for a lifetime, they embody every known requisite
for quality. That is why many manufacturers of
high-grade pianos demand Poehlmann Wire and
Fly Hrand Pins.
SOLE AGENT U. S. A.
American Piano Supply Co.
Diz'ision of
HAMMACHER-SCHLEMMER & CO.
104-106 East 13th St.
New York, N. Y.
of the piano. In due course we have now taken
up the sounding-board or resonance table, and
have recently made some preliminary studies
for the purpose of ascertaining such facts
about its behavior in use as may enable us to
plan and later carry out a more complete in-
vestigation. The results obtained in these pre-
liminary studies are extremely interesting.
The Apparatus
We began by attempting to pick up the move-
ments of the board by means of a magnetic
receiver such as is used to receive and transmit
the vibrations induced by the passage of a
needle along the grooves of a phonograph disk.
The receiver, usually known as a "pick-up," con-
sists of an electro-magnet with an armature to
which is attached a holder for the needle which
works in the grooves of the phonograph record.
Attached usually to such pick-ups are resist-
ances intended to cut down the current strength
across the poles of the magnet. We obtained
a pick-up of this description and removed the
resistance. We then made a contact consisting
of a length of piano wire, No. 26 gauge, one
end of which should go into the holder, while
to the other end was soldered a round thin
disk of tin. This thin disk could be placed on
the surface of the soundboard. In order that
the motions of the board might be conveyed to
the needle and thence to the pick-up three
thumb-tacks were soldered to the disk on the
side remote from the needle. The diameter of
the disk was.one inch. Several needles were
also prepared, each four inches long, but with-
out the foot-support described above.
The soundboard of a fine seven-foot grand
was then carefully measured, and a drawing
was made of it at a scale of one-fourth. This
drawing was then ruled off in equal squares,
each corresponding to an area of 36 square
inches on the piano. The squares were num-
bered on the drawing. On the soundboard of
the piano crayon marks, easily removed, were
placed to identify the corners of each square.
This meant, of course, placing some of the
crayon marks on the plate, but that made no
particular difference.
The pick-up with its needle was then con-
nected with a d. c. amplifier of two stages,
which in turn was connected with the second
Welte Mignon Experts
We install the original Welte-
Mignon Reproducing Actions
in all makes of pianos. Also
general renovating and re-
pairing of all types of player
vibrating element of our oscillograph. The
other vibrating element was connected with
another amplifier leading back in turn to a push-
pull carbon microphone. The procedure was
as follows:
The Method of Experiment
Beginning with the lowest A of the key-
board, every third key was successively and
many times over struck by means of a me-
chanical key depressor. An operator mean-
while watched in the mirrors of the oscillo-
graph two simultaneous wave-forms, one de-
veloped from the pick-up on the soundboard
and the other from the complete sound as
caught by the microphone. By means of a
scale of lines drawn on the mirror, the deflec-
tions of both waves were noted and recorded.
The process was repeated many times over for
each note. From time to time permanent rec-
ords were made, by photography, of the re-
sults being obtained. These photos have now
been carefully examined, and the deflections
for different notes at the same place on the
board, and for the same note at different places,
have been observed and compared. The direc-
tion of the grain of the wood and the angular
position of the pick-up with respect to this
grain have been taken into consideration.
From these preliminary studies certain facts
emerge which can be set forth briefly.
Allowing for the fact that many more ob-
servations must be made before definite quanti-
tative conclusions can be properly drawn, and
for the further fact that the pick-up apparatus
requires still more careful study and improve-
ment, it may be said that:
Preliminary Findings
1. The wave forms recorded as proceeding
from the soundboard are parallel to the wave
forms proceeding from the complete sound as
microphonically taken up. They are, however,
of simpler shapes, in the sense that the upper
harmonics which, for example, are so promi-
nent in the low frequency tones as heard are
reproduced apparently much more feebly in
the motion of the soundboard. This statement
may be taken as accurately expressing the facts
discovered, provided that allowance be made
for possible defects in the pick-up apparatus.
It may be that improvements in this apparatus
will show different results, but it may be said
that the records so far obtained agree in this
PFRIEMER HAMMERS
Always Found in Pianos
of the Highest Quality
Originators of the Re-enforced Tone
Producing Hammer
CHAS. PFRIEMER, INC.
actions.
WELTE-MIGNON PIANO CORP.
704 St. Ann's Ave.
28
-
New York
Wales Ave. & 142nd St., New York
Lytton Building, Chlcaro