IX
THE SWITCHBOARD SPEAKS 
HERE, strange to say, is a chapter on sound; and the reader will
naturally wonder how it ever crept into a book on theatre
lighting. Nevertheless, there is place for it, because the
amazing changes of this growing century have greatly increased
the duties of the stage electrician and obliged him to attend the
spectator's ear as well as his eye. Acoustical effects are
generally devised, created and worked by the property man and his
assistants. The machines that produce the various necessary
sounds are for the most part operated manually; and if there are
a number of these simultaneously employed, a man must be provided
to work each machine. After the machines are made and perfected
it is necessary to train men to work them, for the ultimate
result depends altogether upon expert manipulation.
 Some of these contrivances date back many years, and in only a
few instances do we know who originated them. For occasional
effects several devices of various sizes and shapes are used in
combination. Some of the machines being bulky, they must be
placed wherever available room can be found; and this is not
always the best position, as there may be obstructions to throw
the sound back so that very little of it will reach the
auditorium. Direction from which sound is to come is often
important; and if the device which pro-


"THUNDER" IN OLD WOODEN THEATRES
 These traditional methods of producing storm effects depended
greatly upon timber house-construction. In the thunder-run,
cannon balls, released from a series of pens known commonly as
"the rabbit hutch," crashed and rolled down a number of connected
chutes along the side and back walls of the stage. The
thundercart, with its serrated wheels, was filled with stones or
scrap iron. The top picture is sketched from a photograph
illustrating Marcel Jubin's article "L'Illusion au Theatre" in
Science et Vie, Paris, 1919. The thunder-run is after a drawing
in Scribner's Magazine, October, 1888. And the thunder-cart comes
from an original in Georges Moynet's La Machinerie Theatrale,
1893.

duces it cannot be placed to give this effect, the result will
naturally not be convincing.
In the old days when theatres were built of wood, the vibrations
of the structure contributed to the carrying power and resonance
of sound. This factor has been virtually eliminated in modern
construction where iron beams are made rigid by riveting them
together and encasing them in cement.(l) The old wooden
thunder-cart is a good illustration of how the vibration of the
building was used to simulate thunder. The cart itself produced
as much sound as the beater for a bass drum would without the
drum; and its relation to the production of the effect had about
the same correlation as the drum beater has to the drum.
 The cart was a box of varying size, although, as I recall it,
about three feet long by eighteen inches wide, filled with iron
or stones for weight. To the bottom were fastened two axles, on
which were placed four wheels about twelve inches in diameter and
one and onehalf inches thick. These wheels were the striking
feature. They were made of maple and the edges were serrated like
large saw-teeth. To imitate the rolling crescendo and decrescendo
of thunder, the box was pushed back and forth on the wooden
fly-gallery.
 The wooden "thunder-run," with its rolling cannon balls, also
depended on the vibration of the building. In some of the old
stock houses these runs were built in the dome of the theatre,
running through to the flygallery and continuing down the back
wall of the stage. They had three or four drops; in some the
cannon balls

(1)Engineers seemingly have abandoned their earlier idea of
permitting skyscrapers to rock in high winds. The sway of the
fiftyfour story Chanin Building in New York, for instance, is
rated in only thousandths of an inch. 

would fall as much as twenty feet, causing tremendous
reverberations. These runs are still used and usually are placed
in the fly-gallery; but the effect does not compare with that of
the old days when wooden construction gave its aid in carrying
the vibrations.
 Since the development of the amplifier, sound effects


NEW WORK FOR THE ELECTRICIAN
 The lightning striker consists simply of two poles, the negative
soft iron and the positive carbon, and a magnetic coil that
enables them to strike their own are when circuit is completed. A
wire screen is fitted over the box to confine sparks. The whole
may be hung anywhere desired and operated from the switchboard.
The drum may be used with or without the amplifier. When used
without it the volume can be raised with the solenoid, which
pulls the beaters away from the drum head.

gradually are being taken over by the electrical department; and
it is only a question of a short time before all sound effects
will be created by the stage electrician. Here is the raison
d'etre of this chapter. At present it is a new field with many
possibilities that experiment will bring out. But when the system
has been perfected it will have several distinct advantages over
the old ways, and chiefly because one man can now control all the
effects and from a place where he can see and follow the action.
The loud speakers may be placed so that the sound will come from
the desired direction, and in such positions that the sound waves
will not be interrupted by surfaces that would deflect or muffle
them.
 A number of effects can be produced by amplifying phonograph
records. The apparatus for doing this consists of a turntable, a
"pick-up," a three-stage amplifier and a loud speaker. These
outfits may be bought intact, including the effect records which
are carried in stock.
 The system which I believe will prove practical and that will
finally be adopted is one where the sound is picked up by a
microphone. Small effects may produce the initial sound, because
this need not be great in volume. What is important is that it
shall be the right sound. To obtain that is not as simple as it
may seem, for the sound caught by the microphone is sometimes
unrecognizable when it is amplified and is sent out through the
loud speaker. The rest of the equipment consists of an input
panel, a three-stage amplifier and a loud speaker.
 I am not going to take up the reader's time by detailing the
construction of these appliances, as radio engineers are making
rapid strides in the improvement of sound producing devices, and
instructions and diagrams that I might give would soon be
obsolete. For this reason I confine my description to the large
parts of the apparatus and how they work.
 The "input" panel contains two "mixers." These are controlled by
resistances. Two resistances control the current for the
microphones; two others control the volume. The "mixers" are
hooked up with a microphone transformer, the secondary of which
is connected to a three-stage impedance coupled amplifier. The
output from this will give a little better than ear-phone


WITH THE HELP OF RADIO
 On the two lower shelves of the amplifier panel are the filter
condensers and chokes for both the A and B currents. The lowest
panel is a mixer and input for two 3-button microphones. The next
is an input for one 3-button microphone, this connected with
head-phones used by the operator to gauge reception and for cues.
Then come two double amplifier panels. The top is a mixer and
input for two 3-button microphones.

reception. The input panel is then coupled to a good three-stage
amplifier, two stages of which are push-pull, the last stage
using two hundred and fifty tubes or their equivalent. These
tubes use four hundred and fifty volts on the plate.
 If alternating current is available, a power pack is used to
supply both the filament and the plate voltages; but if only
direct current is procurable, a generator set will be needed to
supply the latter. Although direct current may be used to light
the filaments through proper resistances, I have found a
generator set that will deliver the required amperage at ten
volts the best and simplest. With a field rheostat this voltage
may be kept regulated at all times.
 All of the apparatus used must be of good quality and suitable
for this purpose. The ordinary amplifier such as is used for home
radio will not do. Neither will the home loud speaker. Yet,
persons having a good working knowledge of radio can construct
the outfit themselves. If two or more effects are to be used at
the same time, a separate set of apparatus is required for each
effect.
 Two or more effects may be rendered from the same amplifier
provided they are in combination and the sound is to come through
the same speaker; but where two or more separate and distinct
sounds are needed separate amplifiers and horns are obviously
required for each.
 Using this outfit, quite a number of sounds may be produced with
a mechanically beaten snare drum, such as the whirr of an
aeroplane propeller, the "put-put" of a gas engine or the
rhythmic exhaust of a steam engine. However, the apparatus for
these imitations must be built into a box, so that the microphone
does not also pick up foreign sounds.
 To the shaft of the motor which is to beat the drum, a wooden
disk is fastened by means of an iron flange, this disk being six
inches in diameter and one inch thick. To the circumference of
this are attached at equal distances three pieces of leather
strap, each one inch wide and six to eight inches long. One end
of each piece is left free so that the centrifugal force of the
whirling shaft throws them outward, against the drum head. The
motor itself is fastened to a shelf that has been secured to the
side of the box. As to the snare drum, that is fastened to a
board that slides in a track made of two battens on the bottom of
the box, that the drum may be moved either toward or away from
the motor. By changing the position of the drum and increasing or
decreasing the speed of the motor, the rhythm and pitch of the
sound may be changed. If different substances are placed on the
drum head, such as cardboard, sandpaper or tin, other sounds are
produced. The microphone may be set anywhere in the box; but it
should be suspended by springs or rubber bands.
 An ordinary geared electric drill placed in the box will produce
a roar like steam escaping with heavy pressure behind it; paper
shaken in front of the microphone sounds like the clapping of
many hands when the sound is amplified. To procure the desired
sound different things must be tried. If we experiment long
enough and do not lose patience we finally will stumble upon what
we want. At present, the rule-of-thumb, "cut-and-try" method is
about the only one that can be recommended for working out these
effects.
 But, as a final note of warning, unless you have patience and an
even disposition, don't play with sound.