The Washington times., 1921-03-04
HEAR RHARD|NC
BY NEW DEVICE
Three Rooms Full Of Machinery
Garry Presidents Voice to
Waiting Throngs-

The device which enabled Presi-
dent Harding 10 deliver his inaugural
address from the east front OF the
Capitol. so that II was heard per-
pectiy thousand or fifteen hundred
feet away. is known as the Loud
Speaker
SYSTEM OF MOTORS
II is a system OF motors, generators
wires. transmitters. ampiifiers and
other electrical machinery which has
been In tho course OF construction and
Installation for about . month. re-
quirins the services Of q large force
Of highly trained engineers and ex-
pert workmen- II 10 designed to car
ry the human voice in the open air
all the people who were in the vide
plaza on the east front of the Capitol
who were In the wide plaza on the
east OF the Capitol were able to hear
the speech as well jas IL they stood
ten feet away from tho speaker.
Although there are three rooms
full OF machinery and electrical de-
vices In connection with the loud
speaker, none OF II was In evidence.
and the huge horns through which
the speech was heard were cannon
fiaged by being made q part Of the
roof OF the speakers stand SO far
as the speaker was concerned he saw
nothing OF the apparatus except small
transmitter boxes which were set In
front and to the sides of his speaking
desk. 30 that his voice was caught
In the workings OF the loud speaker
no matter which way he turned
The boxes holding the transmfSter
disks were lined with heavy felt The
transmitters are instruments noted
for extreme sensitiveness and for alb
sence OF distortion in tho transmission
from sound to electrical energy.
When the President spoke, his voice
generated energy by means of the
sensitive transmitters. This energy
was transferred by wires to the COM
plex apparatus which was Installed
under the Capitol steps The energy
led into a little glass bulb, which the
engineers call a 'vacuum tube ampli-
fer" the function of which 10 to re-
ceive energy. multiply II. and send
IL on to other amplifiers until It
reaches . stage sufficient 70 turn
~ fooco hh NoiSo III tihoG8u
hidden horns out to the distant
crowds.
ENGINEERS WATCH APrARArUa
While the speaking was In progress.
dozen engineers were watching
each bit OF apparatus Men were sta
toned at certain points on the Capitol
plaza connected with tho machinery
rooms by telephone. to report to the
men at the amplif1era The working
loud speaker requires . crew as large
as q small vessel
The voice. when II emeress from
the hornA Ia almost an exact duplica-
tion Of the original. but greatly In
creased in power. Il Is possible for
the loud speaking system to obtain an
amplification of several million times
without great distortion OF tho orfgf-
nal wave form
The mouths of the hidden
horns are depressed just enough
so that the audience near at hand
within range of the speakers voice
direct, hear very little from the
horn, those farther away hear both
the speaker and the loud speaking
system. those farthest away hear the
horn only.
NO UNNATURAL EFFDCr.
II might seem that this additional
source of sound. might create a double
effect or an unnatural effect but, IL
does not. The sound from the horn
is exactly in phase with the speech,
and almost the same quality. At
any point where the sound from the
horns is heard. IL Is practically Inn
possible to tell that one is not listen
ing to the speaker himself.
The principles involved are those
Of the telephone The loud speaker is
being installed by the engineers of
the Bell Telephone System including
the American Telephone and Tele-
graph Company and the Chesapeake
and Potomac Telephone Company. Tho
loud speaker Is not . commercial
device. Is not for sale, or for rent and
was q contribution by the Bell sys-
tenn to the inaugural ceremonies It
has been considerably improved since
Il was used at the Republican and
Democratic conventions last summer.
= The loud speaker has been In pro-
cess of development for about ten
VA n ra In the ReIl system IabOratOYies-