The Washington times., 1919-04-28
AIR OFFICERS HEAR
VOICE FROM sky

A remarkable DEMONSTRATION OF the
Masnsvox,. the INSTRUMENT by which
Lieut.. Herbert Metcalf, flying 5000
feet above the Treasury. read the
Presidents appeal for support of ths
Victory loan to 10000 people on the
ground, was given Thursday after
noon before officers OF the United
States air service
The demonstration was conductei
by Z. s: Pridham, who, with p. L. Jeh.
sen, invented the instrument. MAJ.
Gen. Charles T. Menoher, Uncle Sam $
air chief. who recently returned from
years service overseas, and Col.
Clarence c. Culver, inventor OF thu
radio-phone, were present.
The aerial end Of the experiment
was conducted by Lieutenant Metcalf
in Boiling field plane.
He went up from Boiling Field at
1890 o'clock and presently his voice,
bigger than life, began to. come from
the Magnavox. He new up until he
was directly over the Treasury, where
the instrument was installed.
Hear Every Word Distinctly.
Il will dy over the Ellipse in q
large circle and come back to you"
came the voice from the skies. The
plane far above swung in a circle
and came back over the Treasury.
As I pass over you will recite the
alphabet so you can hear the sound
as mOye past" Then the alphabet
came down" every letter clean cut
and distinct. ITS not very good
weather up here; rather hazy. It's
much cooler than thought it would
be. It's getting slightly bumpy now.
I he
turn west and return to Boiling Field.
I'm rather high, but it's rough, and
II don't think 1t wise to ny lower.
So I'll say good-by." And the ex-
pertinent was completed.
The MaEnaYoX is essentially an in
strument for the simplifying of sound
waves, and as such can be used in
connection with the radio phone
wireless, or the ordinary telephone.
By its use the sound waves coming
from the instrument, ordinarily very
faint, are increased in volume TO a
great degree, so that they may be
heard at a long distance from the in
strument. This is accomplished by
which vibrates through large arc,
varying with the amount OF current
used.
with this instrument President
Wilson, sitting at his desk in the
White House. could speak to a crowd
Of 500 900 people in San Francisco,
said the inventor, land every person
In that crowd would be able to heaf
his every syllable with the utmost
clearness."
USa GABti-Noise1 TransmiIteT.
The use of the MagnavoI is made
posgible only by use of another de-
vice. the "anti-noise transmltter
also the inyention OF Mr.. Pridham
and Mr.. Jensen. This instrument au-
tomatically cuts out the tremendous
roar Of the aeroplane motor, or even
Of the machine gun, and enables the
aviator's voice to be clearly heard
even at a whisper. The device has
been in use at the battle front for
some time. but has been kept a secret
for military reasons.
"It can be adapted to the tele-
phone" said Mr.. Pridham, "and by its
use a man in the midst Of a thunder
Gus boiler factory could speak in q
! low voice over the telephone and only
his voice, not any Of the extraneous
noise, would 60 over the wire"
This result is accomplished by al
''open air. diaphragm, permitting
| sound waves to strike upon both side;
| of the plate, thus neutralizinG theii
effect completely. The voice Of thu
| speaker, coming from a point very
| close to one side of the plate, effect;
| oniv that one side,