Evening star., 1938-06-27
NEv' SOUND UNIT
SHOWN BY ARMY
Truck Valued About $4,000
Is Most Powerful
Mobile Unit.

The most powerful mobile sound
INIT the Army has ever had was
demonstrated at Fort Myer. Va, to-
day before an audience OF War De-
partment and State Department ON
eiais and members of the Radio Corp.
cf America Manufacturing Co.. which
produced the sound truck at a cost
Of approximately $4,000.
The new equipment will be used
ofhcially for the first time on July 8,
when President Roosevelt delivers an
address in connection with the dedi-
cation Of the Eternal Light Peace Me-
mortal at Gettysburg. Pa. It will be
employed on the following day to ex-
plain to the audience the maneuvers
performed by Army troops in the
battlefield area.
reached by the mobile sound system,
according to Maj. Gen. j. O..
Mauborgne, chief signal officer OF the
Army, who arranged the demonstra-
ton.
In exhibiting the facility with which
the unit both recorded and amplifled
sound, Gen. Mauborgne first recorded
brief talk explaining the qualities
OF the instrument. During the re-
cording. an airplane flew over the
reservations. When the recording was
reproduced. the sound of the motor
could be plainly detected.
After the reproduction of the re-
cording, Capt. George I. Back of the
Signal Corps, who produced and di-
rected the demonstration, ordered
the operator to pick up and amplify a
conversation between Boiling Field
and an airplane flying 10 miles south
Of the airport,
The entire air-ground conversation
was broadcast over two theater-type
reproducing units mounted perma-
nently in the side walls of the truck.
Variety Of Amplifications.
Capt. Back explained that telephone
conversations, radio programs and
transcriptions also could be picked
up and amplified.
Following the plane broadcast. the
sound truck rolled through Fort
Myer to the other end of the field,
where six external loud speakers,
mounted on two 20-foot collapsible
tripods, were set up.
The ofiicials standing at the Ad-
Ministration Building had no trouble
hearing the talks and music amplified
1000 feet away Here Capt. Back
explained the units are interchange-
able 40 that if one amplifier stops. the
others carry on with only a slight
diminution Of sound.
Whereas the external amplifiers are
used when a wide area of coverare
Is imperative, it was pointed out, the
permanently mounted loud speakers
OF the theater type are employed
where extremely high fidelity of re-
production is primary considera-
tion. The latter type can reach an
audience OF 5000 people.
The sound truck itself was manu-
factured In accordance with Army
specifications. Inside the truck an
operator sits before q panel resembling
the type found in a radio station.
lnefe ALSO Is room TO store the tripods
and amplifiers Of the external sound
unit. A fish-pole antenna stretches
up from the truck to pick up sound.
Among those who stood for over an
hour in drizzline rain to hear the
experimental performance were Acting
Post Commander Col. John Millikan,
Col. Dawson Olmstead Of the Signal
Corps. Col. J. w. N. Schulz. director
Of current procurement in the office
NJ the Assistant Secretary of War; Maj.
J. v. Matejka of the same ofice; Mai.
j. T. Clement. vice president OF
r.. c. A.: J. s. Schwank, manager OF
the engineering products division of
r. c. A.. and Maj. James Watson of
the Signal Corps.