Evening times-Republican. [volume] (Marshalltown, Iowa) 1890-1923, 1920-09-10
DEPARTMENT HEAD OF PHYS
les AT S. U. |. GAINS PRoMi-
,NENcE AS SCIENTIST.
PERFECTS RECEIVERS FOR
ANTI-AIRCRAFT STATIONS
Apparatus Installed at First Station
Erected in United States at Pensa-
coIa-Masnifies Sound 100 Times
Navy Department Gives George
w. Stewart Praise for Invention.
Special to Times Republican.

Special to Times Republican.
Iowa City, Sept. 10.-To Prof.
George w. Stewart. professor and
head of the department of physics at
the university of Iowa, the United
States navy ascribes credit for de-
veloping the acoustic receivers en-
ployed by the anti aircraft station at
the Pensacola naval base. the first
completely equipped anti aircraft
station in the United States. This
apparatus has proved superior to all
other types" according to official
statements, and by tests has been
demonstrated TO be far superior to
apparatus used for similar purposes
during the war by the French and
British.
| In a book on Navy Ordnance Ac-
tivities" the success of this appa-
ratus is related. 1t was while work
! ing for the bureau of steam engi-
neering during the var that Profess
sor Stewart served as chairman OF a
committee Of the National Research
| Council on the location OF invisible
aircraft. The acoustic portions OF the
machine had to be designed with OK
IRENE skill, for. the problem was TO
catch sufficient Intensity of sound to
| actuate the electrical parts Of the
apparatus.
Masnifies Sound 100 Times.
| Professor Stewart perfected acous-
tic receivers which magnified tho
sound 100 times and which could de-
tect the hum of aeroplanes at three
/ times the distance possible with The
naked ear. 1t was proved possible to
tseparate two planes less than a de-
gree apart, to detect the kind of mo
tor In use on the pIane. and to hear
/ the sound of distant aeroplane mo-
/ tors in the midst of all kinds o,
| racket immediately at hand, the adj
| jacent noises being excluded by
means of the peculiar design of re-
1 oeivers used. Using two listening
stations 1t Is possible to plot the
course OF the aeroplane. determine
its speed accurately. and regulate
gun fire accordingly. This gives spe-
weather.
These detectors offer particular
advantages in giving opportunity for
effective use of searchlights against
bombing aircraft at night. The rays
of searehlights could be kept on
bombers from the ground, following
them by sound even when the eye
lost sight of the machines. and at
lacking planes In the air. taking adj
! vantage Of the searchlight beams
| from which the bombers could not
escape, could fire on the bombers out
of the darkness in comparative safe
i ty and drive them to earth.
In the perfected apparatus Profess
sor Stewart made for the first time
in this country an APPLICATION Of a
little known phenomenon in hearing
called by him the binaural difference
Of phase effect. This principle was
also applied independently by work
ers in Europe and has proved so eff
fective that it has formed the basis
Of the submarine detectors. geo.
phones, and all other acoustic de-
ltecting devices brought to perfection
during the war.
The anti aircraft station at Pen
sacola has the only complete system
of its kind in the United States. The
instruments there used are station
airy. however. Professor Stewart II
interested at the present time In the
adaptation of similar apparatus t
battle line warfare by providing {
means by which 1t may be trans
ported about the front and used ii
connection with mobile artiller,
rather than in the defense Of lin.
tied area about city. fortified base
or other strategic point.