The Hawaiian gazette., 1915-11-09
FIND SUBMARINES
BY SOUND SYSTEM
Latest Invention Detects Subsea
Craft BY Noise Made
Under Surface ,-.,-

Writing of the detection Of subma
rines by sound waves the, Scientific
American gives further details of the
experiments we recently noted by viii.
liam Dubilier, an American electrical
engineer with numerous wireless tele-
phone and wireless telegraph inventions
to his credit, who at the time was in
France installing wireless telegraph ap-
paratus on aircraft. Dubilier went to
Cherbourg, on the, English Channel,
where he found Professor Tissot, of the
French Academy of Science, hard at
work on a microphone deteetor system.
The problem of evolving successful
system for detecting submarines by
noises peculiar to these craft was q
most difficult one. In the earlier ex.
pcriments the French simply placed
waterproof microphones below the sur
face says the Army and Navy Journal.
At first the sound waves emitted by the
propellers of submarines were those
sought, but these were found TO re-
semble so closely those of other craft
that they could not be relied upon.
- Fortunately for the experimentcrs, IL
was discovered that the underwater
craft were sources of sound waves of
exceedingly high frequency, quite dis
tinctive from any other sub aqueous
sounds. While the cause of the high
pitched sound is known to the inven.
tors, it cannot be divulged, since it
would then be possible for German
submarine constructors to eliminate the
source of the tell-tale sound waves and
thus render void the purpose of the de-
tector installations. With characteris-
tic sound waves available, there re-
manned the elimination of all other
waves so that the desired sounds would
be available for determination Of fhe
distance Of the submarine and direc-
ton it was travelling.
1t required several months of re-
search work in developing suitable re.
sonance tubes for filtering out all I'M
desirable sounds, as well as a tikkor
interrupter arrangement, which causes
only the peaks Of the desired sound
waves to be heard in the telephone re.
eeivers that are used.
The submarine boat placed at the dis.
posal of the inventors by the French
government was detected several miles
away. 1t was found advisable to in.
crease the range, and this was accom-
pIished by the introduction of Dc
Forest audion amplifer, ultimately re-
sulting in a range of ffty-fve miles.
The military value of the submarine
detector system now used by France
and England naturally prevents the
disclosure of important details, it is
stated, but it is learned that a number
of special micrOphOnes are lowered to
a depth of several fathoms, usually in
a scmi-circle facing out to sea. Each
microphone is so placed as to receive
sound waves best in one direction. By
slowly moving the switch over the sew
eTal contacts the operator can de-
termine from the microphone that re.
spends the loudest the direction of the
submarine.
The system is not available for use
on vessels because of its extreme sensi
tivitv. There arc said to be a large
number of installations for the detec-
ton of submarines along the coast of
England, Scotland and Ireland, and
along the French coast bordering on
the English Channel and extending as
far west as the Bay of Biscay. These
stations are provided with means for
advising fast torpedoboat destrOyers
and armed motor boats of the presence
of hostile submarines.