The Elk Mountain pilot., 1919-11-13
MsNE RzJcM ox0eNaE z1

!ernine the distances at which the shock waves
resulting from the discharge of various explosives
could he henrd. A brief investigation OF the
factors influencing the transfer of energy from u
mining tool to the clay and coa were also made in
order that recommendations could be made as to
the type of mining machine which could be used
to accomplish the most work with the least noise.
In this connection 1t found that sounds
were transmitted only about half as far In clay
as in shnle strata and about onequarter as far In
clay MS IN coni. To give some idea of the sensi-
tveness OF the instrument 1t may be said that
pounding with pick on the bltuminOus coal
be detected for u distance Of 900 feet. and the
direction determined and that pounding with
sledge he heard far l5O feet. These
measurements were made In the Pittsburgh coal
In the vicinity Of Pittsburgh. where the coal
is somewhat hnrrler than In most other bltumlnous
coal beds. The explosion of u OneOunce charge
of dynamite was detected distance Of over 1000
feet through the shale strata.
Sound Tells the implement.
One Interesting feature OF the instrument Is
that the sound transmitted to the Is charac-
teristic OF the implement producing tile sound. To
illustrate: Twelve mining and carpenterlng
operations carried out the coal rlb An
engineer Of the bureau Of mines who had never
used the geOphOne and who did not know what
tools were to be operated was able to recognize
and name nine of the implements at distance Of
several hundred feet through the strata. The
other three sounds were accurately described. but
the tools were not identified.
Now that the war il over. the bureau has turned
to the development OF the Instruments for peace
time uses. For one thing. 1t Is believed that they
will be OF great value to mne-rescue crews who
may be entering mines for exploration and to
locate miners who may have been entOmbed after
a disaster The tests 20 far made in the vicinity
of Pittsburgh show that man pounding the
coal rib with pick piece Of timber or sledKc can
be detected and located from point 600 to 100
feet distant This distance depends greatly on tus
character of coal upon which the man is pounding.
md Intervening rooms and entries seep to hive
surprisingly little effect upon the distance or the
determination of direction.
Pounding with slelge be heard from 200
to 900 feet through the mine cover. depending
upon the quetness Of the day outside since any
wind grentiy interferes with the successful opera
tion Of the Instruments. 1t will at once be seen
that when mines are not too deep they cnn be
"explOred' from the surfnce and 1t VIII thus De
possible to find and locate II miner who IS pound-
ing At the experimental mine In Bruceton. Pa,
n man has frequently been located through l4I
feet Of cover within 80 feet Of the exact point
where he was pounding.
A study is also being made Of the distances that
pounding on rails and pipes can be heard Since
rails are generally buried In the earth or dust In
the entries of n mipe and since this dust dampens
the transmission of the sound. the sounds are not
transmitted very well. The same is true of pipe
lines However. II the pipe lines are not buried,
but are laid blocks and ties the pounding can
he heard grent distances. So far no lines have
been found long enough to show the limit of the
peophone 1t is known, however. that the naked
oar cnn get sounds farther than 1900 feet.
Used to Guide Tunnel Work.
In metal mines expensive surveys have some
times to he made In order that the approaching
tunnel headings may be brought together ac-
curptey Since direction can he determined so
well with the geophones. 1t is thought that they
can he used guide such work. 1t would only
he necessary to go into each heading and locate
the direction from which pounding in the other
heading was coming.
showed that direction he determined much
more ensiy in rock than in coal. This is prob
ably due to the fact that there Is some reverbera-
tion to the sound from hammer blow on coal.
while on stone the sound Is clean cut. 1t SO hap
pened that in this mine rnise was being driven
up about six eight feet distant from a SHAFT.
Observations were made in the drift of the souHc