SOUND HEARING.

Taranaki Daily News, 20 March 1920, Page 11

SOUND HEARING.

POME EXTRAORDINARY ACHIEVEMENTS. * London, Jan. IS. Professor W. H. Bragg, in his extraordinary interesting lectures on sound, delivered in the Royal Institution, told a most interesting story of what had been accomplished by scientists in the way of locating enemy guns, submarine's, aeroplanes, mines, etc., by means of sound. ''Durinji the war much effective work v.'i's accomplished by the use of what, is kno'. v 'n as an under-water telephone. The lecturer showed one of these, and exnlained that by putting it nvpr the yilu it w v a jjofctible, if # je ft

noise, to know the direction from which the sound came, and so to locate the position of an enemy submarine. "Illustrating the effectiveness of the under-water telephone, the lecturer gave several gramophonic records. Tn one instance the passing by of a submarine at two knots an hour, as well as the hammering by one of its crew who was working inside, coxild be distinctly heard. Another instance was that of the working of the engines of a fishing vessel, and the running of the chain in dropping the anchor. A third was the passing of several destroyers, which made a tremendous noise; a fourth, in the shape of a shrill rapid boat, was the sound of a torpedo running into the water. "Professor Bragg aroused amusement by the last record he gave. It was that of signalling by Morse code from a British submarine; and the signaller must have been something of a wag. The lecturer translated the signalling, which was distinctly heard, as follows: T am a Hun.' Professor Bragg further gave renderings of the noise caused In the water by the surrendered German submarines when they eame into Harwich. "The lecturer remarked that the location of enemy positions by sound was the most successful. The instrument used, a Frenc.i invention, is called the geophone. It is after the style of the stethoscope; and has two little boxes at the end, containing a flexible partition on which is mounted a heavy weight- The use of this instrument in locating enemy mining operations was of the greatest service. On one occasion when an English mine was being driven forward conversation was heard some distance away. In a few days it was much closer. The point to discover was in what direction the Germans were mining, and whether or not tliey would break into the English mineAn attack by the British infantry had been arranged for a certain date, in which the mine was to play an important part, so that it was very much to be hoped that the Germans would not break into it and necessitate its being blown up prematurely. By the use of the geophone the location of the enemy mine was discovered. It passed the English mine by only a few feet. So our miners continued their work, which, on the fatal day, proved its worth, for the operation was entirely successful. "Agaffi, sound was used to find the position of enemy gunsy but in this connection we were about a year behind the French, and it was a long time before we caught them up in the njjatteav The lecturer showed what he described as a very famous: slide. It was an instantaneous photograph of a bullet in flight, with the air waves caused by its By observation and calculation it was possible with special microphones to find out where the bullet or shell came from, and also the size of the gun from which it was fired. "By this method, in- conjunction with aeroplane observation, extraordinary accuracy was achieved in fixing the positions of German batteries. Sound ranging under the water had been used to find the position of explosions hundreds of miles from the shore, and was now found, in times of peace, to be of unique usefulness for charting the seas. " '-Sound, you see', remarked Professor Bragg, 'has played a great part in the war. One of the interesting things is that there is not really a bit we know about sound that has not been of some use during the war-'"