SOUND IN WARFARE

New Zealand Listener, Volume 2, Issue 49, 31 May 1940, Page 9

SOUND IN WARFARE

By

Ronald

McIntosh

strange weapons. for the conduct’ of warfare. Not the least remarkable are those which depend upon. sound waves. for their operation. The sound detectors of ‘the anti-aircraft squadrons are perhaps the best known example of the use of these waves. Four large microphones are mounted in pairs which move vertically and horizontally. When the noise of a hostile aeroplane is picked up the microphone arms are moved so that the noise is equally balanced in each earphone. The detector’s sight is then pointing toward the approaching air¢raft. So delicate is this detector that the noise of an aeroplane can be detected more than 15 miles away -but that is only 342 minutes of flying time for the modern bomber. ' To counter these sound locators, the attention of aeroplane designers has been turned to the production of silent bombers-and once again sound has been called in to achieve this end. The’ Germans claim to have co-ordinated and harmonised the noises from twin exhausts so that the sound waves from one cylinder neutralise those from the other. Similarly, it might be possible to neutralise propeller noises by further tuning. M ODERN science has evolved some Submarine Detectors The British Asdig submarine detector is merely an -under-water arrangement of microphones. Even with the crude apparatus used.in the last war, submarines

could be detected at distances greater than ten miles, but now the earphones can be used on a moving ship,.and not only do.they detect the submarine, defining its course, speed and distance, but they also calculate the position of the target for a given time. They have been found nearly 100 per cent. efficient in practice. , Such -devices, however, employ sound only as a defensive weapon. Soon, if researches going on in various parts of the world are successful, deadly vibrations may be used as a means of attack. When Sound Is Deadly Every object on this globe has a definite pendulumlike swing. This knowledge has been employed, for example, in the construction of earthquake proof homes, which are deliberately given a sway that will nct synchronise with the vibrations of an earthquake, for a building:is in danger only when it sways with the same. period as the earth tremors. Every organism created by nature and every object built by man has its own distinctive vibrations, and this rhythm cannot be accelerated without risk of complete destruction. Sound waves vibrating over 19,000 times a second will. produce the ultra-sound wav.s, beyond the range of human ears but, neverthe‘less destructive to animate and inanimate things alike, That deadly sound is a factor with which we must ultimately reckon is proved by the fact that echosounding waves have killed fish; locust swarms have been driven off by piercing sirens, and iceberg masses shattered by tuning the sirens of several ships to the same note. To humans, it may prove fatal by . destroying the red blood corpuscles,