LESS NOISE IN CARS

Evening Post, Volume CIV, Issue 143, 14 December 1922, Page 13

LESS NOISE IN CARS

Although in theory engineers recognise that nowe means wasted energy, in practice it is not always that they make careful efforts to reduce or to avoid/it For ex ample, in railway . trains and tramo&rs, designers and constructor! in a][ parts of the world have taken it for granted that a large .amount of noise js unavoidable The first systematic effort to get away from this rathor unscientific position is being made_ in London. On underground railways noise is apt to be eicessive, owingl to the reflection of the sound 'from the walls of the tunnels! On those railways in London experiments were recently earned out to discover exactly how the noise originated. A special instrument known as tho audiometer was cm. ployed- This instrument shows by the vibration of a beam of light the. intensity of the sound falling on the instrument. A .narrow and more or less straight line indicates moderate sound, while a wide, wavy record indicates a loud noise. The tests made show that the trucks were generally the cause of the trouble, and that the roofs of the cars greatly magnified the -noise. Windows were ateo a source of vibration, and therefore of noise. ' By preventing the windows rattling and by filling the hollow roof of the carriages with asbestos, a remarkable reduction: in the noise on underground lines resulted. Under normal conditions it was impossible to hear the ticking of a watch held close to tho ear, whereas in the impfoved car .the watch could be hca.rd when hold one ■foot away. These v British- experiments are, therefore, likely to lead to a considerable amelioration of one of the serious minor nuisances of travel.