142 Master Minds of Modern Science 



on the London Underground Railways. In a special 

 experimental train it located the three main sources of 

 noise — wheel and rail shock, motor and gear noises, and 

 general loose rattle. These were partly eliminated by 

 filling the hollow roof with asbestos material, by dividing 

 the windows into smaller areas, and by fitting hoods over 

 the wheels, thus deflecting the noise above the level of 

 the ventilating windows. 



There was then, as many of our readers will remember, 

 a deafening rattle on the cars, which made conversation 

 practically impossible while the train was in motion, but 

 in the present rolling-stock, embodying the noise-reducing 

 devices, it was found possible to hear the tick of a watch 

 held one foot from the ear. The important change was 

 not in the mere volume of the noise, but in the elimination 

 of its more harmful elements. 



Twenty years ago it would have been impossible to 

 reduce noise in this way. For our present ability to track 

 almost any noise to its source we are indebted to Pro- 

 fessor Low and his audiometer. 



The Professor believes that this problem of noise will 

 attract increasing attention in the near future. Our 

 cities become noisier every year, and an enormous amount 

 of nerve strain is caused by noises that are quite prevent- 

 able. Professor Low says : 



The future will find noise-reducing devices in use on all 

 traffic, while the same process will be carried into the home 

 and every walk of life. Office windows can be provided with 

 sound deflectors, public buildings and dwelling-places can be 

 1 proofed ' to noise. 



There is confirmation of this in the new London studios 

 of the British Broadcasting Corporation ; although in the 

 heart of London, these are absolutely sound-proof, the 

 audition rooms being ventilated by a method which 

 admits fresh air but no sound. Many London buildings 



