A— MATHEMATICAL AND PHYSICAL SCIENCES 43 



by constructing cabins of double walls containing a suitable filler, by the 

 damping of ' drumming ' panels, etc., and by increasing the amount of 

 absorbent in the cabin. Measurements have been made in aeroplanes 

 in flight and on the main individual sources of noise under experimental 

 conditions. 



The present position is that the noise in the passenger cabins of some 

 of the latest air liners or flying boats is little more than that in a train. 

 This is very well for the passengers ; from the point of view, however, 

 of those who live near aerodromes or on busy air routes the noise of air- 

 craft is still a nuisance which awaits a solution. 



Noise on the Road. 



(i) Ministry of Transport tests. — The growing volume of road traffic, 

 and the ever-increasing speed and acceleration of individual vehicles, are 

 potent contributory factors to the problem of road transport noise. 

 There have, it is true, been certain counterbalancing changes, to wit, the 

 steady gain in quietness of the newer models of the motor bus and motor 

 coach, and the introduction of the trolley bus in place of the much noisier 

 tram car. But these are only drops in the bucket. Backed by the force 

 of public opinion the then Minister of Transport, Mr. Hore Belisha, who 

 proved himself a great ally of quietness on the road, set up in 1934 a 

 Departmental Committee for the purpose of studying the question of 

 motor- vehicle noises. The Committee included representatives of the 

 motor and motor-cycle industries ; and as Chairman of the Committee, 

 I hope I may be permitted to refer to some of its proceedings and 

 recommendations which are contained in the three interim reports ^ so 

 far published. These reports, which may be consulted for fuller informa- 

 tion, are based on an elaborate series of tests, comprising many thousands 

 of observations, which were carried out on behalf of the Committee by 

 National Physical Laboratory. 



(ii) Tests on new motor vehicles. — The first two reports deal with tests 

 on a representative selection of nearly 100 mechanically-propelled 

 vehicles, comprising saloon motor cars, sports cars, motor cycles, goods- 

 and passenger- carrying vehicles, most of which were kindly lent by the 

 industry. It was decided to begin the work by a survey of newly manu- 

 factured vehicles, both of home and foreign origin, which were intended 

 to operate on the roads in this country. 



After careful consideration, the Committee decided to confine their 

 first attention to the ' overall ' noise of vehicles, as representing the aspect 

 of major public interest, and one which might be expected to afford, 

 without undue delay, information which would serve as a trustworthy 

 basis for possible legislative action. No systematic attempt was made to 

 study the composition of the noise, the major components of which in- 

 clude those from the engine, transmission and exhaust, although a partial 

 separation of the ' fore ' and ' aft ' components was possible without 

 difficulty. It was rather felt that further steps could best be left to 



^ " Noise in the operation of mechanically propelled vehicles." O.H.M.S. 

 1935. 1936 and 1937. 



