A.— MATHEMATICAL AND PHYSICAL SCIENCES 49 



quietly in the day time also. Most of us have come to agree that a strident 

 horn rarely, if ever, makes for safety but more frequently leads to in- 

 decision or fear on the part of other road users. The National Physical 

 Laboratory has carried out measurements on motor horns for the Depart- 

 mental Committee of the Ministry of Transport, vs^ith the object of deter- 

 mining the scope and effectiveness of such warning devices and, if 

 possible, of correlating annoyance with some measurable physical factor. 

 The report of the Committee is not yet available. Incidentally it is 

 common experience that a reasonable driver seldom finds it necessary 

 to employ a horn at all, a doctrine to which it is evident that Paris and 

 some other Continental cities do not subscribe. 



(vi) Pneumatic road drills. — Before leaving the subject of road noises 

 I ought to refer to that sporadic producer of undue noise — ^the pneu- 

 matic road drill. Much attention has been given to the question of its 

 silencing : possibly the problem of impact silencing will remain until rotary 

 drills come into use. That there are grounds, however, for believing 

 that some progress is being effected in regard to exhaust silencing would 

 appear from some comparative tests carried out last year under the 

 auspices of the Westminster City Council. Equivalent loudness measure- 

 ments made by the National Physical Laboratory gave an average figure 

 of 102 phons (B.S.) for the unsilenced drills, while the corresponding 

 figures for the silenced drills ranged from 91 to loi phons, the lower 

 values thus bringing the noise nearer to that of general traffic noises in a 

 busy street, say 80 phons. Unfortunately it appeared that, roughly- 

 speaking, the drills making the least noise took the longest time to break 

 a given amount of concrete, though the relative skill and experience of 

 the different operators and labourers in the competing teams must not 

 be lost sight of in comparing the efficiencies of the different drills. 



The Abatement of Noise. 

 While in some European countries there are now severe legal pro- 

 hibitions against noise, the position in this country is rather that of legally 

 identifying a noise with a nuisance. Under the provisions of the Public 

 Health Act of 1936, it is the duty of a local authority, if satisfied of the 

 existence of a nuisance, to serve a notice requiring its abatement, and, 

 in default, to take proceedings in court for abatement or prohibition of 

 the nuisance. There are, moreover, numerous precedents in local Acts 

 already in force, according to which a noise nuisance exists if any person 

 makes or causes to be made any excessive or unreasonable or unnecessary 

 noise which is injurious or dangerous to health. Such noise nuisances 

 often arise from plant and machinery which are operated during the night 

 or early morning, but there are other circumstances which appear to 

 demand a working definition of a noise nuisance. It should be added 

 that if a noise occurs in the course of any trade, business or occupation, 

 it is a good defence that the best practicable means of preventing or 

 mitigating it, having regard to the cost, have been adopted. As regards 

 the noise of motor vehicles, much information concerning legislation will 

 be found in the First Report of the Ministry of Transport Departmental 

 Committee on Noise. 



