A.— MATHEMATICAL AND PHYSICAL SCIENCES 51 



now in hand and should be available for use by the end of the year. 

 Much research work on building acoustics is also being carried out for 

 the Ministry of Health in connection with slum clearance, and for the 

 Architectural Acoustics Committee of the National Physical Laboratory 

 and the Building Research Station. 



To revert to the case of a non-suppressible noise, if most of the noise 

 is transmitted by air, the best remedy, should circumstances render it 

 practicable, is some sort of sound-proof enclosure, the design of which 

 may need careful attention both as regards weight and discontinuity of 

 structure. There is, of course, no such thing as a sound-proof material, 

 and success in sound insulation is largely a matter of design. 



Certain large-scale operations may require ' sound-proof ' buildings to 

 mask them, the doors and windows of which should be heavy and close- 

 fitting and preferably situated on the side remote from that where the 

 noise is liable to be regarded as a nuisance. Doors and windows, 

 particularly high windows and skylights, may require to be doubled 

 and, in extreme cases, it may be necessary to employ double walls 

 mounted on independent foundations. Buildings in which noisy 

 operations are carried on should, if possible, be put under the lee of 

 larger buildings, which may afford advantageous shielding to the locality. 

 In the interior of noisy buildings, it is usually beneficial to the workers 

 to divide groups of noisy machinery, as far as may be possible, into 

 smaller units, each in its own enclosure. Appreciable benefit may also 

 result from lining walls and ceilings with acoustical absorbent, so pre- 

 venting the noise level from building up unduly. 



In the case of structure-borne noises, the remedy is discontinuity 

 somewhere in the structure either in the form of an air gap or as resilient 

 material, for example, under the foundations of noisy or vibrating 

 machinery. 



As an illustration of the abatement of extreme noise, near a residential 

 area, reference may be made to the new Alvis works at Coventry, in the 

 design of which the National Physical Laboratory co-operated. These 

 works are devoted to the excessively noisy operation of testing aero 

 engines on the bench. The entire building, which has double walls, and 

 through which a high wind passes, is fitted, so to speak, with an exhaust 

 pipe and silencer, which takes the form of a horizontal brick tunnel 100 

 feet long, 12 feet high and 10 feet wide, lined with 4 inches of mineral 

 wool and asbestos cloth. This not only serves as an outlet for the wind 

 but reduces the objectionably high noise of the engines to an acceptable 

 figure as heard in the neighbourhood. 



Quiet Housing. 



Those of us who seek isolation in an endeavour to protect themselves 

 from noise, should first of all choose a naturally quiet site for the building 

 they propose to occupy, and then select a room as remote as possible from 

 such noises as there may be, whether from traffic or other sources. That 

 the sound shadows cast by buildings are sufficiently pronounced to be 

 beneficial finds ample illustration in the quiet gardens of busy cities often 



