RIDDING HOUSES OF NOISE

Press, Volume LXXIII, Issue 22194, 10 September 1937, Page 2

RIDDING HOUSES OF NOISE

Building Research In England “FLOATING FLOORS” BEING TRIED (raox ova own coaE*3Po»D*KT.) LONDON, August 18. Architects are assisting the "antinoise” campaign in England by trying to check sound transmission in buildings. Their requests to the Building Research Board for advice on the design of new buildings, having regard to this problem, are declared by the board, in its annual report to the Department of Scientific and Industrial Research, to have been one of the interesting features of. the year. The trend of experimental work increasingly supports the view that this problem of sound transmission is primarily one of planning, it -is stated. A certain degree of sound reduction is obtainable by structural precautions in most cases, but where severe conditions are imposed by the juxtaposition of noisy and quiet rooms it is not usually economical, nor in many instances practicable,, to achieve complete satisfaction in this way. While it is very important to give due attention to the question of noise in the early stages of planning, innumerable cases arise in which the utmost that can be done by this means is insufficient, and it is to meet this urgent problem that experimental work is mainly directed. Work at the National Physical Laboratory has shown that the most promising method of dealing with the transmission of noise through floors is by the provision of a "floating floor,” and experiments have been made with a “floating floor” consisting of a concrete slab insulated from the main structure floor by small pads of rubber. A method of construction has been evolved by which the top slab is raised out of contact with the main floor after it has set so that no “bridging” is possible. By this method, also, the rubber supports may be changed should this become desirable, without breaking the floating slab. A degree of insulation against impacts which might be considered reasonable in most residential buildings is afforded probably by a two-inch slab, raised once inch from the main floor. False Ceilings Tests have been made with false ceilings, some of which were supported on independent joists bearing on the walls, and others were suspended from the structural floor by means of felt-lined clips. Both types, when reasonably heavy, gave a certain amount of added insulation, but no ceiling has yet been tried which is as good as the two-inch floating slab. A false ceiling can at best protect only the room in which it is placed, whereas a floating floor, by cutting off at its source the noise entering the main structure, acts as a protection to the whole building. Cleansing With Water Laboratory experiments have also been made to improve methods of cleaning buildings with water, the only cleaning agent known which can be used without harming the stone. Hitherto chemicals, chiefly caustic soda, have been .widely used. Caustic soda, however, reacts with the .carbon dioxide and sulphur dioxide in the air to form salts which accumulate and cause decay. Many buildings, it is said, have been damaged in this way. The advantage of using .chemicals has been that less mechanical force is needed to apply them. "The experiments,” says the report, "have given most promising results on very badly discoloured limestones. It is found that by directing a fine spray of water on the surface for a

period depending on the nature and condition of the stone, the soot incrustations become so thoroughly softened that they can often be brushed off with a soft paint brush.” In the past, when water has been used, it has been applied merely with a hose and brush. The report says, however, that the spraying of water is not helpful in cleaning sandstone, to which soot adheres so tenaciously that silica grains taken from the surface remain discoloured even after being boiled in caustic soda.