NOISE IN BUILDING

Timaru Herald, Volume CXLVIII, Issue 21573, 8 February 1940, Page 11

NOISE IN BUILDING

IMPORTANT RESEARCH IN LONDON New Zealand cities, where many large blocks, including residential flats, have been built during recent years, are necessarily interested in plans anil projects for the reduction of noise. A report issued by the British Department of Scientific and Industrial Research recommends that the problem should be attacked along three lines: fl) by careful planning so that external and internal sources of noise are as far removed as possible from those parts of the building where quiet is most needed; (2) by suppressing or reducing internal noise, preferably at its source; (3) by providing a structure which will as far as possible prevent the transmission of noise from one part of the building to another.

“There is a tendency,” the report continues, “to consider the structural question as the vital one and to neglect the other approaches. This is wrong, for the desired degree of quiet is obtained most economically by giving consideration to all three of these aspects. Indeed, whilst the provision of a sound insulating structure is often essential, the suppression of noise at the source and protective planning can reduce considerably the degree of structural insulation required, and therefore the cost of insulation. Moreover, it should be realised that in some cases the structural methods at present known are insufficient to provide adequate insulation, even if the cost does not matter.”

The report emphasises that sound reduction in a new building involves consideration of the whole structure at an early stage in the design. Floors, for example, cannot be considered without regard to the remainder of the construction with which they are associated.

When all the present evidence is reviewed, it appears that probably the only satisfactory way of preventing excessive transmission in large buildings will be to break the continuity of the structure, and it many even become necessary to construct units—such as complete flats —as separate boxes floating upon suitable insulation. Experiments on these lines are in progress and are promising. Perhaps the most difficult problem of all is presented by the wireless set, which may be clearly audible through an 181 n. brick wall. Again, it has been found in experiments in a large reinforced concrete building that operating a loudspeaker in one room generated appreciable sound intensity not only in the next room, but in rooms farther removed. In a room 50ft. away the sound intensity was not much less than the intensity in the room next to the loudspeaker.

Failing a solution based on the design of the structure of the building, the only alternative suggested for reducing noises due to wireless in flats is the provision of a central receiver with relays to loudspeakers fixed in predetermined positions in each flat, thus enabling control to be exercised by the management over the maximum volume of output. The arrangement has the advantage of providing good reception to‘the tenants, whereas other electrical equipment and metal used in the construction of the building may cause serious interference with individual wireless sets operating with indoor aerials.