STREET NOISES

Evening Post, Volume CIX, Issue 38, 14 February 1930, Page 11

STREET NOISES

PERNICIOUS EFFECTS

SCIENCE'S TIGHT

Noise has a disastrous effect on the human body, and may even result in death, and the noise which is turning us into a nation of nervous wrecks can be stopped, writes Professor A. M. Low in the "Daily Express" (London).

The recent law against noisy vehicles is a small step in the right direction; but it is little more than the first feeble stumble of a child learning to walk. AVhat is tho use of legislating against noisy motor vehicles, while pneumatic drills and pile drivers are allowed to make tho streets 'intolerable with their din?

The stopping of .noise da a practical possibility. Given a certain amount of air oscillation, it is possible to take hold of it and literally break it up altogether or direct it into harmless channels.

The first step is the discovery of the typo of noise and its source. Tho ear is a bad instrument from, a scientific point of view. It does not appreciate curtain frequencies of sound, and it varies in sensibility. A man, after a good meal, for example, is less likely to notice noiso than a tramp with an empty stomach.

CAMERA TO THE RESCUE,

Photography has solved the difficulty. Sound is photographed for gramophones and the talkies, and the first procedure of an engineer- testing a room or- a car is to photograph the noise from different positions so that he can discover the "shape," direction, and carrying properties of the sound waves.

The necessity of photographing from, all angles is important, because some sounds usually carry more in one direction than in another.

A klaxon horn, for instance, is specially designed to make a noiso that will carry in front and will not mingle with the noise of the traffic.

Heat in large- patches eau liavo the effect of carrying the sound over tho heads of people standing near, so that they may find a motor-ear quiet while others twenty yards away find it noisy.

Photograph's also enable- the acoustical expert to detect the places in which echoes occur and either dilute the reproduction by means of absorbent material or to reflect it evenly so that the "sound" is no longer noisy.'

The property of certain materials to absorb is the scientist's' most useful weapon in his fight against noise. Every singer knows that a full concert hall is better than'an empty one where the reflection is so great that tho echoes interfere with the music.

It is now possible to deal with any sound, provided you know its wave and formation and frequency. Theso sounds that cannot conveniently be reflected away from the ''listener can be absorbed by specially prepared material. This may be either by eelgrass —-a peculiar sea product of Canada —by cellular asbestos, often best of all, or by a number of special preparations. Mats mado of theso materials can be hung in. carefully considered positions round the room or hall. No matter what noise comes through the window from the street below, the mats can be placed to avoid reflections or to render noises of such characteristics that they do not interfere with music or speech. The house of the • future will undoubtedly be fitted with soundproof walls. To make a' noise that disturbs others is one. of tho greatest crimes, and 1 am glad that the law is at last awakening to the fact that, like most evils, it can usually be prevented at the source.