NOISE AND WORK

Evening Post, Volume CXX, Issue 8, 9 July 1935, Page 8

NOISE AND WORK

FACTORY EXPERIENCE

RAISING EFFICIENCY

Three years ago the Industrial | Health Research Board published a report on the effects of noise on the performance of weavers. A second report, describing further investigations, was published by H.M. Stationery Office, says the "Manchester Guardian." It urges that excessive noise is by no means a negligible factor in determining industrial efficiency, and strongly recommends the use of ear-plugs by weavers. The 'report, by H. C. Weston and S. Adams, defines "excessive noise" as noise of such intensity that it is. commonly accepted as objectionable and disturbing. For noise of this kind it would be "convenient to adopt a particular term, and one which is ready to hand is the word "blare." It is suggested that this term, might be used to denote all noises having an intensity level of 80 decibels or more. Examples of such noises are a large number of industrial - machinery noises, such as those produced by looms, various shoe-making' machines, some circular* saws, nail-making machines,. riveting, etc., and among the noises familiar to those unacr quainted with factories examples are those due to pneumatic drills, tube trains, low-flying aeroplanes, and very loud radip reproduction. '■:'■ • EXCESSIVE NOISE. '.' c " There can be no doubt that these examples are sources of excessive noise, or what may be described in a single word as "blare," and that they are unwanted sounds, but as yet there is little definite evidence of their effects upon those who are frequently exposed to them. The noise in a weaving shed is a continuous roar arid clatter, the composite result of a number of sounds of considerable intensity generated usually by various parts of a large number of looms. Gears, cams, and picking mechanism are mainly responsible fbr the noise the intensity level of which, in a shed of medium sike, is about 96 decibels. The noise could be reduced to some extent by modifying the construction of the machines and by replacing worn parts, but the picking mechanism is inherently noisy. The method ' adopted to alter, the normal noise ' environment of .the weavers was t,q,. equip them with special plugs known as ear-defenders. These ear-defenders ,are designed, in such a manner that 'they limit the amplitude of the sound waves impinging on them, so that.their real damping effect comes into play only above a certain intensity level (since intensity is a function of amplitude), and they' cannot reduce the apparent loudness of noise below a certain value. The experiment covered eighteen months, during which the output was recorded of two equally proficient groups, each consisting of ten weavers, one group with and one without eardefenders. The two groups were arranged in such a manner that almost a complete bahlice of weaving efficiency was obtained: INCREASE IN OUTPUT. After describing, the results of the experiment -in detail the report says that in the present case v the effect of the noise normally associated with weaving (which has an intensity of about 9C decibels) is to lower the rate of output by about 3 per cent, of that obtainable when the noise intensity is reduced to a level of 81 decibels. In terms of personal efficiency this is equivalent to an increase of about' 7£ per cent, with subdued noise. ~ The actual reduction of noise intensity. effected was 15 decibels, and, - within the range of intensities considered, this probably represents about a 50 per cent, reduction of apparent loudness. The reduced noise stimulus wassecured by the use of ear-defenders designed to limit the intensity of .sounds transmitted to the ears. These do not effect complete silence, and this cannot be achieved—even if it were desirable —by any form of, earplug, since sound is to some extent transmitted to the aural apparatus by bone conduction. While the wearing of any kind of ear-plug is not the most desirable means of securing comi parative quiet^ it is often the only practical means available. Excessive noise should, of course, be eliminated at its, source whenever this is practicable, but there are cases where an adequate reduction of intensity cannot be. effected in this way, and the use of some form of ear-plug affords a simple and convenient means of. protection. If properly designed and fitted these plugs should cause no discomfort to the wearer.