Document GKm79ZVmajy4zQqzrGp4M4rv4

676 JEROME R. COX, JR. those responsible for plant design, plant equipment, and plant maintena1: * * * * Inadequate knowledge of these principles may lead to misguided attempt' noise control and, consequently, a lack of enthusiasm for further efforts;; education and a general diffusion of knowledge of noise control will remove difficulty. The first step in this educational process is probably an apprecffi of the complexity of the subject. It cannot be mastered by learning a fewrules. One must familiarize himself with new units, new materials, ar concepts. . The difficulties raised by any lack of understanding of the principles of control are rather insignificant compared to those raised by the simple qif' "Does noise control pay?" Noise control seems to have more sources of e: than income. Acoustical materials are rarely inexpensive, and there ,m hidden expenses caused by a slowdown or interruption of production. The^i from noise control is almost always an intangible, and conservation of thi ing of employees must be viewed as a long-term investment that will pi .cel'lent interest in future years. Management must face these facts sc before launching a program for the conservation of hearing. Otherwl program has little chance .of success. / The first step in such a program is an evaluation of the noise e| Methods for making the measurements involved are discussed in Void) The engineering criteria set forth in Section III.T of this chapter allow"i fication of certain kinds of noise exposures and provide a goal for noi-,c| . Cla8sificati.o.n_j3L.npjae__exposures according to their severity makesM? sible to assign priority to the most serious problems and defer thqse;Ji of minor importance. The goal for noise control provided by one of tlieei ing criteria makes it possible to avoid costly, unnecessary quieting, ln'f| the amount of noise reduction required to meet the criterion will infiiv* choice of the approach to the problem. For example, if only 5 d reduction is necessary, sufficient quieting will probably be achieved-`H few minor changes. However, if a reduction of 25 db is desired, a rather,rcr; revision of the entire operation may be necessary. j If the complete solution of one of the more difficult noise probkivw ^ ently impractical, the engineering criteria can be used to evaluate tl.. ^ 5* ^effect_oLsmaller,nojs,e jeductions. .Any significant reduction in -the, noj -f > > is, of course, worth while since it decreases the number of people,,wig ( hearing impairment. A. CONTROL OF NOISE AT THE SOURCE if' 1. Desirability Compared to control of noise at its source, control along the'WSS. path or at the man is relatively simple to plan, but often difficult to. caijrjsSO practice. On the other hand, control at the source yields highly satisfaOtwij&j. NOISE AND THE CONSERVATION OP HEARING 677 t'is well planned. The approach to the problem of noise control at the Should be made in a determined manner. Two important prerequisites are upwill to do the job and an open mind.28 j 2. Is There a Quieter Way to Do the Jobf u*1l itrol at the source may sometimes be accomplished .by substitution of a " method of doing the job. Such substitutions have been listed by two cffS;?8'24 and some notable examples follow: (a) welding instead of riveting, cession riveting instead of -pneumatic riveting, (c) mechanical forging fc($f dfojj forging, (d) grinding, instead of chipping, '(e) electric tools lapf unguieted pneumatic wb)BV'(^.cbn^y.ora...in^e%4spf chutes, (g) me^M'WiPPiog'of^^frpnn.punch.press^esdhs^^hir-blast stripping, ^instead of cold working of metal,' (t) b`elt' drives instead of gears. *Her considerations may outweigh,the.importance of noise in selecting a ?a method of doing a job. Howeyer, whenever this is,.not the case, those lble for, plant layoutsand`:"jequipffieht!fp1am should' be aiert for quiet niit'i,yes.'to noisy jobs. fil `Examination of the quieter methods suggested above discloses two . feiles. A substitute method that eliminates the impact of metal on metal .pi i the rapid flow of air will often bring about considerable quieting. i||j principles may bring to mind other substitutions that provide the ulfe'particular noise problems. S. Examples of the Control of Noise at the Source ' ^control of noise at the source is usually difficult to- plan because -of the Igigneral rules. For instance, identical machines may- require different noise control because of different production problems or different i Sconsiderations. Although it is not possible to-present a cookbook-of jrfjpib'r recipes, certain typical case histories can be rpported. TbpSe/ who * iffilhr problems may be able to determine whether similar steps, are Wto their situations. .. -- .. -- -- ----------------------------- j v.^wwwWWAV/AA',VA-AHJ01iCi^li.JIIU*'*Wi*'SaW. is noisy whether it is sawing or not often can be quieted^'Piny in Ighould be corrected by new bearings. If the,saw< doestnotoS^fpliffeetly lljfbe necessary to remachine the saw collar. A^kerf, signific&ntlyiAsider ^*r"^Miof^EeFsa'w"blaile-rudicates a rinrthat is vibrating excessively, ffehing collars may be used in some situations to reduce rim-vibration. IpisWillianis, Noise can be controlled, Am. Ind. Hyg. Assoc. Quart., 15, 32 (1954). _ * -fiTyzzer, Reducing industrial noise: general principles, Am. Ind. Hyg. Assoc. Quart., I m. ] I 3 s h.1 i I I i; ? \ i i { i i \