1、NASA SP-5108TECHNOLOGYHANDBOOK FOR INDUSTRIALNOISE CONTROLNATIONAL AERONAUTICS AND SPACE ADMINISTRATIONProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-N
2、ASA SP-5108HANDBOOK FOR INDUSTRIALNOISE CONTROLSubmitted toNational Aeronautics and Space AdministrationLangley Research CenterHampton, VirginiaPrepared under Contract NAS1-15721byThe Bionetics CorporationHampton, VirginiaTechnologyNATIONALTransfer DwistbnAERONAUTICS AND SPACE1981ADMINISTRATIONV/ash
3、tngton, D. C.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-For sale by the National Technical Information ServiceSpringfield, Virginia 22161Price - $7.50Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,
4、-,-PrefaceThis handbook gives basic and comprehensive information on the understanding, measurement, andcontrol of noise in industrial environments. It is intended for engineers with or without acoustical experi-ence; to this end, it presents sections on noise problem analysis, instrumentation, fund
5、amental methods ofnoise control, and properties of acoustical materials.The National Aeronautics and Space Administration has been one of the chief instigators of manyimportant research and development studies within the field of aeroacoustics. These have been conductedin-house, by major aerospace c
6、ontractors to NASA, and by academic institutions under the aegis of theextensive NASA research grant program. The material included in this book is limited to that which isclearly applicable to nonaerospace industrial noise control problems. The later chapters, in particular,include more advanced an
7、d source-specific noise control technology. Emphasis has been placed on fannoise reduction, noise transmission control techniques, and jet noise suppression.An extensive bibliography and reference list of books and articles has been assembled. Many of theseresulted from NASA sponsorship, and, to a l
8、esser extent, that of other federal agencies.The author makes no claim to originality regarding the basic factual content of this work. In blendingsome of the more esoteric NASA-sponsored research with fundamental, well-established tenets of noisecontrol, a careful selectivity must be exercised. In
9、preparing this work, many NASA formal publicationsand journal articles were reviewed. The author is solely responsible for the material included here, and heapologizes to those who may feel that their work has been overlooked.W. Graham OrrHampton, VirginiaiiiProvided by IHSNot for ResaleNo reproduct
10、ion or networking permitted without license from IHS-,-,-AcknowledgmentThis document was prepared by The Bionetics Corporation for NASA under contract No.NAS1-15721. The author thanks Kevin P. Shepherd, Ph.D., Project Manager, for his patient assistance inproofreading the text and for his technical
11、counsel. He also extends his sincere appreciation to l_ester J.Rose of NASA Langley Research Center, Technical Representative of the Contracting Officer, for adviceand coordination of review.Too numerous to mention are the many individuals and companies who responded to requests forinformation by pr
12、oviding updates of research work in progress, published reports, and technical specifica-tions of equipment and materials. Source credits are given next to all photographs that appear in the text.Finally, the support of the staff at Bionetics is acknowledged: Alan J. Rosing for his judicious tech-ni
13、cal editing; Sandy Barnes for her splendid artwork; and Frankie Freeze, Michael Platt, and NancyWalton for the exceptional care taken in typing the manuscript.ivProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-ContentsPreface iiiAcknowledgment ivChapt
14、er 1. Introduction . 1Chapter 2. Basic Physics of Sound 3Chapter 3. Measurement Techniques 13Chapter 4. Instrumentation for Sound and Vibration Measurement 3 lChapter 5. Noise and Vibration Control Materials 43Chapter 6. Noise Control Procedures . 71Chapter 7. Specific Noise Sources and Solutions 93
15、Appendix. OSHA Noise Regulations and Assessment of Hearing Impairment . 127Glossary 129Bibliography 135Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-C
16、HAPTER 1IntroductionNoise is commonly described as unwantedsound. This definition implies a strong subjectiveelement in any assessment of the effects of noise,since what may be tolerated by one person may beintolerable to another. Although noise is by nomeans a recent phenomenon, it is only with the
17、rapid industrialization of the last century and theconcomitant accelerated development of powerfulhigh-speed machinery that it has become a pollu-tant of major concern. The effects of noise expo-sure on humans range from disturbance or annoy-ance to temporary or even irreversible deafness.Convention
18、ally, industrial noise control isaimed at alleviating conditions likely to lead tohearing impairment. In 1969 the first federal regu-lation limiting civilian occupational noise exposurewas promulgated under the Walsh-Healey PublicContracts Act of 1936. Initially these limits ap-plied only to certain
19、 government suppliers, butthey were soon extended to all industries by regu-lations under the Occupational Safety and HealthAct of 1970. These standards remain the most per-tinent to industrial occupational noise control andare given in detail in the appendix.Currently, 90 dB(A) is the maximum allow
20、a-ble continuous noise level that can occur through-out an 8-hour day. At higher levels some form ofameliorating action must be taken. There has beenconsiderable pressure from organized labor,NIOSH, I and the Environmental ProtectionAgency 2 to reduce this limit to 85 dB(A) or less,but serious quest
21、ions concerning the benefits andcosts of such a reduction are unresolved.It is estimated that some 3.5 million Ameri-cans now work in environments in which theOSHA noise standards are exceeded, and that 13.5million risk some form of hearing loss. Even witha stricter standard than that currently in f
22、orce, aproportion of workers will be at risk because ofvariations in individual susceptibility to hearingdamage. One study 4 estimates that a total capitalcost of $8 billion would be required to achieveengineering compliance with a standard of 85dB(A).An aspect of industrial noise that is notconside
23、red in detail here is the effect of noiselevels outside the work place on the communityand environment. The Noise Control Act of 1972governs such noise levels and provides for regionalenforcement through state and local noise ordi-nances. 5 One of the main provisions of the NoiseControl Act is the d
24、evelopment of Federal noiseemission standards for major noise sources in thecategories of construction, transportation, motorsand engines, and electrical or electronic equipmentin commerce. The EPA is responsible for enforc-ing this act and is required to develop standardsand suitable labeling of th
25、ese noise sources, as wellas for such noise control devices as hearing pro-tectors. The act, together with the extensive provi-sions of the Quiet Communities Act of 1978, givesEPA a charter to conduct and finance noise con-trol research. The bibliography at the end of thisbook includes several impor
26、tant reports publishedas a result of such work. The EPA is also em-powered to act as the chief coordinator of allFederal agency noise control programs. The EPAhas proposed that community noise levels bereduced to Ldn = 65 dB(A) as soon as possible 2and will enlist the help of state and local govern-
27、ments toward this objective.Partly as a result of research authorized bythe Noise Control Act, increased knowledgeconcerning the nonauditory effects of noise isbeing sought. These effects may arise from non-adaptive physiological responses to noise as a non-specific biological stressor. 6, 7 Some of
28、 the moreimportant responses may be increased cardiovas-cular disease, elevated blood cholesterol levels,increased adrenal hormone production, bloodvessel constriction, and accelerated heartbeat. 7Although no firm scientific consensus hasProvided by IHSNot for ResaleNo reproduction or networking per
29、mitted without license from IHS-,-,-emergedon thepossiblelink betweennoiseandtheseconditions,thepotentialbenefitsof noisereductionarecertainlynotconfinedto thereduc-tionof hearingdamage.Chapters2-4area comprehensiveintroduc-tion to the basicphysicalprinciples,measuringtechniques,and instrumentationa
30、ssociatedwithgeneralpurposenoisecontrol.Chapter3includesanoutlineshowinghowbesttoidentifyandchar-acterizeanoiseproblemsothatsubsequentworkmayprovidethemostefficientandcost-effectivesolution.A detailedmethodologyfor choosingappropriatenoisecontrolmaterialsandtheproperimplementationof controlprocedure
31、sbeginsinchapter5.ThemostsignificantNASA-sponsoredcontributionsto thestate-of-the-artdevelopmentof optimumnoisecontroltechnologiesarecon-tainedin thefinalchapter.Of particularinterestare casesin whichaeroacousticsand relatedresearchhaveshedsomelightonwaysof reducingnoisegenerationat itssource.Equati
32、onsand associatedmathematicsarepresentedinasimple,comprehensiblemanner.Toaidthereader,examplesarepresentedatpertinentpointsin thetext.In addition,thereisa substan-tialcategorizationof thetextandalargeselectionof figuresillustratingparticularitemsof equip-ment, nomograms,and plots of performancechara
33、cteristics.Althoughit isnotexplicitlystated,manyofthereferences,especiallythoselistedat theendofthelaterchapters,resultedfromNASA-sponsoredresearch.Thisenablessuchmaterialto beplacedwithinarelevantandpropercontext.REFERENCES1. NIOSH, Criteria for a Recommended Stand-ard-Occupational Exposure to Nois
34、e. HSM73-11001, 1972.2. Office of Noise Abatement and Control, EPA,Toward a National Strategy for Noise Control,April 1977.3. Office of Noise Abatement and Control, EPA,Noise Technology Research Needs and the Rela-tive Roles of the Government and the PrivateSector, EPA 550/9-79-311, May 1979.4. Bruc
35、e, R. D., et al., Economic Impact Analysisof Proposed Noise Control Regulation, BBNReport No. 3246, April 1976.5. Haag, F. G., State Noise Restrictions: 1979,Sound and Vibration, December 1979, p. 16.6. Elkins, C., Noise: The Invisible Pollutant,EPA Journal, October 1979.7. Center for Policy Alterna
36、tives, MIT (preparedfor EPA), Some Considerations in Choosingan Occupational Noise Exposure Regulation.EPA 550/9-76-007, February 1976.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-CHAPTER 2Basic Physics of SoundSound is a mechanical disturbance of
37、 a wavenature that propagates through any elastic mediumat a speed characteristic of that medium. Whendetected by the human ear, the presence of soundwaves is often described by the subjective attributeof loudness, and this quality is usually quantifiedby averaging over a range of people (see sectio
38、n3.1.3). Loudness is related to the amplitude ofmovement in the transmitting medium next to theeardrum.Sound may be assessed after measurement ofan appropriate physical quantity that varies aboutan equilibrium position as the sound wave orvibration passes the measuring point. Sound pres-sure is the
39、macroscopic physical quantity of mostinterest in fluids and gases. It depends on theamplitude of the disturbance in a material andmost adequately represents the effect of acousticwaves on human response. Figure 2.1 illustrateshow an acoustic pressure disturbance might varyabout the ambient value for
40、 a typical sound wave.Atmospheric pressure is taken as the base line forairborne sound propagation.O-Time,t is)Figure 2.1 - Example of acoustic pressure fluc-tuations about mean ambient pressure. Po is theambient atmospheric pressure,“ p is the acousticpressure; and PT is the total pressure (equal t
41、oPo + PT)-As an illustration of the magnitude of thefluctuations involved, atmospheric pressure isnormally 1.012 x 10 5 N/m 2 at sea level; a barelyaudible signal might fluctuate as little as 10 5N/m 2 from this value, and a painfully loud contin-uous noise only about 10 N/m 2, that is, only0.0170 o
42、f the atmospheric value. (The unit ofnewtons per square meter, N/m 2, is sometimesreplaced by its equivalent, the pascal, Pa.)2.1 SIMPLE WAVE NATURE OF SOUND2.1.1 Introduction to Longitudinal PropagationWave motion or vibration is made possible byinertia and elasticity in a material. Because of iner
43、-tia, matter remains at rest or in uniform motion inthe absence of external forces; this permits thetransfer of momentum between neighboring parti-cles or elements in a medium. Elasticity designatesthe tendency of displaced elements to return totheir original or equilibrium position after the pas-sa
44、ge of a disturbance. Air, water, glass, and suchmetals as steel and iron are relatively elastic.Wave propagation may be demonstrated bythe use of a long helical spring fixed at one end. Ifa disturbance is imparted at the free end, themotion is carried through the adjacent coils, whileat the same tim
45、e the initially displaced coils tend toreturn to their former positions. The net effect isto produce two distinct regions that travel downthe coil structure: in one, a series of neighboringcoils are pushed close together because of the ini-tial action of the disturbance (compression); in theother, t
46、he relative spacing of coils is enlarged be-cause of the removal of the disturbing force andsubsequent overcompensation by the elastic coils(rarefaction).The wave nature of sound in air may also bedemonstrated by the device presented in figure2.2.Provided by IHSNot for ResaleNo reproduction or netwo
47、rking permitted without license from IHS-,-,-O . r Equivalent ofsciilarlng . lpiston FComp resslOn /infinitely long / ! terminationWavelength ;x / V_ _ , /(noreflect,ons)_- Rarefactionotating discFigure 2.2 - Generation of longitudinal progres-sive waves in a tube.The action of the piston in figure
48、2.2 alter-nately pushes the air molecules together or pullsthem apart. It is the inherent elasticity of air, com-bined with inertia, that allows these successive dis-turbances to travel down the tube as the displacedmolecules try to regain their former equilibrium.The net effect on the pressure distribution is maxi-mum pressure amplitude at points of maximumcompression and minimum pressure at points ofmaximum rarefaction. If the disc rotates at a con-stant speed, then the wave form, as represented bythe pressure, will be sinusoidal. Figure 2.3 showssome of the charact
