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LEAD INDUSTRIES ASSOCIATION, INC.
>M MADISON AVINUS
NSW YORK# M. Y. ISOt? UMMi - wu mm at*
Aaosrr Xt>, 1967
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LIA 14 lA 8
Practical Designs for Noise Barriers Based on Lead
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PrrpriiH"d frm AMERICAN INDUSTRIAL HYGIENE ASSOCIATION JOURNAL . Vol. 27, Novrtnher-tVcrmlwT. 1906
Practicul Designs for Noise Burriers Based on Lead
BRUCE FADE*
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gf Acovwicil tkry predict* dw( sheet lr*6 i*4 u<t piutir materials la*<k4 wkfc > V divided lr*d showId W ftfrik( XHmd h*rrien. Sm ran histories mn
ghra M >m hv thh "limp (DM*" k-M toe* applied la practical piidiWnw
Introduction
by the simple rsqwdirtTt of hand-crimping
ONE OF THE m at common solutions to industrial noise problems U the nv cloture of the ixhv source io reduce noise level to bearahle limits Thtt situa tion it fitly rerognurd. The difficulties at-
............ - -- * *---; too. Usually opening arc required foe feed of material or {laru to and from the notsy operation. Almost always there muu be pro vision for access or at least visual inspection. The* aod other requirements often indicate that a complex dupe will be required of the enclosure. And this, in turn, increase* the difficulty of achlev ing monolithic, leak* free construction in practice.
In addition to the* practical difficulties, hkh apply to the construct ion of even a tingle noise enclosure, ilwrc may well be a question of optimising perfortnance of the noise barrier in terms of not* reduction \rrsus weight, thickness, or cost. Tins is par ticulars important wl>e:e noise reduction requirements are unusually demanding, or where a large number of the enclosures will he needed.
the surplus lead to the surface of the pipe
and tjjnng it tl>cTr uith duct-valing tajw.
thTehe lead surplus is created by folding a single I-inch tuck vertically to coincide with
the pipe. The significant fad about these
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ance is rxreUcm and usually in close agree ment with theoretical predictions. This hap py result is all too uncommon In noise con trol work and may be attributed, in large part, to the raw Him which Irak-free con struction is attained on the job.
Second, acoustic theory and practical ex perience alike 0>ow lead (and kad-loaded plastic) sheet to be excellent barriers to not*. 7T.it fact hai iu foundation in the intrinsic lack of stiffness of the sheet. The so-called "tur.p mats'* thus fumidwd blocks noise transmission without any detrimental coincidence effects Another theoretical prCdktion borne out in practice is that, where the lead is correctly used with other build ing materials in a composite noise barrief, it can suppress or help suppress the unfavor able rnirw idmee dip of the other materials.
Sheet lead and lead-loaded flexible plastic Types f Construction
sheet recommend thernwhei in boch par
ticulars cited above. First, from a practical
At one extreme t)w simple hung sheet of
point of view, consider sheet lead uvd as lead or traded plank mentioned above has
a harrier in the plenum l>o\c hung ceilings |Hos*d fffrrtivr. F.vrn at one pound per
The lead sheet, approximately 1 /64-inch squarr fmy (|*f* this simple expedient pro-
thick in a typical caw, is alkmrd to hang dum *t*Kjf 2* db at a nine-ffrqiscncy aver
freely between the roof slab above and dw age trantmiw^ut low Other schemes of to-
hung Ceiling lielow. Perforations for pipe, ctrakivg complexity Have Iwi-n used; there is
conduit, air ducts, etc., can he tightly waled no |rknt in fpnng into great detail concerning
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the type of sm-ice. but 15 psi k typical. To nuifitaic a act dowmtrrara prmirt mi
demand, double V-port rryulaimg vahes air u*rd With this hich -pressure drop and cor* mfmrtdmgly h*h ftow. a w-idr-aprttmm noisr oI 110 lo 130 db is created.
The enclosure (Figure 1) was a 2-inch blanket of fine ) am glaw fiber (6 pounds per cuf*ic foot ( overwrapped with a single layer of reinforced leaded \inyl bisect. Thi* fabric-Ivacked. flexible material weighs G.87 pd and is 0.055 inch duck.
Considerable care was exercised an taping all trams completely closed (Figure 2* with a tape of the same material.
The result was lo rrdure the |>rak inten sity from 130 db to 100 dh. While higher than desirable, this brings the noise into a range * here conventional ear protectors can cofie with k.
Case /--Fluid Soil* mad fi^r Line
An arrangement pioneered at the Public Service Gas and Electric Company of New Jersey haa now been employed all o\<r the North American continent. The noise source was a set of jupes and vahes in a pressure reduction station. C|>stream of the salves the gas i* at a pressure of abwtt 150 fi. Prrwure on the downstream side varies with
F* 2. lapudfd view show* kow leaded ift aid (lass fihr* air applied.
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the *<W,t**v*l rvw rediw (kki AfhMtrd hr tddiAC (Iaas bhn And ha4*-d >tnrf >>rr( to thr tin lo*urf J.r A/i tnirrtol c<xnt^ji(*.iQ turhutr
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ibe <r m<sW 4 thr iur4if.e If prcvW^r rtr ittUr trtniiiM ! igr r**e u)um< intro-
dor inf a (t*d (urfor*l ttf lifra iurtnc And do* linn
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Tltr s a* tmbvne it as increasingly pop. ular |Kintr miner And, ti it nttinu by F*. urr 3, it it a fairly nory one. The "trfore Ufjimml" tunr in Figure 3 the gas tur bine nidi An mclouirr, but before the ad dition of leaded pUvic.
The brforr and after daft
m f*o
tuftr ate (Mini 041 tfUv fariwd out oq a
national*- gas turbine unit measuring S by
16 feet (Ftgurr 4' and inducing 730 kilo-
v.am of electric jHJort. Att for the fnmbuv-
twai it taken in at a rate of 11,000 rfro
vlw*rt the unit ojirratr* At rated load and
tin* intake duct 30 by 10 inches.
To pm\-*de * tlx attort i*ofauon between tire unit and the intake durttn^. a flexible beU Iom <f leaded |ilaiic um nwd The ]%IamT di/eting **riylu-ti 0 87 jwf (Figure Si. The vatrie material *.* used W> Irrje the interior
of the metal Cabinet, and the internal face of tle rahinrt **a* cbm 61>rr hatting re tained by screen cloth.
Sijvilanttaih tle tarne cjK-ti>e wm uv-d in a motile gat turbuv--the power uiut of tle hydrofoil vessel HS Oeniutn (Figure 61. Became weight t*as at a great jwemium m thn foil-borne \rhicle. a still lighter leaded }ilavti< sheet vsat used lu rfT.xt %** en hanced by tuj^iortinc it on 2-foo< Center*. Fl>e tlieet Mrigltcd o*ih 0 48 j**f and m*s utrd. at before, in <r>n;unctxn v*ith gtap fil>rr ab*or|itive material (Figure 7),
Care 6--Skrrt Afrtmt Sow
Tle vride-spertrum ooiie produced by Im pact in expantri of sheet metal is quite a
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LIA 14152
Amsrian ///*/na/ Hyg%m* AiKXMfion Journal
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Ffovpt 7. SrrthiA thrvKik tl* sound bwrT utrd ia HS DtiMu. It m haMraJty im-
4ar <> that vim-4 in ihr twt*>nxrT lurbutf (figure t) ery< th*l lighter leaded vrd
fwer u nnpiorH and i a p< .mi-suspended M KUiQua ucnpcvew
oumnvirt problem. In (xw case, an ecrlrwd
chutf, or duct, was being urd to comey
m f----
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o4 a plant to nor of thr lovrr floon for
packaging Although no actual tound rrea-
ujrrmrmi were made, the noise Irvelx--par-
ticuiarly the enervating high-frequency ncnsrs
--were well beyond die annoyance levd.
Short tempers and worker ineff* iency were
directly traceable to the noise of rmlhoru of
cofTrr beans bouncing through the chute.
Tlie solution was quite simple A sleeve
rf fWibh- leaded vim! sheet weighing 3 psf
wai hung rnudr the vertical chute. The
deeve
made with sealed rami sr* that
noise could not leak through it. Berauar
coffee it a foodstuff, a setood died metal
chute "as intrrled dirough the Jwt at
a liner. TW prime intent v>ai to remove
any possibility of contact of the food with
a lead-bearing material Actually, however,
ihe inner liner probably made d>e arrange
ment morr effective because it forced the
leadrd plastic and sheet metal into loose
contact, thui enhancing the damping effect.
"Ihe result was completely *am/a< tnry. The
beans rjuw only a quiet murmur now, and
frayed nerves have long since healed in that
department.
Cat/ 5--Tranr/cwmer A'otse
Ihe ~humM of big powrt transformers h
an unusually stubborn noise and typifies noise qieetrums of k>w frequency, which sometimes occur in industrial work. Low-frequency jer forruame- of most sound barriers is notori ous!) poor; thui die achieved improvement of 17 to 20 db achieved by Portland General Electric Company it especially noteworthy.
ine transformers m question (Figure V) 'sere each rated at 41.7 Mvat stood about 14 fret high, and required an enclosure measuring apf*oximaie)) 5 by 10 In 14 fret. This enclosure was a built-up laminate of 10-gagr steel. 4-jrwmd U/lb-inrh} had with an interfacing of glass fiber. Some noise rscajwn the enclosure via the radiator network As an indication of the excellent de tailing of t!c design, this loss was held lo onh 5 db. Test* of die completed enclo sure without the radiators in place dlowed a 22-db improvement o\rr the unenclosed transformer. When die radiators were again installed, the level row, cutting d* noise reduction to 17 db.
This ctxuii urton u classed as approxi mately a 40-db noise barrier because of the many openings of this sort that had to be left in the ti andonnet enclosure ax n wax assembled. Had it been complete or sub stantially complete, the reduction would cer tainly hasr been of the order of 40 db.
Cmtr 6--A **QaiV( Room" in Soisy Ent4tonmmi
Franklin Institute in Philadelphia h wcB known for its excellent rontract resrarrh work One project at the institute seat a
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tud> of notx inade by txjnngv Good Vinn^ arc. of fo<irv. rather qow't *n <yw-r*. t*, and tlx orJ\ tpace available for tcrt*
wa* rvc*1 It h.*d rt xMiinw v normal traffic and comrrNjtiori, machinery running (ontir>oouJ> under tct. ocrawnaal li^iit dx-et nxtil w<wk. jr*d the bac kicrrwmd ruint>lr nf d<omiw*r Philadelphia*! hca\y yrret traffic.
Beginning wuh a tooth 13 feet 6 inclx% la 9 fret 6 int hr* by 10 fcrt high with j^auerlmard walls oo wood *<ixk, the int* tuir <4*n*tructrd the wall dxw*n ui srclion in Fvgute 9. Note that tlx original wall war retained and that no new framing or dtv mantling of ctmint *trutuTr* hii required. Other measurra included u*r <A sound-abwwptne lacing on Ox walh and ceiling and addition of man m tlx ceding by dump* in* \*nd on it from abac {tlxcr wa no flor met tlx jo*t' and tarrful iratinc of rrarV.4 and opening* ihnxfghout
Tlx irwill, llvYtoi) iu Ftgutr 10, vest to inrrra*r tlx none rcdiurtton from outwdc tlx morn to tmtdr from 32 lo 43 db. \N'hiW* thn wall would nr* turn rraJTv rrttxal rrquirrmrott (for a broatkaat uudio, for "*. ample', it hai attainrd at a rrawmaldr ro4 in a dmri tinx. Ac'tuaH) it wit ux m-ttIl* Ix-twrm the firy irvquin about tlx uw c4 lead for ooix tontrol and thr rurcridu) u*r of the completed room. No outitde contractor Mat required, tlx work being done by the regular tHuidtng and maintenance atafT
Cate 7 -- A FmnlUy
Wmll i* a A<<*ustusi 7*rrt
Scmxtimet the need arix* for a barrier with a rating of 60 ^ db. /u a practical ttutirr, this oftm man* that *n*tx altnrvati\c tolutKm to tlx f*of4nn thoukJ be ww*ght. wnce it i not usually |fOMiMe to attain r*>
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iir*: of tfii k/1 in prartue One of die
few plarrv vd>err 'ih h fierformarVr realh l :r*ijuirtt! and rralh can lx- st!4incd >i m
>rM l m ihtiex.
TT>** wall drx nlrd Itnr forrm Ox- [trrmincTit dnidmg wall between the murcr and the mm mg rrwnt Aa twch it limit hr - apaMe o{ ditnianthng and reanritib:> a* ten j\arvl of vanom u/ri arr w.-hunuied fn* it AltlxTugh it ti hard!' a thin of light weight w*U. it it ninth th'mrw atxJ lighter
it thiId not be achieved m any rviv l*an **t tthefr it wax not jxifublr to uw* extreme <air m hunting Aivn and imintiim ainaH Irakt through <ra<kt. rlc Neither tint wall rxv any other tivnild lx* cofitjilered a prac tical tnlutnm tn tf^* t\]e (d fifUi j-roldem vtfirre anew it nt^iiirtj ihroo^li tlie barrx-t. fw where leaLire <x flanking fMtht of menetiienl of mocitanwral wear u UalJe to f< a factor.
ih^n the %>Jd uHKrrir block that make* up
iix o'h-r v* alit lit tlx* text fanlitv And of
<ouiw t it emmx-mly handled in cctK>r* xi tfi-af Iim jufirb cf x-vcraJ usr- < an fir
*< < rwtirnodated - a jxoblrin of conudefabrf-
magnitude had am other roe>*trtrct*on at
t*n. !jr *<<hiih rat.ne U-m chotm. TU wall 'fifur II. hat facet of ' j-irw h
*-pd' dvet Wad arfiarated tr 8U inchr* <*/ ifva<r 17ie (*< rt arr arjiaiatrly framed x uh wood To rhriunatr ttnxlural bodg-
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CoAclwtiont
\Nfcie rnw imm hr hi*v krd or rmtamed Tn a barrier, therr arr thrre cardinal rrt^uirr* mmtt to l>e nri in order to get the brat performance:
Firu. t)w n>cife uutaite the harrier h, thf hrelief the tunwiuiwo loti it ii ia|alIe nf.
Second, tlw lev tuJTnrtt tVw Tuirrief |ov *e^tr% llie tirlirr the firrformanre that miy he r\|tr(trd of it.
Hurd, to arbirw- good trammiaMoa lom
m the atvrfir floor. wdrw all*. and cnltAg
A the text facibtt. TTk-c arr waled with
onrifvaitirnmf tnatttr Within t>* wall, each lead f j< r m Ivackr-d with 4 inchrt of hhef fm A v*rj.<d-r. retaining Ixartm around the evt^e id ca<h Jiancl tm rt two jhii jwrvt- -i!
the lead fMr to die frame and pro-
* *i*-x an i^-nirr into whxh calking material < an be dmni.
I Tie |irtfor [i urwr fu/\r of ifc.it wall fiat been < lx~ ked m tle facility itwlf ard. at dvTt.n m ftg'.te 1?. it a remarkable 70 dh It mutt hr mwi r%tord tfiat thit prrfonivancr
leak r ttrMturai featum that roemhutr 'oufd jtatbv
Slier-t lead and lexted pUitic diert fia\< hem dtrrwn lo |iwrti htrh hum rrlatrve to thetf th* knew and vifhcimt *'hxn|inra" to fHTxhjcr excellent rrtuJti m |*rxt*al nn**r Turners Aldicwieh it canrvx lw ctemen-
araied *\ a w*jiarate efTrci in the raw luatnrie-% rr\*rwrd l^rc. part cj the rfTrt tnrnrw
Ucn* frexn the rae with whu h tle materlah < an 1-r focmed to val tv minimise leakv
Received June ?6. 1^66