Practical Application of Sheet Lead for Sound Barriers

Home , Sound transmission class

I DOCUMSNT RISUN ED 031905 EF 003 340 Practical Application of Sheet Lead for SoundBarriers. Lead Industries Association, New York,N.Y. Report No -AIA -39; CSI -DIV -13 Pub Date May. 65 Note-12p. Available from-Lead Industries Association.292 Madison Avenue, New York, New York10017 EDRS PriceMF-S025 HC 10.70 Descriptors -*Acoustical Environment. *AcousticInsulation, *Acoustics, Building Design. *BuildingMaterials. Construction (Process) Identifiers -*Sound Barriers Techniques for improving sound barriersthrough the use of lead sheeting are described. To achieve an idealsound barrier a material should consistof the following properties--(1) high density.(2) freedom from stiffness. (3) gooddamping capacity, and (4) integrity as anon-permeable membrane. Lead combinesthese desired properties to a greater extentthan any other common buildingmaterial. The proper use of lead incombination with other materials cancompensate for their deficiencies and improve the acousticalperformance of the composite barrier.Three ways in which barriers arerated for their effectiveness arediscussed and compared. Practical tips for designing better soundbarriers as well as pitfalls to beavoided are listed.Design and construction informationfor installing practical lead walls is presented and guidelines arerecommended. (TO PRACTICALAPPLICATION OF SHEET LEAD FOR SOUND BARRIER:)

LEAD IS AN EXCELLENT BARRIER MATERIAL for reducing the transmission of air-borne sound.

LEAD IS TECHNICALLY SOUND because it combines high density, natural limpness, good damping capacity, and is non- porous.

LEAD IS A WORKABLE MATERIAL since it is easily formed and fitted, requires no special tools, and can be readily adhered or fastened to other materials.

LEAD IS ACOUSTICALLY GOOD because pound for pound it is a better sound barrier than any other conventional building material.

LEAD IS ECONOMICAL because it is reasonable in cost, takes less space, often saves weight, is easy to install, and is

U S DEPARTMENT OF HEALTH, EDUCATION & WELFARE

salvageable. OFFICE OF EDUCATION

THIS DOCUMENT HAS BEEN REPRODUCED EXACTLY AS RECEIVED FROM THE

PERSON OR ORGANIZATION ORIGINATING IT POWTS OF VIEW OR OPINIONS

STATED DO NOT NECESSARILY REPRESENT OFFICIAL OFFICE OF EDUCATION

POSITION OR POLICY LEAD INDUSTRIES ASSOCIATION 292 Madison Ave. New York, N. Y. 10017

ook Ahead with Lead Practical Sound Barriers Employing Lead

THE NATURE OF SOUND air-borne sound of lower intensity on ness. This is known as its Transmis- The sounds we hear are the re- the opposite side of the barrier. This sion Loss (TL) and represents the is how sound "passes through" a wall. reductioninthelevelof air-borne sult of air pressure waves impinging sound transmitted by a given barrier upon our ultra sensitive ears. The frequency (pitch)of audible pressure WHAT CONSTITUTES as determined under controlled condi- waves ranges from 20-20,000 cycles A GOOD SOUND BARRIER tions. The TL is expressed in decibels per second. The intensity of these pres- A good sound barrier wall is one as a single figure which, in turn, repre- sure waves in terms of their physical whichwillreduceoffendingnoise sents the arithmetic average of nine energy varies over a fantastic range from adjacent areas to the level of the separate TL measurements takenat and accordingly, itis expressed loga- backgroundnoisenormallypresent specifiedfrequencyrangesbetween rithmically in units known as decibels. and accepted in the desired quiet area 125-4000 cycles per second. This por- Sound can be pleasant, acceptable, or to some slightly higher level which tion of the sound spectrum encom- tolerable,objectionable or injurious. is still deemed acceptable to the occu- passes the frequencies most commonly Noise is unwanted sound and in to- pant of the quiet area and which will encountered and most critical in effect day's society the control of noise is fast provide speechprivacyor freedom upon speech intelligibility. becoming a problem of major propor- from annoyance or distraction.For TransmissionLossisafixed tions. Unsuppressed noise can cause example, an 80 db (decibel)noise property of a barrier but varies with petty annoyance, loss of privacy, low- impinging on a 30 db wall will gen- the frequency of the sound. The TL ered working efficiency, higher acci- erate a 50 db noise on the other side. of all materials and barriers increases dent rates and physical impairment of If the normal and accepted level of with frequency but at some point in hearing. background noise in the quiet area is the curve a plateau or dip will occur The information presented here is 50 db, no annoyance will be experi- with most materials where the barrier concerned with air-borne noise rather mced. If, however, the normal back- develops traveling waves (like micro- than impact or structure-borne noise. ground noise levelis 40 db,it will scopicversions of the waves ina Air-bornenoiseincludesfamiliar now increase to 50 db indicating that shaken rug) in sympathy with the dis- sources such as the crying baby, TV the barrier is inadequate. turbing sound waves. & HiFi sets, loud conversation, office The physical properties of a ma- terialor a composite wallthat go When this "coincidence" occurs, machines, motors, pumps, manufac- the amplitude of vibration in the bar- turing operations, etc. It does not in- to make up an ideal sound barrier clude noise from objects dropped or are high density, freedom from stiff- rier increases and more sound is transmitted.Thus, in appraising the ca- foot traffic on bare floors above, water ness, good damping capacity and in- pacity of a barrier one should consider hammerinpipes,vibrationfrom tegrity as a non-permeable membrane. heavy machinery or the rumble of a Lead combines these desired proper- both the stated TL figure and the fre- subway train, all of which are trans- ties to a greater extent than any other quency plotting of the separate values mitted primarily through the ground common building material. The that make up the figure. or the structure involved. proper use of lead in combination with Lead, by virtue of its limpness The pressure waves in air-borne other materials will compensate for and density, does not exhibit this co- sound radiate inall directions from their deficiencies and will improve the incidence dip in the frequency range their source much like ripples in a acousticalperformance of the com- with which we are concerned. Thus, pool radiate from a dropped pebble. posite barrier. when properly combined with other These pressure waves will readily pen- materials, it will improve or dominate etrate a porous barrier. They will also HOW A BARRIER IS RATED their inherent weak spots and improve set a rigid barrier into unnoticed vi- T-) select or design a barrier one the acoustical performance of the com- bration which, in turn, generates new must have a measure of its effective- posite barrier. - 2 Three Ways Barriers Are Rated

70 Ø. 60 4ce*. Solid curve 35 db average

50 NINE-FREQUENCY AVERAGE In 0 40 The average of the TL at nine speci- 0 fied frequencies(125, 170, 250, 350, E 500, 700, 1000, 2000,and4000cycles LC' 30 per second)is the most usual rating for sound barriers. Note that the solid Dashed curve 20 40 db curve averages 35 db and the dashed average curve averages40db on this basis.

0 50 100 200 400 800 1600 3200 640012,800 Frequency in cycles per second

60 SOUND TRANSMISSION CLASS(STC) A standard STC "profile" can be lo- 50 --r- cated just under the performance curve so that the center sectionof the profile 0 oue is just tangent to the curve. The two STC 40 40 outer portions of the profile may aver- Solid curve I the test curve. al I pow wow ems age one db higher than STC 30 F30 1# When this is done the high end of the 40 Dashed curve 4.44 410" profile is at the STC for the barrier. de Note that the solid curve has a better 20 , STC than the dashed, even though its average performance is not ashigh. 10 /

0 50 100 200 400 800 1600 , Frequency in cyclts per second

70 <-N 64 so

PRIVACY ANALYZER 50 A standard "dot field" for one of sev- In eral types of environment is adjusted 40 0 over the test curve until exactly ten In In dots exceed the curve. The index of E _., 30 the dot field template then shows the I privacy analyzer rating.In this case

20 (same solid curve as above), the rating with an "N" dot field is 64.

0 50 100 200 400 800 1600 3200640012,800 Frequency in cycles per second 3 A more recently accepted means performance, an arithmetic average of of expressing the sound attenuation the noise reduction in the speech rarlge capacity of a barrier is known as the from 200-4000 cps also provides a use- Sound Transmission Class (STC) num- ful single figure rating. ber. This method has gained accept- The required index for a barrier in ance because it gives a more reliable any given situation will depend upon singlefiguremeasureofbarriers the amount of background noise pres- which have sharp dips in TL at cer- ent, the degree of quiet desired, the Lead( d Vinyl tain frequencies. amount of absorptive material present There isa furtherimproved and the character and intensity of the method which expresses the adequacy offending noise. Leaded vinyl sheet is a composite of a barrier in the form of a specific For example in a typical private material comprising two vinyl sheets Speech Privacy Index. It narrows the officewithoutairconditioning and with a filler of lead powder embedded field of attention to the 200-4000 cps where reasonable quiet is desired, the invinyl.Itisavailablein weights range, takes into account the type of partition barrier or wall should prefer- from 1/2 to 3 lbs. per sq. ft., up to 1/8" background conditions and rates the ably have a minimum STC rating of in thickness and is completely limp in barrier according toitscapacityto 45 db. Recently revised F.H.A. mini- the acoustical sense. shut out all but that portion of the mum Standard Requirements fo: Where sheetlead and conven- sound which will be unintelligible on Apartment House construction call for tional constructions are ruled out, flex- the receiving side. In ranking tests of party walls with higher STC ratings. ibleleadedvinylsheethasoften various materials or panels for barrier See table, below. answered. Its performance as a freehanging septum is given by the curves in plate 5, page 7 and in the table FEDERAL HOUSING AUTHORITY "TABLE 4-6" Sound transmission ratings for Partitions SOUND TRANSMISSION CLASS (STC)(1) Land-use intensity less than 6.0 Land-use intensity 6.0 or higher ( ow background nonoise2 background noise) (3) Location of ) ( ) (h ig h PITFALLS To Partition Room adjacent to partition Room adjacent to partition 111=11111=WO Bedroom (4) Other Bedroom (4) Other Living unit to Class 50 Class 45 Class 45 Class 40 living unit (5)

Living unit to Class 45 Class 40 Class 45 Class 40 The installedbarrier when testedin corridor (6) place willfrequently fall short of its TL Living unit to Class 55 Class 50 Class 50 Class 45 or STC rating.This can be due to faulty public space installationinfailingto eliminate sound (average noise) (7) leaks in seams, doors, and perimeter joints. Living unit to Class 60 Class 55 Class 55 Class 45 In many cases this lowered performance public space and stemsfromtheexistenceofnumerous service areas flanking paths through which the sound (high noise) (8) waves cancircumventthebarrierwall.

Bedrooms to other Class 45 NA Class 40 NA Common flanking paths include windows, rooms within same back b back electricalfixtures, medicine living unit (9) cabinets, convector panels, cracks or leaky wall joints, door louvres, heating ducts, an NOTES: open plenum above a hung ceiling, low TL (1) Sound Transmission Class as determined by ASTM E90-61T. doors in a high TL wall etc. Failure to ap- (2) See M301 for Land-use intensity. (3)Living units inbuildings having year-round air-conditioning and inliving units ply relatively simple corrective measures to above the 'ighth floor, use column for Land-use intensity less than 6.0. these common defects can seriously jeop- (4) Where bedrooms are separated from corridor or from adjacent living units with wdize theperformance of an otherwise closets or storage walls, the effect of such noise attenuation may be considered good barrier. in partition sound transmission. Even hairline cracks can spoil a good (5)Inhigh-rental apartments where an extreme tenant sensitivityis expected, an increase of 5 db over the values shown is recommended. barrier'seffectiveness.As theexample (6) These values assume floors in corridors are carpeted; otherwise increase 5 db. shows,ifleaks constitute 1/10 of 1 per See M505.6 for corridor doors. cent of the area, a barrier with a potential (7)Public space of average noise includes lobbies, laundries, storage rooms, stair- TL of 38 db can only deliver 29 db. ways, etc. (8) Areas of high noise include boiler rooms, mechanical equipment rooms, elevator shafts, incinerator shafts, garages and most commercial uses. -AVVIIMM110111.01010141a (9) Acoustic separationof bedrooms withinliving unitsisdesirable,but notre- quired. PRACTICAL TIPS For Better Sound Barriers Barrier Acoustical theory shows the importance of mass, under section 5, page 8. limpness, and internal damping. Field experience While it is an expensive material, shows the vital importance of freedom from leaks. relative to sheet lead and other build- The practical tips listed here are based on experi- ing materials, its use is often the least expensive way of solving a problem ence and translate these theoreticalfactors into and not infrequently the only prac- how-to-do-it information. tical solution. One great convenience to the architect or designer is the wide variety of colors, embossed textures, or The importance of MASS printed surface patterns available.It has a durable surface and can lend a A heavy wall is normally a more effective barrier than a' light wall. handsome finish to the treated or cov- The weight of lead in a composite skin should equal and preferably exceed ered area. that of the other material in ordar to offset the coincidence. The penalties of STIFFNESS As a wall is made stiffer, the likelihood of problems with a coincidence dip increases. Be Avoided The presence of studs fastened directly to surface skins increases the stiffness of a wall and increases transmission of sound. 0101011110 ROMM.1....'. Resilient mounting of surface skins is helpful. Thin skins are preferable to thick. Thin sheet lead applied to thin panel skins can solve coincidence problems and reduce drumming noise. Viscoelastic adhesives are better than rigid varieties for laminating leaded panels. Intermittent attachment or free hanging lead sheet can be beneficial. Stiff components of a composite panel are best located near the center or neutral plane. 90 Leaded panel skins in double walls are frequently a more effective barrier 70 COVERAGE- than stiffer, heavier and thicker conventional wall board or plaster skins.

1 .....---- 50 100% 40 What to do about LEAKS (IL) real!, 9919% ,..01"--- Airleaksinwalls thru convectors, back to back electricalfixtures, wire 20 9% raceways and the like should be plugged with fibrous material and a septum Fr 98% 0 98% where required. 4ci Gasketing or calking is most effective. 10 90% Wall or panel joints must be tight. In 400 Never underestimate the importance of small air leaks. w 7 rA 80% A thin lead membrane sealed at the edges is impermeable to air. z 5 aro_ _76%_ Plenum barriers are essential over partitions which stop at a hung acousti- 4 O60% calceiling.Free hanging thin lead sheetisa most effective barrier and 3 pit 50% simple to install. 2 Lightweight low-cost acoustical tile can acquire barrier capacity by an over- lay of thin lead sheet. Gaskets are a must around door openings. 1 Hollow core doors should be avoided. The same is true of louvres. 0 10 20 30 40 50 60 Barrier transmission I s db If in doubt about potential leaks, gasket, calk, or tape during construction. Other considerations A double wallis far more effective than a single one, even when the total weight is no greater. Increasing the air space between skins will improve results particularly in conjunction with a filler or fiber glass, mineral wool or other fibrous material. Inadequate existing walls can be substantially improved by adding a sup- plementalwallcomprising a thinoverlay of absorptivematerial anda leaded decorative surface skin. Tabulation of Practical Sou

Nom. Average Curve DtSCRIPTION Transmission loss at stated frequency Wt. No. TL Frame or Core One Face Other Face (psf) 125 170 250 350 500 700 1000 2000 4000 (db) STC Remarks

WOOD STUD WALLS

-x T(maximum and minimum values) 2 x 4 1 /2" gypsum board1/2" gypsum board 51/2 J 2226 31 37 3840 4446 43 35 40 Riverbank Wood Studs 1 17 22 27 32 3537 41 43 39

A ix

2 x 4 1/2" gypsum board1/2" gypsum board 111/2 28 3536 4543 47 51 56 61 44 47 Riverbank Wood Studs plus 3 lb lead plus 3 lb lead STEEL STUD WALLS

1%" %" gypsum lath %" gypsum lath 131/4 2732 37 41 43 44 46 39 47 39 41 Catalog data Steel Studs plus 1/2" plaster plus 1/2" plaster amr---7- 1w, %" gypsum lath 3/8" gypsum lath 161/4 35 3843 4645 4747 49 58 45 43 Riverbank Steel Studs plus 1/2" plaster plus 1/2" plaster plus 3 lb lead

1%" %" gypsum lath %" gypsum lath 191/4 36 4045 4747 4749 53 61 47 47 Riverbank Steel Studs plus 1/2" plaster plus 1/2" plaster plus 3 lb lead plus 3 lb lead

70 70

1 WOODSTUD STEELSTUD WALLS Ws' steel studs 60 60 CURVE 2D 18 / CURVE sameas 2A plus CURVE2C f / 2x4 WS1/2" gypsumbd , 4lb lead both sides 3 lb leadboth sides sameas 2A plus i / 3lb leadboth sides i f 50 50

.0 0 I -0 1,g 40 v 1,2 40 lg 40 0 swm,m 0 0 c c URVE 2 c 0 0 samCeas 2A plus 0 v. \ 3 lb lead both sides FA CURVE 1A E 30 Shaded areaenclosesextreme 30 . 30 c values infour separatetests ) ci I 43 43 (V3 CURVE2A* 1 2x4 WS H it -1/2" gypsumbd , 15 /s'steel studs,3/8" gypsum it bothsides, nolead lath,1/2 plasterboth sides 20 \.i' 20 *Curve2A only rrcmcatalogdata

10 10

0 0 60 125 250 500 1000 2000 4000 8000 60 125 250 500 1000 2000 4000 8000 Frequency in cycles per second Frequency in cycles per second d Barrier Walls Using SheetLead

Nom. Average Curve DESCRIPTION Transmission loss at stated frequency No Wt. TL Frame or Core One Face Other Face (psf) 125 170 250 350 500 700 1000 2000 4000 (db) STC Remarks

1%" 3/4" gypsum lath 3/4" gypsum lath 211/4 394044484848 50 55 60 48 50 Riverbank Steel Studs plus 1 /2" plaster plus 1 /2" plaster plus 4 lb lead plus 4 lb lead CINDERBLOCK

4" lightweight paint paint 40384038 404548 55 56 45 44 Riverbank test. Much cement block lower TL is typical for installed walls because of leaks.

4" lightweight none 4 lb lead on 41 43 464447 54 5663 67 51 49 Riverbank cement block 1/4" ply'on 1 x 2 fui.ring PERIMETER FRAMED PARTITIONS AND MACHINERY ENCLOSURES

Wood perimeter. %" plywood none 11/4 18 18 16 21 21 24252722 21 24 Riverbank frame

I I K WALLS 50I.PERIMETERFRAMED FREEHANGING PARTITIONSAND LEADEDVINYL SHEET MACHINERYENCLOSURES 60 VE 38 t concrete block on t/4" plywood 40 CURVE 4B 1%" (1x2) same as4A plus 3lb lead 50

CURVE54 3lb ft2 CURVE 4A /-- wood perimeter frame g 40 / O CURVE 3A Vs' ply one side 4" lightweight cement block 520 2 CURVE5B 1 5 lbft2 / painted one side E A------7--,.....-..... 2 30 Ic...... It CURVE 4D _7.__,.1"-"../ / 40 __...... - ...... / "sameas4C plus 3lb...,,,,...... lead 0 20 v ...... " .%'. CURVE 5C.75 lbft2 ...... I CURVE 4C / / I'/ steel frame 30 18ga steel sheet .0" CURVE5D - .5-lb ft2 ,00.0I /N....I- 10 ----1

0 0 250 500 1000 2000 4000 8000 60 125 250 500 1000 2000 4000 8000 60 125 250 500 1000 2000 4000 8000 Frequency in cycles per second Frequency in cycles per second Frequency in cycles per second Tabulation of PracticalSound Barrier Walls UsingSheet Lead (continued)

Average Nom. Transmission loss at stated frequency Curve DESCRIPTION Wt. TL (db) STC Remarks No. Frame or Core One Face Other Faces (psf) 125 170 250 350 500 700 1000 2000 4000 PERIMETER FRAMED PARTITIONSAND MACHINERY ENCLOSURES ti 414445 37 40 Riverbank Wood perimeter 3/4" plywood none 41/4 33333435 3738 frame plus 3 lb lead

41 31 33 Riverbank Steel angle 18 gauge steel none 2 262527 2., 3032 3538 and channel

1 frame

r 46 38 40 Riverbank Steel angle 18 gauge steel none 5 33 32343538 394144 and channel plus 3 lb lead frame LEADED VINYL SHEET

Riverbank Free-hanging leaded virvl sheet 3.0 2626282830 32354145 32 34

28 28 Riverbank Free-hanging leaded vinyl sheet 1.5 222223 23 25 29 303542

Riverbank Free-hanging leaded vinyl sheet .75 16 16 17 16 18 21 243035 22 22

Riverbank Free-hanging leaded vinyl sheet .50 13 13 14 13 15 18 21 2632 18 18

DOORS

28 18 16 Tested at Goodfriend- Hollow core existing existing 2 14 12 12 15 12 19 24 27 Ostergaard Associates wood (with gasketing)

25 26 Tested at Goodfriend Hollow core 2 lb lead existing 4.3 23 20 21 2723 2829 31 32 Ostergaard Associates wood (with plus 1/2" plywood gasketing)

28 31 Tested at Goodfriend Hollow core 2 lb lead plus 2 lb lead plus 6.6 21 2326 3028 29 3233 35 Ostergaard Associates wood (with 1/e" plywood 1/8" plywood gasketing)

35 27 23 Tested at Goodfriend Solid wood existing existing 23 31 232628 21 2927 Ostergaard Associates core door 8 Design and Construction of Practical Leaded Walls

Better leaded walls are being de- directions. Wire brushing the lead will Provide an inner air space veloped andbuilteveryday. The improve the adhesive bond. when wall thickness allows.The limits of performance for new com- Lead can be readily adhered to same weightofmaterialsproperly binations of materials and methods of thinpanels of plywood, hardboard, split into two separate layers and sep- construction have surely not yet been gypsum or asbestos cement board for arated will nearly always outperform reached. Therefore, this section offers use as a sub-assembly in finishing the a single solid wall acoustically. The no last word on good design and con- wall.Suchleadlaminatescanbe more airspace between thelayers, struction.Itisintended,rather,to worked with the tools appropriate to generally, the better the eesult will be. suggest to the designer and builder th(:base stratum and represent the There can be exceptions 'o this when some guide lines for improvingthe easiest method of physically getting the two layersareso mechanically performance of sound barriers. the lead into the wall. the use of lead tied together that they act as one. In sheet of equal or greater weight than this case the stiffness will be much Preparing sheet leadfor the substrate will usually entirely elim- greater and the wall will suffer. The use.Because it is a soft, limp material, inate the coincidence dip found in all common 2 x 4 stud wall is a case in lead is usually shipped in rolls.It is conventional panel materials. point. Thin double wall surface skins easily flattened by unrolling it on any To get the best acoustical per- ofplywood,hardboard or gypsum clean, smooth surface. Where necessary, formance from any wall there are four board when backed with light gauge kinks or wrinkles may be removed by cardinal points to be observed: lead sheet will give better performance use of a roller or dressing with apadded than unleaded skins of any single ma- block or small sandbag. Plug all leaks.The amount terial of equal weight. Staggered studs If the lead is to be mechanically of sound that can leak through the and/or resilient ties between the two fastened or hung looselyitis now tiniest gap or crackis unbelievable. faces of the wall will provide further ready for use. If itis to be mounted The penalty imposed by these leaks improvement for such walls. with an adhesive, the oil film present becomes much greateras the wall's on rolled sheet lead must beremoved. performance is improved. Itis obvi- Absorption inside hollow A solution of trisodium phosphate or ously unwise to jeopardize the im- walls boosts the TL.The hollow any heavy duty alkaline cleanerdoes proved performance of a leaded wall cores described above can act as reso- this quickly. Traces of the alkali are by neglecting to eliminate the leaks. nating chambers unless they contain best flushed off with warm water. Sol- When in doubt, use a gasket, tape, sufficient absorptive material. Inexpen- vent degreasing can also be employed. calking compound or paint.Design- sive glass fiber or mineral wool batting Continuous cast lead sheet has no oil ing skill and meticulous care in actual in these spaces, particularly when in film and requires no treatment. construction are absolutely necessary. contact with the lead backed panel skins, will provide substantial improve Mechanically fastened con- ment. It also provides some damping structionposes no special problems. Always avoid construction which improves the wall's impact noise Because lead is soft, it should not be details that needlessly stiffen behavior and helps produce the charac- nailed or screwed without some sort the wall.Part of lead's effectiveness teristic deadness associated with sound- of bearing pad to distribute the load. comes from itslimpness.If lead is proofing. Otherwise it is liable to tear. It can be rigidly adhered to a stiff wall, the im- nailed through a batten or secured by provement it affords will be minimal. screws with large washers, etc.Itis In using lead to improve a cinderblock 70 also good practice to use a cement or wall, for example, itisfirst adhered calking compound to "butter" studs to 1/4" plywood or other surface skin or furring strips which will receive and then installed on furring strips so calkingor away from the wall. This has been Two 1poundead sheets sheetlead.Where the separatedby 3W' adhesive has some strength, sheet lead shown to give a 6 db improvement.* 50 can be nailed to the wood grid with- Adhered directly to a leak-freestiff Two1- poundleadshoe out any load distributors. wall of this type, the same lead would separatedby1%" Lead adhesively bonded to a sup- have produced a negligible improve- 40 .4 porting panel is usually more conven- ment. rAl<*Single1-pound ient to work with and provides ex- In solid walls, where there is no " 30 lead sheet cellentacousticresults.Viscoelastic isolating air space to allow the lead to adhesives (rubber base "Contact" and assume its natural limpness, place the VEFFECTOF 20 , A) USINGTWOSHEETS' similar types)give an added bonus stiffest materials near the core of the B) INCREASINGSPACE with lead by aiding in damping panel wall, the more flexible near the sur- BETWEENTHEM faces. 10 (Plottedas noisereduction' vibration. Once the lead has been pre- in testroom -transmission pared for lamination the adhesive can loss curveswouldbe similar) be used following the manufacturer's * See curve 3B, page 7. 0 I 50 100 200 400 800 1600 3200 6400 9 Frequency In cycles per second 70

I I I ATTENUATION OF A 60LOW.TL CEILING BOARD WITH AND WITHOUT LEAD Tested at Geiger & Hamme Labs

.0 With 1 lb. sheet lead Lead Plenum V 40 co a Barriers 30 20 Without lead Thin sheet lead makes an excel- Over the ceiling barriersof lent plenum barrier and is simple to one poundlead were tested under 10 install. Inexpensive wallboard has fre- standard conditions with a ceilingof lightweight (0.6 pounds/sq ft) ceiling 0 quently been used above the partition 125 250 500 1000 2000 4000 8000 to carry it to the slab. Awell-installed tile.The attenuation was improved Frequency in cycles per second barrier of this type can be adequate from ?1 db to 39 db in this test. See though it is expensive in view of the figure at right. labor needed to get the required fit around piping, wiring, ducts, etc. In practice a good fit is seldom achieved INSTALLATIONPROCEDURE and thus the effort is wasted. A less For barriers with nopenetrations Overlap vertical edges 1". expensive method employing thin lead and fold sheet produces better results. Attach wood cleat or metal partition Turn up overlapping edges ceiling channel to underside offloor into a tight standing seam. BLOCKING THE PLENUM PATH slab. CIA desired length of leadsheet Drape of 1" will self-seal atbottom. Wherever partitions between rooms severalincheslongerthan plenum Apply tape if desired. stop short of the slababove leaving a height. Fold 1" of top edge overthin space or plenumbetween the hung fiber board, wood batten or gypsum For penetrations up to 2" ceiling and the slab, there is a poten- board strip 1" wide. in diameter space. Fold a vertical 1" tuck in the lead 1" tialsound path through this Fasten to cleat with heavy dutystaples usually beyond the center line of penetration Since this common construction on 4" centersthrough 2 thicknesses of makes use of a lightweight acoustical round in direction of work. ple- lead and the batten strip, or with ceiling, the flanking through the head screws and 3/4" flat washers on Slit the tuck the shortest distancefrom num is usuallyquite serious. Ceiling 8" centers to metal channel. top or bottom to pointof penetration. tiles and other acoustic surfacing ma- of terials are light and porousasthey Push top edge of lead againstceiling Snip or cut the tuck at the location must be to fill their roleof absorbing slab. pipe or wires. sound generated in the room. It isthis property that brings aboutthe muted or hushed quality in the roomin which 1 the noise is being produced. But light- ness and porosity necessaryfor absorp- j tion cannot fill the need fot a barrier material. Thus it is relatively easyfor noisetopass through oneceiling, bounce from the slab, and enter a nearby room through its ceiling. Thin sheet leadis an economic and convenientmaterialtousein blocking the plenum path. There are two methods by which it canbe applied. It may be laid over the ceiling tiles or it may be used as a curtain to continue the vertical partitionfrom the hung ceiling to the slab. The first method is usually called an "over the ceiling" barrier; the second, a plenum barrier. Ventilation and lighting systems, as well asconstruction details of the ceiling will usually govern thechoice between these two methods. The ease of cutting and forming thethin sheet to achieve a good fitaround lighting fixtures, sprinkler heads, pipingand conduit, etc., makes applicationfairly simple and inexpensive.

10 i

Drape the barrier foil over the pipe or Lay a few feet of barrier foil on top wires. Squeeze-fit the lead around pipe of the duct on both sides of partitions or wires. Tape if desired. to reduce drumming noise. Fold over the slit edges of the tuck For patching holes and form a tight standing seam. Cut a piece of barrier lead 4" larger in alldimensions than the hole. Turn For small circular or square 1- pound sheetlead PLENUM up 1" of the lead barrier all around board penetrating ducts %' gypsum BARRIER the hole and also on the patch. Insert (2.6 poundssq. ft Fold a vertical tuck and slit as above. and fold edges together and crimp to NO PLENUMBARRIER Make two diagonal cuts in the tuck at form standing seams. 0 I I I I 100 200 400 800 16003200 6400 penetrat: -, point to accommodate size Frequency in cycles per second of duct. for spaces with critical require- Fold the pie-shaped flaps against the ments duct and tape in place. Lay additional lead barrier with 1" overlap over the acoustical ceiling tile Battens, calked and fastened to slab For large rectangular ducts in the area 6 ft. from the partition in Drape the barrier foil from the cleatthe noisy room. 1- pound sheet lead onto the top of the duct. Precautions to keep in mind Fold top edge of a shorter barrier sheet Be certain that the top edge of the lead over a batten strip and fasten to bot- barrier is folded over a batten strip or Self drape tom of duct with sheet metal screws other smooth edge, cleat or bracket so and washers on 8" centers. that the sheet is fully supported across Partition Make usual standing seams at vertical its width rather than just at points of edges of duct and tape the flaps to the attachment. This will effectively elim- duct edges. inate any danger of tearing at fasteners.

Miscellaneous Helpful Information WEIGHTS OF MATERIAL Weights given are average

LBS. per LBS. per MASONRY & CONCRETE MATERIALS CU. FT. MORTAR & PLASTER CU. FT.

Cinders or ashes 40-45 Plaster 96 Granite, without mortar 158-168 Limestone, marble, without mortar 165 Sand or gravel, dry & loose 90-105 EXTERIOR WALLS & WALL MATERIALS Sand or gravel, dry & packed 100-120 Masonry (Incl. mortar; Sandstone, bluestone, witn mortar 147 no plaster unless noted) lb/sq. ft. 4" brickwork 35 WOOD (12% MOISTURE CONTENT) 8" brickwork 74 Birch, red oak 44 8" concrete, reinforced stone or gravel 100 Cedar 22 12" concrete, reinforced stone or gravel 150 Douglas fir, (coast region) 34 4" concrete block, stone or gravel 27-33 Oak, white 47 8" concrete block, stone or gravel 50-60 Pine, long-leaf southern 29 Pine, short leaf southern 36 PARTITIONS CONCRETE 3" Gypsum block, plaster 2S 21 Cinder, concrete fill 60 4" Gypsum block, plaster 2S 25 Cinder, reinforced 100-115 6" Gypsum block, plaster 2S 31 Stone 144 Gypsum board, 'A" thick 2.1 Lath & plaster, 2" x 4" wood studs 14-16 BRICK MASONRY (INCLUDING MORTAR) Plaster 4-5 Common 120 2" Solid plaster partition . 18

11 WHAT TRANSMISSION LOSS Table(seebelow)representsuch MINIMUM TL REQUIRED FOR "average requirements." IS REQUIRED? 50 Properly designedbarrierswill Ideally, each acoustical problem reduce the sound transmission to ac- would be solved by measuring the level Very quiet offices 40 ceptable levels. of background noise and the level of .0 the noise to be shut out or contained What to do about leaks. In Quiet offices by the barrier. The transmission loss 2 30 The unaided ear held to but not of the barrier, at each frequency, would 0 touching the walls can locate leaks VI then have to be at least the difference ratherwell.Betterstill,adoctor's 2 20 between allowable background level Moderately stethoscope, with the head removed so and the level of disturbing noise. no sy offices thatthe open rubber tube scan be moved along over cracks or joints, will The allowable background noise 10 is often distributed over the frequency locate leaks accurately. spectrum with most of the sound en- Most such leaks will be gaps or 0 cracksand the remedyiscalking, ergy at low frequencies. In other words, 125 250 500 1000 2000 4000 8000 the normal noise background the Third octave band center spackling, or plugging with an ap- combined noise of traffic, air diffusers, Frequency in cycles per second propriate material. Where the gap does distant and unintelligible conversation, table gives a rough gauge of back- not exceed about 1/16", duct sealing etc. is somewhat predictable. Where ground level by listing the NC curve tape will do a credible job. no specific data is available, a "normal" which commonly applies toseveral Where no gap or crack is present large, suspect background can be assumed. The NC, locations. and the leaky area is or Noise Criteria, curves shown here Where intense noiseas from a structural flanking by a nail or bolt, are very commonly used to represent piece of machineryis anticipated, it electrical box, piping, etc. There is background level. The accompanying is usually possible to get information often no simple solution to such built- from the manufacturer about the noise inflanking.Isolatingthe offending 90 levels it will produce. This can vary structural elements with air or a resil- widely between manufacturers. Gar- ient material is desirable but usually 80 entails expensive alterationsthey are .0 bage disposal units, for example, man- ufactured by two companies had noise best designed out of the wall to start 70 ratings(overall) of 76 and 85 db. and kept out by close policing during construction. 60 Similar discrepancies are often found between different make' of pumps, Painting and finishing lead poses one possible problem. The metal 43 50 fans, air conditioners and office machines. Care in purchase and installa- is soft and even though most paints

40 tion of such equipment will help re- adhere well, it can be cut or abraded duce the problems of sound transmis- by physical contact. Veneers, laminates, a .0 fabric finish, and other finishing mate- 30 sion. Where itisimpossible to pin rials are best used over exposed sur- levels,therearedata faces of lead. Where no physical con- 20 down source based on past studies which can be tactis expected, lea i may be painted

10 used.The curves(see above) and with any quality paitlt. 20 75 150 300 6001,200 2,4004,800 75 150 300 6001,200 2,400 4,80010,000 Frequency band in cycles per second

TRANSMISSION HEARING CONDITIONS RATING LOSS OF WALL Noise criteria for different typos of spaces

NC Curve Typical Applications 30 db. or less Normal speech can be understood Poor quite easily and distinctly through NC-20 to NC-30Executive offices and confer- the wall. ence rooms for 50 people NC-30 to NC-35Private or semiprivate offices, 30 to 35 db. Loud speechcanbeunderstood Fair reception rooms, and small fairly well. Normal speech can be conference rooms for20 heard but not easily understood. people 35 to 40 db. Loud speech can be heard, but is not Good NC-35 to NC-40Medium-sized offices and in- easily intelligible.Normal speech dustriel business offices can be heard only faintly, if at all. NC-40 to NC-50 Large engineering and draft- 40 to 45 db. Loud speech can be faintly hoard Very good recommended ing rooms, etc. but not understood. Normal speech for dividing walls between NC-.50 to NC-55 Secretarial areas (typing), is inaudible. apartments. accounting areas (business 45 db. or greater Very loud sounds, such as loud sing- Excellent recommended machines),blueprintrooms, ing, brass musical instruments, or a for band rooms, music prac- etc. radio at full volume can be heard tice rooms, radio and Above NC-SS Not recommended for any only faintly or not at all. sound studios. type of office Lead Industries Association 292 Madison Ave. New York, New York 10017 Look Ahead with Lea PV/ 3/63 (35M) Printed in U.S.