Document Raaz56Lk7nKyDNDOKDGm56jrz

PLAINTIFF'S EXHIBIT SABIN IT E CONTROLLED SOUND HISTORICAL FILE EE'ox/s- -y/lciv/z &Leceiwcl........1 ____ ___ DO NOT DESTROY u {T*our thejiill tide of eloquence alonga Serenely pure, and yet divinely strong ft ^ POPE B B O ll 0611 w I SA BINIT E The practical fireproof sound absorbent for the correction of Auditorium acoustics during con struction, and for the reduction of noise levels in Office, Hospital and Hotel Buildings. United States Gypsum Company CHICAGO BBOU 0612 PI1ST CONGREGATIONAL CHURCH, EVANSTON, ILL. TALMADOB A WATSON, ARCHITECTS K O R EL W O R D ODAY, architects can plan churches, audi O toriums, music halls and similar audience rooms with absolute assurance of proper audition. It is now possible to predict accurately the acoustical results in any room and, further than that, to secure correct acoustics by ad herence to certain fundamental principles of design. This important architectural development is attributable to the late Wallace Clement Sabine, Hollis Professor of Mathematics and Natural / Philosophy at Harvard University, and to Dr. Paul E. Sabine of the Riverbank Laboratories at Geneva, Illinois, who has carried on the work since Prof. Sabines death. This long known, long puzzling problem of architecture is described and solved in the follow ing pages. A complete service for the analysis of such problems, and the guidance of the architect is offered and described. Data are given for the correct application and use of the sound absorbents manufactured by the United States Gypsum Company. 5 B B O ll 0614 Why Sabinite? For many years, the United States Gypsum Company felt that while a fire resistant, hard, decoratable, plastic sound absorbent was badly needed by the architectural profession, it was a material that never could be furnished. Sound absorbing materials were, generally speaking, fabrics or similar soft stuffs inherently combustible--catch-alls for dirt and vermin. Most of them had conspicuous patterns which distracted the attention of audiences and were impractical to decorate. A material porous enough to absorb an effective amount of sound, and still hard enough to be sold as a real plaster, seemed a paradox. Sabinite Acoustical Plaster is this paradox. Why Sabinite Its sound absorption ^Absorbs Sound ,s no'due 10 so,'n" or elasticity, Sabinite Acoustical Plaster absorbs sound be cause of a great multitude of tortuous, minute passages, which have their start in tiny openings at its surface. In these pas sages sound is repeatedly reflected, losing energy to heat and friction at each bump. These passages are inherent in the material. No skill or art unknown to the commonest plasterer is needed to secure them. Being a plaster, Sabinite does not intro duce a new trade in the building. There is no delay. The plaster contractor applies the material in lieu of the usual finish. There are no factional labor disputes, and no waiting for sub-contractors. appearance Sabinite walls and ceil ings do not cause com ment. There is nothing unusual about them. They look like other walls. There is no objectionable pattern. Where wall treat ment is needed, Sabinite serves just like any other plaster. It is not soft, and requires no protection. Its surface does not attract curi ous people as there is nothing unusual about it. Sabinite may be applied on side walls down to the mop-board with full safety in lieu of regular plaster. "Decorating Sabinite. Integral Sabinite walls may be integrally crinfifta l*nted on tbe )ob bytbe addition o of dry pigments. On large orders, Sabinite will be furnished in colors to suit architectural needs. The natural color of Sabinite is a light gray. Spray Sabinite may be painted any 'Prtintino color hy sPraying k with the ruining ^ s Gutta percha Company's "Flow-On Paste,'' calcimine, or any spray ing lacquer. Where surfaces in the modern trend are desired, Sabinite is sprayed with bronze powder in thin lacquer. White gold bronze powder used as a pigment in thinned lacquer is especially suited to theatre ceilings where special lighting and stereopticon illusions are in vogue. Such decoration is quite inexpensive, as in most cases but one coat is needed. 6 B B O ll 0615 ^Brush Where spray painting is not _ . . approved, Sabinite may be rUlfltlTlg brush painted with Phon-O- Lite, a special material manufactured by the Some Outstanding Features ofSabinite^ United States Gypsum Company for appli cation to Sabinite, without appreciably reducing its sound absorption. Incombustible There is nothing in Sabinite which will General directions for aipplying various decorative treatments to Siabhininiittie are given burn. It is composed of incombustible, inorganic aggregates bonded together with on page 16. Specifications for special treatment or un usual decoration problems gypsum plaster, w'hich has been long known as a fireproofing material. are supplied on request. Successive painting or ap plication of color by any of these methods may be made without reducing the sound absorption of Sabinite by a measurable amount. `Durability As Sabin- J ite is com posed of rock, it is unaf fected by dampness, and does not shrink or swell with climatic changes. xJMasonry Where rl?c a / effect of ash- CjjettS lar masonry is desired, Sabinite may be jointed by the plasterer in the same way in which he joints Keene's Cement or imitation Caenstone. The joints may be left plain or filled with colored mortar. Case of Noth- t-Apblicatiore water is added to make Sabinite ready for application at the job. It is spread with a trowel from the hawk, just like ordinary plaster. It is as hard as any plaster finish -- harder than most of them. It bonds firmly to the Frescos and Stencil or u, fresco de- ijvlurals signs may be laid on Sabinite with VICTOR TALKING MACHINE COMPANY, CAMDEN, N. J. base coat. There is nothing in Sabinite to burn, irritate or in any way injure the mechanic applying it. ordinary paint, if the area is restricted to borders. For larger areas, Phon-O-Lite Covering One ton Sabinite, applied in f two coats, each %" thick, will should be used. (jlpaCity cover a surface of sixty (60) square Large areas may also be stained or tinted with spray application of aniline dyes in water or alcoholic solution. Mural painting may be done with Phon-O-Lite with com plete freedom. yards. Analysis of over ioo jobs, shows that it requires 15 hours of plasterer's labor to apply 100 yards of Sabinite to full specifications. To mix this material, from six to eight hours of mixing labor is necessary. The mixing labor, of course, includes the time necessary Casting Fr ornamental work, ceiling c L` coffers, Sabinite may be cast Sabinite and erected like other plaster casts. Special instructions for doing this work will be given on application. Casts so made are easily tinted by including any of to supply the material to the mechanic. economical The low c?st the material, easy application and excel lent covering capacity, coupled with its relatively high sound absorption, makes Sabinite a most economical material per unit the various dry pigments. They produce of absorption. On an auditorium in Texas, an effect that is so delightful that their Sabinite was lower by $3,000.00 than its use has been specified by architects for their decorative value alone. nearest competitor. The area involved was about 1,100 square yards. 9190 uoaa 7 PETWORTH SCHOOL, WASHINGTON, D. C. A. L. HARRIS, SUPERVISING ARCHITECT, DISTRICT OF COLUMBIA Sanitary Because it contains no vege- table^r animal matter, Sabinite is sanitary. There is nothing in it to make nesting material for vermin; nor are the pores large enough to admit flies or other insects. It may be disinfected or washed when necessary. Rats and mice will not gnaw Sabinite. `National Sabinite is made at the . principal mills of the Distribution_ United States Gypsum Company, which are conveniently located for lowest transportation cost. It may be obtained quickly from these centers. t.Applications Ever>' Sabinite job is rr served without cost by SrVlC(L-> the manufacturer. The service man sees that the base coat has been properly raked, and shows the plasterer how to apply the material. A variety of surfaces may be obtained by variation of the floating. For smooth surfaces, Sabinite may be trow eled after the floating process has been com pleted. The service man is always ready to assist the plasterer in obtaining such results. Absorption-} The absorption of Sabinite applied in two coats yi" thick, is 11% at C-4. This absorption increases with increasing pitches to 39% at C-6. The absorption of Sabinite has been established bv tests at the Riverbank Labo ratories, Geneva, Illinois. The facilities for such tests at Riverbank are unsurpassed. The tests made there are consistently lower than those made by other laboratories. Checks of reverberation times computed previous to construction, which are made after the building is completed, invariably show an increase of from 15 % to 17% in value over the absorption coefficient used in the calculation. It is therefore apparent that Sabinite yields a more absorbent result under job conditions than it does when small test panels are produced. Architects should not be misled by claims for superior absorption when considering cost. Some of the non-plastic sound absorb ents have a greater absorption per square foot, but their cost per unit of absorption is usually greater. It is a simple matter to adjust the area of Sabinite to provide the correct number of units to properly handle any reverberation or quieting problem. In most buildings a material of greater absorp tion is a drawback. If an entire ceiling is treated with such material, over-treatment is apt to result, so that the room will be lifeless and unresponsive under full audience conditions. Proper correction in such a room, using a very highly absorbent material means panel treatment in the ceiling. It is difficult to adjust the area of such panels with the architectural scheme for the interior. 8 BB011 0617 Sound `Problems as `They z-Affect ^Architecture This book on sound problems in architecture confines itself to two of the three major phases of the general problem. The first two are treated here; the third is to be treated separately in a subsequent publication. These three problems are: 1. Audience %00ms Treatm"nt of audience rooms in order to provide V- proper hearing conditions for both speech and music. ? 7\Jni*p Ahsnrhtinn The absorption of noise created in and about hotels, ' office buildings, banks, hospitals, restaurants, rail road stations, etc.; to quiet such structures and make them more generally useful to people occupying them. 3. Sound Insulations pTrheevetnret atthLmeentrtanosfmai.snsXiornooonf?'noPiasremfrlroonm otrhuafltoororotm0 to abuting rooms--in short, sound insulation, as compared to sound absorption. (See page 30). While it is true that sound absorbents are useful in preventing transmission of noise, they are not completely efficient in this regard and are, in no sense, offered to the public as sound-insulators. The problems are distinctly different, and consequently are treated separately. The first two of these problems owe their theoretical solution almost wholly to the work of one man, the late Wallace C. Sabine, Professor of Physics in Harvard University. In 1895 he began twenty-five years of in SBORE THEATRE, CHICAGO Z. EROL SMITH, ARCHITECT tensive, careful scientific research in a field that had hitherto been the playground of guess work and opinion. This work made Professor Sabine the founder of what is today, an important branch of engineering science, the control of sound within rooms. One who is interested in the mastery of the details of this subject should refer to Pro fessor Sabine's Collected Papers on Acoustics published by the Harvard University Press. Here, it is proposed to present the outstand ing results of that work for the architect, builder, or owner, who is faced with the practical problem of acoustics in building design ana construction. 8190 T1088 9 Some `Definitions The nomenclature of a science as new as that of acoustics is so possible of misapplica tion that it seems necessary to assist in clarity and understanding, that we define the more important terms before proceeding with Professor Sabine's theory. 9nund Sound *s a wave motion of the air or other elastic medium, capable of producing the sensation of hearing. This wave motion is set up by the vibration of a sounding body, and consists of the succes sive vibrations of the particles of the medium. This vibration of the individual particles produces alternate rarefactions and condensations of the air or other medium at any point of the wave train. Steed of Sound in air travels with a speed 'of about 1119 feet per second oOUtlU at 68 F. Its velocity increases about 1.1 foot per second for every degree rise of temperature. Intensity of Intensity of sound may be _ , J '* defined as the sound energy bound per unit volume of the air through which the sound is traveling. Loudness is the degree of sensation produced LONDON LIFE INSURANCE CO., LONDON, ONTARIO, CANADA JOHN MOORE & COMPANY, ARCHITECTS on the ear corresponding to the intensity of the sound. Loudness increases with intensity, but the difference in loudness between two tones of the same pitch is roughly proportional to the logarithms of their intensities. Hence an increase of as much as 2j% in the intensity of a tone produces a barely perceptible increase in loudness. *esonances Resonance is the enhanced response of the total volume of air included in a room to a musical tone whose pitch coincides with the natural frequency of vibration of that particular volume of air. It is frequently observed in small empty rooms and simply results in an unusual reinforcement of particular low tones in comparison with other tones. It is sometimes a source of annoyance to a speaker upon an enclosed stage, and is undesirable in rooms intended for radio broadcasting or for phonograph recording. Rarely found in large or furnished rooms, it is seldom an important factor in auditorium acoustics. Interfeto,yonce , Interference is a localized phenomenon which may be observed under proper conditions at any point in any room. In the simplest case, it results when sound of definite pitch from a single source reaches a given point by two paths of different lengths. Where this differ ence of path length is an odd number of half wave lengths of the sound, a condensation arriving by one path coincides with a rare faction arriving by the other path; the two components of the resultant sound mutually annul each other. Obviously, there will be other points close at hand where the path difference is an even number of half wave lengths, when the two components will mutually reinforce each other. Interference thus results in an uneven space distribution of sound intensity for a given pitch, and a marked variation at any given point in the intensities of sounds of different pitches. It becomes a serious defect when the focusing action of extended concave reflecting sur faces exaggerates the normal inequality that exists in every room. Spherical domes and cylindrical vaulted ceilings with centers or axes of curvature that fall close to the audi ence or to the speaker are fruitful .sources of defects of this type. Such defects can be avoided by proper design. They can be B B O l1 0619 10 alleviated by the use of sound absorbent materials on the concave surfaces which pro duce them. Prevention is better than cure, and the designer who proposes to use extended curved forms in an audience room should be competently advised as to the acoustical results to be expected. Extraneous Frequently, hearing diffi- . culties resulting from dis turbing noise are ascribed to faulty acoustics. Noise of ventilating fans transmitted along air ducts are delivered to audience rooms, air conditioning machinery improperly mounted, thus setting up vibra tions which are structurally transmitted, and finally street noises, may seriously lessen the intelligibility of speech in rooms that are otherwise satisfactorv. Echo is the distinct repetition of a single short, sharp sound, due to direct reflection of sound from one or more reflecting surfaces. Like interference, echo is a localized defect. It is seldom present as a source of acoustical difficulty except in rooins of large proportions. Extended, un broken rear walls frequently produce direct reflections that are annoying to the speaker, but which are not heard by the audience. Echoes from lofty ceilings, particularly when these are curved so as to produce marked concentration of the reflected sound, fre quently result in poorer hearing conditions in seats near the speaker than in seats farther away. Multiple echoes resulting from repeated reflections may be observed under special conditions in very large rooms. Every auditorium design should be carefully investigated for echoes which would cause annoyance. `Reverberation-; Reverberation may be v called the persistence of sound in a room after it has ceased at its source." Professor Wallace C. Sabine said, ``Sound being energy, once produced in a confined space, will continue until it is either transmitted by the boundary walls, or is transformed into some other kind of energy, generally heat." Auditorium Acoustics Good hearing conditions in an audience room are due not so much to the possession of positive acoustical virtues as to freedom from serious acoustical defects. Professor Sabine classifies difficulties in hearing in audience rooms under two distinct heads: Distortion, which may be due either to the phenomenon of resonance or to that of interference. Confusion, resulting either from echo, ex traneous noise, or excessive reverberation. `Reverberation in Architects and scit^Aud7ie* nce i\ootns etjnietisstosj,uptrjeovnioQufsthtoe acoustics of auditoriums by Professor Wal lace C. Sabine, had always thought that the difficulties caused in such rooms were because of echoes, or because of an inability on the part of the speaker or sound-produc ing source to provide sufficient strength to force the sound to the farthermost listeners. To correct these difficulties, it was common practice to install sounding-boards. Fre quent mention in the discussion of acoustics of twenty years ago is made of wires strung across the room to carry the sound. We, of course, now know that neither of these acces sories to an auditorium were of much service. When the interior surfaces of a room are constructed of materials which are highly reflective, sound waves striking them bounce rapidly from surface to surface, making many circuits of the room in every direction. The room is then filled with sound which continues until all of its original energy is dissipated. Overlapping Ir is easy to appreciate the resultant confusion due to jOUnuS the overlapping of succes sive syllables or notes in an audience room. The first syllable persists, while the next is uttered. Each syllable and note has to com B B O l1 0620 il SAVARIN RESTAURANT, NEW YORK CITY SCHULTZE & WEAVER, ARCHITECTS pctc with preceding sounds for the attention of the audience. This effect is throughout the room. It makes audition uncomfortable, difficult, or impossible, depending solely on the length of time a sound persists. The time a given sound of known intensity and pitch persists is the reverberation time of that particular room. There is no sorrier picture than that of a beautiful auditorium perfect in architec tural magnificence--where the designer has built himself a monument--in which an oration or sermon becomes a jumble, and an organ solo or choral masterpiece a mess of discordant sounds. Regardless of the perfection with which the building is built, it is a total failure if it is useless for audition --in other words, it is not an auditorium, for it can not in any sense be an auditorium if one can not hear clearly and comfort ably in it. In a midwestern city, a group of settle ment buildings was recently built which contained a music school and a chapel of considerable proportions. In the music school, the architect wisely treated the ceil ings with an efficient sound absorbent. The effect was all that he desired. In the chapel, although analysis indicated an excessive re verberation time he felt nothing was needed. He had built similar structures in which the acoustics were most excellent. And he thought that this building would be equally satisfac tory because the structure, general shape, size and contour were the same. He did not consider that different materials were to be used --materials which were highly re flective of sound. The new building was made larger than the one for merly used by the congregation, in order to accommodate the increase in numbers they confidently expected with their finer quarters. The completed structure is intol erable, acoustically. The congrega tion can hear but little of the sermon and then only when they concentrate in certain parts of the church. The choir master in the choir loft is apprised of changes in the service by means of notes quickly penciled by the minister. He can not get these orally, although only 7 or 8 feet from the pulpit. The congregation has dwindled. The church can hardly afford to spend the money to bring a contractor into the room with his scaffolds, have them re erected, the old plaster torn off and sound absorbing plaster put on at a cost several times as great as what it would have cost had the auditorium been properly treated during construction. Almost daily these pictures come to us of buildings useless for their prime pur pose. While acoustical correction is not denied their owners, the cost compara tively, is beyond the means of the average church. These things need not be. There is no mystery about acoustics. Buildings identical in shape and form rarely present the same reverberation time. An analysis should be made of every auditorium. The United States Gypsum Company makes these for any architect without cost and without obligation. B B O ll 0621 12 <JJJe Reverberation Theory ofTrofessor Wallace C. Sabine How It Is ^Applied torPlaimed Structures ^Before They oAre `Builts Pvrpaiisp If a sustained source of R_everjberati.on sound within a room is suddenly stopped, the sound will be observed to persist for an appreciable period thereafter. The residual sound dies away more or less rapidly to inaudibility. The time required for it to decrease in a given room to 1/1,000,000 of its initial intensity is called the Period of Reverberation. This time is readily computed when the total volume of the room and the sum of the sound absorbing power of all the surfaces exposed to the sound are known. Professor Sabine showed that T (the time required for sound within a given room to decrease to 1/1,000,000 of its initial intensity) is given by the equation {1} T=05/ where V is the volume of the room in cubic feet and A the total sound absorbing power. The contribution of any exposed surface to the total sound absorbing power is the prod uct of the area of the surface by a certain fraction, called the absorption coefficient for that surface, so that the total absorbing power A in the reverberation equation is the sum of the products obtained by multiplying the area of each exposed surface by its particular absorption coefficient. An approximate value for A for an empty room without any considerable area of sound absorbing materials such as carpets or draperies, seat cushions and the like may be found from an empirical formula given by Dr. Paul E. Sabine of the Riverbank Labora tories as a result of a study of a large number of auditoriums. This formula is: 2s (2) A=S.29 V 3 SB.29'j/p'2 That is to say, to find the total absorbing power of any empty audience room with masonry walls and ceiling and seats of wood, take the volume in cubic feet, extract the cubic root, square it and multiply by .19. The result used in the reverberation equa tion given above will give the reverberation time in the empty room. It is well known that the presence of an audience materially changes the acoustical properties of an auditorium. This is due to the fact that the total sound absorbing power is very largely increased by the clothing of the auditors. Experiments show that for each person seated in a wooden seat, as assumed above, the total absorbing power of a room is increased by 4.3 units. Thus for the conditions of use, A as given by equation 2. should be increased bv 4.3 times the number of persons in the audience. To illustrate the foregoing by a simple example: Suppose the dimensions of a room intended to seat 1,000 persons are 100' x6o' xio' Then V, the volume = 110,000 cu. ft. and A, the absorption = .19 (no,ooo)M Log 110,000 =5.0791 5.0791 xi 3 Log .19 = 3.3861 = 9.4614 --10 Log A =1.8485 A =706 Note: The calculation may be made with ample accuracy on a slide rule. BRONX COURT HOUSE, NEW YORK CITY MAX HAUSLE, ARCHITECT B B O l1 0622 13 CITY AUDITORIUM, BEAUMONT, TEXAS F. STE1NMAN fit SON, ARCHITECTS If it is desired to compute the reverbera tion times (a) with an audience, (b) with half audience, and (c) with full audience we have as shown in the following table: Audience None 500 looo A Absorption of Empty Room 706 706 706 Absorption of Audience None 1150 4300 Reverberation Time y T=.05-r 8.5 Secs. 7.1 1.7 Experiments show that a reverberation time greater than z.o seconds produces a marked decrease in the intelligibility of speech. In the example, therefore, we have a room that will be satisfactory for large audiences but not so for a small audience. In audience rooms generally, the capacity audience is the exception rather than the rule. In the design of this room, therefore, an increase in absorbing power is desirable, in order to produce conditions that will be acoustically comfortable with small as well as with large audiences. Suppose the 6,000 sq. ft. of the ceiling be plastered with a material whose absorption coefficient is .11 instead of .015, the absorp tion coefficient for ordinary plaster. Then each square foot of this new material will add .185 units over the ordinary plaster which it replaces. The 6,000 square feet would add 6,000 x .185 = 1,110, and the absorbing power of the empty room becomes 1,816 instead of 706 units. Under the new conditions then, values: Audience None 500 1000 we have A 1816 3966 6106 the following T 3-3 M x.o We have here a room that will meet the requirements for comfortable hearing condi tions with any audience greater than 300 persons. Sfie Proper Some author- j. ities on sound 1Reverberation Time seemtofeel for (^Audience %' ooms that the rever beration time most desirable in a room varies with the volume of the room. It is their practice to permit a longer lapping of sound in rooms of large volume than they permit for rooms of small volume. This results in a flexible standard for the reverberation time that is quite confusing, particularly to laymen. It is caused by the fact that the formula in current use does not take into consideration the reduction of the intensity of sound from a given source as the volume and absorbing power of the room increases. In an endeavor to eliminate this difficulty, Dr. Paul E. Sabine has made a considerable studyof the equation of Professor Sabine, (T =.05^). Dr. Sabine says that the time "T"during which a sound remains audible in a room after the source has ceased, theoretically depends upon five factors: "V"--the total volume of the room; "A"--the total absorbing power of the room measured in square units of perfectly absorbing surface; --the acoustic output of the source, expressed in cubic units per second of sound of threshold intensity; "T"--the time during which the source speaks and "V"--the velocity of sound. These five quantities are related by a some what complicated expression, which how ever, may be reduced to a very practicable form, by assuming that "T" is sufficiently long to fill the room with sound, and that "E" the acoustic output of the source is approximately equal to that of the organ pipes which Professor Sabine used in his experiments. BB011 0623 14 Upon these assumptions Dr. Sabine gives the equation (3) Tl = 0083/(9.1 -logwA) Here T, is the time required, measured from the instant the source is stopped, for the sound from a source of standard pitch and standard acoustical power to decrease to inaudibility. The bracketed expression is the logarithm of the average intensity of sound throughout the room set up by the standard source and is seen to diminish as A the absorbing power of the room increases. This is what Professor Sabine has called the "initial intensity of the residual sound." Upon the assumption that this is 1,000,000 times the minimum audible intensity (since the logarithm of 1,000,000 is 6), equation (3) reduces to the simpler form Vol. Seats ! Cubic Feet Small Auditorium, 1 Moscow . . 4.450! . . . Little Theatre, New York. . . 6,000 300 New England Con servatory Room 7,400 Moscow Conserva tory. Moscow, . . 90,000 550 Leipzig Gewand- haus. Leipzig . 406,000 1,600 Opera House. Ac ademy or Music, Brooklyn............. 430,000' 2,200 House of Unions Hail, Moscow . . . 440,000 1,600 Big Theatre, Moscow............... 486,000' 2,300 Opera House, Boston... . 500,000 2,350 Moscow Conserva tory Big Hall, Moscow............... 600,000 2.150 Symphony Hall, 1 Boston................. 650,0001 2,600 Masonic Auditori um, Cleveland... 726.000' 2.300 Eastman Theatre, Rochester............ 790,000 3,340 Hill Memorial, Ann Arbor .... 795,000' 5,000 Auditorium Theatre 1 Chicago............... 950,000! 3,640 Reverberation Time Equa Eouation tion No. 1 No. 3 1.06 1.20 1.10 1.30 2.35 1.15 1.14 1.19 1.19 1.98 1.60 1.75 1.55 1.51 1.31 1.44 1.25 1.23 2.00 2.31 2.40 2.08 1.70 1.90 1.63 1.92 1.95 1.65 1.33 1.48 Authority W. C. Sabine Lifshitz W. C. Sabine Tallant Lifshitz Lifshitz P. E. Sabine Lifshitz W. C. Sabine Wataon Tallant P. E. Sabine Fig. 1 Equation (3) gives the reverberation time, assuming a standard source of sound, inde pendent of the volume and absorbing power of the room. Equation (1) gives the time required for sound of any given initial intensity to die away to 1/1,000,000 of its initial intensity. It appears then, that equation 3 is simply equation 1 with a correction term for the change of the initial intensity with a change of absorbing power of the room and the change in volume of the room. This results in an ability to fix the reverber ation time within limits which are proper for any room without regard to its volume. Using equation 3, "T" was computed by Dr. Sabine for fifteen different rooms which are in actual use and without criticism in the matter of reverberation, and which varied in volume from 3,500 to more than 1,000,000 cubic feet. (See Fig. 1.) The results were compared with those obtained by equation 1. From this comparison is deduced the follow ing working rule: That the time of reverberation for an auditorium with its average audience as computed by equation 3, should lie between one and two seconds. For speech, and light music, it shouldfall in the lower half of this range, while for music of the larger sort it may lie near the upper limits. Having arrived at a useful criterion of excellence, the designer's problem becomes simply a question of adjusting the absorbing power and the volume to obtain the desired result. The volume consideration is controlled in great measure by the dictates of the archi tectural design. It is not always possible to reduce ceiling height without throwing a room completely out of scale. With a useful absorbent at his command', the designer is given much greater liberty in design than the modern high reflective materials of construction will allow, because of the possibility of including specially designed absorbent materials properly tempered in area to the acoustical result desired. 15 BBOU 0624 16 BB011 0626 17 Securing Quiet with Sahinite in Offices, Hospitals, Hotels, etc. Sfie Cost Scientists and psuedo-scientists have quite frequently, of late, OJ I\piS(L> made attempts to determine the <-AugmentatiotL-> is not usually . known that the con- OJ IXptSeS struction of a build economic worth of quiet, or more particu ing, particularly the plaster and other mate larly, the economic loss caused by noise. In rials which are highly reflective of noise, our present knowledge, most of these efforts increases the audible noise in the room as may be classified as mere guesses, more or much as three-fold. less aided by superficial tests, yet anyone will Reverberation, the multiple reflection of grant great advantage to the thinking indi sound back and forth in a room, increases vidual who is permitted to think in a reason the general level of sound intensity. Each ably quiet room. The more exacting mental sound produced, persists for an appreciable tasks, requiring concentration and the length of time, and during this time con exercise of every mental faculty are most tributes to the sum total. The corresponding disturbed by noise. Those more manual in case in lighting will illustrate this. Con character are least disturbed by noise, but sider two rooms identical in every regard, even manual tasks show a very definite except that the walls and ceilings of one are noise effect. In his "Economics of Fatigue highly light reflecting (white) while those and Unrest," Dr. Morris gives interesting of the other are highly light absorbing figures on this point. He finds that in an (black). Let lamps of equal candle power American motor factory, the average be placed at the center of each room. It monthly absence rate for the entire plant was is easy to see that the general intensity of 6.13%. In nine departments where eye illumination will be much greater in the strain was found, the percentage was 6.19%. white-walled, than in the black-walled In thirteen poorly ventilated departments, room. Similarly, a given amount of light 6.45%- In the five noisiest departments, the through a window into each of the two percentage was 6.8i%, an increase in the rooms will give better general illumina relative absence rate for the noisy rooms of tion in the white-walled, than in the black- over 11%. Dr. Morris also found a notice walled room. In exactly the same way, able increase in requests for transfer from highly sound reflecting walls and ceilings noisy departments in comparison with simi serve to raise the general level of sound lar requests from intensity from a other departments. given source of This problem of noise, as it pertains to business, is being in creasingly considered sound. Ordinary plas ter surfaces are almost perfect sound reflec tors, absorbing less by business men, and than 3% of the sound consequently it is energy and reflecting receiving greater 97%. Dr. Paul E. consideration by the architectural profes sion in the design of business buildings. Even more far-reach ing in its effect is the noise produced in and near hospitals. Here, Sabine reports that in one case the total measured amount of sound in a room due to the operation of a typewriter was 3.3 times the sound that as everyone knows, quiet is essential. 300 west adams st. building, CHICAGO j. j. jensen, architect was Produced by each impact of the type. 18 B B O l1 0627 Figure II on this page illustrates this phenomenon very well. In a given room the tabulators, accounting and bookkeeping machines, and the conversation of employes, rate of decay of a single tap from a type present a perfect bedlam of sound. School writer was noted. Assuming that such taps rooms, gymnasia, swimming pools, restaur succeed each other at intervals of of a ants and, above all, hospitals, under modern second, the figure shows the total contribu construction, suffer from excessive sound re tion that is made by the taps which occurred flection. In such buildings the use of an acous in the second immediately preceding. In this tical absorbent has solved the noise problem. particular room the residual sound of the A prominent office building manager has preceding second alone said that within a few raises the total amount of sound in the room at any instant to about three times that of a single tap. years, the office build ing which has not noise absorption treatment included in the conveni ences offered tenants, The use of Sabinite Acoustical Plaster for walls and ceilings has proven an extremely effective method of reducing noise, as mod ern fireproof construc tion provides almost will be antiquated and suffer accordingly as a revenue producer. The general manager of a large life insurance company in referring to their recently com no absorbent surfaces. pleted office building Business offices, with said: "This building thenoisefrom telephone cost us one million bells, from typewriters, Fig. II dollars. The complete B B O ll 0628 19 Sabinite treatment cost us $10,000.00. This building is worth twomilliondollars, because of the quiet, comfort, and peace of mind afforded to all of our employees by the Sabinite." The relatively large amount of acoustical absorbents already in use, particularly in the offices of insurance companies, has given acoustical engineers an excellent opportunity to observe the effects of such installations. In a large Chicago office, which is located on three floors of a recently constructed twelvestory reinforced concrete building, Sabinite Acoustical Plaster was applied to the ceilings of two floors. The contrast is at once apparent upon entering the treated and the untreated offices. The treated rooms do not have the constant murmur which at times reaches such proportions as to be called a roar. The atmosphere is more that of a private drawing-room. When the company moved into this office from their old quarters, the effect on its employes was immediately noticeable. In their previous location they had found through subconscious practice that, to be heard by their neighbors, speech had to be increased in intensity to almost a shout. In the new offices, within three or four days, every employee had so modulated his voice because of the lack of necessity for shouting that the drawing-room atmosphere of the new location elicits spontaneous comment by visitors. Street noises are, of course, noticeable at the open windows in the summer, but 15 to 10 feet back from these windows the sound is hardly appreciable. Shortly after this office was opened, con struction was started on a building immedidiately west of the one in question. The hissing, thumping noise of a steam piledriver, sharp and very annoying in its effect, was heard with the usual distinctness at the west windows. Moving back into the room one or two bays, the noise, while heard, was not in any sense annoying or noticeable unless attention was called to it. Still, if one went to the windows on the east side of the room, a half block away from the noise, it could be heard there coming around the buildings and enteringthe windows. Back from the east wall it was not at all noticeable. B B O ll 0629 LINCOLN HALL, SCHOOL OF LAW, NORTHWESTERN UNIVERSITY, McKINLOCK CAMPUS, CHICAGO JAMES GAMBLE ROGERS, ARCHITECT. CHILDS A SMITH, ASSOCIATES 20 Wfe Proper Sound has a uniformly in creasing absorption for sound as the pitch Absorbentfor Quieting increases, making it comparable, square foot for square foot 'Buildings in absorption values, with absorbents or In the consideration of the proper sound absorbent for office, hospital and similar quieting treatment, informed architects and builders give thought to the per centage absorption of dinarily rated higher in that regard at C4. By the same token, Sabinite is noticeably, superior when com-, pared at C6 to many absorbents whose ab sorption is about as great as SabiniteatC4. the various materials under consideration at pitches above the standard octave above middle C (C4) which is used as the fundamental note in auditorium analysis. The sound absorb ent used in a quieting problem should be intensely practical in application. It should be adaptable to any surface or condition. It should lend itself to Careful investiga MATERNITY HOSPITAL, BOSTON, MASS. architectural treat tion has determined ANDREWS, JONES, BISCOE & WHITMORE, ARCHITECTS ment in keeping with that the pitch of office the general design of machines varies between C5 and C6. Absorb the room and, above all, it should be a per ents vary considerably in their abilities to manent lasting part of the structure. It should absorb sounds of different pitch. With some not add a combustible element of any sort, of the absorbents offered to the public, there or in any way inject additional fire hazard is a comparative reduction of as much as 50% in office, hotel or hospital. Sabinite is a in their absorption efficiency for the higher plastic incombustible material which pitches. This is not so with Sabinite, which meets all of these requirements. B B O ll 0630 FIRST CHRISTIAN CHURCH, ADA, OKLA. ALBERT S. ROSS, ARCHITECT LONDON LIFE INSURANCE COMPANY, LONDON, CANADA JOHN MOORE & COMPANY, ARCHITECTS 21 JTigJjf It is unusual to find a . * material which is designed Z_s for sound absorption which has any great reflective power for light. Paradoxically, Sabinite in its natural color, reflects 6i%of the light which im pinges on it, comparing very favorably with ordinary materials. Wall paper, for instance, rarely reflects more than 55% and generally less than 50%. The light reflection of Sabinite may be enhanced by painting with a light cream or gloss white, and greatly increased by spray ing with white gold lacquer. Sanitation^ For installations in hos pitals, it is suggested that Sabinite be given two coats of spraying lacquer. A clear lacquer may be used if the natural color of Sabinite is desired to conform with the decorative scheme, or a colored lacquer, if a colored surface is more appropriate. It may then be washed with soap and a brush or treated with disinfectants at regular intervals, providing the hospital with a sanitary, cleanable sound absorbent. to the side walls of corridors. It is more necessary to do this than to apply Sabinite in the wards and rooms themselves unless the hospital is located on a noisy street where sound absorbents on the ceilings will reduce the noise which would otherwise cause discomfort to the patients. The noises caused by the wheeling of travs of food, the clatter of dishes, and disturbances in patients' rooms escape into the corridors and are carried into all of the rooms leading from the corridor. The introduction of Sabinite in the corridor will absorb this noise, mak ing all the rooms leading from it quiet and restful. In hospitals it is quite common as well to treat the ceilings and side walls of the labor and delivery rooms. It is excellent practice to apply Sabinite to the ceilings of all sculleries, kitchens and pantries which directly connect with the portions of the building used by patients. Hotels In hotels, elevator shafts as well as corridors are noise conveyors. Quiet guest rooms may be secured by treat ing the corridor ceilings with Sabinite. Many of the sounds occuring in guest rooms, and which seem to be transmitted through partitions, really come over the doors and through the transoms from the halls. One has but to remember his hotel experiences to know how annoying the clanging of elevator gates can be when the hall transoms are open. B B O ll 0631 22 Ceiling treatment, particularly in restaurants, lunch rooms and coffee shops, is recommended in hotels, as the clatter of dishes and the rattle of silverware is annoy ing to guests. It is also advisable to apply a sound absorbent on the ceilings in the kitchens and sculleries and the main dining room for obvious reasons. The ballrooms and large meeting rooms of hotels used for conventions and other purposes are notoriously bad for speech. The use of Sabinite on the ceiling usually suffices to correct such conditions. Sabinite provides a complete answer to the sound absorption question in hotel buildings. It is applicable to every point where treat ment is required, and is unaffected by varying conditions of moisture or temperature. And, too, it may be readily cleaned and decorated to suit the changing needs in such buildings. Plan ruAnalysis Jhe United States ,,. J Gypsum Company service provides a complete plan service without charge and without obli gation, which will predict the reverberation time in anv audience room for the architect. This service includes analysis of the effect of curved or other sound concentrating surfaces, and investigation for objectionable echoes. In each case it indicates changes in design where they seem advisable. Where the reverberation is too great for comfort, recommendations are made covering the area of Sabinite needed to properly correct the room. These analyses are carefully checked and calculated by acoustical engineers. All plans which are in any way unusual receive the personal criticism of Dr. Sabine. Because of the facilities afforded at the Wallace Clement Sabine Laboratory at Riverbank, this service keeps pace with the progress in acoustics. The architect can confidentially use it, knowing that his audience rooms will always receive favor able comment from both listeners and performers. He is assured that this service will never suggest treatment where none is needed nor will it ever suggest the inclusion of so much treatment that the resultant room is dead and lifeless, a fairly common occurrence since sound absorbents are being used more generally. BBOU 0632 23 Some Sabinite Installations Location Building Architect Globe ARIZONA U. S. Postoffice James A. Wetmore Washington, D. C. CALIFORNIA Compton Masonic Building Laguna Beach La Jolla Presbyterian Church Presbyterian Church Wright & Gentry Long Beach L. F. Hartley G. S. Walker Los Angeles First National Trust and Dodd & Richards Savings Bank San Bernardino Shaw Funeral Parlor J. V. Rice San Bernardino Junior College Library San Francisco Galideo High School Whittier Public Library Howard E. Jones John Reid, Jr. Hunt & Chambers London London London London Toronto CANADA Ealing School London Life Ins. Co. CitvHal! Technical High School Yorkminster Baptist Church L. E. Carrothers John Moore Sc Co. Thornton McBride L. E. Carrothers George, Moorhouse & King Washington Washington DISTRICT OF COLUMBIA McKinley High School Petworth School A. L. Harris A. L. Harris Coral Gables Jacksonville Jacksonville Marianna FLORIDA City Hall Riverside Presbyterian Church St. Vincents Hospital U. S. Postoffice St. Petersburg St. Joseph Church Phineas E. Paist Mark & Sheftall Gerald A. Barry James A. Wetmore Washington, D. C. Henry L. Taylor Chicago Chicago Chicago Chicago Chicago Chicago Chicago Chicago Chicago ILLINOIS Calumet State Bank Chicago Stock Exchange State Bank Building Savoy Ballroom Jackson Storage Warehouse Northwestern University Law School McKinlock Campus Olivet Institute Roosevelt High School Shore Theatre 300 W. Adams St. Bldg. John Eberson Graham, Anderson, Probst & White Levy & Klein Hall, Bisbee & Rhenisch James Gamble Rogers, Childs & Smith, Associate Architects Perkins, Fellows & Hamilton J. C. Christensen Z. Erol Smith Jens J. Jensen Location Chicago Chicago Chicago Chicago Chicago Evanston Evanston Glencoe Glencoe Glen Ellyn Glen Ellyn Hinsdale Naperville Rockford Building Architect Wieboldt Hall Coolidge & Hodgdon University of Chicago University of Chicago Chapel Bertram Grosvenor Goodhue Associates New York City Englewood Masonic Temple Dean & Dean Consumers Warehouse Robert S. Smith American Spiral Pipe Wks. Weiss Si Niestadt First Congregational Church Talmadge & Watson Chicago State Bank & Trust Co. Childs & Smith Chicago Glencoe High School Armstrong, Furst & Tilton, Chicago Synagogue, North Shore Alfred S. Alschuler Congregation Israel Chicago Masonic Temple Betts & Holcomb Chicago Glenbard High School Coolidge & Hodgdon Chicago Hinsdale State Bank W. G. Barfield Chicago E. E. Sargent Ins. Co. Carl J. Horn Logansporr, Ind. Rockford Theatre F. G. Klein Fort Wayne Indianapolis . INDIANA Chamber of Commerce Building Guy Mahurin Indiana Theatre Ballroom Rubush & Hunter Louisville KENTUCKY Phoenix Cafeteria D. X. Murphy & Bros. LaFayette New Orleans Belfast LOUISIANA Court House Sinai Temple Wm. T. Nolan New Orleans Emile Weil, Weiss, Drevfous & Seiforth, Moise H. Goldstein MAINE City National Bank Thomas M. James Co. Boston Boston Worcester MASSACHUSETTS Massachusetts Maternity Hospital John Hancock Mutual Life Ins. Co. Worcester Electric Light Company Andrews, Jones, Biscoe Si Whitmore Parker, Thomas & Rice Frost, Chamberlain & Edwards . 24 CE9o r rose Location Building Architect MICHIGAN Detroit Grand Rapids Grand Rapids Grand Rapids Kalamazoo Mt. Pleasant M. C. R. R. Fruit Auction Bldg. East Grand Rapids High School Godwin School Kellogsville School Vegetable Parchment Paper Co. Normal School A. B. Nies Robinson & Campeau J. & G. Daverman J. Si G. Daverman Billingham & Cobb Malcolmson & Hig ginbotham, Detroit MINNESOTA Fergus Falls Mankato Minneapolis St. Paul St. Luke's Hospital St. Joseph's Hospital Physics Building University of Minn. Federal Building J. V. Vanderbilt Minneapolis E. Breilmaier & Sons Co., Milwaukee C. H. Johnston & Son St. Paul James A. Wetmore Washington, D. C. NEBRASKA Omaha Steinauer Holy Name Church and E. J. Sessinghaus School St. Anthony Parish Church Lahr & Stangel Omaha NEW JERSEY Camden Elizabeth Hackensack Montclair Ogdensburg Victor Talking Machine Co. Auditorium Union Co. Court House Y. M. C. A. First Church of Christ, Scientist Ogdensburg School Eng. Dept., Victor Talking Mach. Co. Oakley & Son Louis E. Jallad New York Charles D. Faulkner Chicago C. Willard Wands, Associate, Caldwell, N.J. Rasmussen & Wayland New York NEW YORK Alfred Alfred High School A. W. E. Schoenberg Olean, N. Y. Brentwood, L. I St. Joseph Academy Robert J. Reiley New York Bronx Court House Max Hausle New York Buffalo Gethsemane Lutheran Church James Walker New Rochelle National City Bank Townsend, Steinle Si Haskell, New York New York City Fox Film Company Owners Engineering Dept. New York City New York City New York City Niagara Falls St. Bartholomews Church Savarin Restaurant No. l Park Avenue C. A. Auffmordt Si Co. (Importers) Mount Saint Mary's Nurses Home Bertram Grosvenor Goodhue Associates Schultze Si Weaver Goodwillie Si Moran Kirkpatrick & Cannon Poughkeepsie Saranac Lake Friends Meeting House Harriecstown Town Hall Alfred Busselle New York Scopes & Feustmann Syracuse St. Paul's Church Paul Wolter White Plains Court House Theodore Richards Asheville Greensboro NORTH CAROLINA Asheville High School Pilot Life Insurance Co. D. D. Ellington Zantzinger, Borie & Medarv, Phila. Location Building Architect Crosby Valley City Akron Cincinnati Cincinnati Ada Buffalo NORTH DAKOTA High School Sisters of Mercy Hospital Ira Rush, Minot George P. Stauduhar Rock Island, III. OHIO St. Thomas Hospital Warner A McCornack Cleveland Kahn Packing Co. Henschien & McLaren Chicago Gibson Hotel Roof Joseph Urban, N. Y., G. W. Drach, Inc., Cincinnati, Assoc. OKLAHOMA First Christian Church Court House Albert S. Ross Maurice Jayne Oklahoma City Bradford E. Stroudsburg Ellwood City Gettysburg Knoxville Latrobe New Castle Pittsburgh Pottstown Sharon Washington PENNSYLVANIA Presbvterian Church Normal School Lincoln High School Gettysburg Nat'l. Bank St. Canice Church Citizens Bank New Castle Junior High School Hendrvx & Benton Davis Si Lewis Scranton W. G. Eckles Co. New Castle Simons, Brittain & English, Pittsburgh W. P. Hutchins Pittsburgh Bartholomew & Smith Pittsburgh Albert S. Thaver Peoples Bank Building Masonic Temple First Presbyterian Church Washington Hospital Press C. Dowler A. S. Kepner Nicklas & Rodnck Cleveland Schmidt, Garden Si Erikson, Chicago Florence SOUTH CAROLINA Circle Grade School Wilkins Si Hopkins Vermilion Yankton Beaumont Dallas San Antonio SOUTH DAKOTA Masonic Hall City Auditorium Walter J. Dixon Mitchell Walter J. Dixon Mitchell TEXAS Citv Auditorium F. Sreinman & Son Dallas National Bank Coburn, Smith & Evans Bexar County Court House Phelps & Dewees Richmond Green Bay LaCrosse Madison Milwaukee Oshkosh Racine Wausau Whitewater VIRGINIA First Baptist Church Herbert L. Cain WISCONSIN High School Foeller & Schober Logan Junior High School Merman & Skogstad Medical School Arthur Peabody University of Wisconsin St. Roberts School Herbst & Kuenzli Normal School Arthur Peabody Horlick High School J. Mandor Matson Y. W. C. A. Oppenhamer & Obel High School E. J. Hancock Eau Claire BB011 0634 25 FIRST CHURCH OF CHRIST, SCIENTIST, MONTCLAIR, N. J. CHARLES D. FAULKNER, ARCHITECT. C. WILLARD WANDS, ASSOCIATE How to Specify Sabinite. Sabinite May Be Specified as Follows: (Short Form Specifications) "A"--All walls and ceilings marked "Acoustical Treatment" on the plans shall receive two coats of Sabinite Acoustical Plaster applied according to the full specifi cations of the United States Gypsum Com pany and under the supervision of their Service Department. "B"--The auditorium will be given acoustical treatment in strict accordance with the recommendations and specifications of the United States Gypsum Company who will provide data on which plaster con tractor may present his bid. (Full Form Specifications) All walls and ceilings shown on the plans to receive acoustical treatment will be given a scratch and brown coat of gypsum mortar containing not more than two parts of sand by weight to one part of plaster. The scratch coat must be thoroughly broomed before the brown coat is applied. The brown coat must be deeply raked after straightening. Sabinite Acoustical Plaster should then be applied as follows: To the half-green base coat, first apply one \i* coat of Sabinite, mixed according to the manufacturer's 26 SE9o n o a a directions, adding nothing but water to the materia] as supplied. The first coat should be straightened with a darby and thoroughly broomed with a clean broom as soon as the water has left the surface, the broom to be kept clean of all droppings and aggregate during the operation. The second coat is to be floated with a clean cork float to an even and porous surface. All applications of Sabinite Plaster are to be made only after the plasterers have received full individual instructions from a representative of the Service Department of the United States Gypsum Company. Specifications for Tinted Sabinite.j Colored Sabinite may be prepared on the job by the inclusion of dry color in amounts not to exceed 25 lbs. per ton of Sabinite. The usual precautions for handling colored plasters should be observed. The manufacturer will submit samples of Sabinite in color or match colors submitted by the designer on request. Integrally tinted Sabinite should be a shade lighter than the same color would be in paint because the texture of Sabinite casts a slight shadow. Tainting Sabinite by the Spray ^Method Sabinite may be spray painted with a DeVilbis Type A gun wdth K cap and M.F. nozzle or similar apparatus of equivalent effect, manufactured by other companies, the compressor to be operated at a pressure of 40 to 60 pounds per square inch, the nozzle to be held from 18 to 2.4 inches from the surface for United States Gutta Percha Company's semi-fluid Flow-on Paste or from 11 to 18 inches from the surface for the various lacquers. The U. S. Gutta Percha Company's semi-fluid Flow-on Paste thinned with Oleum Spirits or Varnolene is the approved oil paint for Sabinite when applied with a spray. Any good grade of spraying lacquer may be similarly used. In spray painting over Sabinite with either material, go over the surface only once, releasing the trigger of the gun at the end of each stroke. Be sure that the material applied is not sufficiently thinned nor applied sufficiently heavy to "run" on the surface of the work. After the first coat has dried, apply a second coat to even up the surface and to remove any "brush" marks. B B O ll 0636 27 `Trush `Tainting Submits Preparation of Surface. The surface to be painted must be gone over with a small block of wood and lightly rubbed to remove higher projecting particles in the surface. The wall or ceiling is then brushed lightly with a small whisk broom to clean it of loose particles which might adhere to the surface. The only paint approved for application over Sabinite by brush painting is Phon-OLite. It comes mixed to about the right consistency for application, a little thicker than ordinary ready mixed paint. If too thick, say almost jelly-like, it should first be stirred up well and then thinned with a little turpentine, or preferably sub-turpen tine. A half pint of sub-turpentine or tur pentine per gallon is the maximum thinner permitted. Phon-O-Lite may be tinted to any desired shade from its natural white by mixing color ground in oil, with turpentine or mineral thinner and then stirring it into the paint to secure the desired shade. Where colored Phon-O-Lite is desired, the tint should be obtained before adding any thinner. Application is with an ordinary paint brush, used liberally, but not attempting to fill up all the rougher places in the surface. Cover only about one square yard at a time and then double back and stipple the surface vigorously with a large flat, long bristle stipple brush. The stippling carries the paint into the low places, helps distribute it uniformly, and removes any tendency to lap. One coat applied and stippled as described is in all cases sufficient for the job. The covering capacity of Phon-O-Lite varies with the nature of the surface. PhonO-Lite should cover from seven to ten square yards per gallon of material. How to Obtain Sabinite Sabinite Acoustical Plaster mav be obtained from any dealer handling United States Gypsum Company materials. Repre sentatives of the United States Gypsum Company will be glad to secure full and complete analyses of auditoriums for any interested architect without charge or obligation, or plans may be sent direct to anv office of the United States Gypsum Companv for that purpose. Every installation of Sabinite is serviced regardless of location or size without charge. This service provides a fully competent instructor to show the plas terers how the material is to be applied and to acquaint the architect's superintendent with the method of obtaining correct and efficient application. Z.G90 n o a a 28