US3253675A

US3253675A - Light-transmitting acoustic absorber and method

Info

Publication number: US3253675A
Application number: US483467A
Authority: US
Inventors: Jordan J Baruch
Original assignee: Bolt Beranek and Newman Inc
Current assignee: Bolt Beranek and Newman Inc
Priority date: 1955-01-24
Filing date: 1955-01-24
Publication date: 1966-05-31
Anticipated expiration: 1983-05-31
Also published as: GB821923A

Description

J. J. BARUCH May 31, 1966 LIGHT-TRANSMITTING ACOUSTIC ABSORBER AND METHOD Filed Jan. 24, 1955 4 $heetsSheet 1 INVENTOR. JORDAN J. BARUCH m a! m ATTORNEYS J. J. BARUCH 3,253,675

May 31, 1966 LIGHT-TRANSMITTING ACOUSTIC ABSORBER AND METHOD 4 Sheets-Sheet 2 Filed Jan. 24, 1955 c: a: c

oecccou IFQQIQoTM cac% K I I9 I l5 l7 INVENTOR.

JORDAN J. BARUCH "mwm ATTORNEYS J. J. BARUCH May 31, 1966 LIGHT-TRANSMITTING ACOUSTIC ABSORBER AND METHOD Filed Jan. 24, 1955 4 Sheets-Sheet 5 4. 2 O O O O PZmzQInEOQ ZOCnEOmm/Q IOO IOOO FREQUENCY IN CYCLES PER SECOND INVENTOR. JQRDAN J. BARUCH ATTORNEYS y 1966 J. J. BARUCH 3,253,675

LIGHT-TRANSMITTING ACOUSTIC ABSORBER AND METHOD Filed Jan. 24, 1955 4 Sheets-Sheet 4 wwtm ill" /0 INVENTOR.

JORDAN J. BARUCH BY and m ATTORNEYS United States Patent Assonsnn The present invention relates to apparatus for absorbing acoustic energy, and more particularly absorbing acoustic energy while permitting the transmission of light.

Many attempts have been made throughout the years to provide a surface, such as a ceiling, that will absorb acoustic energy and yet will permit the transmission of light through the absorbent ceiling. Unfortunately, those materials that are known to be both acoustically absorbent and light-transmitting are relatively flexible, not structurally rigid enough or otherwise suited for con struction purposes. It is very desirable, however, to illuminate a room or other area by means of suspended light fixtures and yet to provide some technique for absorbing acoustic energy produced in the room or area and directed upward toward the light fixtures. It has been proposed, for example, to interconnect the light fixtures with acoustically absorbing panels. A ceiling light fixture may comprise, for example, a fluorescent lamp disposed within a reflector and covered by a translucent glass or other light-diffusing material. Conventional acoustically absorbent materials have been disposed between the reflectors of adjacent light fixtures, forming a 'false ceiling. This arrangement is subject to the principal disadvantage that the regions between the light fixtures along which the acoustically absorbent material is disposed do not permit the transmission of light so that large areas of the false ceiling remain un-illurn'inated. If a large degree of acoustic absorption is to be produced, therefore, the amount of illumination available from the ceiling light fixtures is decidedly limited. In addition, the sizable translucent glass or other covers for the fixtures reflect appreciable sound energy directed thereupon. Another prior-art technique for attempting to solve this problem has been to suspend lights below a fixed ceiling, to cover the lights with a translucent or other screen, as of glass or plastic, and to suspend sound-absorbing baffles of rigid absorptive materials from the screen. The baffles may also be replaced by acoustically absorbent fibrous material housed in perforated containers. If an appreciable degree of acoustic absorption is required, however, the baffles suspended from the translucent false ceiling covering the lights must be of considerable depth and the spacing therebetween must be small-a condition which materially interferes with the amount of available illumination. In addition, such depending baffles present an esthetically unpleasant appearance and detract from the desired effect of a smooth ceiling. Other proposals have also been advanced for'solving this problem including the use of sound-absorbing louvers suspended from the ceiling and between which light fixtures may be disposed to illuminate the room. Such proposals are also subject to the abovernentioned and other disadvantages.

An object of the present invention, therefore, is to provide a light-transmitting acoustically absorbent device that shall not be subject to any of the above disadvantages and that, on the contrary, is suitable not only for use as a false ceiling but for use as any other type of soundabsorbing light-transmitting surface. In summary, the present invention resides, from the broadest point of view, in a relatively rigid light-transmitting member having openings covered by preferably light-transmitting sound-absorbing material. Preferred constructions and details are later discussed.

"ice

An additional object is to provide a new and improved composite light-transmitting acoustically absorbent material.

Other and further objects will be explained hereinafter and will be more particularly pointed out in the appended claims.

a The invention will now be described in connection with the accompanying drawings, FIG. 1 of which is a perspective view, partly cut away to illustrate details of construction, of a preferred embodiment of the invention, adapted for use as a false ceiling;

FIG. 2 is a fragmentary sectional view, upon an enlarged scale, taken upon the line 2-2 of FIG. 1 looking in the direction of the arrows;

FIG. 2A is a fragmentary, diagrammatic end view of a modification;

FIGS. 3 and 4 are fragmentary sectional views of further modifications;

FIG. 5 is a view similar to FIG. 1 illustrating the invention applied to a system embodying air-conditioning or other ducts;

FIG. 6 is a similar view illustrating a further modified application of the invention;

FIG. 7 is a graph illustrating acoustic performance of a typical embodiment of the present invention; and

FIGS. 8, 9 and 10. are'views illustrating methods of fabricating various forms of the invention.

Referring first to FIG. 1, the invention is illustrated in connection with its adaptation as a false ceiling for a room or other space. It is to be understood, however, that this is by way of illustration only, and that the invention may be used in any other place where it is desired to employ its acoustic-absorption and light-transmitting properties. Conventional fluorescent or other light fixtures l are shown suspended at 3 from a fixed ceiling 5. Depending from the fixed ceiling 5 below the light fixtures l are a plurality of struts 7 carrying supporting beams 9, T-shaped in cross section. The struts 7 are secured to the vertical projections 11 of the T-beams 9. Between the horizontal members 13 of the T-beams 9 are detachably secured or supported sheets of light-transmitting acoustically absorbing material made in accordance with the present invention.

This material comprises a relatively rigid light-transmitting carrier member l5 having a plurality of relatively closely spaced openings, perforations or apertures 17 passing therethrough between its upper and lower surfaces. Where it is desired that the light from the sources of illumination l he diffused in the space below the carrier member 15, that member may be translucent. If transparency is desired, on the other hand, it may be transparent. Many other desired esthetic effects may be obtained through corrugation, FIG. 2A, embossing or otherwise'decorating the carrier member 15, as desired. Among useful materials for the carrier 15 are styrene, polystyrene, polyester resins, and relatively rigid polyvinyl plastics such as polyvinyl chloride and acetate, known as Vinylite, to mention but a few. It is, of course, well known that these and other plastic materials can be fabricated to provide light-transmission by diffusion, translucency or transparency, to any desired degree. In addition, it is also well known that such materials can be easily fabricated with the necessary perforations 17 and with any desired degree of corrugation, embossing or other decorative or ornamental surfacing.

The light-transmitting carrier member 15, however, is not of itself acoustically absorptive. On the contrary, it reflects acoustic energy impinged thereupon to a considerable degree. Were such a carrier member 15 utilized in the manner shown in FIG. 1, therefore, acoustic energy rising upward in the room would merely reflect from the portions of the member 15 between the perforaopenings 17 becomes absorbed.

tions or apertures 17 back downward into the room. That acoustic energy which entered the perforations f7, however, would pass through the same into the bounded air-space region between the member 15 and the fixed ceiling 5'. This energy would be reflected back downward from the ceiling 5 and some of it would pass back through the perforations 17 into the room below. While the carrier member provides all the required lighttransmission and is sufliciently rigid to be suspended as a false ceiling between the beams h, it could not serve to quiet the sounds in the room below the ceiling. In accordance with the present invention, this quieting is effected through the use of a further light-transmitting member or material, that, unlike the carrier member 15, has substantial resistivity to acoustic energy and is thus an effective sound absorber. This further light-transmitting member or material of substantial resistivity to acoustic energy is illustrated at 19. It may, for example, be constituted of one or more layers of relatively loosely woven cloth or other fabrics, fiber glass layers, matte or screen surfaces, acetate cloths and porous paper products such'as those commonly used to contain tea leaves in tea bags, to mention but a few. If the resistive material 19 is sufi'iciently loosely woven or otherwise porous, it will permit the transmission of light therethrough, but it is then relatively flexible and cannot support itself. The relatively rigid self-supporting carrier member 15 is thus needed to support the material 19. By covering the openings 17 in the carrier member 15 with the resistive material 19, moreover, the acoustic energy entering the Through the selection of a material 19 having sufficient acoustic absorbing prop erties and the appropriate number and size of openings or perforations 17, the desired end of a relatively rigid composite light-transmitting acoustically absorbent false ceiling or other surface is attained. The greater the area occupied by the openings 17, the greater the degree of sound absorption. A suitable range for some roomabsorption purposes is an opening area of from about 15 to about percent of the area of the member 715. insofar as appearance is concerned, any desired contrast of colors or light and dark effects may be easily produced through the use of differentl

contrasting materials

15 and 19.

In FIG. 1, this light-transmitting sound-absorbing material 19 is shown laminated between upper and lower surfaces or layers 14 and is of the carrier member 15'. Such a laminated construction may be attained in several ways including laminating by heat, pressure, or otherwise, the material 19 between the layers is and 16 of the carrier member 15. The composite material of FIGS. 1 and 2 may also be formed by impregnating a desired cloth or other sound-absorptive layer 1% with plastic material, as illustrated in FIGS. 8, 9 and 10. in FIG. 8, the composite material 15, i7, i9 is shown being fabricated with the aid of a silk screen device. The material 19 is covered by a standard silk screen 21 having a plurality of spots 23 corresponding to the desired perforations 1.7, and serving as masks. The plastic material 25, such as a polyester resin, preferably in unpolymerizcd state, is forced by means of'a squeegee member 27 along the silk screen 21 into the material 19. In this manner, the material 19 will become impregnated with upper and lower coatings of plastic material 25 except at the region of the spots 23, thus producing composite material similar to that illustrated in FIGS. 1 and 2. If desired, a hot plate, not shown, may be placed directly under the silk screen to prevent running of the plastic and to effect a rapid polymerization of the plastic.

Another fabrication technique is illustrated in FIG. 9 where the plastic material is sprayed from a spray gun 27 through a gird 29, such as a screen, upon which have been mounted opaque masks 31, corresponding to the regions where it is desiried to form the ultimate perforations 17. The plastic material from the spray gun 27 is sprayed through the screen r29 against the material 19. Again heat may be applied to effect rapid gellation of the plastic material.

As still another illustration, the material 19 may be placed within a mold 33, FIG. 10, provided with cooperative bosses 35 that clamp the cloth or other member 39 at periodically spaced intervals, corresponding to the regions at which it is desired to produce the apertures 17. Plastic material in an unpolymerized state is forced into the cavities 3'7 of the mold between the bosses 25 to provide the upper and lower carrier coatings [for the material 19. In order to secure rapid gelation of the plastic material, the mold 33, of course, may also be heated. For the production of long strips of material, the upper and lower sections of the mold 33 may be cylindrical or shaped as long continuous belts. While the above discussion has proceeded upon the assumption of the use of particular plastic materials, it is to be understood that any liquid or semi-solid materials capable of being formed into a solid, including thermoplastics and water emulsions, may also be utilized.

While the light-transmitting acoustically absorbent layer 19 has previously been described as laminated between upper and

lower layers

14 and 16 of the carrier member 15, it may, if desired, be laminated along the outer upper and outer lower surfaces of the carrier member. :In FIG. 3, therefore, the light-transmitting carrier member 15 is illustrated of single-piece or layer construction with the acoustically absorbent material 119 secured along the bottom thereof, covering the light-transmitting apertures 17. The material of FIG. 3 may be easily fabricated by impregnating, cementing or heat-fusing the materila 19 to the plastic or other carrier member 15.

In HG. 4, still a further modified construction is illustrated in which an acoustically absorbent fibrous material 2 is impregnated with plastic carrier material 15 except at a plurality of regions 17, corresponding to the perforations 17 of, for example, FIGS. 1 and 3. The fibrous material 2 at the regions 17 will serve a purpose similar to that served by the sound-absorbing material 19 covering the openings .17 in the embodiments of FIGS. 1 and 3. The separation of the fibers in the material 2 should, of course, be such that the overall trans'lucency of the composite light-transmitting acoustically-absorbent device 2-115 is not seriously impaired.

Alternate arrangements for mounting the light-transmitting sound-absorbent devices of the present invention are shown in FIGS. 5 and 6. In FIG. 5, the mounting is effected with the aid of I beams 8 for receiving the composite false-ceiling material instead of the T beams 9 of FIG. 1. The plastic or similar carrier-member sheet is flexed inward resiliently to insert the same between, or to remove the same from, adjacent I-beams 8. The

material

15, 17, d9, which may take any of the forms previously discussed, moreover, here serves, also, as a plenum for an air-conditioning or other air-carrying duct 10. The air within the duct lit for example, may spread out under the ceiling 5 and diffuse gently down through the apertures 17 of the light-transmitting acoustically-absorbent false ceiling. In this way, localized drafts in the area are additionally eliminated with no sacrifice in illumination or acoustic absorption.

A somewhat different construction is illustrated in FIG. 6 in which the false-ceiling material of the present invention is supported in a frame-type structure. The fluorescent or other lights 41 may be installed between the studs 12. of the structure and the sheets of materials 15, '17, d9 may be fabricated in sizes that f t the center-to-center spacing between the studs 12 to which they may be fastened directly by mailing, screwing or in any other manner. The resulting ceiling has a tfinished surface and permits the attainment of the illumination and acoustic absorption results of the present invention.

As an illustration of the performance of a typical installation utilizing the material '15, 17, 119 of the present invention, reference is made to the graph of FIG. 7 where the absorption coefficient of acoustic energy is plotted along the ordinate as a function of sound frequency, plotted along the abscissa. It will be observed that, in the neighborhood of from about 200 cycles to about 5,000 cycles, the absorption coefficient of the material of the present invention is Well over 0.5, and that a maximum absorption coefficient of about 0.8 is attained in the region of from about 400 to about 700 cycles per second, a region where there is considerable acoustic energy produced in normally used roorns. These results are obtainable, for example with a thin polyvinyl carrier E about twenty-thousandths of an inch having about twentyfive percent area occupied by perforations 17 and a non woven rayon-acetate tea-bag paper material 19. The apertures 17 may be about of an inch in diameter, spaced about 5 of an inch on centers.

Not only is the present invention useful, as before stated, for false ceilings, but it is useful wherever else it is desired to permit the transmission of illumination and the absorption of acoustic energy, such as along a wall, a floor or any other surface, including even lamp or lighting shades or fixtures. It is also to be understood that composite light-transmitting-sound-absorbing material need not be formed in the substantially planar form illustrated. It may be fabricated in any desired shape or, after fabrication it may be post-formed intothe desired configuration. In view of its provision for acoustic resistivity through the use of a large number of air passages or perforations 17, more-over, the invention is inherently extremely useful in systems where air distribution is effected, such as, for example, in heating, ventilating or air conditioning systems. The use of the invention in such systems, in addition to providing lighttransmitting and acoustic-absorbing properties, provides for draft-free ventilation with no unsightly diffusers or other apparatus to mar the appearance of the ceiling or other surface. If the room in which the present invention is to be utilized were employed for such purposes as painting, or other operations whereparticles could normally plug the perforations 17, a steady flow of air through the perforations 17 could be effected in order to guard against the depositing of dirt and other particles within the perforations 17.

Further modifications will occur to those skilled in the art and all such are considered to fall within the spirit and scope of the present invention as defined in the appended claims.

What is claimed is:

1. In a building structure, an illuminating and sound absorbing ceiling construction comprising a plurality of wall forming elements, suspending means mounting such elements in assembled relation as a ceiling spaced from the building structure, a source of illumination disposed between the building structure and such suspended ceiling, the elements forming such suspended ceiling comprising assembled elements, the face thereof a light transmitting composite of a perforated sheet together with an imperfonate'air-porous sheet, the perforations in the perforated sheet substantially uniformly distributed and the imperforate air-porous sheet secured to the perforated sheet along the periphery of the perforations, and mounted and secured to such composite sheet a light transmitting cellular structure, the cells of which are normal to the composite face sheet.

2. A composite sound absorbing assembly comprising, serially composited, a perforated sheet, an imperforate air and sound porous sheet, the perforations of the perforated sheet substantially uniformly distributed over the area of sheet, and the imperforate air porous sheet secured to the perforated sheet along the peripheries of the perforations and mounted and secured to the composited perforated and imperforate sheet, a cellular structure constituted of juxtaposed tubular elements each extending through the thickness of the cellular structure and having the end thereof mounted to the composited sheets in continuous contact with a face of the imperforate air and sound porous sheet.

3. A composite sound absorbing element comprising in combination a cellular core constituted of juxtaposed tubular elements each defined by walls extending continuously through the thickness of the cellular core portion and defining cells extending continuously through .the thickness of the core and substantially normal to the face surface thereof, and secured to a face surface of the core portion a sound porous sheet having air permeability of between and 200 cubic feet per minute at 0.5" hydrostatic pressure, the sound porous sheet adhered to the ends of the walls forming the cells of the core whereby the sound porous sheet constitutes a connected system of contiguous air-and sound porous diaphragms.

4.'A composite sound absorbing element comprising in combination a cellular core constituted of composited corrugated sheets comprising walls forming juxtaposed tubular elements, the walls thereof extending continuously through the thickness of the core portion and defining cells extending continuously through the thickness of the core and at one face of the core air and sound porous diaphragmatic elements extending transversely of the ends of each of the cells formed by the cell walls extending through the thickness of the core, and each of the diaphragmatic elements secured to the ends of the wall circumscribing the cell over which such diaphragmatic element extends.

5. A sound absorbing unit comprising a sheet-form cellular core portion in which the cells extend normal to a face surface and through the thickness thereof, a sound porous sheet adhered to a face surface of the cellular core portion, said sound porous sheet having air permeability of between 90 and 200 cubic feet per minute at 0.5 hydrostatic pressure, and a facing sheet adhered to said sound porous sheet, about 5 to 15% of said facing sheet comprising substantially regularly dispersed perforations of about 0101 to 0.05 square inch area, each, extending through the thickness of said facing sheet.

6. A sound absorbing and translucent structural element comprised of composited elements, a core portion and a facing portion, the core portion formed of strips of light transmitting sheet material, such strips deformed across the width thereof and adhered along spaced lines forming a cellular construction in which the cells extend through the thickness of the core portion and a composite facing secured to said core portion, said composite facing comprising a light transmitting, air-porous sheet and a perforated light transmitting perforated sheet, the perforations in said perforated sheet substantially uniformly dispersed and of cross sectional area of about 0.01 inch to 0.05 inch each and comprising about 5 to 15% of the sheet area.

7. A light transmitting sound absorbing unit comprised of light transmitting sheet materials secured in assembled relation, the core thereof a cellular sheet of adhered strips on edge, the cells thereof extending through the thickness of the sheet and adhered to a face thereof and to one another, an air-porous sheet and a perforated sheet, the perforations thereof substantially uniformly distributed and comprising about 5 to 15% of the sheet area.

8. A sound-absorbing unit comprising a sheet-form cellular portion in which the cells extend normal to a face surface and through the thickness thereof, a soundporous sheet adhered to a face surface of the cellular portion, said sound-porous sheet having air permeability of between 90 and 200 cubic feet per minute at 0.5 inch hydrostatic pressure, and a facing sheet adhered to said sound-porous sheet, at least about 15% of said facing sheet comprising substantially regularly disbursed perforations of about a few hundreds square inch in area, each, extending through the thickness of said facing sheet.

9. A light-transmitting sound-absorbing device comprising a perforated light-transmitting thin-sheet carrier member having a thickness of approximately the order of magnitude of twenty-thousandths of an inch and sufiiciently rigid to render the member self-supporting, and

at least one flexible porous layer of thickness less than the said thickness :0f the carrier member and resistive to acoustic energy, the layer being integrally laminated to the carrier member with the layer secured to' the peripheries of and covering the perforations.

10. A light-transmitting,sound-absorbing device corn.- ---prising 'a'perforated light-transmitting thin-sheet carrier 9 member having a thickness of approximately the order of magnitude of twenty=thousandths of an inch and sumciently rigid to render the member self-supporting, and at least one flexible porous light-transmitting layer. of thickness less than the said thickness of the carrier mem-. her and resistive to acoustic energy, the layer being integrally laminated to the carrier member with the layer secured to the peripheries of and covering the perfora tions. U

11. A sound-absorbing device comprising a perforated thin-sheet carrier member having a thickness of approximately the order of magnitude of tWenty-th'ousandths of an inch and sufficiently rigid to render the member self supporting, and at least one flexible porous layer of thickness less than the said thickness of the carrier. member and resistive to acoustic energy, the layer being integrally laminated to the carrier member with the layer secured to the peripheries of and covering the perforations.

References Cited by the Examiner UNITED STATES PATENTS 1,956,773 5/1934 Pflueger 240-9 2,011,252 8/1935 Modigliani.

2,310,154 2/1943 Schlenker 181-31 2,562,711 7/1951 Gessler et a1. 181-33 X 2,659,807 11/1953 Wakefield 240-9 2,659,808 11/1953 Beckwith- 2409 2,694,233 11/1954 Page 20-4 2,703,627 3/1955" DEustachio 181-33 2,704,865 3/1955 Siering 181-33 X 2,706,314 --4/195 5 Siering 240-9 X 2,710,335 6/1955 Wong 240-9 2,715,449 8/1955 Lemmermam 2,745,001 5/1956 Guth 240-78 2,850,109 9/1958 Benjamin 181-33 1 2,870,857 1/1959 Goldstein 181-33 OTHER REFERENCES Wakefield Ceiling Catalog, copyright July 13, 1951.

LOUIS J. CAPOZL Primary Examiner.

ARTHUR SHAPIRO, LEO SMILOW, NORTON AN- SHER, ISAAC LISANN, C. W. ROBINSON, JOHN C. MACNAB, Examiners.

D. SELTZER, N. I. LATKER, S. I. TOMSKY, Assistant Examiners.

Claims

9. A LIGHT-TRANSMITTING SOUND-ABSORBING DEVICE COMPRISING A PERFORATED LIGHT-TRANSMITTING THIN-SHEET CARRIER MEMBER HAVING A THICKNESS OF APPROXIMATELY THE ORDER OF MAGNITUDE OF TWENTY-THOUSANDS OF AN INCH AND SUFFICIENTLY RIGID TO RENDER THE MEMBER SELF-SUPPORTING, AND AT LEAST ONE FLEXIBLE POROUS LAYER OF THICKNESS LESS THAN