US2334502A - Sound-absorbing structure - Google Patents

Description

Nov. 16, 1943. J, s, PARKlNsoN ETAL 2,334,502

SOUND-ABSORBING STRUCTURE Filed Nov. 8, 1940 INVENTOR ./o/f/v 5. pAK/A/soN vlaw/y..

TTORNEY y Patented Nov. 16, 1943 SOUND-Ansoanmo STRUCTURE John S. Parkinson and William A. Jack, 3rd,

North Plainfield, N. J., asslgnors to Johns-Manville Corporation, New York, N. Y., a corporation of New York Application November 8, 1940, Serial No. 364,806

19 Claims.

Our present invention relates to sound-absorbing structures, and ,in its more specific phase is directed to sound-absorbing treatments of air conduits, such as the air intake and exhaust stacks of test stands employed for the testing of airplane motors, propellers, and the like.

To determine in advance the life and durability of a motor, such as an airplane motor, or propeller under severe conditions, it has been necessary to provide test stands on which the motors may be mounted and run for extended periods of time under substantially normal operating conditions. A stand for this purpose has conventionally comprised a U-shaped structure in which the motor is mounted at the base of the U and the legs of the U form stacks or conduits, the air drawn by the propeller entering through one oi the stacks and being expelled through the other.

The excessive noise produced in such testing operations has long presented a serious problem. Heretofore, the stacks have been given a soundabsorbing treatment comprising ribbon walls parallel `to the direction of air ilow and, for example, on from 12 to 24" centers, the walls being built up of sound-absorbing panels or blocks. Also, in some instances a grid construction, built up from porous blocks, has been tried. The instant invention has for its principal ob-v ject the provision of an improved sound-absorb ing system for stacks of this type or for other air conduits and the like where similar problems in noise quieting are presented. v Another object of the invention is to provide a sound-absorbing system for the purposes referred to which will be substantially lower in cost and of higher efilciency than present constructions.

A further object of the invention is to provide a sound-absorbing system for air conduits in which the necessary supporting or framing elements occupy a minimum of space whereby the greatest proportion of the conduit area allotted to the sound-absorbing treatment can be utilized i'or the sound-absorbingunits per se.

A further object of the invention is to provide a construction of the type referred to, which is Y inherently stronger` than those heretofore proposed, with consequent reduction of cost of both fabrication and erection, and which, moreover, can be employed with equal facility in stacks of large and small diameter. The construction of the instant invention is also one which will permit the height of the stack to be decreased without loss in sound-absorbing emciency, thus providing for a reduction in cost in the stack structure itself.

Our invention will be more fully understood and further objects and advantages thereof will become apparent when reference is made to the more detailed description thereof which is to follow and to the accompanying drawing, in

which: ,u I

Fig. i is a vertical sectional view. with parts broken away. of a test stand including stacks embodying the invention; e

Fig. 2 is a plan view ot one of the stacks shown in Fig. l;

Fig. 3 is an enlarged view, partly in section and partly in elevation, of a sound-absorbing column and support therefor employed in the construction of Fig. 1;

Fig. 4 is a detail sectional view illustrating a modification of the column structure;

Fig. 5 is a view similar to Fig. 3 illustratingi, another modification of the column structure;

Fig. 6 is a detail view similar to Fig. 4 illustrating a further modification-'of the column structure; and

Fig.y 7 is a view, partly in elevation and partly in section, showing a variation oi' the column supporting means.

Referring now to the drawing, and particuiarly to Fig. 1, .there is disclosed a test stand structure-basically of the type conventionally employed for the testing of airplane motors, propellers, and the like. It will be understood that the structure shown is merely illustrative and that the invention is equally applicablel to other types of stacks and to air conduits for other purposes.

In the'- construction depicted, the test stand comprises a substantially U-shaped building including a motor mounting il in 'a room I2 form-A ing the base ofthe U, and upstanding air intake and exhaust stacks I l and IB, `respectively. The outer walls of the structure, including the stacks,v may be formed of masonry, reinforced concrete, fabricated sheets, or the like, in accordance with conventional practice, andthe stacks may be of any desired dimensions, depending upon the size of motor, propeller, and the like, which are to be tested and the noise given oir thereby. A control room, not shown, is located adjacent the motor mounting for observing the various testing equipment.

In accordance with the instant invention, the stacks il and il, which are preferably of the same height, are provided with means to absorb a substantial proportion or the noise created by the motor and propeller, this means comprising a plurality of columns 2l built up of sound-absorbing units 22. A sumcient number oi' the units 22 are super-posed one on the other to make the columns of the desired height. In the embodiment shown, two of the units are employed in each column, each unit being, say, of a length of 8 to form a column i6' in height. However, as will be understood. individual units may be made of any desired length and the'columns may be built up to greater or less heights than that given to meet particular problems. The columns are preferably placed in rows (see Fig. 2) and` take up, say, a maximum of 25% of the total area of the stack. Also, it is preferred to uniformly space the columns in both directions, but

again. variation in arrangements may be made to cope with particular problems without departing from the-scope of the invention.

The columns in accordance with the preferred construction" are suspended from I-beams 24, which are in .turn supported by opposed walls of the stacks, preferably adjacent the uppery ends thereof, by any suitable means, for example, by embedding the beams in the stack walls as indicated. Rods 26 pass through notches or perforations in the flanges of beams 2l and extend axially through the columns. The lower ends of vthe rods of each row of columns project through suitable perforations in a supporting member 28, such as a shallow channel iron. One oi the latter preferably extends the length of each row and has its ends secured to the stack walls in any suitable manner, for example, by expansion bolts passing through end flanges 29. In someA instances the ends of members 28 neednot be secured to the Walls, it being understoodthat the support for the columns is primarily through their vsuspension from beams 24. Rods 26 may be headed at the upper ends, or maybe threaded to receive a nut at this location, and are similarly 'preferably threaded to receive a nut on their ends projecting below` member 2l whereby the several units .making up each column may be drawn into close engagement to one another. Where the height of the columns is such that weaving or other lateral movement of the same may. take place from the action of the air passing at a high velocity through the stack, a reinforcing or stiffening member forcing member 30 may be a channel iron, or simply a flat metal strap having perforations to receive the several rods of a row of columns, and including end portions 'secured to thev walls of the stack by expansion bolts or any other suitable means. f

Referring now to Figs. 2 and 3, the units 22 V making up columns 20 comprise, in thepreferred form of the invention, elongated hollow con.

tainers filled with a suitable soundsabsorbing material 38. The side walls y32 ci the containers are preferably formed of sheet metal and are cylindrical in shape inasmuch as a greater thick. ness of sound-absorbing material is thereby obtained for a minimum of cross sectional area. However, the units may be of square orother cross section .if desired. The walls22 are provided` with a multiplicity 0f closely spaced perforations 2l having a sufficient total larea to permit entry of sound waves into 4 the sound-absorbing material within the container. The containers or units are provided with heads 36, at least at their lower ends, secured in any suitable manner. for example, by weldinglv riveting. or. the like. The sound-absorbing material 38 may be discs 30 may be employed. .Rein.

of a mineral wool felt centrally perforated to receive rod 28 as indicated in Fis. 3, or, in lieu thereof. loose mineral wool, nodulated wool, or loose or bonded granular or fibrous sound-absorbing material, and the like may be employed, as indicated generally at 360 in Fig. 4.

As shown in Figs. 4 and 5, other materials than metal may be employed for at least the side walls of the containers or units 22; for example, Fig. 4 shows the Wall as comprising a perforated hardened compressed asbestos-cement tube, such as a perforated section of Transito pipe. A tube 4of this type may be headed by discs 38 of a similar or other material inset on shoulders 40 and secured in place by an expander ring 42 or the like. Alternatively, the heads may be cemented in place or any other suitable fastening means y may be used.

list

-quired, the number Referring to Fig. 5, the containers are shown as composed of a bonded aggregate of any of the numerous types now conventionally employed in the manufacture of porous sound-absorbing building blocks. In such case the inherent porosity of the material may be sufficient to admit the entrance of' sound to the absorbent filling, or, if necessary'or desirable, further perforations may be made. In any event the inherent porosity oi' the material in itself provides a sound absorber, amplifying the sound-absorbing function of the contained material. Also, if desired, such bonded aggregate blocks may be employed, per se, as the sound-absorbing material, as illustrated in Fig. 6. In this instance the blocks, preferably cylindrical, are provided with a central hole or perforation to receive suspended rod 26.

The preferred method of installation of a sound-absorbing treatment in accordance with the invention may vary somewhat, depending upon Whether the cross braces 30 are employed. In any event, the rods are preferably first inserted within the perforations or notches in the flanges of beam 24 and a nut, preferably of a locking type, applied to hold the rods firmly in suspended position. If no cross bracing is reof the units 22 required to make up the column height are slipped endwise on each rod of a row and a member 28, perforated at suitable intervals to receive the rods, is inserted on their threaded ends. Nuts are then drawn tightly on the threaded end portions to secure member 28 to the columns and to hold the several units of each column in firm endwise contiguous relationship. The ends of member 28 are then preferably secured to the side walls of the stack. If a cross brace 30 is to be employed for each row, sufficient of the units are threaded on each rod to extend to the location selected for the cross brace. The cross brace, having spaced perforations similarly as the member 28. is then vthreaded on the rods and the remaining units and member 28 installed as before. The ends of the cross braces are then secured to the side walls of the stack.

Referring to Fig. '7, there is illustrated a modified form of supporting means for the columns of particular applicability when the latter require but a single unit 22. Thus, the units may be fastened at their upper ends to the I-beams 24, for example by strap 50, having its end portions welded or otherwise secured to the I-beam, and including a U-shaped central portion fitting within the depressed head of the unit. Il' it is desired to suspend the unit as in the preferred embodiment, the strap 50 may be secured to the unit as by bolts 52. The lower end oi' the unit rests upon beam i4 which may be formed with an abutment, comprising, for example, adisc welded to the beam, to position the lower end of the column. In this instance beam M may be of suincient strength to support the weight of the columns r may be merely a bracing 'member as reduction equal to feet of the wall type constructions heretofore employed. At',` the same time, the `cost per foot of the treatment is substantially lowered.. Also, the lesserheight oi.' treatment permitted by the invention vproduces an appreciable saving in the cost ofthe stack required, or, conversely, if very severe noise lconditions are to be met, a greater noise reduction can be provided without .requiring an excessive height of structure. Furthermore, the const ruction lends itself to use with` stacks `or the like of any height or any cross sectional dimension with equal facility. Inasmuch as the construction is inherently stronger than ribbon wallsor grids, the cost of fabrication anderection is greatly reduced due to the `lighter weightmaterials which may be employed. l

Although the invention has been describedas having particular applicability .to vertical stacks, it will be4 understood that it'may be employed equally as well for horizontal installations, for` example, in a horizontal tunnel. Also, the column type sounding-absorbingunits may .be ern-- ployed in many other cases when it is desired, to isolate acoustically one locality `from another,` and their use is not to be considered a's limited.

to air-flow stacks or tunnels.

Having thus described Vour invention ratherv` full detail, it will be understood that these details need not be strictly adhered to, but that various changes and modifications will suggest themselves to one skilled in the art, all falling within the scope of the invention as defined by the subjoined claims.

What we claim is:

1. A soundabsorbing structure comprising spaced outer walls and a plurality of columns of sound-absorbing units, each column supported in spaced relationship to the others between said walls and exposing their lateral surfaces to the sound to be absorbed.

2. A sound-absorbing structure comprising spaced outer walls and a plurality of columns of sound-absorbing units, each column in spaced relationship to the others between said walls and exposing their lateral surfaces to the sound to be absorbed, said units comprising sound-porous hollow elements containing sound-absorbing material.

3. A soundabsorbing structure comprising spaced outer walls and a plurality of columns of sound-absorbing units supported in spaced rows between said walls, each column of a row being spaced from the others and exposing its lateral surfaces to the sound to be absorbed, said units comprising perforated hollow elements containing a sound-absorbing material.

4. A sound-absorbing structure comprising spaced outer walls and a plurality of columns of sound-absorbing units supported in spaced ,rowsbetween said wallsand exposing their lateral l.surfaces to'tl'ie` sound to be absorbed. said units comprising perforatedy metal containers .with-a iiiling of a sound-absorbing material.

5. A sound absorbing structure comprising spaced outer V walls `and a plurality of columns of'sound-absorbing units supported in spaced rows, betweensaid walls and exposing .their lateral surfaces. to thesoundto be absorbed, said units comprisngperforated containers, formed of a hardenedcementitious material with a filling of va sound-absorbing material.

6.`A sound -absorbing structure ,comprising spaced outerwallsand a pluralityofv columns mound-absorbing units supported in spaced rows betweensaid walls and exposing their lateral surfaces tothe. s oundto be absorbed, said units comprising elongated porous blocks including a beaded aggregata 7. A s'tack.structure comprising spaced outer walls, a pluralityoicolumns of sound-absorbing units, each ,column supported in spaced -relationship` to theothers between said walls and exposing its lateral suifaces `to the sound tobefabsorbed, rods `extending longitudinally through `said col,- umns and supporting the columns thereon, and means carried by said walls for supporting said rods...

l.8. Astack structure comprising spaced youter walls' al,plural ity oL-rows of columnsof soundabsorbing units between said walls, eachcolurnn beingA spaced from the other columns; and expos-v ingits. lateral surfaces tofthe sound to beabsorbed rodsv extending longitudinally-l through said `columns, means supportedfromzsaidfwalls from which said rods aresuspendedand mem-w bersv Vconm-actingl said rods beneath said-columns to retain saidunits-onsaid rodsiand;maintain thelowerends or said columns in ixed ,relationship vto one another. v i

.v .9, A. sta/klstructure comprising v:spaced louter walls, a .pluralityof 'rows of. columns of soundabsorbing unitsbetween said walls, each. column being snacediromthe other columns and Vexpos-v ingits lateral surfaces to the sound to be absorbed, said' units comprising perforatedv hollow.

elements containing a sound-absorbing medium, rods extending longitudinally through said columns, beams supported from said walls and from which said rods are suspended, and means on said rods beneath said columns retaining the columns on said rods and maintaining the lower ends`of said columns in fixed relationship to one another.

10. A stack structure comprising spaced outer walls, a plurality of rows of columns of soundabsorbing units between said walls, each column being spaced from the other columns and exposing its lateral surfaces to the sound to be absorbed, said units comprising headed perforated metal containers with a sound-absorbing filling, beams supported from said walls above said rows' of' columns, and means suspended from said beams supporting said columns.

l1. A stack structure comprising spaced outer walls, a plurality of rows of columns of soundabsorbing units between said walls, each column being spaced from the other columns and exposing its lateral surfaces to the sound to be ab` sorbed, each of said columns comprising a plurality of superposed units, said units comprising headed perforated metal containers with a. soundabsorbing lling, beams supported from said walls above said rows of columns, and means suspended i'rom said beams supporting said columns, said means comprising rods projecting axially through said columns and members connecting said rods beneath said columns and aillxed to said side walls.

12. A stack structure comprising spaced outer walls, a plurality of rows of columns of soundabsorbing units between said walls, each column being spaced from the other columns and exposing its lateral surfaces to the sound to be absorbed, each of said columns comprising a plurality ot superposed units, said units comprising headed perforated metal containers with a soundabsorbing nlling, beams supported from said walls above said rows of columns, and means suspended from said beams supporting said columns, said means comprising rods projecting axially through said columns, members connecting said rods beneath said columns and secured to said side walls, and reinforcing elements connecting the rods of a row between adjacent units on each rod and including end portions secured to said side walls.

13. A stack structure comprising spaced outer walls. a plurality of rows of columns of soundabsorbing units between said walls, each column being spaced from the other columns and exposing its lateral surfaces to the sound to be absorbed, beams supported from said walls, and means suspended trom said beams supporting said columns, said means comprising rods projecting longitudinally through said columns and members connecting said rods beneath said columns and affixed to said side walls.

14. A stack structure comprising spaced outer.

walls, a. plurality of rows of columns of soundabsorbing units between said walls, each column being spaced from the other columns and exposing its lateral surfaces to the sound to be absorbed, each of said columns comprising a plurality of superposed units. beams supported from said walls, and means suspended from said beams supporting said columns in position, said means comprising rods projecting longitudinally through said columns and members connecting said rods beneath said columns and maintaining said units on said rods, and reinforcing members 1n contact with said rods between adjacent units supporting l said rods from said side walls.

4-5 said beams.

15. A stack structure comprising spaced outer walls, a plurality of columns of sound-absorbing units between said walls, each column being spaced from the other columns and exposing its entire lateral surfaces to the sound to be absorbed, beams supported from said walls. rods supported from said beams extending axially through said columns, and Achannel members secured to said walls and maintaining said columns on said rods.

16. A sound-absorbing unit for a stack structure or the like comprising a hollow perforated casing, a sound-absorbing filling within said casing comprising a. plurality oi' superposed pads of a felted fibrous material, and aligned apertures in the ends of said casing and said nlling to permit the passage therethrough of a supporting rod.

17. A sound-absorbing unit for mounting on' a supporting rodvof a stack structure or the like. said unit comprising a cylindrical casing forming the outer wall of the unit, said casing having a multiplicity of perforations extending therethrough, a illling of sound-absorbing material within said casing and heads on opposite ends of said casing, said heads having aligned openings dimensioned to receive said supporting rod therethrough.

18. A sound-absorbing unit for mounting on a supporting rod extending axially through the unit, said unit comprising a hollow porous block forming the outer wall of the unit, a nlling of sound-absorbing material therein, and end members for the hollow block, said end members having aligned openingsdimensioned to receive said supporting rod therethrough.

19. A sound-absorbing structure comprising a plurality of columns of sound-absorbing units, each of said columns being spaced substantially equidistant from adjacent columns and exposing its lateral surfaces to the sound to be labsorbed and lmeans supporting said columns, said means comprising beams at opposite ends of said columns and members positioning said columns on YJOHN S. PARKINSON.

WILLIAM A. JACK, 3RD.

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