US1705778A

US1705778A - Sound-absorbing chamber

Info

Publication number: US1705778A
Application number: US181590A
Authority: US
Inventors: Treadway B Munroe; Waterfall Wallace
Original assignee: MUNROE
Current assignee: MUNROE
Priority date: 1927-04-06
Filing date: 1927-04-06
Publication date: 1929-03-19
Anticipated expiration: 1946-03-19

Description

March 19, 1929. T. B. MUNROE ET AL SOUND ABSORBING CHAMBEli Filed April 6, 1927 2 Sheets-Sheet O 6 j 0 3 nwzb 0 Q 0 March 19, 1929. T. a. MUNROE ET AL 1,705,778

SOUND ABS ORBING CHAMBER Filed April 6, 1927 2 Sheets-$heet 2 y ZZBJYan/We I flidlace Wafer/ ll r degree.

Patented Mar. 19, 1929;

UNITED STATES PATENT OFFICE.

TREADWAY B. MUNROE AND WALLACE WATERFALL, OF CHICAGO, ILLINOIS; SAID WATERFALL .ASSIGNOR T0 SAID MUNROE.

SOUND-ABSORBING CHAMBER.

Application filed April 6, 1927. Serial No. 181,590.

This invention relates to receptacles or cells having high sound absorbing qualities, and has for its object to provide a construction more eificient in use than those heretofore proposed.

With these and other objects in view the invention consists in the novel details of construction and combinations of parts as will he more fully hereinafter disclosed and particularly pointed out in the claims.

Referring to the accompanying drawings forming a part of this specification, in which like numerals designate like parts in all the views:

Fig. 1 is a perspective view of a structure made in accordance with this invention, and broken away to show the interior construction thereof;

Fig. 2 is a vertical sectional View of the device shown in Fig. 1; 1

Fig. 3 is a partial sectional view, similar to Fig. 2, showing a modified form of construction;

Fig. 4 is a vertical sectional view, similar to Fig. 3, showing a still further modified form of the invention;

Fig. 5 is a'horizontal sectional view taken as on the line 5-5-of Fig. 4, and looking in the direction of the arrows;

Fig. 6 is a partial sectional view showing still another modification of the invention;

Fi 7 is a view similar to Fig. 6 showing a difi erent arrangement of the bafiies; and

Fig. 8 is a partial perspective view illus trating the construction of a part of the structure as produced by this invention.

In order that this invention may be the more clearly understood it is said that there are many mechanical devices now in use which create considerable noise, the sound of which is objectionable, and it is the purpose of this invention to provide such an enclosure for said devices that the sound emanating therefrom may be absorbed to a high Knowledge is had of such sound absorptive material as hair felt, etc. but such material is unsuited for the present purpose chiefly due to its non-rigidity.

In Patent No. 1,554,180 issued to W. S. Trader, dated September 15, 1925, and entitled Sound absorbing board for walls and ceilings, there is disclosed a wallboard constructed from Celotex which is a felted mass of strong bagasse fibers, so compacted as to be capable of use as an artificial lumber in that it can be sawed and nailed, and has sufficient strength in many cases to be substituted for lumber. There is also mentioned in said patent the use of another building board known on the market as Insulite which is made from wood pulp tailings and which likewise has a porous fibrous body portion and which is possessed of considerable strength so that the same can be nailed, etc. The material Celotex, however, is to be preferred in that it is peculiarly adapted to the purpose of this invention, because of its cellular construction, or in other words, it has internal cells producing a more or less porous interior into which sound waves may penetrate with consequent reduction through absorption due to heat consuming friction generated on its interior by the sound waves traversing its fibrous mass. This fibrous board, generally indicated by the numeral 1, is provided on one side with a great plurality of relatively closely spaced apertures 2 which, however, do not extend completely through the board 1 as clearly shown in the drawings. The ragged irregular surfaces of the apertures 2 communicate directly with the open interstices or air cells with which the interior of the Celotex board 1 is provided and therefore the sound waves will readily pass from the walls of said apertures into the interior cellular casing of the fibrous board, where they penetrate the tangled mass of fibers and strike against the individual fibers in such a manner as to render impossible their reflection from the board.

The invention more particularly is directed to the construction of a receptacle or sound absorbing cell formed from this perforated Celotex material, as illustrated in Fig. 1, provided with a top 3, a bottom 1, and the necessary plurality of sides 5. Inasmuch as this material has high heat-insulating quality, not only is the bottom member 4 provided with an opening 7 but one of the side Walls such as 8 is also provided with an opening 9, preferably nearer the top of the receptacle, said openings being provided for ventilation. If, for example, the device which creates the obnoxious sound in a motor, indicated by the dashed line 10, it would be necessary to ventilate the enclosing receptacle so that the heat generated could escape to prevent damage to the motor. The motor 10 would be mounted upon a base 11 supported above the floor 4 of the receptacle as by the standards12, the base 11 being positioned to straddle the opening 7 in said bottom for a purpose presently to appear. The motor 10 could be connected through its shaft 13 to any suitable mechanism not shown but which could also be included within the sound deadening chamber.

In order that too high a percentage of the sound waves may not escape from the cham her along with the heat created by the device therein, a battle construction is provided-in association with each of the openings 7 and 9. Referring more particularly to Figs. 1 and 2, the battle is formed of an auxiliary piece of the Celotex material such as 15, spaced as by the posts 16 from the bottom 4 immediately over the opening 7, but it should be observed that the baffle 15 is of such dimensions that it will substantially overlap the limits of said opening. The amount of overlapping is dependent upon the space provided between the baflie 15 and the bottom member 4, the important feature of this relationship being to cause the path of each sound wave to be so broken in escaping from the chamber that a high degree of absorption will be obtained. Stated in other words, some of the sound waves from the motor 10 will seek the opening 7, but in so doing they will strike the surfaces of the bottom member 4 and the baffle 15, be reflected from each and absorbed to such an extent by frictional engagement with the rough surfaces of the Celotex material that only a relatively small amount of the sound will leave the chamber.

The side wall such as 8, likewise provided with an opening 9, hassccured thereto a baffie 20 of the Celotcx material spaced as by the posts 21, and overlapping said opening just as the baffle 15 overlapped its associated opening 7 and for the same purpose. In the drawings the arrows indicate the natural air draft through the chamber and are so drawn to clearly show the tortuous path traversed in entering and leai 'ing the chamber.

With reference to Fig. 3 it will be seen that the opening 7 in the bottom 4 has associated therewith a baffle composed of-an upper member 25 secured to a lower member 26 both of Celotex material, the apertures 2 of which are oppositely directed or in other words are disposed on the exposed surfaces of the baflie. By providing such a construction, a larger percentage of sound absorption is obtained due to the apertures 2 of the lower member 26 and the apertures of the bottom 4 facing each other so that the sound waves, in escaping between said members. will be subjected to a larger absorptive area than was'the case in the single bafiie 15 discl0sed in Fig. 2 with its unapertured surface opposite the apertured surface of the bottom member.

In Fig. 4 is disclosed a modified form of bafiie construction wherein the bottom 4 has secured thereto, and extending around the opening 7, a wall 30, surrounded by a spaced wall 31 dependently secured to a horizontally disposed bafile men'ibe'r 32 supported in spaced relation above the wall 30 as by the supporting posts 33. The

members

30, 31 and 32 are likewise of lelotex material and the member 31 stops short of the bottom member 4 to permit passage of air waves, but greatly reduced passage of sound waves thereunder, as clearly shown. Bv such a construction the sound waves from within the chamberv are given -a still more tortuous path to follow in escaping therefrom and in this connection it might be stated that the

walls

30 and 31 which are spaced from each other are provided on their opposing faces with the apertures 2 for sound absorption. F 1g. 5 clearly shows the spacing of the walls 30 and'31 as well as the location of the supporting posts 33. which may be secured to the baffle and bottom members inany suitable manner. I

Tn Figs. 6, 7 and 8 are disclosed a still further modified form of. battle construction wherein the bottom 4 has suitably secured thereto, along two parallel edges of the open ing 7, vertically disposed supporting walls indicated by the numeral 35 to and between which are secured a plurality of obliquely disposed baffle members 36 of Celotex material in relatively close spaced relation to each other. In Fig. 6 one-half the baffle members 36 are shown inclined in one direction to the bottom member 4 and the other half of said baflies are shown oppositely inclined to said bottom member, with the two central baffle members 37 contacting with each other. Fig. 7 shows all of the battles 36 in parallel relation with each other. By this oblique baffle construction it will be seen that the sound waves cannot escape from the chamber except after reflection from the surfaces of the Celotex material from which the bafiles are constructed and inasmuch as the said material is provided with the apertures 2 on one surface thereof the total surface area of contact with the sound waves is increased all as will be readily understood. Further, this construction permits a more rapid rate of ventilation as the air draft is less obstructed. The directional flow of the draft through the chamber may also be controlled in accordance with the nature of the device within the chamber by use of the obliquely disposed baffles, 'all as will be readily understood.

It has been found in actual practice that a very high percentage of sound absorption is attained by the construction as above disclosed. That is to say, in one specific instance of an electric refrigerating device, supplying its own cooling medium, in which the mechanical operating unit built into the refrigerator was found obnoxiously noisy, a construction employing the features above disclosed was installed. In this particular instance a chamber in accordance with theabove disclosure was built within the walls 50 and the bottom 51 of the refrigerator, said bottom 51 having therein a ventilating opening 52 co-acting with a similar opening in one of the side walls to provide for the ventilation of the electric motor and pump mechanism supported by the bottom member 51. In other words, there was installed in this refrigerator a construction as disclosed in Fig. 2 of the drawings so that the opening 7 in the bottom of the sound absorbing chamber was in registry with the opening 52 in the bottom 51 of said refrigerator, and the opening 9 of said sound absorbing chamber was in open communication with the other ventilating opening in the side wall of said refrigerator. Further the power unit of the refrigerating device was inclosed in the sound absorbing chamber and supported from the bottom floor 4 thereof so that substantially full effect was had of the apertured surface for absorption of the sound waves, and so that the weight and disposition of said unit would in no way affect the baffle plate 15 associated with the ventilating opening 7. The result was a surprisingly high diminution of noise, the sound absorption being approximately Thus it will be seen that by this invention there is produced a sound absorbing chamber the walls of which comprise building boards of fibrous material of a vegetable nature such as bagasse, said boards having sound absorptive properties due to the porous interior construction thereof, as well as the independent artificial openings extending inwardly from a surface of the material, whereby sound waves may enter said openings and be absorbed by said porous interior. In combination with such a wall there is provided means to ventilate the chamber which are the openings 7 and 9, as well as means comprising the baflies which are of the same material as the walls and which coact with the walls to absorb a high percentage of the sound waves attempting to escape through the ventilating openings along with the air currents.

It is obvious that those skilled in the art may vary the details of construction as well as the arrangements of parts without departing from the spirit of the invention and therefore it is not desired to be limited to the above disclosure except as may he demanded by the claims.

VVhatis claimed is:

1. A sound absorbing chamber the walls of which comprise building boards of fibrous material with sound absorptive properties; positive ventilating means for said chamber including an air inlet and an air outlet; and

means comprising a cover for one of said air passages said means coacting with said walls to absorb a high percentage of the sound waves attempting to escape through said ventilating means.

2. A sound absorbing chamber the walls of which comprise building boards of fibrous n'laterial with sound absorptive properties; positive vmtilating means for said chamber including an air inlet and an air outlet; and means comprising independent members of said wall material coa-cting with said air passages and walls to absorb a high percent-age of the sound waves attempting to escape through said ventilating means.

3. A sound absorbing chamberthe walls of which comprise building boards of fibrous material with sound absorptive properties; means including passages to continuously ventilate said chamber; and means comprising a fibrous battle spaced from and coact ing with said passages and walls to absorb a high percentage of the sound waves accompanying the air through said ventilating means.

4. A sound absorbing chamber the walls of which comprise building boards of fibrous material with sound absorptive properties; means including passages to continuously ventilate said chamber; and means comprising a fibrous battle spaced from and coacting with said passages and walls to absorb a high percentage of the sound waves accompanying the air passing around each battle and through said ventilating means.

5. A sound absorbing chamber the walls of which comprise building boards of fibrous material with sound absorptive properties; means comprising passages in said walls to continuously ventilate said chamber; and means comprising a fibrous baflle having artificial surface openings said bailie held in spaced relation to a wall and passage and coacting with said walls to absorb a high percentage of the sound waves in the air surrounding said baflle and passing through said ventilating means.

6. A chamber having a Wall provided with openings extending from the inner surface thereof to admit sound waves; an air passage extending through one of said walls; and a cover for said passage likewise provided with openings extending inwardly from a surface thereof to admit sound waves, said cover internally spaced from said wall and covering only the portions thereof adjacent said passage whereby air in entering and leaving said chamber through said passage is caused to pass around and over said surface of said cover with resultant absorption of a high percentage of sound waves accompanying said a1r.

7. A chamber having a wall provided with openings extending from the inner surface thereof to admit sound waves; an air passage extendingthrough one of said walls; and a cover for said passage likewise provided with openings extending inwardly from a surface thereof to admit sound waves, said Cover internallyspaced from but rigidly secured to said wall and covering only the portions thereof adjacent said passage whereby air in entering and leaving said chamber through said passage is caused to pass around and over saidsurface of said cover with resultant absorption of a high percentage of sound a cover with resultant absorption of a high percentage of sound waves accompanying the air. 9. A chamber having'a wall provided with openings extendlng from the inner surface thereof to admit sound waves; an air-passage extending throughone of said walls; and a cover for said passage comprising parallel obliquely disposed members likewise provided with openings extending inwardly from a surface thereof tovadmit sound Waves, said cover internally spaced from said wall and covering only the portions thereof adjacent said passage whereby air in entering and leaving said chamber through said passage is caused to pass around and over said surface of said cover with resultant absorption of a high percentage of sound waves accompanying said air. 7

10. A chamber having a wall provided with openings extending from the inner surface thereof to.admit. sound waves; an air passage extending through one of said walls; and a cover for said passage comprising parallel members obliquely disposed to the asso ciated wall, said members likewise provided with openings extending inwardly from a surface thereof to admit sound waves, said cover internally spaced from said wall and covering only the portions thereofv adjacent said passage'whereby air in entering and leaving said chamber through said passage is caused to pass around and over said surface of said cover with resultant absorption of a high percentage of sound waves accompanying said air.

11. A sound absorbing structure having therein a sound producing source, the structure comprising a chamber in which the sound producing source is positioned, the chamber having entrance and exit openings whereby a cooling medium is circulated into and out of the chamber, means relative to the cooling medium exit whereby a substantial part of the cooling medium discharge stream will in escaping at the exit be deflected in its path of flow, the means causing deflection of the cooling medium stream comprising a relatively open porous material whereby sound waves impacting thereon may pass thereinto to be absorbed and dissipated.

In testimony whereof we affix our signatures.

TREADVVAY B. MUNROE WALLACE WATERFALL.