US2276788A - Building construction - Google Patents

Description

March 17, 1942. R. F. NORRIS BUILDING CONSTRUCTION Filed June 27, 1938 ff ff ,Za l? Patented Mar. 17, 1942 BUILDING CONSTRUCTION Ralph F. Norris, Madison, Wis., assigner, by mesne assignments, to Burgess Battery Company, Chicago, Ill, a corporation` of Delaware Application June 27, 1938, Serial No. 215,981

(Cl. SiS-40) (i Claims.

This invention relates to sound-absorbing constructions and particularly to a sound-absorbing unit which may be used to line the ceiling of a room whose sound reverberation time or noise level is to be reduced.

The object of this invention is to provide a low cost sound-absorbing unit or panel which has desirable acoustical characteristics in that it will absorb sounds within the ordinary audible frequency rangey with greater uniformity than is obtainable by means of presently available materials. Further objects' include the production of an extremely light and simple construction which may be manufactured with uniformity and which may conveniently be handled and installed Without excessive breakage and consequent waste.

I A further object is to provide an efficient soundabsorbing unit equipped with air-distribu-ting means whereby the acoustical construction may also be utilized to function as an air distributor for a Ventilating system for the room acoustically treated.

The invention consists essentially of a shallow box-like foundation structure of suitable rigid sheet material containing a sound-absorbing medium, said sound-absorbing medium being covered by a double diaphragm which serves as one of the broad sides of the box-like structure in place of the rigid material. A collection of such units is arranged on the ceiling ofthe room with the double diaphragm exposed to the sound waves to be attenuated. The air-distributing acoustical units are provided with a number of openings adapted to permit predetermined quantities fo air to pass into the room through the partition formed by a collectionof these units from the plenum chamber between the wall or ceiling and said partition,

The invention is disclosed in detail in the following description with the aid of the drawing, in which l Fig. 1 is a fragmentary plan View of the soundabsorbing unit;

Fig. 2 is a sectional View of said unit;

Fig. 3 is a perspective view of an air-distributing acoustical unit;

Fig. 4 is a sectional view taken on line 4-4 of Fig. 3 shown with a preferred supporting means; and

Fig'. 5 is a sectional view taken on line 5-5 of Fig. 3 and also shown with the preferred supporting means.

The basic unit shown in Figs. 1 and 2 s comcardboard or chipboard substantially filled with a sound-absorbing material 2 and a double diaphragm 3, 4 which serves to close the box-like foundation structure and thus retain sound-absorbing material 2 .within it. The foundation structure l may conveniently and economically be formed from a unitary sheet of material and bent to form side walls 5 and 6, the marginal zones being incompletely inwardly retroverted to provide bracing members 'l and 8. A rigid structure is then completed by cementing the edges of the sheet material to the broad backing member, as at 9 and l0. Shredded newsprint may be employed as the sound-absorbing material 2, or other well-known materials of this ty'pe may be used, such as exfoliated vermiculite, balsam wool, cotton linters or other vegetable fibers. Membranes 3 and 4 are preferably air pervious and should be flexible and capable of mutually independent vibration. Sheet material such as strong, than lter paper or artificially perforated creped or plain kraft paper is suitable for this purpose although a thin, air-impervious material, such as tissue paper, maybe used. The membranes forming the double diaphragm 3, 4 are sound transparent whether constructed from the former or the latter-class of materials. Sound transparent" as used herein, is taken to designate the property of a given-material to transmit a substantial proportion "of sound waves incident upon one surface thereof regardless of whether such transmission takes place by direct passage of the sound Waves through apertures therein or by vibration of the material itself.'

The diaphragm membranes 3 and 4 may be mounted on' the foundation structure after the sound-absorbing material has been arranged in it by cementing or otherwise fastening the edges to the sides thereof. -These membranes are in loose contact with each other and are not stretched tautly in mounting but are loosely vibratile. All of the materials. from which the unit is made are preferably pretreated in a Wellknown manner to render them ameproof or rireproof. The optimum thickness of the units from the acoustical standpoint /is about 11/2 inches. 'The other dimensions are determined partly by considerations of shipping convenience. Also, they should not be too large in at least one dimension as too great a span would result in excessive sagging of the diaphragm facing. A convenient size is about 12 x 24 inches. The units are very light in weight and may be readily mounted by cementing or otherwise aflixing the posed of a box-like foundation I of thin,v hard backing element of the foundation structure to the surface of the ceiling or the units may be cemented to suitably supported furring strips.

Sound waves impinging upon the exposed diaphragm facing 3, 4 are substantially absorbed by the combined operation of the sound-absorbing material 2 and the double diaphragm 3, 4.

The sound-absorbing material within the struc` mechanics of the cooperation between the sound-.

. proximately the position shown in Figs. ,4 and 5 absorbing material andthe double diaphragm 3, 4

4 in attenuating sound waves are not definitely known.

' The air-distributing sound-absorbing unit shown in Figs. 3-5 is of fundamentally the same construction as that above described. The foundation structure Il is'provided with a series of openings I2 in the back portion thereof. A

second set of openings I3 is provided along the" units are arranged below the ceiling of a room to be acoustically treated and ventilated in spaced relation thereto and abutting each other in the form of a partition forming a plenum chamber between it and the ceiling into which Ventilating air is continuously introduced, the Ventilating' air is caused to pass through openings I2 and I3 and into the room in quantities determined by the amount of open area provided by the openings. It will be seen that in this way. the air may be caused to enter the room over a large area and without drafts. `This type of air-distributing arrangement is disclosed in Norris Patent No. 2,172,771, datediSeptember 12, 1939.

A preferred supporting apparatus is shown in Figs. 4 and 5. in the above referred to patent application as well as in Norris Patent No. 1,726,500, dated Algust 2, 1929. tacle I8 of perforated sheet metal or equivalent material is provided to receive a sound-absorbing joint between lthe sound-absorbing unit and the A pan or shallow flanged recep` This apparatus is also disclosed so that the lower diaphragm will be spaced above the exposed surface ofthe supporting pans. This is desirable from the standpoint of appearance of the assembled structure and also to prevent closing of the perforations in the sheet metal when the latter is painted. When the unit is used `as an air distributor as well as an acoustical treatment, the space between the diaphragm facing and the perforated sheet metal permits an expansion of the air entering it through openings I3 and thus permits the Ventilating air to enter the room through substantially all of the perforations on this exposed surface of the perforated metal supporting pan. It is thus seen that the perforated metal itself forms a part of the air-distributing apparatus.

The economic advantages f the invention are obvious. The improved acoustical characteristics whereby absorption of sound in the 20G-500 cycle range is greatly increased over that obtainable by means of a sound-absorbing material alone `are highly desirable. The relatively uniform absorption achieved by the unit throughout the ordinarily troublesome frequency range (256- 2048 cycles per second) together with low manuf* facturing cost make the construction commercially important.

Iclaim:

1. A sound-absorbing unit of the type def scribed comprising a foundation structure formed from a single piece of self-supporting material, said structure having a broad back surface, relatively narrow sides and means for bracing said sides relatively to said broad back surface, said means comprising bracing members formed by linccmpletely retroverting the marginal zones of said sheet inwardly and fastening `the edges i the area between said sides and enclosing said" sound-absorbing material within said structure.

2. A sound-absorbing unit of the type described comprising a foundation structure formed from a single piece of self-supporting material, said structure having a broad back surface,vrela tively narrow sides, and bracing members formed by incompletely retroverting the marginal zones of said sheet inwardly and fastening the edges if thereof to said back surface, sound-absorbing material disposed within said structure and a sound-transparent facing diaphragmv spanning the area between said bracing members and enclosing said sound-absorbing material within said structure, Isaid diaphragm joining said bracing members along 'a line spaced inwardly from said adjacent flange of pan I8. This arrangement is shown in Fig. 5. g lSimilar strips 22 may be arranged along opposed edges of the broad back surface of foundation structurel I. These strips serve as air seals [between the furring strip I9 and the sound-absorbing unit as shown in Fig.

- 4. A more satisfactory air iiow control is obtainable when these air seals are provided since all of the air flowing from the plenum chamber into the room must flow through the openings specially provided therefor.

`Obviously, the sound-absorbing unit of Figs:

i 1 andv 2 may be used with the supporting means shown in Figs. 4 and 5V. However, it is preferable that theV membranes forming the `double diaphragm facing for the soundabsorbing material be attached to the foundation structure` at a psides of said structure. 1

3. An .air-distributing and sound-absorbing unit comprising a box-like foundation structure formed from Aa single sheet of material.` said structure having a broad back surface, relatively narrow sides, and bracing members, openings in the marginal portion of said back surface establishing communication between the space adsaid structure and the space bounded by the l sides, bracing members and said marginal `porytions of said back surface, openings along the lower edge of. at least one of said bracing mem-` bers, and a sound pervious diaphragm spanning the area between said bracing membersabove said openings therein, said diaphragm enclosing aid sound-absorbing material within Asaid strucure.

4. The construction of claim 3 in which said bracing members are formedby incompletely retrovertingl the marginal zones of said sheet inwardly and fastening the edges thereof to said back surface.

5. In a combined air-distributing and acoustical construction for a room, a perforated sheet metal pan, means for supporting said pan below the ceiling of said room in spaced relation thereto, and an airflow control and sound-absorbing unit disposed within said pan, said unit comprising a box-like foundation structure having a broad back surface and relatively narrow sides, said structure having enclosed ducts interiorly adjacent at least one side thereof, openings in said back surface establishing communication between the space adjoining the exterior side of said back surface and said duct, openings in the wall of said duct opposed to the contiguous side of said structure along the edge thereof remote from said back surface, sound-absorbing material within said structure, a sound-transparent diaphragm spanning the open area of said box-like structure and enclosing said sound-absorbing material therewithin, said diaphragm joining the inner Wall of said duct above said openings and being in a plane substantially parallel wit.. said back surface, and air seal means for preventing the fiow of air between said unit and the sides of said perforated sheet metal pan, said unit being disposed within said pan with the diaphragm exposed to the interior of said room through the perforations in the sheet metal of said pan.

6. An air-distributing and sound-absorbing unit comprising a box-like foundation structure formed kfrom a single sheet of self-supporting material, said structure having a broad back surface, relatively narrow sides, and bracing members formed by incompletely retroverting the marginal portions of said sheet inwardly and fastening the edges thereof to said back surface, openings in marginal portion of said back surface establishing communication between the space adjoining the exterior side of said back surface of said structure and the space bounded by the sides, bracing members and said marginal portion of said back surface, sound-absorbing material disposed within said structure, and a sound-transparent facing diaphragm spanning the area between said bracing members and enclosing said sound-absorbing material within said structure, said diaphragm joining said bracing members along a line spaced inwardly from said sides of said structure, said bracing members having openings therein below the line of juncture of said facing diaphragm therewith.

RALPH F. NORRIS.

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