Patent Publication Number: US-7909136-B2

Title: Soundproof assembly

Description:
CROSS REFERENCE TO RELATED APPLICATION(S) 
     This application is related to commonly assigned U.S. patent application Ser. No. 10/658,814 filed Sep. 8, 2003, by Kevin J. Surace and Marc U. Porat, entitled “Accoustical Sound Proofing Material and Methods for Manufacturing Same”, and U.S. patent application Ser. No. 10/938,051 filed Sep. 10, 2004, by Kevin J. Surace and Marc U. Porat, entitled “Acoustical Sound Proofing Material and Methods for Manufacturing Same,” both of which are incorporated by reference herein in their entirety. 
     FIELD OF THE INVENTION 
     This invention relates to an acoustical damping structure which may be utilized for doors, floors, walls and ceilings to prevent the transmission of sounds from one area to another. 
     BACKGROUND OF THE INVENTION 
     Soundproof doors or sound transmission resistant doors have been around for a number of years and have typically been constructed of wood or metal in order to achieve or reduce sound transmission. Although sound transmission through the structure has been reduced, the doors have been rather bulky and heavy. An issue with these doors is how to make them with a high Sound Transmission Class (STC) rating and at the same time avoid the mass requirement of the prior art doors. In the prior art providing an increased STC over standard doors has been achieved by using heavy doors in order to prevent the transmission of acoustic energy from one side of the door to the other. Typical prior art soundproof doors have been made of solid, heavy materials to prevent sound transmission. Typical current soundproof doors have a mass of from about eight to ten pounds per square foot, which can result in a door weighing from three hundred to five hundred pounds, and in some cases as much as one thousand pounds. This significant amount of weight adds stress to the associated structure and in addition is not desirable for household use in view of the significant weight involved. A typical household door of a non-soundproof construction has an STC rating of about twenty-seven as opposed to the prior art, unitary soundproof doors which typically have an STC rating in the forties. 
     Thus what is required is a soundproof structure which has improved STC ratings, but avoids the heavy weight which has been typical of prior soundproof doors. 
     SUMMARY OF THE INVENTION 
     The present invention provides a soundproof assembly which has significantly reduced weight, yet provides an STC rating equivalent to solid doors having twice the weight. In accordance with the invention, a soundproof assembly is provided which includes one or more laminar structures which are, in one embodiment, separated by an air gap and in another embodiment separated by a layer of material. In one embodiment, both a front and a rear panel of the structure are laminar, while in another embodiment, one of the front or rear panels is laminated and the other is solid. 
     In one embodiment, the laminar structure includes interiorly, a constraining layer, with the constraining layer having one or more layers of viscoelastic glue on opposite sides. First and second exterior layers of material, are provided on opposite sides of the viscoelastic glue. The exterior layers may be cellulose or wood based, ceramic, metal or a composite material. 
     In constructing the soundproof assembly, the front and rear portions may be separated by spacers to provide an air gap intermediate the front and rear sections. 
     In another embodiment, a wood surround is provided about the peripheral edges of the soundproof structure. Additionally, for appearance purposes a veneer may be provided. The veneer merely serves a cosmetic function and it is not necessary for the achievement of improved STC characteristics of the soundproof structure. 
     In a further embodiment of the present invention, a method of forming a soundproof assembly is provided. In this method, a first panel having a laminar structure is supported adjacent to a second panel with the first and second panels being spaced apart by one or more spacers to provide an air gap between the adjacent surfaces of the first and second panels. 
     In a second embodiment, both the first and second panels have a laminar structure. 
     In providing a panel having a laminar structure, the laminar structure is produced by providing a first layer of material which is cellulose or wood based, applying one or more layers of viscoelastic glue to a surface of the first layer of cellulose material, providing a constraining layer of material, and placing this constraining layer of material on the exposed surface of the viscoelastic glue. Next, one or more layers of viscoelastic glue are provided on the exposed surface of the constraining layer and a second layer of material which is cellulose or wood based is placed on the viscoelastic glue which is exposed on the constraining layer of material. Alternative materials for the first and second layers of material include ceramic, metal, or a composite material. In one embodiment, the constraining layer of material is a layer of metal and in other embodiments, the constraining layer of material may be a solid petroleum-based synthetic material such as vinyl, plastic composite, rubber, ceramic, a composite material or any other material that has a Young&#39;s Modulus of 10 GigaPascals (GPa) or greater. 
     In another embodiment, the laminar structure is constructed by utilizing three layers of material which are cellulose or wood based and two layers of a constraining material interior of and intermediate the three layers of cellulose or wood based material. The constraining layers have a viscoelastic glue layer interposed between each of them and the adjacent layer of cellulose material. In the embodiment which includes two constraining layers and three cellulose layers, both of the constraining layers may be formed of a metal, a solid petroleum based synthetic material such as vinyl, plastic composites, rubber, ceramic composite, or another material having a high Young&#39;s Modulus above 10 GigaPascals (GPa). Alternatively one of the constraining layers may be one of the foregoing materials and the other may be another of the foregoing materials. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a front view of one embodiment of a soundproof assembly in accordance with the invention; 
         FIG. 2  is a cross-section taken along the lines of  2 - 2  of  FIG. 1 ; 
         FIG. 3  is a front view of a second embodiment of the present invention; 
         FIG. 4  is a cross-sectional view taken along the lines  4 - 4  of  FIG. 3 ; 
         FIG. 5  illustrates an alternate embodiment of a laminar panel which may be utilized in the present invention; 
         FIG. 6  is a front view of a soundproof assembly in accordance with an embodiment of the invention; 
         FIG. 7  is a cross-sectional view taken along the lines  7 - 7  of  FIG. 6 ; 
         FIG. 8  is a front view of a further embodiment of the present invention; 
         FIG. 9  is a cross-sectional view taken along the lines  9 - 9  of  FIG. 8 ; 
         FIG. 10  is a front view of a further embodiment of the present invention; 
         FIG. 11  is a cross-sectional view taken along lines  11 - 11  of  FIG. 10 ; 
         FIG. 12  is a front view of yet another embodiment of the present invention; and 
         FIG. 13  is a cross-sectional view taken along the lines  13 - 13  of  FIG. 12 . 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENT(S) 
       FIG. 1  is a front view of soundproof assembly  1  which includes a front panel  2  and a rear panel  3  which is best illustrated in  FIG. 2 . Rear panel  3  is connected to front panel  1  via spacers  4 ,  5 , and  6 , which are illustrated in  FIG. 1  in dotted line outline and shown in the top view in  FIG. 2 . As will be appreciated by reference to  FIG. 2 , front panel  2  and rear panel  3  are symmetrical in construction, the details of which are described below. Spacers  4 ,  5 , and  6 , hold front panel  2  and rear panel  3  in a spaced apart relationship to provide an air gap between the panels. 
     As will be appreciated by reference to  FIG. 2 , the opposing edges of front panel  2  and rear panel  3  have a cover layer of material indicated by reference characters  7  and  8  which close the opposite edges of the panels. The bottom edges of soundproof assembly  1  are also enclosed by a cover indicated by reference character  9  in  FIGS. 1 and 2 , and similarly a top cover layer  10  encloses the upper portion of soundproof assembly  1 . This accordingly provides an enclosed air space within soundproof assembly  1 . In the embodiment illustrated in  FIGS. 1 and 2 , the use of three spacers  4 ,  5 , and  6  results in the air gap enclosure indicated by reference characters  11  and  12  in  FIG. 2 . In one embodiment acoustically absorptive material such as fiberglass, cellulose, mineral wool, or foam is included in the air gap enclosures  11  and  12 . The embodiment illustrated in  FIGS. 1 and 2  includes veneer  13  on the front panel  2  and veneer  14  on the rear panel  3  for aesthetic purposes. The use of veneers  13  and  14  is not necessary to provide the structure of the present invention, however they may be useful, if for example, the soundproof assembly will be used as a door or other structure where an attractive appearance is desirable. 
     In the embodiment illustrated in  FIG. 2 , the front panel and rear panels are constructed alike. It is of course not required that the two panels be alike in order to practice the invention; however in this embodiment that is the case. In the alternative embodiment illustrated in  FIGS. 3 and 4 , the two panels are dissimilar in construction.  FIG. 5  illustrates an alternative construction for laminar panels, which may be used in practicing the present invention. 
     Returning to  FIG. 2 , front panel  2  is comprised of a laminar combination of layers of materials including external layers  15  and  16 . Layers  15  and  16  in one embodiment are cellulose, or wood based layers. In one embodiment of the invention, layers  15  and  16  are ¼ inch thick plywood; however other thicknesses may of course be utilized depending on the desired characteristics of the weight and sound transmission reduction to be achieved. Alternatively, layers  15  and/or  16  could be ceramic, metal, or a composite material which includes a fiber such as fiberglass, Kevlar or carbon fiber. As used herein, the term composite material means a material which includes two or more materials combined in such a way that the individual materials are distinguishable. 
     Intermediate the interior surfaces  18  and  19  of layers  15  and  16  respectively, are a first layer of viscoelastic glue  20  and a second layer of viscoelastic glue  21 . Intermediate glue layers  20  and  21  is a constraining layer indicated by reference character  17 . This construction, as will be appreciated by reference to  FIG. 2 , provides a laminar structure. 
     Constraining layer  17  is, in one embodiment, a layer of metal, which may be for example  30  gauge, galvanized steel. It will of course be appreciated that other thicknesses may be used as well as other materials such as sheets of ultra-light weight titanium and laminated layers of metal including laminate of aluminum and titanium. If galvanized steel is utilized, it should be non-oiled and of regular spackle. The non-oil characteristic is required to ensure that the viscoelastic glue layers  20  and  21  will adhere to the metal. Regular spackle ensures that the metal has uniform properties over its entire area. Constraining layer  17  is constructed of a metal; typical ranges of thicknesses are from 10 gauge to 30 gauge depending on the weight, thickness, and STC desired. Of importance, the constraining layer  17  should not be creased because creasing will ruin the ability of the metal to assist in reducing the transmission of sound. Only completely flat, undamaged pieces of metal can be used in the laminar structure. Constraining layer  17  may alternatively be a layer of ceramic material, or a layer of composite materials, such as, for example, fiberglass, Kevlar or carbon fiber. 
     Constraining layer  17  may be alternatively mass loaded vinyl or a similar material. A suitable mass-loaded vinyl may be purchased from Technifoam in Minneapolis, Minn., and have a thickness of ⅛ of an inch; however, other thicknesses may of course be used. 
     As will be appreciated by reference to  FIG. 2 , viscoelastic glue is applied on opposite sides of constraining layer  17 . This viscoelastic glue has the property that the energy in the sound and vibrations which strikes the glue, when constrained by surrounding layers, will be significantly absorbed by the glue thereby reducing the sound and vibration&#39;s amplitude across a broad frequency spectrum, and thus reducing the energy of sound transmitted through the resulting laminar structure. Typically, this glue is made of materials as set forth in Table 1, although other glues having the characteristics set forth directly below Table 1 can also be used in this invention. 
     
       
         
           
               
            
               
                   
               
               
                 Quiet Glue ™ Chemical Makeup 
               
            
           
           
               
               
            
               
                   
                 WEIGHT % 
               
            
           
           
               
               
               
            
               
                 Components 
                 Min 
                 Max 
               
               
                   
               
            
           
           
               
               
               
            
               
                 Acetaldehyde 
                 0.00001%  
                 0.00010% 
               
               
                 acrylate polymer 
                 33.00000% 
                 65.00000% 
               
               
                 Acrylonitrile 
                 0.00001% 
                 0.00100% 
               
               
                 Ammonia 
                 0.00100%  
                 0.01000% 
               
               
                 bis(1-hydroxy-2-pyridinethionato)  
                 0.01000% 
                 0.10000% 
               
               
                 Zinc  
                   
                   
               
               
                 Butyl acrylate 
                 0.00100%  
                 0.10000% 
               
               
                 butyl acrylate, methyl methacrylate, 
                 5.00000% 
                 15.00000% 
               
               
                 styrene, methacrylic acid 2- 
                   
                   
               
               
                 hydroxyethyl acrylate polymer 
                   
                   
               
               
                 CI Pigment Yellow 14 
                 0.01000% 
                 0.02000% 
               
               
                 Ethyl acrylate 
                 0.00001% 
                 0.00010% 
               
               
                 ethyl acrylate, methacrylic acid, 
                 1.00000% 
                 5.00000% 
               
               
                 polymer with ethyl-2-propenoate 
                   
                   
               
               
                 Formaldehyde 
                 0.00100%  
                 0.01000% 
               
               
                 Hydrophobic silica 
                 0.00100% 
                 0.01000% 
               
               
                 paraffin oil 
                 0.10000% 
                 1.00000% 
               
               
                 polymeric dispersant 
                 0.00100% 
                 0.01000% 
               
               
                 potassium tripolyphosphate 
                 0.00000% 
                 0.00200% 
               
               
                 silicon dioxide 
                 0.00100% 
                 0.10000% 
               
               
                 sodium carbonate 
                 0.01000%  
                 0.10000% 
               
               
                 stearic acid, aluminum salt 
                 0.00100%  
                 0.10000% 
               
               
                 Surfactant 
                 0.00100% 
                 0.10000% 
               
               
                 Vinyl acetate 
                 0.10000%  
                 1.00000% 
               
               
                 Water 
                 25.00000% 
                 40.00000% 
               
               
                 zinc compound 
                 0.00100%  
                 0.10000% 
               
               
                   
               
            
           
         
       
     
     The physical solid-state characteristics of QuietGlue include: 
     1) a broad glass transition temperature which starts below room temperature; 
     2) mechanical response typical of a rubber (i.e., high elongation at break, low elastic modulus); 
     3) strong peel strength at room temperature; 
     4) weak shear strength at room temperature; 
     5) swell in organic solvents (e.g., Tetrahydrofuran, Methanol); 
     6) does not dissolve in water (swells poorly); 
     7) peels off the substrate easily at temperature of dry ice. 
     In constructing front panel  2 , viscoelastic glue layer  21  is applied to interior surface  19  of layer  16 . Various thicknesses of glue may be utilized and can range from a few millimeters of up to about ⅛ inch. After application of viscoelastic glue layer  21 , constraining layer  17  is placed on viscoelastic glue layer  21 . Following that, viscoelastic glue layer  20  is applied to upper surface  22  of constraining layer  17 . The thickness of viscoelastic glue layer  20  may be in the range of the thickness used for viscoelastic glue layer  21 ; however it is not necessary that both of the glue layers be of the same thickness. 
     Next, layer  15  is placed on the upper surface of the glue layer  20 . The assembly is then subjected to dehumidification and drying to allow the panels to dry, typically for 48-hours. Of course, it will be appreciated from  FIG. 2  that front panel  2  and rear panel  3  are constructed as indicated above and cut to the appropriate lengths and heights prior to assembly into soundproof assembly  1 . In addition to dehumidification, the panels  2  and  3  are subjected to 0.5 to 10 pounds per square inch (psi) pressure during the drying process. And, the panels  2  and  3  may also be heated up to 150° F. for about 24 to 48 hours. 
     As will be appreciated by reference to  FIG. 2 , spacers  4 ,  5 , and  6 , are placed intermediate to front panel  2  and rear panel  3 . Spacers  4 ,  5 , and  6 , are secured in place by glue, nails or other mechanical fasteners. 
     The gap between outer surface  23  of wood layer  15  and outer surface  24  of wood layer  25  is indicated by reference character D 1  in  FIG. 2 . The distance D 1  may have any number of values, for example, from 5 mils to 1 inch. If soundproof assembly  1  is to be a door, the typical range for D 1  would be from Y 4  inch to ½ inch. As shown in  FIG. 2 , a sheet of mass loaded vinyl indicated by reference character  30  is included in the space between panels  2  and  3 . Inclusion of sheet  30  is optional, however. Besides vinyl, a suitable material for sheet  30  may be the same as that used for constraining layer  17  described above. 
     Rear panel  3  may be constructed similarly to front panel  2 , but it is not required that such a construction be utilized. Wood cellulose layers  25  and  26  may have similar thicknesses to the thicknesses of layers  15  and  16  in front panel  2 ; however, different thicknesses may be utilized. Additionally, each of the wood/cellulose layers in the combination are not necessarily required to have the same thickness, although that is true in the embodiments illustrated. In rear panel  3 , a constraining layer  27  may be of a material like any of those layers described above with regard to constraining layer  17 , but constraining layer  27  may be made of a different material than constraining layer  17 . 
     After front panel  2  and rear panel  3  have been affixed to spacers  4 ,  5 , and  6 , the surround covers  7 ,  8 ,  9 , and  10 , are applied and preferably attached to the peripheral edges of rear panel  2  and rear panel  3  by glue, nails or other mechanical fasteners. 
     As noted above, the veneer  13  and  14  may optionally be applied to the outer surfaces of front and rear panels  2  and  3  respectively. 
       FIG. 3  illustrates another embodiment of the present invention. In this embodiment, soundproof structure  33  is shown in a front view and includes a front panel  34  and cover sections  35 ,  36 ,  37  and  38 , which are similar to corresponding cover sections in the embodiment of  FIG. 1 . In the construction of soundproof assembly  33 , spacers are also utilized to separate front panel  34  from the rear panel  3 , which has the same construction as the corresponding panel in the embodiment of  FIG. 2 . Spacers  4 ,  5 , and  6 , which may be of the same construction as the spacers used in the embodiment of  FIG. 2 , are also provided to separate front panel  34  from rear panel  3 . Although in this embodiment and that of  FIG. 2 , three spacers are utilized, it is optional to exclude the center spacer  5 , provided that sufficient rigidity is achieved by using only the spacers  4  and  6 , which are positioned, at the outer edges of soundproof assembly  33 . 
     The interior of a soundproof assembly  33  will be better appreciated by reference to  FIG. 4 , which is a cross sectional view taken along the lines  4 - 4  in  FIG. 3 . As will be appreciated by reference in  FIG. 4 , the rear panel  3  is constructed in like manner to the rear panel  3  in the embodiment of  FIG. 2 . However, in soundproof assembly  33 , the front panel of  34  is constructed of a solid piece of wood/cellulose material indicated in  FIG. 4  by reference character  34 . Front panel  34  may be for example, ⅝ inch thick and constructed of a cellulose or wood material. Other suitable materials include for example, ceramic, plastic, composite material or metal. The distance D 2  between the inner surface  39  of front panel  34  and the inner surface  24  of rear panel  3  may be for example the same distance as D 1  in the embodiment of  FIGS. 1 and 2 . In this embodiment, spacers  4 ,  5 , and  6  are secured to the associated panels  3  and  34  utilizing the same construction technique as that utilized in the embodiment of  FIG. 2 . A sheet of mass loaded vinyl indicated by reference character  43  is included in air gap enclosures  44  and  45 . Sheet  43  may be of the same type of material as described above with regard to sheet  30 . As shown in  FIG. 4 , the ends and the center of sheet  43  are secured in place by spacers  4 ,  5  and  6 , which is the same technique used for sheet  30  in the embodiment of  FIG. 2 . If soundproof assembly  33  is utilized as a door, for example, the outer periphery is sealed by cover sections  35 ,  36 ,  37 , and  38 . 
     Front panel  34  in soundproof assembly  33  may be constructed by using, for example, a solid wood or cellulose material or alternatively a plywood layer or one of the alternative materials noted above. The thickness from surface  39  to surface  40  may be for example, ⅝ inch. Another thickness may of course, be utilized, with a greater thickness providing additional improvement in STC. Soundproof assembly  33  may also include the veneers  41  and  42  if it is desirable to provide a more aesthetically pleasing appearance to soundproof assembly  33 . The thickness of veneer layers  41  and  42  is a matter of design choice. 
       FIG. 5  illustrates an alternative laminar panel  46 , which may be utilized as one or both panels of the soundproof structures as that illustrated in  FIGS. 1 ,  2 ,  3 , and  4 . Laminar panel  46  includes a first outer layer  47 , which may be constructed of a cellulose/wood material having a thickness in the range from about 100 mils to 2 inches as measured from outer surface  48  to inner surface  49 . Alternatively, outer layer  47  may be a layer of metal, ceramic, fiberglass, a composite material including fiberglass, Kevlar or carbon fiber, or a petroleum-based synthetic material such as vinyl, plastic composite, or rubber. 
     In this embodiment, glue layer  50  is applied to surface  49  and thereafter a constraining layer  51  is placed on the surface of glue layer  50 , which is opposite to surface  49  of first outer layer  47 . Constraining layer  51  may be any of the above described constraining layers discussed in the embodiments of  FIG. 1 ,  2 ,  3 , or  4 . Glue layer  52  is applied to surface  60  of pine laminar sheet  53 , which is of a type commonly used in plywood. Pine laminar sheet  53  may have a thickness of from about 100 mils to about 2 inches; however, it may also be medium density fiberboard (“MDF”) or other wood types. Alternatively, in place of pine laminar sheet  53 , any of the following may be used: a layer of metal; a layer of ceramic material; a layer of solid petroleum based material such as vinyl, plastic composite or rubber; or a layer of composite material such as fiberglass, Kevlar or carbon fiber. 
     Next, glue layers  54  and  55  are provided on opposite sides of a second constraining layer  56 . Glue layers  54  and  55  may be of the type described above with regard to the embodiments of  FIGS. 1 ,  2 ,  3 , and  4 . The structure is completed by the application of second outer layer  57 , which may be, for example, of the same type of material utilized in first outer layer  47 . The thickness of second outer layer  57 , as measured from inner surface  58  and outer surface  59 , may be for example, in the range from about 100 mils to 2 inches. Second outer layer  57  may alternatively be any one of the alternative materials described above for first outer layer  47 . 
     In constructing laminar panel  46 , typically glue layer  50  is rolled onto surface  49  of first outer layer  47 , and glue layer  52  is rolled onto surface  60  of pine laminar sheet  53 . Glue layer  54  is applied by rolling it onto surface  61  of pine laminar sheet  53 . Glue layer  55  is applied also by roller or another suitable technique to surface  58  of second outer layer  57 . Constraining layer  51  is then sandwiched between the surfaces of glue layers  50  and  52 , and constraining layer  56  is placed intermediate to glue layers  54  and  55  and the entire structure is then subjected to a compression force of about 1 pound per square inch. When a suitable pressure is described prescribed, the compressive force may be applied for a length of time such as from about 24 to 48 hours. The entire structure then becomes a laminar panel suitable for use in a soundproof structure. 
     Referring to  FIG. 6 , soundproof assembly  65  is illustrated in a front view. A number of the elements in soundproof assembly  65  are also utilized in soundproof assembly  1  illustrated in  FIGS. 1 and 2 , and accordingly common reference characters are utilized in  FIG. 6 . In soundproof assembly  65 , front panel  2  and rear panel  3  which are utilized in soundproof assembly  1  are directly connected utilizing a glue layer rather than the spacer construction which is utilized in soundproof assembly  1 . More particularly, referring to  FIG. 7 , which is a cross-sectional view taken along lines  7 - 7  of  FIG. 6 , front panel  2  and rear panel  3  are secured to each other by having glue layer  66  interposed between their respective inner surfaces  24  and  23 . Glue layer  66  may be any generally available construction adhesive or alternatively glue layer  66  may be a viscoelastic glue such as viscoelastic glue  28  described above in connection with the description of  FIGS. 1 and 2 . The thickness and the application techniques may be the same as described above in connection with, for example, glue layer  28  ( FIG. 2 ). As will be appreciated by reference to  FIG. 7 , the elimination of the air gaps used in the soundproof assembly of  FIG. 1  provides a more compact structure. 
     In an alternate embodiment of the present invention soundproof assembly  75  is provided, this assembly being illustrated in  FIGS. 8 and 9 . Because soundproof assembly  75  utilizes a number of common structural elements found in soundproof assembly  33  of  FIGS. 3 and 4 , common reference characters are utilized in connection with the two soundproof assemblies. In a fashion similar to soundproof assembly  65  described above, the front and rear panels are connected by a glue layer  76  rather than being spaced apart with spacers as employed in soundproof assembly  33 . As will be appreciated by reference to  FIG. 9 , soundproof assembly  75  utilizes front panel  34  and rear panel  3  which are constructed as illustrated in  FIG. 4  and described above in connection with that figure. Accordingly, additional explanation of the construction of the two panels is not required here. Glue layer  76  may be, as described above in connection with soundproof assembly  65 , any commonly available construction adhesive or alternatively viscoelastic glue such as viscoelastic layer  28  described in connection with the embodiment illustrated in  FIG. 2 . 
     Turning to  FIGS. 10 and 11 , soundproof assembly  85  is illustrated. In this embodiment, front and rear panels,  2  and  3  respectively, are constructed as described above in connection with, for example,  FIG. 2  and soundproof assembly  1 . Like reference characters are utilized in  FIGS. 10 and 11  for structures which have been previously shown and described in connection with soundproof assembly  1 . 
     As illustrated in  FIG. 11 , interior layer of material  86  is interposed between the respective interior surfaces of front panel  2  and rear panel  3 . In the embodiment of soundproof assembly  85  illustrated in  FIGS. 10 and 11 , interior layer  86  is a wood/cellulose based layer. However, no particular material is required for layer  86 , nor is any particular thickness necessary. Layer  86  may alternatively be various types of materials including, such as, for example, metal, a solid petroleum-based synthetic material such as vinyl, plastic composites, rubber, ceramic composite, or fiberglass. Interior layer  86  may be constructed as a solid sheet of material or may alternatively include apertures. For example, interior layer  86  may be constructed as a honeycomb structure or a planar sheet of material with holes through the sheet. Material for a honeycomb structure may be, for example, aluminum. Additionally, acoustically absorptive material such as fiberglass, cellulose insulation, mineral wool, foam or a granular material may be included in the apertures. Front panel  2  and rear panel  3  are secured to interior layer  86  by glue layers  87  and  88 . These glue layers may be composed of the same materials as described above in connection with the soundproof assemblies  65  and  75 . In the embodiment of  FIG. 11 , interior layer  86  is coextensive in its height and width with front and rear panels  2  and  3  respectively. This is of course a design choice and interior layer  86  could be made to only partially fill the space between the inner surfaces of panels  2  and  3 . 
     Turning to  FIGS. 12 and 13 , another embodiment of the invention is disclosed. Soundproof assembly  95  utilizes front panel  34  and rear laminar panel  3  which have been amply described above in connection with the prior embodiments. In the soundproof assembly  95 , interior layer of material  96  is spaced between the respective inner surfaces of front panel  34  and rear panel  3 . The composition of interior layer  96  may be selected to be the same as that used for interior layer  86  in the embodiment illustrated in  FIGS. 10 and 11 . The structure of interior layer  96  may be any of those described above in connection with interior layer  86  of soundproof assembly  85 . Front panel  34  and rear panel  3  are secured to interior layer  96  utilizing adhesive layers  97  and  98 . The composition of these adhesive layers may be the same as adhesive layers  87  and  88  described above in connection with soundproof assembly  85  illustrated in  FIGS. 10 and 11 .