ACOUSTICAL WALL BOARD AND WALL SYSTEM

Abstract: A composite wallboard (300) (and system when attached to an existing wall) is disclosed. The composite wallboard has a plasterboard layer (308), an insulation layer (306) and a perforated board layer 302. It is preferred that the perforated board layer be attached to an existing wall (102). The insulation layer attaches the plasterboard layer to the perforated board layer while at the same time decoupling these two. Where the composite wallboard is attached to a typical stud wall, Helmholtz resonators (600) can be defined. This increases the low frequency sound absorption of a wall system (400) that uses the composite wallboard. Installing a wall system that includes the composite wallboard is a single-step process, which saves a great deal of labor relative to the use of resilient channel.

Description: ACOUSTICAL WALL BOARD AND WALL SYSTEM FIELD OF THE INVENTION The invention is generally directed toward the field of wallboard, and more particularly to the fields of composite wallboard and acoustical wallboard composition, and is also directed toward the field of Acoustical Wall Systems. BACKGROUND OF THE INVENTION In the art of sound attenuation, it is known to use resilient channel to decouple plasterboard (also known as drywall) from the stud wall to which it is attached. This is depicted in Fig. 1, where a stud wall 102 is formed of a base plate 104 to which are attached vertical studs 106. A header (not depicted) is typically found at the top of the studs 106 in a position opposite to the base plate 104. Typically, the base plate, studs and header are formed of "2x4" material, made either of wood or steel. Strips of resilient (steel) channel 108 are mounted perpendicularly to the studs 106. A sheet of drywall 110 is attached to the strips of resilient channel 108. Fig. 2 depicts a cross-section of Fig. 1 along the view line II-IF. The resilient channel 108 has feet portions 204 and a center section 202. Screws 112 are used to attach the feet portions 204 to the studs 106. Screws 112 are also used to attach the plasterboard 1 10 to the center section 202 of the resilient channel 108. The resilient channel succeeds in attaching the plasterboard 110 to the studs 106 while decoupling the plasterboard 110 from the studs 106. Depending upon the degree of its resiliency, the channel 108 can provide varying levels of decoupling between the plasterboard 110 and the studs 106. This can reduce the amount of vibration transmitted from the plasterboard 110 to the studs 106, and vice-versa. A disadvantage of the use of resilient channel is that the resilient channel 108 must be attached to the studs 106 before the plasterboard 1 10 is attached to the resilient channel 108. Moreover, the resilient channel 108 must be attached carefully in a periodic manner so that it will be easy to locate the center sections 202 when attaching the plasterboard 1 10. Thus, a person using resilient channel to attenuate sound transmission must obtain not only plasterboard but also a supply of resilient channel, then that person faces a two- step process to attach the plasterboard 110 to the studs 106 via the resilient channel 108. In contrast, attaching plasterboard 110 directly to the studs 106 is a single-step process. In other words, the resilient-channel technique is much more labor-intensive. SUMMARY OF THE INVENTION The invention, in part, provides an acoustical isolation wall system that can be assembled in one-step rather than in two-steps. An advantage of the invention is that it substantially decouples the stud wall from the plasterboard. Decoupled is used here to mean that the wallboard does not physically touch the stud. Another advantage of the invention is that is provides tunable low frequency sound absorption via the use of Helmholtz resonators. The invention, in part, provides a composite wall board comprising: a plasterboard layer; an insulation layer; and a perforated board layer. Such an insulation layer attaches said plasterboard layer to said perforated board layer while decoupling said plasterboard layer from said perforated board layer. The invention also provides, in part, a wall system comprising: an existing wall; and a composite wall board attached to said stud wall; said composite wall board including a plasterboard layer; a insulation layer; and a perforated board layer; wherein said insulation layer attaches said plasterboard layer to said perforated board layer while decoupling said plasterboard layer from said perforated board layer. The invention also provides, in part, a method of constructing a wall system in a room having at least one subject wall, the method comprising: providing a composite wallboard that includes a plasterboard layer; a insulation layer; and a perforated board layer; and attaching said composite wallboard to said subject wall. The foregoing and other objectives of the present invention will become more apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. BRIEF DESCRIPTION OF THE DRAWINGS The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus do not limit the present invention. Fig. 1 is a three-quarter perspective depiction of a background wall system. Fig. 2 is a cross-sectional view of Fig. 1 taken along the view line II-IF. Fig. 3 is a three-quarter perspective depiction of a first embodiment of the composite wallboard according to the invention. Fig. 4 is a three-quarter perspective depiction of an embodiment of a wall system according to the invention that incorporates the embodiment of Fig. 3. Fig. 5 is a cross-sectional view of the embodiment of Fig. 4 taken along the view line V-V. Fig. 6 is a schematic depiction of a basic Helmholtz resonator. And, Fig. 7 is cross-sectional view of a second embodiment of the composite wallboard according to the invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Fig. 3 is a three-quarter perspective depiction of a first embodiment of a composite wallboard 300 according to the invention. The composite wallboard 300 includes a perforated, rigid board 302, insulation material 306 and plasterboard 308. Examples of the insulation layer 306 are board fiberglass (approximate density of 3-12 lbs/ft (48.03 - 192.12 kg/m )), open-cell melamine foam (approximate density of 0.7 lbs/ft 3 (11.21 kg/m 3 )) or mineral wool board (approximate density of 3-5 lbs/ft 3 (48.03 - 80.05 kg/m )). Commercial examples of the insulation layer 306 include a board formed of compressed fiberglass insulation such as the Type 703 model of semi-rigid glass fiber insulation board sold by Owens Corning and a board formed of open cell melamine foam such as is sold under the brand name of BASOTECT V 3012 Melamine Foam marketed by the BASF Corporation. Preferably, the insulation is in the range of Vz (1.27) to 1 l A (3.81) inches (cm) thick. The perforated board 302 is preferably a synthetic board or a particle board, e.g., oriented-strand board (OSB) or a material that is similar to that from which peg board is made, or even plywood. Typically, the perforated board 302 will be between about 1/8 inch ( .3175 cm) and % inch (.635 cm) thick. Alternatively, the board 302 need not be perforated, though not having the holes forfeits the advantages of the Helmholtz resonators discussed below. The holes 304 in the perforated board 302 are preferably of varying diameters and are preferably randomly distributed. Alternatively, the holes can be of the same diameter and distributed in a pattern. The sizing and distribution of the holes will be discussed more below. The plasterboard 308 is preferably a board made of several plies of fiberboard, paper or felt bonded to a hardened gypsum plaster core. Alternatively, the plasterboard 308 could be replaced with paneling or a cement-based backer board. The thickness of the plasterboard 308 is preferably in the range of inch (.635 cm) to 5/8 inch (1.59 cm). The 5/8 inch (1.59 cm) size represents the largest commercially available plasterboard and is preferred because it exhibits the best sound attenuation properties. Fig. 4 is a three-quarter perspective depiction of a sound attenuation wall system 400 according to the invention. In Fig. 4, the composite wallboard 300 is attached to a stud wall 102. Fig. 5 is a cross-section of the wall system 400 taken along the view line V-V. In Fig. 5, screws 112 are used to attach the perforated board 302 to the studs 106. As noted above, the perforated board 302 is attached to the front surface 310 of the stud wall 102. When a covering material 504 (Fig. 5) is attached to the back surface 312 of the stud wall 102, a cavity is defined by the studs 106, the base plate 104 and the header plate (not depicted), the covering material 504 and the perforated board 302. The holes 304 in the perforated board 302 act to define Helmholtz resonators within the cavities. The diameter of the holes is related to the frequency desired to be absorbed by the Helmholtz resonator. Thus, the diameter of the holes will depend upon the circumstances to which the invention is applied. The theory and physics of Helmholtz resonators are known. Thus, only a brief discussion of the theory and physics will be provided in regard to Figure 6. A cross- sectional view of a basic Helmholtz resonator 600 is illustrated in Figure 6. The volume, V, of air in the chamber 602 of the Helmholtz resonator 600 is linked to the environment 612 (containing a sound source) outside the resonator 600 via an aperture 606 in the body 604. The aperture 606 has a cross-sectional area, S, and a length, L, indicated via items 608 and 610, respectively, in Figure 6. When sound impinges on the aperture 606, the air in the neck of aperture will be induced to vibrate. In turn, this causes the volume of air in the cavity to undergo periodic compression and expansion. The friction between the air particles in the aperture 606, and the resistance to air flow associated with the neck itself, cause the energy in sound waves to be absorbed. The efficiency of this absorption is at a maximum when resonance occurs, with the efficiency diminishing at frequencies above and below the resonant frequency. The general equation governing the performance of a Helmholtz resonator is: where f 0 = resonant frequency (Hz) C = velocity of sound (m/sec) L = depth of hole (m) S = cross-sectional area of hole (m 2 λ ) V = volume of chamber (m 3 ) D = diameter of hole (m) (assumed circular). By appropriately selecting V, L and S, the resonant frequency of the Helmholtz resonator can be controlled. The composite wallboard, and the wall system incorporating such a composite wallboard, according to the invention operate as diaphragmatic absorber that converts acoustical energy, especially low frequency acoustical energy, into mechanical vibrations. The resilency of the insulation layer 306 makes it possible for the acoustical energy to be transformed into mechanical vibration. This prevents the transmission of the acoustical energy through the composite wallboard or the wall system that incorporates it. An alternative embodiment 700 of the composite wallboard according to the invention is depicted in Fig. 7. In the cross-sectional view of Fig. 7, an insulation layer 702 is sandwiched between the plasterboard layer 308 and the perforated board layer 302. The insulation layer 702 has a non-uniform distribution. The portions 704 completely fill the distance 706 between the perforated board 302 and the plasterboard 308. The portions 708 and 712 only span distances 710 and 714, respectively, i.e., they incompletely fill the distance 706 between the perforated board 302 and the plaster board 308. Such non- uniform distribution of the insulation layer can be used to tune the sound absorbing qualities of the composite wallboard 700. If viewed from the front of the composite wallboard 700, i.e., from a perspective normal to (and looking through) the plasterboard 308, the insulation layer 702 would appear to be a stripped pattern and/or a checker board pattern. The composite wallboard according to the invention is preferably installed by screwing (or nailing) through the plasterboard 308 and into the perforated board 302 such that the screws (or nails) only contact the perforated board 302. The screw/nail holes, as well as the seams between the composite wallboards, are then finished in the typical manner associated with plasterboard. Alternatively, the perforated board 302 could simply be glued to the studs 106. An advantage of the composite wallboard according to the invention is that no nail pops can occur in the plasterboard 308. Alternatively, the plasterboard 308 could be attached to the studs 106, resulting in the perforated board 302 facing into the room. This would cause the composite wallboard to act as a mid-range and high frequency sound absorbing surface. To make this surface more attractive, it could be covered with an acoustically transparent fabric such as that used in the Acoustic Room System marketed by Owens Corning. Alternatively, the insulation layer 702 could be replaced by a known honeycomb material (not depicted), such as in any one of U.S. Patent Nos. 4,496,024; 4,522,284; and 4,084,367. It is also commercially available from the Tenneco Packaging company. The honeycomb material is typically made of paper and optionally can be impregnated with resin, and is available in a variety of sizes and paper weights. Such a honeycomb material would enhance the sound attenuation effect of the Helmholtz resonators, but would not decouple as well as the insulation layer 702. Again, it is an advantage of the invention that is provides a composite wallboard that attaches to an existing wall and yet is decoupled from that wall so as to attenuate sound transmission through the wall. Moreover, this composite wallboard can be installed in one-step, which represents a considerable savings in labor relative to the resilient-channel technique of the Background Art. The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.

Claims: WHAT IS CLAIMED IS: 1. A composite wall board 300 comprising: a plasterboard layer 308; an insulation layer 306; and a perforated board layer 302; wherein said insulation layer attaches said plasterboard layer to said perforated board layer while decoupling said plasterboard layer from said perforated board layer. 2. The composite wall board 300 of claim 1 , wherein said insulation layer 306 is glued to said plasterboard layer 308 and said perforated board layer 302. 3. The composite wall board 300 of claim 1, wherein said insulation layer 306 is one of mineral wool, open cell melamine foam or board fiberglass. 4. The composite wall board 300 of claim 1, wherein said insulation layer 306 has a density of about 0.7 lbs/ft 3 (11.21 kg/m 3 ). 5. The composite wall 300 of claim 1, wherein said perforated board layer 302 has at least one of non-uniformly sized-perforations and non-uniformly distributed perforations. 6. The composite wall 300 of claim 1, wherein said perforated board layer 302 is a particleboard. 7. The composite wallboard 300 of claim 1, wherein said insulation layer 306 is non- uniformly distributed between said perforated board layer 302 and said plasterboard layer 308. 8. A wall system 400 comprising: an existing wall; and a composite wall board 300 attached to said stud wall 102; said composite wall board including a plasterboard layer 308; a insulation layer 306; and a perforated board layer 302; wherein said insulation layer attaches said plasterboard layer to said perforated board layer while decoupling said plasterboard layer from said perforated board layer. 9. The wall system 400 of claim 8, wherein said perforated board layer 302 is attached and coupled to said existing wall but said plasterboard layer 308 is decoupled from said existing wall. 10. The wall system 400 of claim 8, wherein said existing wall is a stud wall 102. 11. The wall system 400 of claim 10, wherein said stud wall 102 has a covering material 504 on a side opposite said composite wall board 300 such that a Helmholtz resonator 600 is defined by said perforated board layer 302, the studs 106 in said stud wall and said covering material. 12. A method of constructing a wall system 400 in a room having at least one subject wall, the method comprising: providing a composite wallboard 300 that includes a plasterboard layer 308; a insulation layer 306; and a perforated board layer 302; and attaching said composite wallboard to said subject wall. 13. The method of claim 12, wherein said step of attaching mechanically connects said perforated board layer 302 to said subject wall, and said insulation layer 306 attaches said plasterboard layer 308 to said perforated board layer while decoupling said plasterboard layer from said perforated board layer and said subject wall. 14. A composite wall board 700 comprising: a first board layer 308; a connective layer 702 adhered to said first board layer; and a second board layer 302 adhered to said connective layer; wherein said connective layer attaches said first board layer to said second board layer while decoupling said first board layer from said second board layer. 15. The composite wall board of claim 14, wherein said acoustically-isolating connective layer 702 is one of mineral wool, open cell melamine foam or low density fiberglass. 16. The composite wall board of claim 14, wherein connective layer 702 is acoustically-isolating.

Inventors: ALTER HARRY A, BAUMBERGER SEAN, ALTER, HARRY, A., BAUMBERGER, SEAN
Applicants: ALTER HARRY A, BAUMBERGER SEAN, OWENS CORNING FIBERGLASS CORP, ALTER, HARRY, A., BAUMBERGER, SEAN, OWENS CORNING
Application year: 2000
Main classification: B32B3
IPC codes: B32B3, B32B13, E04B1, G10K11