CA1098451A - One-piece dual density acoustical panel - Google Patents

Abstract

ONE-PIECE DUAL DENSITY ACOUSTICAL PANEL
ABSTRACT OF THE DISCLOSURE
A one-piece dual density rigid acoustical core panel of significantly different density at each opposing surface, one of said surfaces having the required smoothness and flatness to facilitate the application of decorative coverings, while the opposite surface is textured to form a regular pattern of indentations which act to regulate the increased density adjacent to the flat surface.
The panel provides the most economical method available of achieving the required combined characteristics of acoustical ab-sorption, thermal insulation, surface flatness, thickness toler-ance, panel rigidity, tackability, flame-safety and impact resistance. The method for producing the panel comprises pressing a molding tool into an uncured layer of fibrous material of predetermined uniform thickness and density at an elevated temperature to form and set the textured surface and the opposing smoother surface at the desired densities.
A process is also described for fusing a molded integrated frame about the perimeter of one of the above mentioned core panels, said frame being of greater thickness than the maximum thickness of the panel to create an air space behind the acoustical panel for the purpose of increasing acoustical absorption characteristics of the panel by introduction of a dead air space which in some design applications dissipates sound energy more efficiently than if there were no dead air space behind the panel.

Description

ONE-PIECE DUAL DENSITY ACOUSTICAL PANEL
BACKGROUND OF THE INVENTION

The present invention relates to a rigid acous-tical core panel member for panel assemblies, partition assemblies and the like and more particularly to a core member of the type described being a one-piece rigid struc-ture of dual density.
Numerous acoustical core materials are presently available for providing acoustical absorption in furniture systems, partitions, free standing acoustical screens, wall panels, ceiling systems and the like. Many of the existing products suffer deficiencies due to the fact that they require laminations of secondary members or require secon-dary manufacturing processes such as sanding or framing in order to achieve the required panel rigidity, flatness, impact resistance, tackability, thickness control and acoustical performance. The equipment and labor necessary to produce such laminations or secondary production proces-ses are expensive and, due to the addition of bonding materials, the product may suffer a deficiency in acoustical performance and may constitute a possible reduction in fire and smoke performance.
It has further been well-known in the acoustical industry that introduction of dead air space behind an acoustical absorber which is contingent with a wall or partition assembly significantly increases absorption values of the absorber due to the fact that the air space behind the ~`
absorber lengthens the path of impinging sound waves passing through the absorber to the wall or partition so as to attenuate and thereby reduce the intensity of reflections.

2.

.

g~.l , -~
:

It is also a known fact that at certain frequencies, a partition will become acoustically trans~
parent to the resonant panel or "natural frequency" response characteristics. Up to the present time, techniques for in-' ~ '~
: : .

~ ~ , 2a.

- . ~

lQ~8~;i troducing dead air space within a given panel thickness have been obtainable only at considerable cost and through the use of special materials and structures. Further, there have been no means available, until the present ~;
invention, to include an air space in an acoustical panel which, when filled with proper acoustical fill ma~erial, eliminates the reduction in performance at the "natural frequency" of the partition or panel.
A BRIEF DE:SCRIPTION OF THE PRESENT INVENTION
The present invention solves all of the above- ~
mentioned deficiencies by the provision of a rigid core ~-material of one-piece construction which economically meets ~`
all of the necessary requirements of its acoustical design uses and applications.
`::
A one-piece core is comprised of fibrous mater-ials bound together with thermosetting resins in such a ~anner as to produce a panel having a first flat surface ~ ' ~
wherein the density adjacent said flat surface is uniform and of a substantially high density per cubic foot while the opposing surface which is textured has a lower density per cubic foot.
This structure overcomes the deficiencies of all conventional single density core panels and blankets, as well as the deficiencies of multiple layer composite core panels and further provides for an exact quantitative speci-fication of the dual densities to be produced thereby t allowing for maximization of each required design function.

.~ 3.

S~

The panel molding techniques employed allow for exact construction of the panel properties to obtain the desired absorption values, tackability, smoothness of sur-face, flatness of surface, impact resistance, flame safety requirements, bonding characteristics, panel rigidity, panel deflection and .
' ~ ~ .

.

' ~':` ' ~
3a.

~31_ 1 ~4 ~

strength values, thickness tolerances and panel resiliency, all of said characteristics being obtained at equivalent cost to standard insulations that provide for sound absorption only.
The novel core panel of the present invention, in one preferred embodiment thereof, is formed by providing a layer or layers of uncured raw fibrous material of sub-stantially uniform thickness and uniform density. The -~
-uncured material is pressed between a pair of molding members, one of which is designed to provide a substantially smooth, flat surface while the other of which is designed to provide a "waffle-like" configuration, the aforesaid pressing operation being performed at a predetermined ele-vated temperature. The uncured layers may preferably be formed of glass fibers bound in a thermosetting binder.
The operation yields a one-piece core panel having a sub-stantially smooth, flat surface which is ideal for use in mounting a decorative treatment thereto and which provides requisite rigidity without any safrifice in either sound absorption, thermal conductance or flame safety charaater-istics.
; The present invention also further comprises method and apparatus for creating a molded integrated frame member about the perimeter of a dual density panel of the type described, said frame being of greater height than the maximum thickness of the panel so that the resulting panel assembly, when mounted within furniture, partitions, wall 4.

~QQ8~

panels, and other interior design components, serves to incorporate an air space into the structure and behind the acoustical panel to significantly increase acoustical absorption characteristics, the resulting air space being provided in a simple and yet inexpensive manner by forming a rigid, plastic frame about the panel with a frame thick-ness sufficient to create a dead air space of the desired , 4a.

`` lOQ8451 volume. The completed product may then be wrapped in suitable decorative treatment, placed upon a substrate and then covered with decorative treatment or the like whereby the interior air space cooperates with a dual density board to further signifi-cantly increase the sound attenuation characteristic. If de-sired, the dead air space may be filled with low density acoustical blanket fill, for example, so as to prevent the occurrence of a resonant panel response characteristic of partitions which might lead to a reduction in performance of the panel under certain conditions.
The frame provides a rigid assembly not provided by the core panel per se; provides a precise assembly thickness capable of lying within a very tight tolerance range; and provides the highly desirable dead air space.
It is therefore one object of the present invention to provide a novel one-piece dual density core panel for use in applications requiring a combination of characteristics not heretofore being capable of being obtained in one-piece panel structures, the present invention providing an apparatus having a dual density construction and exhibiting the salient characteristics of rigidity, tackability, excellent sound absorption, thermal insulation properties and high flame safety levels wherein the core panel so obtain~d is easy to use, mount and decorate.
Another object of the present invention is to provide a novel method for producing a one-piece, dual density panel of the type described above.
Still another object of the present invention is to provide a novel core panel construction and method for producing same, the construction including an integrated ., , ~`

, iO~8~Sl dead air space therewith by providing a rigid frame about the dual density core panel to yield a simplified inexpensive structure providing increased sound attenuation at a considerable savings in both cost and materials.
These objects are attained by the invention which con-templates a one-piece dual density panel which has specified thermal and acoustical insulat~on properties comprising a fib-rous material dispersed in a thermosetting resin binder. The panel has a first surface and a second surface, with the first surface of the panel being a substantially smooth planar surface and the second surface of the panel including a substantially regular pattern of relatively uniform indentations. The panel has a first density substantially uniformly along the entire first surface of the panel and substantially throughout the entire thickness of the panel at the locations of the indenta-tions and it has a second density along the second surface of the panel between the indentations, with the first density being substantially greater than the second density~ The panel also includes a rigid molded frame fused to the panel along the perimeter thereof and it has a frame width substantially greater than the maximum thickness of the panel so as to create - a shallow recess defined by the frame and the second surface of the panel. That shallow recess is adapted to form a hollow air space when mounted upon a surface.
The invention also contemplates a method for forming one-piece dual density panels having a desired maximum thickness and specified thermal and acoustic ratings comprising providing at least one panel having a first surface and a second surface.
The panel formed comprises a fibrous material dispersed in an uncured thermosetting resin binder, and the panel further has -5a-~ lQQ84~1 `
~-~ substantiall~ uniform thicknes~ a~ least as great as the desired maximum thi~ckness and has a substant~ally uniform density. The first surface of the panel ~s eng~ged with a plate having a sub-stantially smootll planar surface, the second surface of the panel is engaged w~th a tool having a contoured surface including a substantially regular pattern of rclatively uniform projcctiolls thereon. The tool is urged towards the plate with the panel therebetween while maintaining the panel at a temperature sufficient to cure the thermosetting resin binder, whereby a substantially regular pattern of relatively uniform indentations is formed in the second surface of the panel, and whereby the density of the panel substantially uniformly increases along the entire first surface of the panel and substantially throughout the entire thickness of the panel at the locations of the pro-jections. The density of the panel remains substantially less than the increased density along the second surface of the panel between the projections.
In a preferred embodiment, the invention additionally contemplates a method for forming one-piece dual density panels having a desired maximum thickness and specified thermal and acoustic ratings, the method comprisiny providing at least one panel having a first surface and a second surface. The panel formed comprises a fibrous material dispersed in an uncured thermosetting resin binder, and the panel further has a sub-stantially uniform thickness at least as great as the desired maximum thickness and has a substantially uniform density and at the same time being substantially free from prior compression or heating. The first surface of the substantially uncompressed and unheated panel containing the uncured thermosetting resin binder is engaged with a plate having a substantially smooth planar surface, the second surface of the panel is engaged with -5b-l~S4~;1 a tool having a contoured surface including a substalltially regular pattern oE relatively uniform projections forming a waffle-like pattern. The tool is urged towards the plate with the panel therebetween in order to compress the panel and form a substantially regular pattern of relatively uniform indentations in the second surface of the panel while maintaining the panel at a temperature sufficient to cure the thermosetting resin binder `
in a single step, and whereby the density of the panel su~-stantially uniformly increases along the entire first surface of the panel and substantially throughout the entire thickness of the panel at the locations of the projections. The density of the panel remains substantially less than the increased density along the second surface of the panel between the projections.

.

-5c-.
.~, ~84S1 A BRIEF DESCRIPTION OF THE FIGURES
The above as well as other objects of the present invention will become apparent when reading the accompanying description and drawings in which:
Figure la is a top perspective view of a one-piece dual density panel designed in accordance with the principles of the present invention;
Figure lb shows a bottom perspective view of thc panel of Figure la;
Figure 2 is an elevational view showing a preferred manner in which the core panel of Figures la and lb is formed;
Figure 3 shows an elevational view similar to that shown in Figure 2 and is useful in describing the manner in which the densities of the dual density board may be readily adjusted,and Fig. 3a is an alternate embodiment thereof showing a reversal in the pattern of the projections.
Figures 4 - 10 show perspective views of various applications and embodiments of the dual density panel of the present invention.
Figure 11 shows a perspective view of a one-piece molded acoustical frame assembly for providing a sound attenuating structure incorporating a dead air space therein.
Figure 12 shows a sectional view of the structure of Figure 11 further incorporating acoustical fill in the dead air cavity.
Figure 13 shows a simplified perspective view of apparatus used for forming the assembly of Fi~ures 11 and 12.

DETAILED DESCRIPTION OF THE INVENTION
AND ITS PREFERRED EMBODIMENTS
Figures la and lb show a one-piece dual density core panel 10 which is formed of a fibrous material such as, for example, fibre glass and which is provided with one surface 10a which is substantially smooth and flat while the ' ', opposite surface 10b is provided with a regular pattern of depressions or indentations 10c wherein the raised portions of surface 10b surrounding each of the indentations 10c sub-stantially define a "waffle-like" pattern. The panel may be formed of fibre glass of a substantially uniform density and bound together with a thermosetting binder. Suitable binders are phenolic, silicone, melamine and urea resins.
The fibrous material may be fibre gla~s, or mineral wool, for example.
The preferred manner in which the one-piece dual density core panel is formed is to provide a substantially flat sheet of uncured material of reasonably uniform (and known) thickness and density. The sheet is placed between a first metallic plate 12 (see Fig. 2) having a substantially smooth, flat surface 12a. A metallic forming tool 13 having a regular pattern of truncated round, shaped or pointed substantially conical projections 13a, which may or may not be flattened at their tops 13c, is pressed upwardly into the aforementioned uncured sheet 10. The pictured tool member is truncated to show one preferred shape of the indentation tool. Other shapes such as triangular or round could be just as successfully employed, and are part of this inven-- tion.
The tool 13 is moved by drive means D (which may be piston driven) toward surface 12a of cooperating metallic member 12 and is pressed into the uncured panel until the 7.

7~ u! ~

~Q~34Sl recesses 13b between projections 13a are uniformly spaced a distance Tl from surface 12a, distance Tl being the total thickness of the panel after undergoing the forming treat-ment shown in Figure 2. The process is maintained at a temperature level sufficient to cure and set the binder by heating means H.

: ~ 7a.

,:,. ..
. . , ,::
:~ ~ :. : :

As can clearly be seen, the portions of the panel being treated between the upper surface 13c of each projection 13a and surface 12a of cooperating metallic plate 12 undergoes maximum compression whereas the portion of the panel between recesses 13b and surface 12a undergoes minimal compression in the region between projections. The effective compression between a pair of adjacent projections such as, for example, the projections 13c and 13c' of Figure 2 can be seen to taper off to either side of the upper surfaces 13c so as to "merge" in the region Rl between projections thereby providing a substantially constant high density region immediately at and beneath surface lOa and providing a substantially constant low density region at and immed-iately beneath the projections formed in the panel by the recesses 13b of tool 13, these lowest density regions being designated R2.
The manner in which the densities in regions Rl and R2 may be most easily adjusted can best be understood from a consideration of Figure 3 wherein the height of the single projection 13a of tool 13 (only one such projection being shown in Figure 3 for purposes of simplicity) is adjusted to provide requisite adjustments in core densities therefore providing a corresponding change in the indentation formed in the core panel 10. In the example shown in Figure

3, and providing there is no change in the thickness or density of the uncured sheet, increasing the depth of the indentation from an indentation formed by a projection having Sl a height A to an indentation formed by a projection having a height B, increases the density of the board in the region of surface lOa while the overall thickness of the board is controlled by the final spacing of elements 12 and 13. Thus, the stress density characteristics o the fibrous core panel are determined by the distance Tl-A ~or Tl-B, as the case may be).

, r'': 8a.

~ 845i Dual density panels of the type described have been formed with equal success over the range of design para-meters such as:
Surface densities, 3-30 lbs. per cubic foot;
typical core panel thicknesses 1/8 - 3 inches; typical tool indentation depth from 1/16 - 2 7/8 inches; typical core indentation surface area from 0.02-114 sq. inches (per indenta-tion-chosen to control uniformity of density at the working surface); typical projection configurations, flat top, round top, pointed top, curved top, square, rectangle or trapezoidal top; available forms: flat sheets, sheets having a curved radius and die-cut parts.
Some examples of one-piece dual density core panels formed in accordance with the method of the present inventio are as follows:
1. Two uncured layers each having a substantially uniform thickness of one inch and a density of 0.85 lbs. per cubic foot were treated with a tool to form indentations having a depth of 3/16 inches. The core panel is formed of fiber glass in a thermosetting binder of phenolic resin. The two members 12 and 13 were pressed together to form a one-piece panel having a total thickness of 3/8`' and a surface density at the non-textured side of 9 lbs. per cubic foot. The temperature level maintained during the treatment was in the range from 350 to 450~F and the members 12 and 13 preferably being maintained in position as shown, for example, in Figure 2 for a period of 0.5 minutes.
2. Three uncured layers each having a sub-stantially uniform thickness of one inch and a density of 1.00 lb. per cubic foot were treated with a tool to form indentations having a depth of 5/8 inches. The core panel is formed of fibre glass in a thermosetting binder of phenolic .~i _ 9_ .

1q! Q'~3451 resin. The two members 12 and 13 were pressed together to form a one-piece panel having a total thickness of 1" and a surface density at the non-textured side of 8.0 lbs. per cubic foot. The temperature level maintained during the treatment was in the range from 350 to 450F and the members 12 and 13 preferably being maintained in position as shown, for example, in Figure 2 for a period of 1.5 minutes.
A core panel produced in accordance with the methods set forth hereinabove may be utilized to replace any standard absorber product in any acoustical application where standard materials do not supply the needed properties. In field uses, the core panels may be exposed to continuous operating temperatures of the order of 450F without experiencin~ any degradation in either appearance or operating charac-tcristics.
For example, as shown in Figure 4, the finished one-piece dual density panel 10 may be positioned with its textured side against a metallic or other barrier septum 14. Although not shown in Figure 4, the core panel may be coextensive with the septum 14.
In other applications, a pair of one-piece dual density core panels 10 and 10' may be arranged back-to-back with the textured surfaces in engagement wherein the smooth surfaces are provided on both sides of the resultant core.
As shown in Figure 6, the one-piece core panels 10 and 10' may be arranged substantially in the same manner as shown in Figure 5, but with a metallic or other dense acoustical barrier 15 positioned therebetween to add additional significant transmission loss acoustical qualities to the resultant com-posite structure so as to absorb sound and even totally blocksound transmission through the composite assembly.

', :
: :'.............. :

The smoother surface lOa of the one-piece core panel assembly lends itself readily to the application of a decorative material or finish enabling "tiles" of the core panel to be mounted upon a suspended ceiling framework 16 as shown in Figure 7 with the decoratively finished side facing downward to provide an aesthetically appealing acoustical ceiling tile having the requisite thermal, acous-tical, strength and flame withstanding characteristics.
Figure 8 shows the manner in which two panels 10 and 10' may be mounted with their smooth faces in engage-ment for utilization in acoustical furniture to increase available dead air space area under fabrics or blanket insulations.
Figure 9 shows the manner in which one suitable decorative sheet or coating is affixed to the flat surface lOa of panel 10 to provide a tile or panel lending itself readily for use as an acoustical wall or ceiling treatment.
Figure 10 shows an arrangement in which a pair of one-piece dual density panels 10 and 10' are arranged with the textured surfaces in engagement and wherein the smoother exterior surfaces are covered with a decorative fabric or sheet 17 (also as shown in Figure 9). The need for an adhesive to affix the back-to-back core panels is eliminated through the employment of the channels 18-21 each having channel arms which are arranged to embrace the marginal por-tions of the flat surfaces lOa and lOa' to provide an aesthetically appealing edge finish around all four edges of :` 11.
~, :. ' '': ;

the assembly as well as to securing the assembly components together. One of the decorative channels 18 may be provided with suitable openings 18a for receiving threaded fasteners 22 having eyelets for suspending the decorative panels, for example, from a ceiling. The channels 18-21 may be secured to the panels by a force-fitting arrangement, by adhesive means, by providing "corner lla.

. , ; , .:

l~qS4~
keys" at the engaging corner of each decorative channel or any other suitable mounting assembly may be provided.
The pattern of projections provided on the tool may be the reverse of that shown in Figures 2 and 3. For example, as shown in Figure 3a, the truncated conical shaped projections 13 may be replaced by truncated conical shaped recesses 13' surrounded by and defined by the projections 14'. The resulting dual densities substantially conform to those obtained with the tool of Figures 2 and 3.
Figures 11 and 12 show another preferred embodiment 30 of the present invention which is comprised of a dual density one-piece core panel member 10 of the type described hereinabove and shown, for example, in Figures 1-3a. Member 10 has molded thereto a rigid fr,ame comprised of the four joined sides 31a-31d, adjacent ends of said sides being joined to one another forming corners Cl-C4 and further being joined to the sides of the core panel 11 so as to form a unitary one-piece structure. The sides 31a-31d defining the frame are formed of a suitable plastic material such as, for example, epoxy or a suitable thermosetting plastic and is produced by forming the frame in a molding process and then fusing the frame to the panel. Alternatively, the frame may be both molded and fused to the panel at the same time.
As can best be appreciated from Figure 12, the width D2 of the frame members measured in the direction shown in Figure 12 is substantially greater than the maximum thickness Dl of the core panel 10 so as to create a recess defined by the frame and textured or dimpled surface lOa to create a dead air space 32.
;

l~æ~s~ ~

The structure 30 may be employed in contract furniture, partitions, wall panels and other interior applications. For example, the structure of Figure 11 may - be completely wrapped in a fabric and mounted as a panel upon an interior wall, the textured or dimpled surface lOa being positioned to confront such an interior wall. For example, the panels may be formed in the conventional 4 ft.
x 8 ft. size and mounted as finishing panels for a room or other enclosed areas. As another alternative, the assembly may be employed as an integral part of a free standing acoustical screen. For example, considering a section of S ft. x 5 ft. screen supported by two legs of six inch height for a space or work area divider, the central portion of the acoustical screen may, for example, be a 5 ft. x 5 ft. masonite center spacer board having frames of the same dimension mounted on opposite surfaces of the spacer board with the smooth surfaces lOb (Figs. 6 and 12) consti-tuting the exterior surfaces of the screen assemblies and thereby defining a pair of dead air spaces. The exterior surfaces may then be covered with a suitable fabric treatment~
As another application, the free standing acoustical screens described hereinabove may be provided with further sound attenuating qualities by filling each dead air space 32 (see Fig. 12) with a suitable acoustical blanket fill 33 such as, for example, a low density fiber glass or mineral wool blanket having a density less than 4 lbs. per cubic foot, to eliminate any resonant panel effect. Alternatively, a 13.

~ ~ .
- . . . ..

34~

uniform density board (rigid or semi-rigid) may be inserted in the dead air space; or sprayed sound absorptive fill may be used therein.
As another application somewhat similar to that shown in Figure 5 or Figure 10, assemblies of the type shown 13a.

::, .: . .. .
- ~
: . .

: -:

45~ :

in Figure 11 may be mounted in back-to-back fashion so as to define an interior dead air space of double volume (i.e. twice D2 minus Dl) and the resulting back-to-back assembly may be utilized as acoustical ceiling baffles.
Applications of the frame assembly are about as broad as those for the individual core panel described hereinabove.
The acoustical characteristics are greater than those obtained through the use of panels not incorporating such frames and is further an extremely advantageous cost efficient method for achieving panel rigidity, maximum acoustical absorption and required thickness tolerances at extremely low cost as compared with products and processes presently available.
Maximum absorption is attained by use of the dual density rigid acoustical absorber panel 10 which has its lower density per cubic foot surface, i.e. the dimple surface lOa, facing the dead air space while the smooth surface facilitates the application of fabrics treatment, spraying or other treatment or finish of the panel for decorative appeal purposes. The molding process utilized to form the frame members makes it possible to control panel thickness to a very high degree of precision which is not capable of being achieved by the core panel per se.
In addition, the materials of the frame member and core panel are highly compatible with one another so as to assure simple and yet intimate fusion and joining between the elements forming the assembly.

-- 14.

. : :: .:
:, :
- . - ~ . , . ::

Figure 13 shows one technique for forming the frame about a dual density core panel 10 in which a heated (metallic) substrate 40 is provided with an elongated recess or channel 41 filled with an epoxy or other suitable thermosetting material. One edge of the core panel 10 is ~ positioned immediately above and adjacent to one side of : the , 14a.

~s~

recess 41 filled with the epoxy 42. The recess has a width D which conforms to the desired width of the final frame to be formed as was described hereinabove (Fig. 12). Heat is applied to the substrate 40 sufficient to set the epoxy and fuse the adjacent edge of the core panel thereto. Channel 41 is coated with a suitable release agent so as to facilitate removal of the epoxy or other thermosetting material once it has become set. Each of the remaining three sides of the panel are created in a similar fashion to form the completed frame.
Although there has been described a preferred embodiment of this invention, many variations and modifica-tions will now be apparent to those skilled in the art.
Therefore, this invention is to be limited, not by the ~ !

specific disclosure herein, but only by the appended claims.

.

Claims (13)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A one-piece dual density panel having specified thermal and acoustical insulation properties comprising a fibrous material dispersed in a thermosetting resin binder, said panel having a first surface and a second surface, said first surface of said panel being a substantially smooth planar surface and said second surface of said panel including a substantially regular pattern of relatively uniform indentations, said panel having a first density substantially uniformly along said entire first surface of said panel and substantially throughout the entire thickness of said panel at the locations of said indentations and a second density along said second surface of said panel between said indentations, said first density being substantially greater than said second density, and said panel including a rigid molded frame fused to said panel along the perimeter thereof and having a frame width substantially greater than the maximum thickness of said panel so as to create a shallow recess defined by said frame and said second surface of said panel, said shallow recess being adapted to form a hollow air space when mounted upon a surface.

2. The one-piece dual density panel of Claim 1 wherein said fibrous material comprises fiberglass.

3. The one-piece dual density panel of Claim 1 wherein said thermosetting resin binder is selected from the group consisting of phenolic, silicone, malamine and urea resins.

4. A method for forming one-piece dual density panels having a desired maximum thickness and specified thermal and acoustic ratings, said method comprising providing at least one panel having a first surface and a second surface, said panel comprising a fibrous material dispersed in an uncured thermosetting resin binder, said panel further having a substantially uniform thickness at least as great as said desired maximum thickness and a substantially uniform density, engaging said first surface of said panel with a plate having a substantially smooth planar surface, engaging said second surface of said panel with a tool having a contoured surface including a substantially regular pattern of relative-ly uniform projections thereon, and urging said tool towards said plate with said panel therebetween while maintaining said panel at a temperature sufficient to cure said thermo-setting resin binder, whereby a substantially regular pattern of relatively uniform indentations is formed in said second surface of said panel, and the density of said panel substan-tially uniformly increases along said entire first surface of said panel and substantially throughout the entire thick-ness of said panel at the locations of said projections, while the density of said panel remains substantially less than said increased density along said second surface of said panel between said projections.

5. A method for forming one-piece dual density panels having a desired maximum thickness and specified thermal and acoustic ratings, said method comprising providing at least one panel having a first surface and a second surface, said panel comprising a fibrous material dispersed in an uncured thermosetting resin binder, said panel further having a substantially uniform thickness at least as great as said desired maximum thickness and a substantially uniform density and being substantially free from prior compression or heating, engaging said first surface of said substantially uncompressed and unheated panel containing said uncured thermosetting resin binder with a plate having a substantially smooth planar surface, engaging said second surface of said panel with a tool having a contoured surface including a substantially regular pattern of relatively uniform projections forming a waffle-like pattern, and urging said tool towards said plate with said panel there-between in order to compress said panel and form a substantially regular pattern of relatively uniform indentations in said second surface of said panel while maintaining said panel at a temperature sufficient to cure said thermosetting resin binder in a single step, whereby the density of said panel substantially uniformly increases along said entire first surface of said panel and substantially throughout the entire thickness of said panel at the locations of said projections, while the density of said panel remains substantially less than said increased density along said second surface of said panel between said projections.

6. The method of Claim 4 or Claim 5 wherein said relatively uniform projections on said tool form the major portion of the surface of said tool, and said surface of said tool between said projections is formed by a substantially regular pattern of relatively uniform indentations thereon.

7. The method of Claim 4 or Claim 5 wherein said thermosetting resin binder is selected from the group consisting of phenolic, silicone, melamine and urea resins.

8. The method of Claim 4 or Claim 5 wherein said substantially uniform thickness of said uncured panel is substantially greater than said desired maximum thickness.

9. The method of Claim 4 or Claim 5 wherein said fibrous material comprises fiberglass.

10. The method of Claim 4 or Claim 5 wherein said uniform projections include tapered side walls.

11. The method of Claim 5 further comprising the steps of molding a frame structure conforming to the perimeter of the panel and fusing the frame structure to the panel so as to form a shallow recess defined by the frame and the textured surface of the panel.

12. The method of Claim 11 wherein the frame is formed of a material compatible with the material of the core panel member so as to be intimately fusible therewith.

13. The method of Claim 12 wherein the frame is made of a material taken from the group comprised of epoxy or a suitable thermosetting plastic material.