FIELD OF THE INVENTION

The application relates to the field of construction materials, and more particularly to sound attenuating construction materials.

BACKGROUND

Existing sound attenuation materials are expensive to manufacture and install, have high mass and/or weight, and/or fail to provide adequate sound attenuation.

As such, there is a need for improved sound attenuation materials.

SUMMARY OF THE INVENTION

These and other objects are accomplished in the construction materials with engineered sound attenuating properties and methods, which are described in the present disclosure. In particular, according to at least one embodiment, a new sound attenuation material includes a plurality of particles, each comprising a core and an elastic or compliant coating around the core, and a matrix surrounding the plurality of particles, where the core is denser than the matrix. The core may also be denser than the elastic or compliant coating. The elastic or compliant coating may include filler material having a density lower than that of the matrix, such as polymer or glass micro-balloons. The particles may be spherical or another shape, such as irregular shards, and may be of various shapes. The plurality of particles may include several different masses of particles. The matrix may be a construction material. The matrix may comprise gypsum, cement, concrete, polymer, or ceramic. The matrix and/or the elastic or compliant coating may be foamed. The matrix may include reinforcing fillers, which may have one or more of: polypropylene fibers, gravel, carbon nanotubes, starch additives, paper fibers, and glass fibers.

In at least some embodiments, the core of at least one of the plurality of particles may be metal, mineral, or ceramic, for example, steel or tungsten. The elastic coating of at least one of the plurality of particles may be an elastomeric polymer. The elastic coating of at least one of the plurality of particles may be polyurethane, silicone, or rubber.

In at least a further embodiment, the core of at least one of the plurality of particles may have a diameter of 10 nm to 100 cm and density of 2.0 to 20 g/cc, and the elastic coating of the at least one of the plurality of particles may have a thickness of 10 nm to 20 mm, an elastic modulus of 0.005-0.5 GPa, and a density of 0.01 to 2.0 g/cc. In some embodiments, the core of the at least one of the plurality of particles has a diameter of 1 mm to 5 cm, and the elastic coating of the at least one of the plurality of particles has a thickness of 0.1 mm to 10 mm, an elastic modulus of 0.01 to 0.1 GPa, and a density of 0.05 to 0.3 g/cc.

A new method of manufacturing sound attenuating materials includes adding an elastic or compliant coating to core particles and drying the coating, mixing the coated core particles into a matrix material, and pouring the mixture into a mold. The core particles are denser than the matrix material and may also be denser than the elastic or compliant coating. The method may also include drying the mixture. The core particles may have a range of masses. Each mass of core particle corresponds to a resonant frequency, and the masses of the core particles are selected based on pre-selected frequencies to be attenuated by a final construction material. The proportion of each mass core particle is determined based on a predetermined desired level of attenuation at the corresponding resonant frequency. The method may also include foaming the matrix material by air- or gas-entrainment, blowing agents, polyurethane reactions, or vacuum application.

In some embodiments, a sound attenuation material comprises a plurality of particles, each particle in the plurality of particles comprising a core and an elastic or compliant coating around the core, and a matrix surrounding the plurality of particles. In at least one embodiment, the core is denser than the coating. In at least a further embodiment, the coating is foamed.

The elastic or compliant coating may further comprise filler material having a density lower than that of the matrix. The filler material may contain polymer or glass micro-balloons.

In at least one embodiment, one or more of the plurality of particles are spherical. The plurality of particles may also comprise several different masses of particles.

The matrix, in at least some embodiments, is a construction material. Accordingly, the matrix may comprise gypsum, cement, concrete, polymer, ceramic, reinforcing fillers, and combinations thereof. The reinforcing fillers may include one or more of polypropylene fibers, gravel, sand, carbon nanotubes, starch additives, paper fibers, glass fibers, and combinations thereof.

In at least one embodiment, the core of at least one of the plurality of particles is metal, mineral, ceramic, steel, and/or tungsten. The core of at least one of the plurality of particles may have, for instance, a diameter of 10 nm to 100 cm and a density of 2.0 to 20 g/cc. In some embodiments, the core of at least one of the plurality of particles may have a diameter of 1 mm to 5 cm.

In at least a further embodiment, the elastic coating of at least one of the plurality of particles is an elastomeric polymer. The elastic coating may also comprise polyurethane, silicone, and/or rubber. In additional embodiments, the elastic coating of at least one of the plurality of particles has a thickness of 10 nm to 20 mm, an elastic modulus of 0.005-0.5 GPa, and/or a density of 0.01 to 2.0 g/cc. The elastic coating of at least one of the plurality of particles may also have a thickness of 0.1 mm to 10 mm, an elastic modulus of 0.01 to 0.1 GPa, and/or a density of 0.05 to 0.3 g/cc.

The plurality of particles in at least one embodiment is pan-coated. The plurality of particles in a further embodiment is coated using a fluidized bed coating process. The plurality of particles may also be homogenously distributed in the matrix. Additionally, at least one particle in the plurality of particles may comprise of more than one core.

In some embodiments, a method of manufacturing sound attenuation materials comprises adding a foamed elastic or compliant coating to core particles and drying the coating, mixing the coated core particles into a matrix material, and pouring the mixture into a mold. In at least one embodiment, the core particles are denser than the matrix material. The method may also further comprise drying the mixture. In additional embodiments, the method comprises foaming the matrix material by air- or gas-entrainment, blowing agents, polyurethane reactions, and/or vacuum application.

In at least some embodiments, the core particles have a range of masses. Each mass of a core particle may additionally correspond to a resonant frequency, wherein the masses of the core particles are selected based on pre-selected frequencies to be attenuated by a final construction material, and wherein the proportion of each mass core particle is selected based on a predetermined desired level of attenuation at the corresponding resonant frequency.

In further embodiments, a sound attenuation material comprises a plurality of particles, each comprising a core and an elastic or compliant coating uniformly distributed around the core, and plasterboard comprising a matrix surrounding the plurality of particles. The sound attenuation material may comprise a core that is denser than both the coating and the matrix. The matrix may further be denser than the coating. In at least one additional embodiment, the coating and/or the matrix are foamed. The matrix may additionally comprise an elastic material, including any of the elastic materials described herein.

A method of manufacturing sound attenuation particles in some embodiments comprises preparing a polymer solution by dispersing polydimethylsiloxane and a plurality of acrylic microspheres in mineral spirits, charging a pan coater with a plurality of metal cores, coating the plurality of metal cores with the polymer solution, and blowing hot air on to a particle bed of the pan coater during the coating, thereby generating a plurality of sound attenuation particles comprising the plurality of metal cores coated with the polymer solution.

In at least one embodiment, the coating of the plurality of metal cores with the polymer solution further comprises spraying the polymer solution onto the plurality of metal cores using an air atomized spray gun. Such spraying may be achieved over the course of, for example, eight hours.

In at least one embodiment, a plurality of metal cores may be added to a system whereby metal cores are fluidized using forced air, and polymer solution may be sprayed onto the plurality of metal cores at intervals (e.g., intervals ranging from 10 seconds to several minutes) such that the cores become coated with a dried polymer. In some embodiments, the polymer spray and drying process may be repeated (e.g., 100 to 1000 to several thousands of times) to achieve various polymer thicknesses (e.g., 0.1 mm to 10 mm).

The plurality of metal cores in some embodiments comprises a plurality of steel balls. The plurality of steel balls may have diameters selected from the group consisting of l/4th of an inch, l/8th of an inch, l/16th of an inch, and combinations thereof. The plurality of metal cores in additional embodiments comprises a plurality of tungsten pellets.

A method of manufacturing sound attenuation materials in some embodiments comprises manufacturing sound attenuation particles according to one or more of the methods described herein and manufacturing a sound attenuation matrix by mixing a base material with a first portion of water, thereby generating a slurry; mixing a foaming agent with a second portion of water, thereby generating a foam; adding the foam to the slurry, thereby generating a sound attenuation matrix, and adding the sound attenuation particles to the sound attenuation matrix, thereby generating the sound attenuation material. In at least an additional embodiment, the method further comprises pouring the sound attenuation material into a mold; and/or drying the sound attenuation material. The base material may be either plaster or cement. In at least one embodiment, 7 wt% to 25 wt% of the sound attenuation particles are added to the sound attenuation matrix.

A method of manufacturing a sound attenuation material in some embodiments comprises manufacturing sound attenuation particles according to one or more of the methods described herein; adding the sound attenuation particles to polyurethane expanding insulation foam, thereby generating a foam composite, and allowing the foam composite to set, thereby generating the sound attenuation material.

In some embodiments, a sound attenuation material comprises the sound attenuation material made according to one or more of the aforementioned methods.

It should be appreciated that the purpose of the sound attenuation particles and/or materials described herein is to provide a sound attenuation response for one or more frequencies present in various sounds. Such a response is provided by diminishing the amount of energy present in a sound wave. Thus, the materials and construction of a given type of sound attenuation particle, including the size, coating, amount of filler material, and type of filler material, affect the range and type of sound attenuation response.

Foaming, including the foaming of the matrix and/or the coating described herein, is a method of producing or modifying materials, including sound attenuation materials, to reduce their density, resulting in softer and/or lighter versions of these materials. Examples of foaming methods include, for instance, air entrainment, blowing agents, polyurethane reactions that produce carbon dioxide, vacuum applications, and incorporating low-density fillers (e.g., low- density micro-balloons). These foaming methods may be used to foam coatings of the particles to reduce the density of the particles, as well as the matrix surrounding the particles. Therefore, foamed material and foamed sound attenuation particles require different manufacturing techniques than producing non-foamed, standard sound attenuation particles.

Additionally, the foaming of sound attenuation particles affects both the density and the sound attenuation response of those particles. Specifically, a foamed version of a given type of sound attenuation particle will result in a different sound attenuation response than a nonfoamed, standard version of the same type of sound attenuation particle. For instance, various low-density fillers can be used for a foamed coating, such as microspheres or micro-balloons. The ability to control the density of the particles and apply a low-density, foamed coating is important for even particle dispersion and settling. Foamed coatings can therefore reduce the density of particles independent of the density of the matrix (which is not part of the particles themselves and instead refers to the material surrounding the coated particles).

In the context of sound attenuation particles, it has been discovered that applying a foamed coating to these particles provides distinct advantages, including beneficial acoustic band gap properties and lower overall composite density, as shown in further detail herein.

Therefore, based on the foregoing and continuing description, the subject invention in its various embodiments may comprise one or more of the following features in any non-mutually- exclusive combination:

• A sound attenuation material comprising a plurality of particles, each particle in the plurality of particles comprising a core and an elastic or compliant coating around the core; and a matrix surrounding the plurality of particles;

• The core of the plurality of particles being denser than the coating;

• The elastic or compliant coating being foamed;

• The elastic or compliant coating further comprising filler material having a density lower than that of the matrix;

• The filler material comprising polymer or glass micro-balloons;

• One or more of the plurality of particles being spherical;

• The plurality of particles comprising several different masses of particles;

• The matrix surrounding the plurality of particles being a construction material;

• The matrix comprising one or more of gypsum, cement, concrete, polymer, ceramic, and reinforcing fillers;

• The reinforcing fillers comprising one or more of polypropylene fibers, gravel, sand, carbon nanotubes, starch additives, paper fibers, and glass fibers;

• The core of at least one of the plurality of particles being made of one or more of metal, mineral, ceramic, steel, and tungsten;

• The core of at least one of the plurality of particles having a diameter of 10 nm to 100 cm;

• The core of at least one of the plurality of particles having a density of 2.0 to 20 g/cc;

• The core of at least one of the plurality of particles having a diameter of 1 mm to • The elastic coating of at least one of the plurality of particles being an elastomeric polymer;

• The elastic coating comprising one or more of polyurethane, silicone, and rubber;

• The elastic coating of at least one of the plurality of particles having a thickness of 10 nm to 20 mm;

• The elastic coating of at least one of the plurality of particles having an elastic modulus of 0.005-0.5 GPa;

• The elastic coating of at least one of the plurality of particles having a density of 0.01 to 2.0 g/cc;

• The elastic coating of at least one of the plurality of particles having a thickness of 0.1 mm to 10 mm;

• The elastic coating of at least one of the plurality of particles having an elastic modulus of 0.01 to 0.1 GPa;

• The elastic coating of at least one of the plurality of particles having a density of 0.05 to 0.3 g/cc;

• At least one of the plurality of particles being pan-coated and/or fluidized-bed- coated;

• The plurality of particles being homogenously distributed in the matrix;

• At least one of the plurality of particles comprising more than one core;

• A method of manufacturing sound attenuation materials comprising adding a foamed elastic or compliant coating to core particles and drying the coating; mixing the coated core particles into a matrix material; and pouring the mixture into a mold;

• The method further comprising drying the mixture;

• The method further comprising foaming the matrix material by air- or gasentrainment, blowing agents, polyurethane reactions, and/or vacuum application;

• The core particles being denser than the matrix material;

• The core particles having a range of masses;

• Each mass of a core particle corresponding to a resonant frequency;

• The masses of the core particles being selected based on pre-selected frequencies to be attenuated by a final construction material;

The proportion of each mass core particle being selected based on a predetermined desired level of attenuation at the corresponding resonant frequency;

A sound attenuation material comprising a plurality of particles, each particle comprising a core and an elastic or compliant coating uniformly distributed around the core; and plasterboard comprising a matrix surrounding the plurality of particles;

The core being denser than the coating and/or the matrix;

The matrix being denser than the coating;

The coating and/or the matrix being foamed;

The matrix comprising an elastic material;

A method of manufacturing sound attenuation particles comprises preparing a polymer solution by dispersing polydimethylsiloxane and a plurality of acrylic microspheres in mineral spirits; charging a pan coater and/or fluidized bed coater with a plurality of metal cores; coating the plurality of metal cores with the polymer solution; and blowing hot air on to a particle bed of the pan coater and/or fluidized bed coater during the coating, thereby generating a plurality of sound attenuation particles comprising the plurality of metal cores coated with the polymer solution;

The coating of the plurality of metal cores with the polymer solution further comprising spraying the polymer solution onto the plurality of metal cores using an air atomized spray gun;

The spraying of the polymer solution being over the course of eight hours;

The plurality of metal cores comprising a plurality of steel balls;

The plurality of steel balls having diameters of l/4th of an inch, l/8th of an inch, and/or 1/16th of an inch;

The plurality of metal cores comprising a plurality of tungsten pellets;

A method of manufacturing a sound attenuation material comprising manufacturing sound attenuation particles according to one or more of the methods described herein; and manufacturing a sound attenuation matrix by mixing a base material with a first portion of water, thereby generating a slurry; mixing a foaming agent with a second portion of water, thereby generating a foam; adding the foam to the slurry, thereby generating a sound attenuation matrix; and adding the sound attenuation particles to the sound attenuation matrix, thereby generating the sound attenuation material;

• The method further comprising pouring the sound attenuation material into a mold;

• The method further comprising drying the sound attenuation material;

• The matrix material being either plaster or cement;

• 7 wt% to 25 wt% of the sound attenuation particles being added to the sound attenuation matrix;

• A method of manufacturing a sound attenuation material comprising manufacturing sound attenuation particles according to one or more of the methods described herein; adding the sound attenuation particles to polyurethane expanding insulation foam, thereby generating a foam composite; and allowing the foam composite to set, thereby generating the sound attenuation material; and

• A sound attenuation material made according to one or more of the aforementioned methods.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1A illustrates a composite material with designer filler material for sound attenuation, according to an embodiment of the present disclosure.

Figure IB is a graph that displays the amount of amplitude reduction over a range of frequencies for four types of sound attenuation particles (control cement, steel beads, steel beads with silicone, and steel beads with foamed silicone).

Figure 1C is a graph that displays the amount of transmission loss over a range of frequencies for the same four types of sound attenuation particles as in Figure IB (i.e., control cement, steel beads, steel beads with silicone, and steel beads with foamed silicone).

Figure 2A illustrates a composite sound-attenuating panel, according to an embodiment of the present disclosure.

Figure 2B illustrates sound attenuation in the composite panel of Figure 2A, according to an embodiment of the present disclosure.

Figure 3 is a size distribution comparison of uncoated and coated tungsten particles.

Figure 4 illustrates an acoustic attenuation test conducted on a panel similar to or the same as shown in Figure 2A.

Figure 5 shows impedance tube testing results for a wallboard according to an embodiment of the present disclosure, as well as controls.

Figure 6 shows STC values from impedance tube, thickness, and density for the same samples as Figure 5.

Figure 7 shows ultrasonic testing results for commercial wallboard samples.

Figure 8 shows ultrasonic testing results for a wallboard sample according to an embodiment of the present disclosure, as well as a control.

Figure 9 is a flow diagram of a method for manufacturing sound attenuation particles, according to an embodiment of the present disclosure.

Figure 10A is a flow diagram of a method for manufacturing a sound attenuation material, according to an embodiment of the present disclosure.

Figure 10B is a flow diagram of a method for manufacturing a sound attenuation matrix, according to an embodiment of the present disclosure.

Figure 11 is a flow diagram of a further method for manufacturing a sound attenuation material, according to an embodiment of the present disclosure.

Figure 12 shows impact sound testing for two cement samples according to embodiments of the present invention, as well as a control.

Figure 13 shows impact sound testing for a concrete sample according to an embodiment of the present invention, as well as a control.

Figure 14 shows sound transmission results from a tapping machine for a concrete sample according to an embodiment of the present invention, as well as a control.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Solutions to the problem of expensive and/or inadequate sound attenuation materials are found as set forth in the following.

This application details construction materials with engineered sound attenuating properties, and methods in terms of various exemplary embodiments.

In various embodiments described herein, sound-absorbing panels, coatings, and foams are created by incorporating designer filler materials. The fillers are layered particulates with specific geometries and mechanical properties that impart particular sound attenuating properties.

Figure 1A illustrates a composite material with designer filler material for sound attenuation, according to an embodiment of the present disclosure. As shown in Figure 1A, the particles consist of a dense core 110 surrounded by an elastic or compliant coating 120. They are characterized by their layered structure and mechanical properties. The particles act as locally resonant structures within a surrounding matrix 130.

Turning now to Figure IB, a graph displays the amount of amplitude reduction over a range of frequencies for four types of sound attenuation particles (control cement 140, steel beads 142, steel beads with silicone 144, and steel beads with foamed silicone 146). As can be seen, the foamed particles 146 (i.e., the steel beads with foamed silicone) provided much greater amplitude reduction than the non-foamed version of the same particles at nearly all the frequencies tested.

Similarly, Figure 1C is a graph of the amount of transmission loss over a range of frequencies for the same four types of sound attenuation particles as in Figure IB (i.e., control cement 140, steel beads 142, steel beads with silicone 144, and steel beads with foamed silicone 146). As can be seen, the foamed particles 146 (i.e., the steel beads with foamed silicone) provided greater transmission loss than the non-foamed version of the same particles at nearly all the frequencies tested.

Figure 2A illustrates a composite sound-attenuating panel, according to at least one embodiment. Specifically, Figure 2A shows particles such as those illustrated in Figure 1, where the surrounding matrix 130 is configured into plasterboard, which may be used as a building material. The dense core 110 can oscillate within the elastic coating 120, positioned within the matrix 130, attenuating sound energy depending on its frequency as shown in Figure 2B.

Figure 2B illustrates sound attenuation in the composite panel of Figure 2A, according to at least one embodiment. At and around the resonant frequency of the dense cores, the cores vibrate, absorb the sound energy, and transform it into kinetic energy, reducing the sound energy delivered to the other side of the matrix/plasterboard. In Figure 2B, the sound source 200 emits a sound 202, partially reflected 204 by the board 206 and partially transmitted 208 through the board. However, the transmitted sound energy 208 is attenuated by absorption of the sound energy by particles 210 as the sound energy passes through them, causing them to vibrate, as shown by the bands around the particles 210.

The matrix may be gypsum, cement, concrete, polymer, ceramic, or another material in which the particle filler can be embedded. Foamed versions of these materials may also incorporate filler. Foaming may be achieved through known methods such as air- or gasentrainment, blowing agents, polyurethane reactions, or vacuum application. The matrix material may also include additional structural components such as reinforcing fillers, and may be incorporated in a composite structure itself, such as a laminated panel. These materials have excellent sound-absorbing properties at low weight. Reinforcing fillers may be those known to be of use in the matrix material in various circumstances, such as polypropylene fibers, gravel, sand, and/or carbon nanotubes. For example, commercial gypsum wallboard often includes starch additives, paper fibers, and/or glass fibers. Gypsum wallboard in which particle filler is included for sound attenuation purposes may also retain these other fillers.

The dense core may be metal, mineral, or ceramic. The core is preferably steel or tungsten but may be any material that is denser than the surrounding matrix. The elastic coating may be polyurethane, silicone, rubber, or any other elastomeric polymer. The elastic coating is preferably filled with low-density filler, such as polymer or glass micro-balloons, to control its mechanical properties and, importantly, its density and the total density of the particles. By way of example, low-density filler in the elastic matrix may make the particles softer, which may be advantageous in some applications.

The particles may have a core size of 10 nm to 100 cm, in some embodiments 1 mm to 5 cm, core density of 2.0 to 20 g/cc, coating thickness of 10 nm to 20 mm, in some embodiments 0.1 mm to 10 mm, coating elastic modulus of 0.005-0.5 GPa, in some embodiments 0.01 to 0.1 GPa, and coating density of 0.01 to 2.0 g/cc, in some embodiments 0.05 to 0.3 g/cc. It should be appreciated that a coating density of as low as 0.05 or 0.01 g/cc indicates foamed coatings as described herein, since un-foamed polymer coatings generally have a density range of between 1.0 to 2.0 g/cc. Larger particles may be used in large composite structures, such as concrete slabs and walls used for highway sound isolation, to achieve a very low-frequency sound attenuation. In concrete slabs, large particles of about 5 cm or up to 20 cm may be used.

The acoustic band gap frequency of the composite material depends on the size and density of the core and the elastic modulus of the elastic coating of the filler particles. The attenuation frequency range generally increases with decreasing particle core size and broadens with particle core size distribution. Each particle size has a different frequency response, and the amount of attenuation achieved at a given frequency is primarily a factor of the concentration of the particles with the appropriate frequency response. Therefore, fewer particles at a given size and more particles at nearby sizes will reduce the attenuation at the frequency corresponding to the given size but increase attenuation at the frequencies correlating to the nearby sizes, effectively reducing the magnitude of attenuation while broadening the attenuation effect across the frequency spectrum. In this way, the sound attenuating properties of the composite can be controlled. Multiple particle sizes can be combined to cover larger frequency spans, resulting in broadband sound isolation in the audible range, similar to examples 8 and 11 detailed below. Alternatively, select frequencies can be isolated for designer sound attenuating properties. By selecting low frequencies for attenuation, vibration isolation may be achieved, such as for roadways and other structures such as bridges or building foundations. Vibration isolation may improve material durability. Total filler particle concentrations must be kept at levels that ensure adequate mechanical strength of the overall material for the given application. In some instances, excessively high filler particle concentrations result in unacceptable material weakness. The described sound-attenuating materials may also exhibit superior crack propagation performance, as cracks in the matrix material may be halted at the intersection of the matrix material with a filler particle.

The particles may be created by various coating methods that result in a layered structure with an inner core and outer coating. The coating is preferably well distributed over the particles. In some embodiments, there may be multiple cores per particle. Such multiple-core particles may result from manufacturing a block of cores in the matrix material and then shredding the block to obtain the individual particles. The preferred coating methods are pan-coating and/or fluidized bed coating. In the pan coating method, particles are rolled in a drum, and the coating material precursor solution is applied, often while being dried and/or cured with hot air and/or moisture. In the fluidized bed coating method, particles are moved around (z.e., fluidized) using air and simultaneously sprayed with the coating material precursor solution, often while being dried and/or cured with hot air and/or moisture. Other types of mixers may also be used to produce the particles. Coating thickness and uniformity are essential for precise control of particle density. However, acceptable sound attenuation may often be achieved without such precise density or shape control. Therefore, manufacturing methods that produce highly spherical particles may depend on the cost versus the density control needed for a given application.

By controlling the coating thickness and using a coating and core density that span that of the matrix precursor, the density of the particles can be tuned to match the surrounding matrix. This is important to achieve even particle distribution throughout the matrix and prevent separation due to differences in the matrix precursor density and particle density. An even distribution of the coating on the particles leads to uniform density to avoid settling or floating particles with different densities. In the case of multiple particle sizes in the same material, the densities of each can be matched to the matrix to ensure homogeneous dispersion in the surrounding matrix.

Turning now to Figure 9, a flow diagram for a method 900 for manufacturing sound attenuation particles is shown. Specific embodiments of the method are described in further detail in the Examples below. Generally, this method comprises a step 902 of preparing a polymer solution; a step 904 of charging a pan-coater with a plurality of metal cores; a step 906 of coating the plurality of metal cores with the polymer solution; and a step 908 of blowing hot air on to a particle bed of the pan coater. Step 908 may occur during coating step 906.

In at least one embodiment, the polymer solution is prepared by dispersing poly dimethylsiloxane and a plurality of acrylic microspheres in mineral spirits.

In at least an additional embodiment, the coating step 906 further comprises a sub- step 910 of spraying the polymer solution onto the plurality of metal cores using an air atomized spray gun. Such spraying may be achieved over a period of, for instance, eight hours.

The aforementioned plurality of metal cores may comprise a plurality of steel balls and/or a plurality of tungsten pellets. In some embodiments, the plurality of steel balls have diameters selected from the group consisting of l/4th of an inch, l/8th of an inch, 1/16th of an inch, and combinations thereof.

Another flow diagram is shown in Figure 10A, which displays a method 1000 for manufacturing a sound attenuation material. Specific embodiments of the method are described in further detail in the Examples below. Generally, this method comprises a step 1002 of manufacturing sound attenuation particles, a step 1004 of manufacturing a sound attenuation matrix, and a step 1006 of adding the sound attenuation particles to the sound attenuation matrix, thereby generating the sound attenuation material. It should be appreciated that step 1002 of manufacturing sound attenuation particles may itself comprise any method described herein for manufacturing sound attenuation particles, including, but not limited to, method 900.

In at least one embodiment, step 1004 of manufacturing the sound attenuation matrix comprises further sub-steps shown in the flow diagram of Figure 10B, specifically: a sub-step 1008 of mixing a base material with a first portion of water, thereby generating a slurry; a substep 1010 of mixing a foaming agent with a second portion of water, thereby generating a foam; and a sub-step 1012 of adding the foam to the slurry, thereby generating the sound attenuation matrix.

Method 1000 may additionally comprise, as shown in Figure 10A, step 1014 of pouring the sound attenuation material into a mold; and step 1016 of drying the sound attenuation material.

In at least one embodiment, the base material is either plaster or cement.

In at least a further embodiment, between 7 wt% to 25 wt% of the sound attenuation particles are added to the sound attenuation matrix.

Turning now to Figure 11, a flow diagram is shown of a method 1100 for manufacturing a sound attenuation material. Specific embodiments of the method are described in further detail in the Examples below. Generally, method 1100 comprises step 1102 of manufacturing sound attenuation particles; a step 1104 of adding the sound attenuation particles to polyurethane expanding insulation foam, thereby generating a foam composite; and a step 1106 of allowing the foam composite to set, thereby generating the sound attenuation material.

It should be appreciated that step 1102 of manufacturing sound attenuation particles, like step 1002, may itself comprise any method described herein for manufacturing sound attenuation particles, including, but not limited to, method 900.

It should further be appreciated that various embodiments include a sound attenuation material manufactured according to one or more of the methods described herein.

EXAMPLES

Example 1: Preparation of Coated 14" Diameter Steel Cores

Particles consisting of 14" diameter steel ball cores encapsulated in an elastic coating were prepared in a lab-scale pan coater. A polymer solution was prepared by dispersing 226 g polydimethylsiloxane (100% Silicone Sealant from DAP) and 6.8 g acrylic microspheres (920 DE80 d30 from Akzo Nobel) in 912 g mineral spirits (Odorless Mineral Spirits from Klean Strip). The pan coater was charged with 500 g of steel cores (Low Carbon Steel Balls from McMaster Carr). The density of the starting substrate was 7.7 g/cm ³ . Hot air at 80 °C was blown onto the particle bed during the coating process. The polymer mixture (25 °C) was sprayed onto the steel cores at a rate of 7 mL/min with an air atomized spray gun (WA740 HVLP Plus from Walther Pilot). The coating process was carried out over a period of 8 hrs. The discharged particles exhibited high uniformity and maintained the same sphericity and roundness as the starting core material (>0.9 Krumbein- Sloss shape factors). The resulting particles had a diameter of 10.8 +/- 0.2 mm, coating thickness of 2.2 mm, and density of 1.9 g/cm ³ .

Example 2: Preparation of Coated 1/8" Diameter Steel Cores

Particles consisting of 1/8" diameter steel ball cores encapsulated in an elastic coating were prepared in accordance with the aforementioned procedure. Through the layered coating approach, the density of the particles was reduced from 7.7 g/cm ³ (uncoated) to 2.0 g/cm ³ (coated). The resulting particles had a diameter of 5.4 +/- 0.3 mm and a coating thickness of 1.1 mm.

Example 3: Preparation of Coated 1/16" Diameter Steel Cores

Particles consisting of 1/16" diameter steel ball cores encapsulated in an elastic coating were prepared in accordance with the aforementioned procedure. Through the layered coating approach, the density of the particles was reduced from 7.7 g/cm ³ (uncoated) to 2.2 g/cm ³ (coated). The resulting particles had a diameter of 2.6 +/- 0.3 mm and a coating thickness of 0.5 mm.

Example 4: Preparation of Coated 0.8 mm Diameter Tungsten Cores

Particles consisting of 0.8 +/- 0.1 mm diameter tungsten carbide pellets encapsulated in an elastic coating were prepared in a pan coater. A polymer solution was prepared by dispersing 383 g polydimethylsiloxane (100% Silicone Sealant from DAP) and 11.5 g acrylic microspheres (920 DE80 d30 from Akzo Nobel) in 1160 g mineral spirits (Odorless Mineral Spirits from Klean Strip). The pan coater was charged with 500 g of tungsten pellets (20/40 Tungsten Carbide pellets from TungCo). 20/40 pellets have 90% of their particles between 20 and 40 mesh (U.S. Standard Sieve Series) as described in ASTM E-l 1. Hot air at 80 °C was blown onto the particle bed during the coating process. The polymer mixture (25 °C) was sprayed onto the tungsten cores at a rate of 14 mL/min with an air atomized spray gun. The coating process was carried out over a period of 8 hrs. The discharged particles were uniform in size and exhibited an equivalent degree of sphericity and roundness as the starting core material (>0.9 Krumbein-Sloss shape factors). The resulting particles had a diameter of 1.7 +/- 0.4 mm, coating thickness of 0.45 mm, and density of 2.1 g/cm ³ .

The size distribution (fraction 310 at each diameter 320) of the uncoated tungsten and coated particles are graphically illustrated in Figure 3. The uncoated shot is smaller in size and has a tighter distribution, with a peak fraction of between 0.4 and 0.45 at a diameter of 0.9mm and all shot falling between 0.6mm and 1.1 mm, compared to a peak fraction of the coated particles of just over 0.15 at 1.7mm diameter and a size range of 1mm to 2.2mm.

The results of the tests from Examples 1-4 are also outlined in Table 1.

Table 1. Particle characterization results comparing different substrate sizes and materials.

Example 5: Preparation of Plaster Board with Particles from Example 1

To 1 part water was added, by sifting, 2 parts plaster, which was allowed to soak for 1 min. The slurry was mixed in a Fann blender for 60 sec at 4000 rpm. Separately, 0.1 g of foaming agent ("MasterCell 30" from BASF) and 4 g of water were mixed at 4000 rpm for 60 sec to generate a stable foam. The foam was added to the unfoamed plaster slurry and blended for an additional 60 sec at 4000 rpm. To the thus-prepared slurry was added 20 wt% particles as prepared in Example 1, mixed in by hand. The resulting mixture was poured into a 6" x6" xl/2" oiled glass mold faced with heavy paper stock and allowed to set for 12 hrs. The sample board was then removed from the mold and dried in a convection oven at 70° C for 24 hrs. A measure of the acoustic attenuation was conducted using a pair of 24 kHz transducers in a pitch-catch configuration using a frequency sweep. In such a known configuration, one transducer transmits a frequency against the surface of the sample board, while the other transducer, some distance away on the same side of the sample board, receives the frequency as it is reflected back after propagating along the board surface. Propagation along the board surface is highly correlated to propagation through the board.

Figure 4 illustrates such a configuration, with emitting transducer 400, receiving transducer 402, composite board 404, original signal 406, signal propagating through the surface of the board 408, and finally the signal received at the second transmitter 410. A neat plasterboard was prepared in the same manner as above to serve as a control; it did not contain any coated particles. The thus-prepared composite plasterboard exhibited 65 dB increased attenuation over the control at a center frequency of 3,500 Hz with 3,500 Hz bandwidth (1,750 Hz to 5,250 Hz). The bandwidth is the range over which attenuation is at least 10% of the peak attenuation (65dB). Thus, at least 6.5dB of attenuation was demonstrated between the range from 1,750 to 5, 250 Hz.

Example 6: Preparation of Plaster Board with Particles from Example 2

To 1 part water was added, by sifting, 2 parts plaster, which was allowed to soak for 1 min. The slurry was mixed in a blender for 60 sec at 4000 rpm. Separately, 0.1 g of foaming agent ("MasterCell 30" from BASF) and 4 g of water were mixed at 4000 rpm for 60 sec to generate a stable foam. The foam was added to the unfoamed plaster slurry and blended for an additional 60 sec at 4000 rpm. To the thus-prepared slurry was added 20 wt% particles from Example 2, mixed in by hand. The resulting mixture was poured into a 6" x6" xl/2" oiled glass mold faced with heavy paper stock and allowed to set for 12 hrs. The sample board was then removed from the mold and dried in a convection oven at 70° C for 24 hrs. A measure of the acoustic attenuation was conducted using a pair of 24 kHz transducers in a pitch-catch configuration using a frequency sweep. Neat plasterboard was prepared in the same manner as above to serve as a control; it did not contain any coated particles. The thus-prepared composite plasterboard exhibited 65 dB increased attenuation at a center frequency of 8,500 Hz with 8,000 Hz bandwidth. Example 7: Preparation of Plaster Board with Particles from Example 3

To 1 part water was added, by sifting, 2 parts plaster, which was allowed to soak for 1 min. The slurry was mixed in a blender for 60 sec at 4000 rpm. Separately, 0.1 g of foaming agent ("MasterCell 30" from BASF) and 4 g of water were mixed at 4000 rpm for 60 sec to generate a stable foam. The foam was added to the unfoamed plaster slurry and blended for an additional 60 sec at 4000 rpm. To the thus-prepared slurry was added 20 wt% particles from Example 3, mixed in by hand. The resulting mixture was poured into a 6" x6" xl/2" oiled glass mold faced with heavy paper stock and allowed to set for 12 hrs. The sample board was then removed from the mold and dried in a convection oven at 70° C for 24 hrs. A measure of the acoustic attenuation was conducted using a pair of 24 kHz transducers in a pitch-catch configuration using a frequency sweep. Neat plasterboard was prepared in the same manner as above to serve as a control; it did not contain any coated particles. The thus-prepared composite plasterboard exhibited 60 dB increased attenuation at a center frequency of 14,000 Hz with 15,000 Hz bandwidth.

Example 8: Preparation of Plaster Board with Particles from Examples 1, 2, and 3

To 1 part water was added, by sifting, 2 parts plaster, which was allowed to soak for 1 min. The slurry was mixed in a blender for 60 sec at 4000 rpm. Separately, 0.1 g of foaming agent ("MasterCell 30" from BASF) and 4 g of water were mixed at 4000 rpm for 60 sec to generate a stable foam. The foam was added to the unfoamed plaster slurry and blended for an additional 60 sec at 4000 rpm. To the thus-prepared slurry was added 7 wt% particles from Example 1, 7 wt% particles from Example 2, and 7 wt% particles from Example 3, which were mixed in by hand. The resulting mixture was poured into a 6" x6" xl/2" oiled glass mold and allowed to set for 12 hrs. The sample board was then removed from the mold and dried in a convection oven at 70° C for 24 hrs. A measure of the acoustic attenuation was conducted using a pair of 24 kHz transducers in a pitch-catch configuration using a frequency sweep. Neat plasterboard was prepared in the same manner as above to serve as a control; it did not contain any coated particles. The thus-prepared composite plasterboard exhibited 50 dB increased attenuation at a center frequency of 10,000 Hz with 20,000 Hz bandwidth. Example 9: Preparation of Foam Cement Board with Particles from Example 4

Unfoamed cement slurry was mixed at a water:cement ratio of 0.44 in a Fann blender in accordance with API Specification 10A by mixing 141 g water with 354 g of API Portland Class H hydraulic cement. Separately, 0.1 g of foaming agent ("MasterCell 30" from BASF) and 4 g of water were mixed at 4000 rpm for 60 s to generate a stable foam. The foam was added to the unfoamed cement slurry and blended for an additional 60 s at 4000 rpm. To the thus-prepared foamed slurry was incorporated 25 wt% particles from Example 4 with a mixing blade attached to a handheld drill until a uniform distribution of particles was achieved. The resulting mixture was poured into a 6" x6" xl/2" oiled glass mold faced with heavy paper stock and allowed to set for 12 hrs. A measure of the acoustic attenuation was conducted using a pair of 24 kHz transducers in a pitch-catch configuration using a frequency sweep. Neat plasterboard was prepared in the same manner as above to serve as a control; it did not contain any coated particles. The thus-prepared composite plasterboard exhibited 55 dB increased attenuation at a center frequency of 14,000 Hz with 16,000 Hz bandwidth.

Example 10: Preparation of a Composite Sandwich Plaster Board

A composite sandwich panel was prepared by joining two plaster panels with an elastic layer. To 1 part water was added, by sifting, 2 parts plaster, which was allowed to soak for 1 min. The slurry was mixed in a blender for 60 sec at 4000 rpm. Separately, 0.2 g of foaming agent ("MasterCell 30" from BASF) and 8 g of water were mixed at 4000 rpm for 60 sec to generate a stable foam. The foam was added to the unfoamed plaster slurry and blended for an additional 60 sec at 4000 rpm. The resulting mixture was poured into two 6" x6" xl/2" oiled glass mold faced with heavy paper stock and allowed to set for 12 hrs. The sample boards were then removed from the mold and dried in a convection oven at 70° C for 24 hrs. To 200 g of polydimethylsiloxane (PDMS) was added 75 g of 20/40 tungsten carbide pellets. The polymer was mixed by hand until a homogenous mixture was achieved. In the bottom of a 6" x6" x5/8" mold was placed a prepared plasterboard. To the top of the plasterboard was added a 1/8" thick layer of the polymer tungsten mixture. A prepared plasterboard was placed on top of the polymer layer. The assembly was lightly clamped to allow squeeze-out of the excess polymer and to ensure even spacing between the plaster panels. Two neat plasterboards were prepared in the same manner as above and adhered together with epoxy to serve as a control. The thus-prepared composite plasterboard exhibited 50 dB increased attenuation at a center frequency of 10,000 Hz with 20,000 Hz bandwidth.

Example 11: Preparation of Expanding Polyurethane Foam Board with Particles from Examples 1, 2, and 3

In another embodiment, particles from Examples 1, 2, and 3 were incorporated into polyurethane expanding insulation foam (GREAT STUFF from Dow Chemical Company) to create an acoustic insulation filler. Two hundred grams of GREAT STUFF foam was discharged from the aerosol canister into a beaker. To the foam was added 10 wt% particles from Example 1, 10 wt% particles from Example 2, and 10 wt% particles from Example 3, which were mixed in by hand until a uniform distribution of particles was observed. The foam composite was placed in a 6" x6" xl" oiled glass mold and allowed to set for 12 hrs. A control foam sample was also produced that contained no particles. A measure of the acoustic attenuation was conducted using a pair of 24 kHz transducers in a pitch-catch configuration using a frequency sweep. The thus-prepared composite foam insulation exhibited 30 dB increased transmission loss at a center frequency of 10,000 Hz with a bandwidth of 20,000 kHz.

Example 12: Preparation of Cement Slabs with Particles from Example 1

In yet another embodiment, a large composite cement slab was prepared with particles from Example 1. To a 5 cu. ft. rotary drum cement mixer was added 17 kg of water and 40 kg of Portland cement (Type I-II from Hawaiian Cement). The slurry was mixed for 5 min. To the thus-prepared slurry was added 25 wt% particles from Example 1, and the slurry was mixed for an additional 5 min. The composite slurry was poured into a 20" x20" x4" mold and allowed to set for 24 hrs. A measure of the acoustic attenuation was conducted using a pair of 24 kHz transducers in a pitch-catch configuration using a frequency sweep. The thus-prepared composite cement slab exhibited 50 dB transmission loss at a center frequency of 2,000 Hz with a bandwidth of 4,000 Hz compared to a cement slab with no particles.

Example 13: Testing of Enhanced Construction Materials

Impedance tube and ultrasonic acoustic testing of soundproof wallboard according to embodiments of the present disclosure were conducted to demonstrate its enhanced resistance to both airborne and structure-borne acoustic transmission.

Cored (1 1/4" diameter) papered gypsum wallboard samples, both according to embodiments of the present disclosure and commercial versions, were tested according to a modified version of ASTM E2611 - 09, Standard Test Method for Measurement of Normal Incidence Sound Transmission of Acoustical Materials Based on the Transfer Matrix Method, using a transmission loss and impedance tube. This method measures transmission loss as a function of frequency for airborne sound. Lightweight (light) and heavier (neat) gypsum samples (beta calcium sulfate hemihydrate, water, surfactant foam, and no other additives) were tested along with the enhanced samples containing the additive according to an embodiment of the present disclosure (same nominal density as light). Commercial sound-reducing construction materials A and B were also tested as controls. The transmission loss results are shown in Figure 5, while the calculated STC (Sound Transmission Class) values and corresponding sample thickness and density measurements are shown in Figure 6, each showing results for the light 508, neat 506, enhanced 502, material A 510 and material B 504 samples. In Figure 6, the left bar 602 is the thickness in cm, the center bar 604 is the STC, and the right bar 606 is the density in g/cc. It can be seen that the enhanced sample, according to an embodiment of the present disclosure, substantially outperforms the other samples in STC.

Papered wallboard samples (6" x 6" x 1/2") were tested using an ultrasonic transducer setup with source and receiver transducers, amplifiers, signal generator, and data acquisition card. Measurements were made in an indirect mode with the source and receiver on the same side of the sample. This test indicates resistance to structure-borne acoustic transmission as a function of frequency. Results for commercial boards A 704 and C 702 are shown in Figure 7, while the results for control 802 and enhanced (embodiment of the present disclosure) 804 boards are shown in Figure 8. Control and enhanced boards 802, 804 have the same density as commercial board A 704. Again, the enhanced sample 804 substantially outperforms the others.

Example 14: Preparation of Coated Stainless Steel Cores using Fluidized Bed Coater

Stainless steel (SS) shot particles were encapsulated with an elastic coating using a fluidized bed coater. Specifically, the SS shot particles were primed and air-dried with volatile siloxane to improve the quality and speed of adhesion with a polymer solution. This polymer solution was prepared by dispersing polydimethylsiloxane (100% Silicone Sealant) and acrylic microspheres (thermoplastic microsphere encapsulating a gas) in mineral spirits (Odorless Mineral Spirits). The fluidized bed coater was then charged and fluidized with the siloxane primed SS shot particles. During the coating process, the fluidized bed coater was kept at a temperature of 80°C. The polymer solution (at 25 °C) was sprayed onto the primed SS shot particles with an air atomized spray gun. The resultant coated particles were uniform in size and exhibited an equivalent degree of sphericity and roundness to the starting core material (>0.9 Krumbein- Sloss shape factors).

The SS shot particles for this example can have a diameter ranging from 0.149 to 1.680 mm. 10 to 10,000 mF of volatile siloxane can be used to prime the SS short particles before coating. For the polymer solution, between 0.85 and 170 kg polydimethylsiloxane and between 0.034 to 6.8 kg acrylic microspheres can be combined in 2.55 to 510 kg mineral spirits. The polymer solution may have 0.5-2% acrylic microspheres and a specific ratio of microspheres/silicone/mineral spirits of between 1/50/150 to 1/12/38. The fluidized bed coater can be charged and fluidized with 5-1000 kg of the siloxane primed SS shot particles. Spraying of the solution onto the primed SS short particles can be achieved at a rate of 10-20 mL/min with the air atomized spray gun. The entire coating process may be carried out over a period of 8-24 hrs. Resulting particles have a diameter of 0.25-4.76 mm, a coating thickness of 0.1-3.0 mm, and a density of 2-3 g/cm ³ .

Example 15: Preparation and Testing of Sound Attenuating Cement and Concrete

Samples of sound attenuating cement and concrete were generated. Typical samples had a size of 8” x 8” x 2” and a density of 16 lbs per gallon. For the cement samples, as a base material, Portland cement (from Quikrete) that had an appropriate water-to-cement ratio to achieve the targeted density (e.g., 16 lbs per gallon) was used. For the concrete samples, sand and gravel were incorporated into the cement base material, thereby resembling the concrete used in flooring. The concrete for this example had a ratio of 1:2:2 parts by volume of cement:gravel:sand, as well as an admixture (a liquid superplasticizer from Iksung), resulting in a ratio of approximately l:2:2:0.1 parts by volume of cement:gravel:sand:plasticizer.

Each of two different types of sound attenuating particles were then mixed into both the cement and concrete, generating two cement samples and two concrete samples. Specifically, the two types of sound attenuating particles tested were: (1) stainless steel (SS) shot particles encapsulated with a first polymer coating, and (2) tungsten carbide (WC) particles encapsulated with a second polymer coating. The respective coating for both types of particles was applied via spraying in a fluidized bed coater.

The first set of sound attenuation particles were generated by taking 6 kg of SS shot particles (16/35 stainless steel) and applying the first polymer coating, which has a formulation of 1254.0 g mineral spirits, 416 g silicone (737 silicone from Dow), and 11.4 g microballoons (Expancel 920 DE 80 d30 microballoons). The second set of sound attenuation particles were generated by taking 5.22 kg of tungsten carbide particles (14/24 tungsten carbide) and applying the second polymer coating, which has a formulation of 1386.0 g mineral spirits, 460 g silicone (737 silicone from Dow), and 12.6 g microballoons (Expancel 920 DE 80 d30 microballoons). Both sets of polymer solutions were generated by adding the mineral spirits to the silicone and stirring at 400-500 rpm for 30 min. The microballoons were then added to the solution and further stirred at 450 rpm for 20 min. The resultant polymer solution was filtered through a paint mesh filter, which removes unmixed chunks of the polymer solution, thereby resulting in the polymer solution being sufficiently homogenous to prevent clocking of the spray nozzle and to provide sufficient coating.

Each of the two sets of sound attenuation particles were added into the cement and the concrete at approximately 8.6 wt% of the total dry mixture, resulting in homogeneous slurries with good handling properties (e.g., easy to pour and well distributed) and final cured materials with evenly distributed particles (e.g., the particles are evenly distributed and/or separated throughout the slurry and the final cement and/or concrete block, with minimal to no agglomeration of particles).

For testing, a testing box was constructed to acoustically isolate a sound meter for the impact sound transmission testing of concrete and cement samples. The box was insulated with acoustic foam and a space was made on the side for sound meter insertion and a hole was created at the top for placing samples. A ball drop fixture was built for dropping steel and rubber coated steel balls from a consistent height and placed above the sample and box. Direct and indirect impact noises were used, either by directly dropping the ball on the surface/impacting the surface with a rubber hammer, or by utilizing a wooden “bridge” which allowed the impact sound to be generated just above the surface. A Larson-Davis sound meter was used to collect impact sound transmission data. A rubber hammer was also used to create direct and indirect impact sounds. In addition to the ball drop and hammer-based impacts, a tapping machine (Cesva MI005) with electronically controlled impacts was used to ensure that repeatable impact noises were being generated. The tapping machine was situated above tested samples with a space below for the sound meter. The middle three hammers of the tapping machine were used to generate impact sounds. Acoustic noise samples were recorded for ten seconds and processed for spectral analysis.

Results from direct impact hammer testing of the cement samples at high amplitude indicate a decrease in sound transmission at low frequencies. The two different sound attenuation particle types tested had different levels of sound attenuation in the cement samples, as shown in Figure 12. Trace 1202 shows the behavior of a control sample, while trace 1204 shows the first set of sound attenuation materials (i.e., the SS-based particles) and trace 1206 shows the second set of attenuation materials (i.e., the WC-based particles). As can be seen, both of the particle types showed lowered acoustic transmission most consistently at frequencies ranging from 8-300 Hz. At these frequencies, the cement samples with the WC-based particles (trace 1206) performed the best at reducing sound impacts.

Testing of the concrete samples from direct impact testing using the ball drop and hammer as impact sources displayed a similar behavior to the cement samples. Figure 13 shows the behavior of a control sample (trace 1302) as compared to the concrete sample with the WC- based particles (trace 1304). As can be seen, the WC-based particles show reduced sound transmission over a large frequency range (e.g., a 5-12 dB decrease at frequencies up to 300Hz).

Finally, testing was performed on the concrete samples using the tapping machine to create a highly repeatable impact sound. Results from this test are shown in Figure 14, with a control sample (trace 1402) compared against the concrete sample with the WC-based particles (trace 1404). The WC-based particles showed up to a 10 dB reduction at frequencies ranging from 10 Hz to 160 Hz.

The results of the aforementioned testing show the acoustic band gap properties of the sound attenuation materials at low frequencies (e.g., 10 to 500 Hz), which decreases sound transmission substantially (e.g., by 5 to 30 dB) at these frequencies.

While specific preferred embodiments and examples of fabrication and testing of the invention have been illustrated and described, it will be clear that the invention is not so limited. Numerous modifications or alterations, changes, variations, substitutions and equivalents will occur to those skilled in the art without deviating from the spirit and scope of the invention and are deemed part and parcel of the invention disclosed herein.

Further, the invention should be considered as comprising all possible combinations of every feature described in the instant specification, appended claims, and/or drawing figures which may be considered new, inventive and industrially applicable.

Multiple variations and modifications are possible in the embodiments of the invention described here. Although certain illustrative embodiments of the invention have been shown and described here, a wide range of modifications, changes and substitutions are contemplated in the foregoing disclosure. While the above description contains many specifics, these should not be construed as limitations on the scope of the invention but rather as exemplifications of one or another preferred embodiment thereof. In some instances, some features of the present invention may be employed without a corresponding use of the other features.

Accordingly, it is appropriate that the foregoing description be construed broadly and understood as being given by way of illustration and example only, the spirit and scope of the invention being limited only by the claims which ultimately issue.