Patent Description:
The use of hearing protective and noise attenuating devices are well known, and various types of devices have been considered. Such devices include earplugs and semi-aural devices including foam or rubber materials that are inserted into, or placed over, the ear canal of a user to physically obstruct the passage of sound waves into the inner ear.

Compressible or "roll-down" type earplugs generally comprise a compressible, resilient body portion and may be made of suitable slow recovery foam materials. The earplug may be inserted into the ear canal of a user by first rolling it between fingers to compress the body portion, then pushing the body portion into the ear canal, and subsequently allowing the body portion to expand to fill the ear canal.

Push-to-fit type earplugs have also been considered, and may include a compressible attenuating portion and a stiff portion that extends from the attenuating portion. To insert a push-to-fit type earplug, the user grasps the stiff portion and pushes the attenuating portion into the ear canal with an appropriate level of force. The attenuating portion compresses as it is accommodated in the ear canal. Push-to-fit type earplugs may allow the earplug to be quickly and easily inserted in an ear canal, and may promote hygiene by minimizing contact with the attenuating portion of the earplug prior to insertion.

<CIT> describes an earplug, comprising: a sound attenuating element; and a stem; wherein the sound attenuating element comprises a flange which extends rearwardly over a portion of the stem; and wherein the sound attenuating element and the stem are integrally formed of a resilient compressible material, in particular the resilient compressible material is an extruded foam material. It is described that foamed materials may be of an open or closed cell material, and that in a more preferred embodiment at least about <NUM>% by volume of the overall cell volume will include closed cells. <CIT> also describes a method of manufacturing an earplug comprising: forming a hollow tube of a resilient compressible material (in particular said forming the hollow tube comprising extruding the tube of a foam material); permanently deforming the hollow tube to form a closed solid portion; allowing an open portion of the hollow tube to remain adjacent to the closed portion; pivoting the open portion outwardly and over the closed portion to delimit a sound attenuating element and a stem. It is described that the resulting closed portion has a greater density than the open portion and that the closed portion forms the stem of the earplug when the open portion is hinged backward into the sound attenuating position.

Although push-to-fit type earplugs exhibit desirable characteristics in various applications, they may be costly and may pose difficult manufacturing challenges.

The present invention provides an earplug including a body having a sound attenuating portion and a semi-rigid stem portion having a relatively greater stiffness than the sound attenuating portion. The body is made entirely of a closed-cell, slow-recovery foam, the sound attenuating portion having a first density ρ1 and the stem portion having a second density p2, and p2 is greater than <NUM>ρ1 (i.e. ρ2 > <NUM>ρ1). The sound attenuating portion is chemically bonded to the stem portion.

In some embodiments, the present disclosure provides methods of making an earplug described herein, which are two-shot molding processes as set out in claims <NUM> and <NUM>.

The above summary is not intended to describe each disclosed embodiment or every implementation. The Figures and the Detailed Description, which follow, more particularly exemplify illustrative embodiments.

The disclosure may be further explained with reference to the appended Figures, wherein like structure is referred to by like numerals throughout the several views, and wherein:.

This disclosure presents the disclosed subject matter by way of representation and not limitation. It should be understood that numerous other modifications and embodiments can be devised by those skilled in the art which fall within the scope of this disclosure.

An earplug that provides hearing protection for a user, and a method of making an earplug, is provided in the present disclosure. An earplug according to the present disclosure includes a body having a sound attenuating portion and a semi-rigid stem portion having a relatively greater stiffness than the sound attenuating portion. The body is made of a closed cell, slow-recovery foam. The density of the sound attenuating portion may be relatively lower than the density of the stem portion, such that at least part of the sound attenuating portion may be comfortably inserted into the ear canal of a user and the relatively stiffer stem portion may be grasped by a user to handle the earplug. The sound attenuating portion has a first density ρ1 and the stem portion has a second density p2, and | p2 > <NUM>ρ1|.

The present disclosure further provides methods of making an earplug that minimizes difficult and expensive manufacturing techniques while providing a push-to-fit type earplug that may be easily handled and comfortably worn. Methods include providing a mold having a first unvented cavity in the form of a stem and a second vented cavity in the form of a sound attenuating portion. Methods include two-shot molding processes. As detailed infra, in exemplary embodiments, an exemplary earplug as described herein may be made by a two-shot molding process including the steps of dispensing foamable material into an unvented cavity of a mold, partially curing the foamable material in the unvented cavity, dispensing foamable material into a vented cavity of the mold, and curing the foamable materials in the unvented and vented cavities, wherein as the foamable materials cure, a chemical bond is formed between them to form a push-to-fit type earplug including a compliant sound attenuating portion and a relatively stiffer and/or denser stem portion, and in other exemplary embodiments, a sound attenuating portion may be formed in a first shot and the stem portion formed in a second shot. Upon curing the materials, a push-to-fit type earplug is formed including a sound attenuating portion having a first average density and the stem portion having a second average density that is greater than <NUM> times the first average density.

<FIG> show an exemplary push-to-fit type earplug <NUM> according to the present disclosure. In an exemplary embodiment, earplug <NUM> includes a body made entirely of closed cell foam. The body has a first end <NUM> and a second end <NUM>, and includes a sound attenuating portion <NUM> and a semi-rigid stem portion <NUM>. Stem portion <NUM> is partially surrounded by sound attenuating portion <NUM>, and is partially exposed to allow a user to grasp stem portion <NUM> to handle earplug <NUM> and to facilitate insertion of earplug <NUM> into an ear canal of a user. Stem portion <NUM> does not extend to first end <NUM> and only sound attenuating portion <NUM> is present at first end <NUM>. Only stem portion <NUM>, and not sound attenuating portion <NUM>, is present at second end <NUM>. That is, earplug <NUM> includes a leading end section formed entirely of less stiff and/or less dense foam, a rear section formed entirely of stiffer and/or denser foam, and an intermediate section including stiffer and/or denser foam covered by the less stiff and/or less dense foam.

In an exemplary embodiment, sound attenuating portion <NUM> has a tapered or cone shape, and has a diameter at its widest point that is greater than a diameter of stem portion <NUM>. In various other embodiments shown in <FIG>, for example, sound attenuating portions <NUM>, <NUM>, <NUM>, <NUM>, respectively, may be hemisphere-shaped, bullet-shaped, bell-shaped, mushroom-shaped, or otherwise shaped to provide a desired fit or to suit a particular application.

During insertion of earplug <NUM>, stem portion <NUM> provides a handle which may be gripped by a user. Earplug <NUM>, and specifically sound attenuating portion <NUM>, is brought proximate to the user's ear and inserted into the ear canal. Sound attenuating portion <NUM> compresses as it is positioned, and stem portion <NUM> provides sufficient stiffness to facilitate insertion. In use, sound attenuating portion <NUM> is positioned substantially within an ear canal to block the passage of sound and stem portion <NUM> extends outwardly from the ear canal to provide a handle to remove the earplug.

In various exemplary embodiments, sound attenuating portions <NUM> may include a flange <NUM> extending outwardly and defining a flange cavity <NUM>. Flange <NUM> may collapse inwardly into flange cavity <NUM> upon insertion into an ear canal of a user.

In an exemplary embodiment, stem portion <NUM> exhibits relatively greater rigidity or stiffness than sound attenuating portion <NUM>, without introducing hard edges or surfaces that may reduce comfort of a wearer of earplug <NUM>. Stem portion <NUM> provides sufficient rigidity that earplug <NUM> may be positioned for use at least partially in the ear of a user by pushing sound attenuating portion <NUM> into the ear canal with an appropriate force. That is, earplug <NUM> having a sufficiently stiff stem portion <NUM> combined with an appropriate sound attenuating portion <NUM> allows earplug <NUM> to be positioned for use at least partially in the ear of a user without the need to first compress or "roll down" sound attenuating portion <NUM>. Direct insertion without the need to first compress or "roll down" sound attenuating portion <NUM>, for example, promotes hygiene by limiting contact with sound attenuating portion <NUM> prior to placement in the ear. Stem portion <NUM> also exhibits an appropriate level of flexibility such that it may slightly deform to the contours of the ear canal when positioned for use, as discussed in greater detail herein.

The body is made entirely of a closed-cell, slow-recovery foam. Accordingly, sound attenuating portion <NUM> and stem portion <NUM> are both made of a slow-recovery foam. Slow recovery foam does not immediately return to its original shape after compression, but rather expands relatively slowly to its original shape. A stem portion made of slow recovery foam, and not including an additional non-foam stiffener element, provides a unique feel to a user handling the earplug. Further, a stem portion made of slow recovery foam is able to flex, bend and compress, for example, when a portion of earplug <NUM> is inserted into an ear canal of a user. As a result, a stem portion made of a slow-recovery foam, as opposed to a solid plastic, elastomeric, rubber or non-foam material, for example, may provide a more comfortable fit as perceived by a user of earplug <NUM>. Additionally, an earplug <NUM> including a sound attenuating portion <NUM> and stem portion <NUM> made of a slow recovery foam may provide the ability of both sound attenuating portion <NUM> and stem portion <NUM> to compress when inserted into an ear canal, thus better conforming to a user's ear canal. Such an earplug is more likely to remain comfortable in a user's ear canal, even during prolonged periods of use.

Creep compliance measures the evolution of strain with time at a constant load. Greater compliance suggests an increased propensity of material to conform under a load. A slow recovery foam that is sufficiently stiff to be pushed into an ear canal while exhibiting creep compliance within an appropriate range is able to at least slightly conform to an ear canal of a user and may result in greater perceived comfort by a user, especially when used for longer periods of time. For example, the combination of a stem portion <NUM> made entirely of slow recovery foam and having such creep compliance values may provide a particularly desirable fit.

Stem portion <NUM> may be made of one or more materials and processes resulting in a specified hardness. A desired hardness may depend on the dimensions of stem portion <NUM> such that stem portion <NUM> exhibits a desired stiffness. For example, an earplug <NUM> exhibiting relatively high hardness values in combination with slow recovery foam properties, for example, provides a unique feel to a user when handling the earplug and upon insertion into an ear canal.

Sound attenuating portion <NUM> and stem portion <NUM> are made from one or more foam materials that can suitably bond to, and are otherwise compatible with, one another. Sound attenuating portion <NUM> and stem portion <NUM> are joined by a chemical bond. The terms "chemical bonding" or "chemically bonded" refer to physical phenomena responsible for the attractive interactions between atoms and molecules. Such bonds include covalent and ionic bonds, as well as hydrogen and Van der Waal's bonds and can depend on the manufacturing process, chemical composition and available functional groups of the foam of sound attenuating portion <NUM> and/or stem portion <NUM>, as discussed in greater detail herein. In an exemplary embodiment, chemical bonding between foam sound attenuating portion <NUM> and foam stem portion <NUM> is facilitated by the use of identical or chemically similar compositions, and the materials of sound attenuating portion <NUM> and stem portion <NUM> are selected such that the primary source of bonding between the foam sound attenuating portion <NUM> and foam stem portion <NUM> is chemical bonding. An additional adhesive is not required to bond sound attenuating portion <NUM> and stem portion <NUM>, and such an adhesive is not present between sound attenuating portion <NUM> and stem portion <NUM> in an exemplary embodiment.

In some exemplary embodiments, sound attenuating portion <NUM> and stem portion <NUM> are formed from a composition including a blend of polyether polyurethane and an acrylic polymer, such as Hypol <NUM> available from The Dow Chemical Company and Encor <NUM> available from Arkema, Inc. In other exemplary embodiments, sound attenuating portion <NUM> may include a blend of polyether polyurethane and an acrylic polymer and stem portion <NUM> may be formed from a material composition including a diisocyanate and a polyol, such as Modur PF available from Bayer, Corp. Other suitable materials for forming sound attenuating portion <NUM> may include foamed thermoplastic resins, and other soft, pliable foams that may be comfortably positioned in an ear canal of a user. Other suitable materials for forming stem portion <NUM> may include foamed thermoplastic resins, and other suitable materials that may be foamed to exhibit an appropriate stiffness such that sound attenuating portion <NUM> of earplug <NUM> may be easily inserted into the ear canal of a user while allowing a desired level of compliance to provide a comfortable fit. In various exemplary embodiments, various additional materials may be included, such as pigments, cell regulators, deionized water, and/or other suitable materials as known in the art. The resulting material is a hydrophilic or hydrophobic, slow recovery, and dynamically stiff foam.

In an exemplary embodiment, stem portion <NUM> has a generally circular or rounded cross-section such that stem portion <NUM> exhibits a generally cylindrical shape. A circular cross section may minimize edges that may cause discomfort by contacting portions of a user's ear. In various other exemplary embodiments, elongate core may have a triangular, square, or other suitable cross-section, or may have a cross-section that varies along the length of earplug <NUM>.

In some exemplary embodiments, earplug <NUM> defines a channel. Earplug <NUM> having a body defining a channel may be manufactured such that components of a receiver or of a communication system, for example, may be attached to earplug <NUM>. Alternatively or in addition, a channel may accommodate one or more filters or other passive hearing elements to provide an attenuation curve having a desired shape. For example, filters positioned in a channel may cause nonlinear attenuation of high level impulses produced by explosions, gunfire, or the like. A channel may also provide a recess that a cord may be attached to, such that first and second earplugs may be joined, or that ends of a headband may be attached to in a semi-aural hearing protector.

Materials of sound attenuating portion <NUM> and/or stem portion <NUM> may be selected to control the friability of the sound attenuating portion <NUM> and stem portion <NUM> such that they may not easily be broken or disintegrate during use. The friability of an earplug may be controlled in part by selecting a material having an appropriate molecular weight, with higher molecular weight generally resulting in a less friable earplug. In an exemplary embodiment, sound attenuating portion <NUM> and stem portion <NUM> includes a foam polymer having a molecular weight between <NUM>,<NUM> Daltons and <NUM>,<NUM> Daltons, as measured by gel permeation chromatography analysis as known in the art, such as according to ASTM D6474 - <NUM>.

The density of sound attenuating portion <NUM> and stem portion <NUM> can be controlled during manufacturing to provide a specified density as desired for a particular application and to control the density of sound attenuating portion <NUM> as compared to stem portion <NUM>. Sound attenuating portion <NUM> and stem portion <NUM> may exhibit densities that vary slightly at different locations, for example, such that sound attenuating portion <NUM> has an integral outer skin that is denser than the remainder of sound attenuating portion <NUM>. Such a skin may be present on one or both of sound attenuating portion <NUM> and stem portion <NUM>. Alternatively, sound attenuating portion <NUM> and stem portion <NUM> may have substantially uniform densities. In an exemplary embodiment, irrespective of the presence of an integral outer skin or varying densities within sound attenuating portion <NUM> and stem portion <NUM>, sound attenuating portion <NUM> has a first density ρ1 and the stem portion has a second density p2. First and second densities ρ1 and p2 can be found by averaging the densities at each location of sound attenuating portion <NUM> or stem portion <NUM>. In some cases, first and second densities can be approximated by measuring mass and volume of sections or portions of sound attenuating portion <NUM> and stem portion <NUM> to calculate first and second densities ρ1 and p2.

The density provides an indication of the ability of sound attenuating portion <NUM> or stem portion <NUM> to compress or otherwise conform when subjected to an external force. First average density ρ1 of sound attenuating portion <NUM> is selected such that sound attenuating portion may provide a comfortable fit by conforming to the ear canal of a user, while providing a desired level of sound attenuation. In various exemplary embodiments, the first average density ρ1 of a sound attenuating portion <NUM>, comprising a polyurethane foam for example, is between <NUM>/m<NUM> and <NUM>/m<NUM>, or <NUM>/m<NUM> and <NUM>/m<NUM>, or may be about <NUM>/m<NUM>. The second average density p2 of stem portion <NUM> is greater than the first average density ρ1, and in various exemplary embodiments is between <NUM>/m<NUM> and <NUM>/m<NUM>, <NUM>/m<NUM> and <NUM>/m<NUM>, or may be about <NUM>/m<NUM>. The second average density p2 of stem portion <NUM> is greater than <NUM> times the first average density ρ1 of sound attenuating portion <NUM> (i.e. | p2 > <NUM>ρ1|). In some cases, the second average density p2 of stem portion <NUM> may be <NUM>, <NUM>, <NUM> or more times the first average density ρ1 of sound attenuating portion <NUM>.

In an exemplary embodiment, sound attenuating portion <NUM> has a first relative density ρ1r and stem portion <NUM> has a second relative density p2r. Relative density refers to the density of a foam (i.e., the bulk density) divided by the density of the solid material forming the cell walls, etc., of the foam. Relative density is therefore generally greater in foams having smaller cells and/or thicker cell walls and lower in foams having larger cells and/or thinner cell walls. A relative density of foam provides an indication of the total cell volume and can provide an indication of a stiffness of foam made of a particular material. That is, for a given material and cell structure, a lower relative density suggests a lighter and/or more flexible foam, while a greater relative density suggests a heavier and/or stiffer foam. A relative density of non-cellular polymers, or other polymers not commonly referred to as foams, may exhibit a relative density of <NUM> or nearly <NUM>, because the density of the sample and the density of the material of which it is made are equal or approximately equal due to limited, or completely absent, cell volume.

Relative densities of sound attenuating portion <NUM> and stem portion <NUM> may be controlled to provide an earplug <NUM> having desired characteristics. In an exemplary embodiment, sound attenuating portion <NUM> has a first relative density that is lower than a second relative density of stem portion <NUM>. In an exemplary embodiment, sound attenuating portion <NUM> has a first relative density ρ1r of between approximately. <NUM>, or of about. Stem portion <NUM> has a second relative density p2r of between approximately. <NUM> and <NUM>, <NUM> and <NUM>, or of about <NUM>. Accordingly, second relative density p2r may be greater than ρ1r, or approximately <NUM>, <NUM>, <NUM>, <NUM> or more times first relative density ρ1r.

The modulus and hardness of sound attenuating portion <NUM> and stem portion <NUM> can be controlled during manufacturing to provide a specified modulus and/or hardness as desired for a particular application and to control the modulus and/or hardness of sound attenuating portion <NUM> as compared to stem portion <NUM>. In various exemplary embodiments, a stem portion <NUM> may have a hardness between approximately <NUM> kPa and <NUM> kPa, <NUM> kPa and <NUM> kPa, or between about <NUM> kPa and <NUM> kPa, and a modulus between approximately <NUM> kPa and <NUM>,<NUM> kPa, <NUM> kPa and <NUM> kPa, <NUM> kPa to <NUM> kPa. In various exemplary embodiments the stem portion is formed from a composition including a diisocyanate and a polyol. In various exemplary embodiments, sound attenuating portion <NUM> may have a hardness between approximately <NUM> kPa and <NUM> kPa, or between about <NUM> kPa and <NUM> kPa, and a modulus between approximately <NUM> kPa and <NUM> kPa, <NUM> kPa and <NUM> kPa, or between about <NUM> kPa and <NUM> kPa. Accordingly, an exemplary earplug may have a sound attenuating portion <NUM> having a first modulus that is <NUM>/<NUM>, <NUM>/<NUM>, <NUM>/<NUM>, <NUM>/<NUM>, or other fraction of a second modulus exhibited by a stem portion <NUM>, and may have a sound attenuating portion <NUM> having a first hardness that is <NUM>/<NUM>, <NUM>/<NUM>, <NUM>/<NUM>, <NUM>/<NUM>, or other fraction of a second hardness exhibited by a stem portion <NUM>. Accordingly, a stem portion <NUM> as described herein may be provided that exhibits a modulus and/or hardness that is greater than a modulus and/or hardness of a sound attenuating portion <NUM>, while both stem portion <NUM> and sound attenuating portion <NUM> are made from a closed-cell, slow recovery foam, for example. The above modulus and hardness values have been found by the present inventors to provide a desired level of stiffness such that stem portion <NUM> may be used as a handle to facilitate insertion of sound attenuating portion <NUM> at least partially into an ear canal, while providing compliance and conformability such that the earplug may be comfortably worn by a user, particularly during extending periods of use.

The present disclosure provides methods of making an earplug <NUM>, as described above. In general the methods include steps of dispensing a foamable material(s) into a mold, the mold having a first unvented cavity in the form of a stem and a second vented cavity in the form of a sound attenuating portion, and curing the material to form a push-to-fit type earplug including a sound attenuating portion having a first average density and the stem portion having a second average density that is greater than <NUM> times the first average density. Such processes allow an earplug comprising a body made entirely of foam, and in some exemplary embodiments made of a uniform chemical composition, that provides a stiff stem to facilitate insertion and a soft, pliable sound attenuating portion that may be comfortably worn by a user.

In general, an earplug is formed in a dispensing molding process in which a mold cavity forming the stem portion is unvented, for example is not vented or has limited venting, to result in a relatively stiffer and/or denser stem portion, while a mold cavity forming the sound attenuation portion is allowed to vent or provides relatively greater venting to result in a relatively less stiff and/or less dense sound attenuating portion. Accordingly, a body is formed having a sound attenuating portion with a stiffness and/or density that is lower than the stiffness and/or density of a stem portion. Such a process allows an earplug made entirely of foam, and in some cases made of a uniform chemical composition, that provides a stiff stem to facilitate insertion and a soft, pliable sound attenuating portion that may be comfortably worn by a user.

An earplug of the present invention may be made by a two-shot molding process including the steps of dispensing foamable material into an unvented cavity of a mold, partially curing the foamable material in the unvented cavity, dispensing foamable material into a vented cavity of the mold, and curing the materials in the unvented and vented cavities to form a push-to-fit type earplug including a compliant sound attenuating portion and a relatively stiffer and/or denser stem portion. In an exemplary embodiment, a mold <NUM> includes mold inserts <NUM>, <NUM>, and <NUM>. Mold inserts <NUM> and <NUM> may be interchangeable or used in combination to provide a stem cavity <NUM> and a sound attenuating cavity <NUM>, respectively. In a first configuration shown in <FIG>, a stem cavity <NUM> is defined by mold inserts <NUM> and <NUM>. In a second configuration shown in <FIG>, a sound attenuating portion cavity <NUM> is defined by mold insert <NUM>, mold insert <NUM>, and/or a portion of a foamed material in stem cavity <NUM>.

In an embodiment, a foamable material is dispensed into a volume of stem cavity <NUM> defined by mold insert <NUM> in a first shot. Mold insert <NUM> is then clamped to mold insert <NUM> to form a substantially closed stem cavity <NUM> that provides limited or no venting. The foamable material is allowed to partially cure, and as applicable at least partially expand or form, before mold inserts <NUM> and <NUM> are separated. In a second shot, a foamable material is dispensed into a volume of a sound attenuating portion cavity <NUM> defined by mold insert <NUM>, for example, and mold insert <NUM> is clamped to mold insert <NUM> to form a vented sound attenuating portion cavity <NUM>. Excess gas is allowed to escape from cavity <NUM>, out of the mold and/or partially into stem cavity <NUM>, as the foamable material expands. In various exemplary embodiments, cavity <NUM> has a total vent area between <NUM><NUM> to <NUM><NUM>, <NUM><NUM> to <NUM><NUM>, or about <NUM><NUM>. The foamable materials in the stem cavity <NUM> and the sound attenuating portion cavity <NUM> are allowed to cure and, as applicable expand or form, before mold inserts are separated. As the foamable materials cure, a chemical bond is formed between materials in sound attenuating portion cavity <NUM> and material in stem cavity <NUM>.

In other exemplary embodiments, a sound attenuating portion may be formed in a first shot and the stem portion formed in a second shot. In some exemplary embodiments, stem portion is formed and chemically bonded to a sound attenuating portion without being removed or reinserted into a mold cavity, in contrast to traditional insert molding processes, for example.

Mold <NUM> may be prepared as appropriate for a selected foamable material and as desired to achieve an earplug having selected characteristics. In various exemplary embodiments, mold <NUM> is warmed to a desired temperature, for example about <NUM>° C, and an interior surface contacted by foamable material may be coated with polypropylene, or other suitable material that facilitates release of a formed earplug.

<FIG> shows a mold <NUM> of an exemplary method of making a push-to-fit type earplug in a single-shot molding process, such a single-shot molding method not being part of the claimed two-shot molding methods. Such a single-shot method includes steps of dispensing foamable material into a mold, the mold having a first unvented cavity in the form of a stem and a second vented cavity in the form of a sound attenuating portion, and curing the material to form a push-to-fit type earplug including a compliant sound attenuating portion and a relatively stiffer and/or denser stem portion. As shown in <FIG>, a mold <NUM> includes mold inserts <NUM> and <NUM>. Mold inserts <NUM> and <NUM> provide a stem cavity <NUM> and a sound attenuating cavity <NUM>, respectively. Stem cavity <NUM> is defined at least in part by mold insert <NUM> and sound attenuating portion cavity <NUM> is defined by mold insert <NUM>, mold insert <NUM>, and/or a portion of a material in stem cavity <NUM>.

In a single-shot molding process, a foamable material is dispensed into a volume of stem cavity <NUM> and/or sound attenuating cavity <NUM> in a first shot. As the foamable material expands, material will be present in both stem cavity <NUM> and sound attenuating cavity <NUM>. Excess gas is allowed to escape from sound attenuating cavity <NUM> while stem cavity <NUM> is unvented, resulting in an elevated pressure relative to at least portions of sound attenuating cavity <NUM>. The foamable material is allowed to at least partially expand, form, and/or cure before mold inserts <NUM> and <NUM> are separated. As the foamable material cures, the material in stem cavity <NUM> forms a relatively stiffer and/or denser stem due to increased pressure while the material in sound attenuating cavity <NUM> forms a relatively less stiff and/or less dense sound attenuating portion.

The operation of embodiments according to the present disclosure will be further described with regard to the following detailed examples. These examples are offered to further illustrate the various specific embodiments and techniques. It should be understood, however, that many variations and modifications may be made while remaining within the scope of the present description.

Modulus is the constant of proportionality describing a relationship between stress and strain in the elastic regime. Hardness is the maximum contact pressure sustained by a sample under stress. Modulus and hardness were measured according to the following procedure.

Samples were prepared by sectioning an earplug lengthwise and adhering the uncut surface to a <NUM> (<NUM> inch) diameter aluminum puck using HARDMAN DOUBLE/BUBBLE Extra-Fast Setting Epoxy #<NUM>, specified as having a mixed viscosity at <NUM> of <NUM> Pa-seconds (<NUM>,<NUM> cps). Epoxy was positioned around the edges of the sample at a thickness of the height of the sample, while avoiding epoxy on the cut surface of the sample or otherwise infiltrating the body of the sample. Tests were conducted using an AGLINET G200 Nanoindentor in XP mode using a <NUM> spherical ruby probe with the aluminum puck mounted on the sample stage of the nanoindentor such that the exposed cut surface of the sample was flat and normal to the nanoindentor axis. Testing was conducted using an i. ) approach distance of <NUM> with approach velocity of <NUM>/s; ii. ) surface find criteria of <NUM> N/m; iii. ) strain rate of <NUM> ^s-<NUM>; iv. ) depth setpoint of <NUM> to <NUM>; and v. ) dwell time after peak load of <NUM> seconds.

The following equations were used to determine Modulus and Hardness, with E = Reduced Modulus (kPa); H = Hardness (kPa); S = Stiffness (N/m); Pmax = Maximum Load (N); hmax = Maximum Displacement (m); R = Radius of Indenter (m); and A = Contact Area (m<NUM>). <MAT>
<MAT>
<MAT>.

The earplugs of Examples <NUM> through <NUM> were prepared in a two-shot molding process using a mold shown and described with respect to <FIG>. A mixture including <NUM> parts Hypol <NUM> polyether polyurethane prepolymer, available from The Dow Chemical Co. , <NUM> parts Encor <NUM> acrylic latex material, available from Arkema, Inc. , <NUM> parts water based pigment available from DayGlo Color Corporation, and <NUM> parts surfactant cell regulators was prepared and dynamically mixed using a dynamic high shear mixer at an average rate of between <NUM> revolutions/grams of material pumped and <NUM> revolutions/grams of material pumped.

Molds were prepared by applying an H-<NUM>-1N mold release available from Releasagen Manufacturing Inc. and heating the molds to approximately <NUM>. Mixed material was dispensed into sound attenuating portion cavity and a mold top was placed on the mold to provide a vented cavity in the form of a sound attenuating portion. After partially curing, the mold top was removed and replaced with a mold insert to form an unvented stem cavity. A second mixture including <NUM> parts Hypol <NUM> polyether polyurethane prepolymer, available from The Dow Chemical Co. , <NUM> parts ENCOR <NUM> acrylic latex, available from Arkema, Inc. , <NUM> parts water based pigment available from DayGlo Color Corporation, and <NUM> parts surfactant cell regulators, were dispensed into the stem cavity and allowed to blow, form and cure. The cured earplug was extracted from the mold and dried. Modulus and hardness data was collected according to Procedure <NUM> at a central stem location approximately at a middle of the cut surface, and at a sound attenuating location on the cut surface. Results are reported in Table <NUM> below.

The earplugs of Examples <NUM> through <NUM> were prepared in a two-shot molding process using a mold shown and described with respect to <FIG>. A mixture including <NUM> parts Mondur PF diisocyanate prepolymer available from Bayer Corporation, <NUM> parts blend of polyols including ARCOL PPG <NUM>, ARCOL LHT <NUM>, and MULTRANOL <NUM>, available from Bayer Material Science, and <NUM> part blend of catalysts including NIAX catalyst A-<NUM>, available from Momentive Performance Materials, and BICAT V and BICAT Z, available from Shepard Chemical Company, <NUM> parts powder pigment available from DayGlo Color Corporation, and <NUM> parts cell surfactants was dynamically mixed using a dynamic high shear mixer at an average rate of between <NUM> revolutions/grams of material pumped and <NUM> revolutions/grams of material pumped.

Molds were prepared by applying release coating <NUM> mold release available from Huron Technologies Incorporated and heating the molds to approximately <NUM>. Mixed material was dispensed into the stem cavity and a mold top was placed on the mold to provide a closed, non-vented cavity in the form of a stem. After partially curing, the mold top was removed and replaced with a mold insert to form a sound attenuating portion cavity. The dynamically mixed material was dispensed into the cavity and allowed to blow, form and cure while venting of the sound attenuating portion cavity allows some gas to escape. The cured earplug was extracted from the mold and dried. Modulus and hardness data was collected according to Procedure <NUM> at a central stem location approximately at a middle of the cut surface, and at a sound attenuating location on the cut surface. Results are reported in Table <NUM> below.

The earplugs of Comparative Examples A through D were <NUM> E-A-R PUSH-INS SOFTOUCH uncorded foam earplugs available from <NUM> Company of St. Paul, Minnesota. Modulus and hardness data was collected at a central stem location approximately at a middle of the cut surface. Results are reported in Table <NUM> below.

The samples of Comparative Examples E through G were standard EPDM <NUM>-E foam available from American National Rubber Company. The foam was in the shape of a <NUM> diameter puck having a thickness of <NUM>. The puck was secured to the nanoindentor sample stage and modulus and hardness data was collected according to Procedure <NUM>. Results are reported in Table <NUM> below.

Modulus and Hardness values of Table <NUM> suggest the earplugs of Examples <NUM> through <NUM> have greater compliance at the sound attenuating portions as compared to the stem portions, and the stem portions of Examples <NUM> through <NUM> have significantly greater compliance as compared to the stem portions of the earplugs of Comparative Examples A through D.

Claim 1:
An earplug (<NUM>) comprising:
a body comprising a sound attenuating portion (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>) and a semi-rigid stem portion (<NUM>) having a relatively greater stiffness than the sound attenuating portion;
wherein the body is made entirely of a closed-cell, slow-recovery foam, the sound attenuating portion (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>) having a first density ρ1 and the stem portion (<NUM>) having a second density p2, and | p2 > <NUM>ρ1|, and wherein the sound attenuating portion (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>) is chemically bonded to the stem portion (<NUM>).