Patent Publication Number: US-2010119076-A1

Title: Hearing Protection Device Ear Seal With Acoustic Barrier

Description:
Various embodiments of the invention relate to hearing protection devices, and more specifically to an improved ear seal for use in headsets and the like that incorporates an acoustic barrier that attenuates the level of external noise that reaches the interior of the ear cup. 
     BACKGROUND  
     Hearing protection devices such as headsets, headphones and hearing protectors are useful in a variety of endeavors ranging from aviation to military and industrial uses, to home audio use and others. In the industry, the term “headset” generally refers to device that includes a microphone and speakers in each ear cup. The term “headphone” refers to a device that has speakers only, and is therefore a receive-only communications device. A “hearing protector” is an earmuff-only device that is used only for protection of the user&#39;s hearing. 
     Most hearing protectors have two ear cups that are connected to a headband. Each ear cup includes an ear seal that encircles the user&#39;s ear—the ear seal has a ring of cushioning material that fits against the user&#39;s head around the ear, and helps attenuate the level of noise that reaches the ear. The ear seal is an important component of a hearing protector, as it provides comfort, and more importantly, contributes to the attenuation of external noise so that the interior of the ear seal is relatively quieter than the exterior. 
     It is of course desirable to minimize the amount of environmental noise that reaches the interior of the ear cup, and hence the user&#39;s ear. There are several approaches to noise attenuation, and these may be generally categorized into active and passive noise reduction strategies. Active noise reduction, or noise cancellation, relies upon reversing of waveform polarity to cancel undesirable noise. This type of noise reduction is very effective at low frequencies and can be selective, for example to cancel airplane engine noise. 
     Passive noise reduction on the other hand is a form of soundproofing that relies upon physical barriers to block, absorb or dampen the energy of sound waves. Ear seals are one form of passive noise reduction. Generally speaking, from a noise attenuation perspective it is best to have a thin ear seal because the noise attenuation properties are better. However, a thin ear seal is likely to be less comfortable, so there is inherently a tradeoff between the comfort of the device and the level of noise reduction that the designer must balance. For example, a variety of foam products, gels and liquid may be used for cushioning/noise attenuation materials in ear seals. The physical properties of the cushioning material directly affect the level of noise attenuation, and comfort. Thick, soft foam tends to conform well to the wearer&#39;s head and is quite comfortable, but soft foam does not attenuate noise very effectively. Dense foam is generally better at cross sectional noise attenuation, but tends to be heavier and conforms to the wearer&#39;s head less effectively, and is less comfortable. 
     There is a need for ear seals for use in hearing protective devices that provide more effective noise attenuation, yet are comfortable and highly conformable. 
     SUMMARY  
     To address this and/or other needs, the present invention devised, among other things, exemplary hearing protection devices, such as headsets, headphones, or protective earmuffs, which include a novel ear seal. In one exemplary embodiment, the ear seal includes a ring-like ear cushion and an acoustic barrier ring arranged coaxially with the circumaural ear cushion. The acoustic barrier ring comprises a physical barrier located within the ear seal that is more acoustically dense than the cushioning material so that the barrier acts as a physical barrier to prevent sound from reaching the interior of the ear seal. In some embodiments, the acoustic barrier ring is at least partially buried in the ear cushion. However, in other embodiments the barrier ring lies outside and adjacent the ear cushion. Moreover, in some embodiments the barrier ring takes the form of a circumferential flange extending axially from a base portion of the ear seal. In operation, the barrier ring generally increases the passive acoustic attenuation of the ear seal, and thus mitigates the conventional tradeoff between comfort and noise attenuation. This ultimately enhances the ability of headsets, headphones, and earmuffs to block undesirable noise. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
       The invention will be better understood and its numerous objects and advantages will be apparent by reference to the following detailed description of the invention when taken in conjunction with the following drawings. 
         FIG. 1  is a perspective view of a headset of a type that incorporates an ear cup having an ear seal with an acoustic barrier according to the present invention. In  FIG. 1  the ear seal is shown partially cut away. 
         FIG. 2  is a cross sectional view of the ear seal and a portion of the ear cup illustrating an acoustic barrier associated with the ear seal. 
         FIG. 3  is a cross sectional view similar to  FIG. 1  but of an alternative embodiment of an ear seal according to the present invention, illustrating an acoustic barrier that is formed as an integral part of the ear seal. 
         FIG. 4  is an exploded view of an ear seal, illustrating the acoustic barrier of  FIG. 2  in isolation from the foam used in the ear seal. 
         FIGS. 5 through 7  are illustrations of some of the many forms that the acoustic barrier according to the present invention may take. 
         FIG. 5  is a first alternative embodiment of an acoustic barrier according to the present invention. 
         FIG. 6  is a second alternative embodiment of an acoustic barrier according to the present invention. 
         FIG. 7  is a third alternative embodiment of an acoustic barrier according to the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS  
     The following detailed description, which references and incorporates the above-identified figures, describes and illustrates one or more specific embodiments of the invention. These embodiments, offered not to limit but to exemplify and teach, are shown and described in sufficient detail to enable those skilled in the art to implement or practice the invention. Where appropriate to avoid obscuring the invention, the description may omit certain information known to those of skill in the art. 
     A headset  10  of the type that incorporates an acoustic barrier according to the present invention is illustrated in  FIG. 1  as including first and second ear cups  12  and  14  interconnected with a headband  16 . The ear cups  12  and  14  are pivotally connected to the headband  16  in a conventional manner, for example with a U-shaped connector  18 , so that the ear cups are independently adjustable to better fit the user&#39;s head. The headband  16  is designed to exert inwardly directed pressure—“side pressure”—on each ear cup when the headset is being worn. This pushes the ear cups against the user&#39;s head, creating a seal around each ear. Each ear cup includes a headphone speaker, shown schematically at  22 , and a microphone  20 . External communications connections are not shown in the figures. The headset  10  illustrated in  FIG. 1  is exemplary only and is intended only to show the general type of hearing protection device into which the acoustic barrier of the present invention may be used. It will be appreciated that the acoustic barrier described and claimed herein may be incorporated into any hearing protection device of any design, including headsets as described herein, headphones, and hearing protectors of the muff type. For example, the acoustic barrier may be incorporated into an active noise reduction (ANR) headphone or headset, such as that shown in U.S. Pat. Nos. 6,704,428; 6,735,316 and 7,215,766, which are incorporated herein by this reference. 
     Each ear cup  12  and  14  includes a housing  24  to which U-shaped connector  18  is attached. Housing  24  is typically a plastic or metal material and houses the headphone speaker  22 , other electronics and components that may be used in the device, and serves as a base for the ear seals  26 . For example, the headset  10  illustrated in  FIG. 1  is shown schematically as including ANR circuitry, exemplified by circuit board  23 . It will be appreciated that the acoustic barrier described herein may be beneficially incorporated in a headset that utilizes ANR circuitry and components, or a headset that does not use ANR technology. It will further be appreciated that the ANR circuit board  23  shown in  FIG. 1  is shown in an highly schematic manner to illustrate only that the invention described herein may be used with ANR equipped headsets. 
     Each ear seal  26  comprises a generally circular ring of cushioning material  28  that attaches directly to the housing  24  such that the ear seal encloses the headphone speaker  22 . The cushioning material  28  conforms to irregularities in the user&#39;s head. When the headset  10  is worn, the wearer&#39;s ears are completely encircled by the ear seals  26  with the ear seals conforming to the wearer&#39;s head around the pinna under the side pressure applied by headband  16 . The side pressure provides 100% contact between the ear seal and the user&#39;s head, even when the wearer is speaking. The ear seals  26  thus provide an effective and isolated chamber or interior cell  25  where the ears rest when the headset is worn. The environment external of the ear seals is referred to herein as the exterior cell. 
     As indicated above, the design of the ear seals and the cushioning materials used to fabricate the ear seals has a direct and important, and often limiting effect on the level of noise attenuation, and the comfort of the headset. Design of hearing protectors to maximize passive noise reduction involves consideration and balancing of a variety of factors, including the weight of the device, and the amount of side pressure applied by the device on the wearer&#39;s head. Each of these factors directly impacts noise attenuation: the best possible goal would be a very light device that requires minimal side pressure and is very comfortable for long periods of time, yet provides a high level of attenuation. As noted, good passive noise reduction requires contact between the ear seal and the wearer&#39;s head 360° around the ear. This is referred to as 100% contact. Since no two user&#39;s heads are shaped identically, and because the contour of the user&#39;s head changes as the user speaks, it is important that the ear seals are designed with the ability to provide 100% contact at all times on all users. 
     Many different cushioning materials may be used in the ear seals. These include for example open and closed cell foam, silicone gel, liquid, and liquid foam. Choice of one of these over another depends upon other factors. For example, of the materials just listed, silicone gel has the best cross sectional attenuation properties (i.e., the best ability to block external noise) but has the least ability to conform to the wearer&#39;s head and thereby create the desired condition of 100% contact and conformance between the user&#39;s head and the ear seal. Table 1 provides a list of some basic properties of some common materials used in ear seals. 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Ear Seal Material Characteristics 
               
            
           
           
               
               
               
               
               
            
               
                   
                   
                   
                 Side 
                 Ear 
               
               
                 Ear Seal 
                 Attenuation 
                 Ability to 
                 Pressure 
                 Seal 
               
               
                 Material 
                 Properties 
                 Conform 
                 Needed 
                 Weight 
               
               
                   
               
               
                 Silicone Gel 
                 Best 
                 Worst 
                 High 
                 1.2 oz  
               
               
                 Liquid 
                 Very Good 
                 Best 
                 Medium 
                 .6 oz 
               
               
                 Foam/Liquid 
                 Good 
                 Good 
                 Medium 
                 .6 oz 
               
               
                 Temp-Sensitive 
                 Good 
                 Very Good 
                 Low 
                 .5 oz 
               
               
                 foam 
               
               
                   
               
            
           
         
       
     
     From the foregoing it will be appreciated that selection of one particular material over another requires balancing of the goal of comfort with the best noise attenuation. Liquid demonstrates the best conformance to uneven surfaces such as found on a typical head, but requires relatively higher side pressure because of the vertical orientation of the ear seal; the liquid flows to the lowermost portion of the seal unless the side pressure is sufficient to squeeze the fluid up around the ear. On the other hand, silicone gel tends to provide better attenuation since it stays in place in the ear seal. Foam/liquid and thermal-conforming foams do not have as much cross-sectional density as either liquid or silicone gel to provide the same levels of passive attenuation. 
     From a comfort standpoint, silicone gel ear seals may not be the best choice because, as noted above, the gel is a dense material and does not easily conform to the many variations posteriorly of human ears. Moreover, silicone gel only conforms under relatively high pressure, compared to the other materials listed. And silicone gel is quite heavy at twice the weight of the other ear seals. Liquid seals require medium side pressure for a good seal, and temperature-sensitive foam materials are excellent for conformability, minimum side pressure, and ear cavity volume. Furthermore, temperature sensitive foam is particularly effective when the user is wearing glasses. The conformability of the foam helps minimize the localized pressure of the arms of the glasses pushing on the wearer&#39;s temples. 
     It will be readily appreciated that the different criteria noted above must all be considered when designing a headset. The present invention as embodied herein and as defined by the claims may be used with any material used for ear seals, including those materials specifically listed above, and enhances the noise attenuation of the ear seal regardless of what type of cushioning is used. Nonetheless, for purposes of the present description of the invention, the ear seal it is illustrated herein and shown in the drawings being used with temperature sensitive foam. This is done by way of example only, and not by way of limitation. 
     Turning now to  FIG. 2 , ear seals  26  have in the illustrated embodiment an internal foam core  28  and an external cover  30 . The external cover  30  is typically is a soft material such as synthetic leather, vinyl, cloth, leather or similar material that tends to be comfortable, since it rests on the wearer&#39;s head. The external cover material contributes little to noise attenuation properties of the ear seal. 
     As noted above, many different cushioning materials may be used in place of the foam used in foam core  28 . Accordingly, the ear seal is at times referred to herein as a circumaural ear ring. This term contemplates an ear seal that uses any cushioning material. The internal foam core  28  described in the present embodiment is preferably soft, conformable foam that provides good noise attenuation qualities. Thermally conforming foam sold under the brand name CONFOR, available through E-A-R Specialty Composites (www.earsc.com), a division of Aearo Company (www.aearo.com) is one example of foam that works well for internal foam core  28 . CONFOR is slow recovery urethane foam that softens when exposed to warm temperature, and therefore tends to conform very well to a wearer&#39;s head around the ear to provide pressure-free conformance and comfort. CONFOR also provides good noise attenuation performance. The foam core  28  used in accordance with the present invention has a height and width dimension, illustrated on  FIG. 2  with the dimensions H and W, respectively. 
     The flattened base  32  of the internal foam core is bonded to a backing layer  34 , which typically is a flexible material such as cloth, but may also be materials such as KEVLAR, plastic and the like. Backing layer  34  is in turn bonded to a backing plate  36 , which preferably is a semi-rigid plastic material. The backing plate is a sometimes referred to as the ear shell. As illustrated in  FIG. 2 , in the assembled ear seal  26  the external cover  30  completely covers the internal foam core  28  and is attached to backing plate  36 . The cover  30  may be attached to backing plate  36  in any convenient manner, and in  FIG. 2  is shown attached to the backing plate with stitches  38 . Cover  30  may also be bonded to the backing plate. It will be understood that there are many alternative and equivalent manners in which to assemble an ear seal of the type described herein. 
     For reference purposes herein, flattened base  32  defines a first plane that is parallel to the plane defined by shelf  40 , described below. Likewise, the surface of the ear seals  26  that contact the user&#39;s head, i.e., the outer surface of cover  30 , is generally flattened and defines a second plane. The first and second planes are generally parallel, and the first plane is sometimes referred to as the back plane, and the second plane as the front plane. 
     The ear seal  26  is an independent unit that is detachable from ear cup  14 . With reference once again to  FIG. 1 , ear seal  26  is attached to a circumferential shelf  40  formed on housing  24  that extends around the housing. The backing plate  36  and ear seal  26  have the same circumferential shape as the shelf  40 , so the ear seal mates with the ear cup. The ear seal is typically connected to the ear cup with snap-in clips (not shown) such that the ear seal is firmly and securely attached to the housing yet may be easily removed. 
     Acoustic barrier  42  comprises a relatively thin strip of material that is relatively denser than the foam cushioning material used in the ear seal, in this case foam core  28 . Because the acoustic barrier  42  is denser than the cushioning material, it provides significantly increased cross sectional noise attenuation compared to the foam. Acoustic barrier  42  is associated with the foam core  28  such that the strip extends in a direction that is generally transverse to the plane of the shelf  40 —i.e., the first plane—onto which ear seal  26  fits when headset  10  is assembled, and also the plane defined by backing material  34  and backing plate  36 . Stated another way, there is a central axis extending through the middle of each ear cup  12  that is transverse to the first and second planes; the wall of the acoustic barrier  42  extends parallel to the central axis. As shown in  FIG. 1 , the orientation of the acoustic barrier within the ear seal results in the strip providing a physical acoustic barrier that blocks external noise from reaching the interior cell  25 ; the strip attenuates noise having its origins in the exterior cell by physically blocking the sound waves from entering the interior cell  25 , and by reflecting the sound waves back to the exterior cell as illustrated schematically in  FIG. 2  with arrow N. Since the acoustic barrier  42  provides effective noise attenuation, each of the ear cups  12  and  14  defines an interior cell  25  that is more effectively acoustically isolated from the exterior cell. While the term “blocking” is used to refer to the attenuation of noise entering the interior cell, it will be appreciated that this is a relative term and that not all noise is excluded from entering the interior cell. 
     A variety of materials may be used to fabricate acoustic barrier  42 , but in all cases the material is denser than the cushioning material used in the ear seal such as foam core  28 . Preferred materials for acoustic barrier  42  include copper, KEVLAR, rubber, plastics of various types, foams having relatively high density than the cushioning material used for foam core  28 , and fiberboard-based materials. It will be appreciated that other materials work well, too. Testing has shown that of the specific materials listed above, copper provides the best noise attenuation properties. However, virtually any material that is more dense than the cushioning material will suffice for acoustic barrier  42 . It is also envisioned that acoustic barrier  42  could be formed with a liquid polymer material injected into the foam core, wherein the polymer hardens to form the barrier. Because the acoustic barrier is very thin and light, it does not appreciably increase the weight of headset  10  and has no effect on the conformability of the ear seal to the user&#39;s head. 
     In some cases the material selected for acoustic barrier  42  will be dependent upon the type of foam used for foam core  28 . For example, if a relatively dense and non-compressible foam is used for foam core  28 , the material selected for acoustic barrier  42  may be relatively stiffer. On the other hand, if foam core  28  is formed of soft foam, a relatively more flexible material may be appropriate for the acoustic barrier. 
     As shown in  FIGS. 4 through 7 , acoustic barrier  42  may take on several different forms, as detailed below. The barrier may be a continuous endless ring of material as shown in  FIGS. 4 ,  5  and  6 , or may be an elongate strip having opposite ends as shown in  FIG. 7 . Of course, if an elongate strip is used the opposite ends of the strip may overlap one another when the acoustic barrier is assemble with/embedded into the foam core. Regardless of the form used for acoustic barrier  42 , the strip has a length dimension, a height dimension and a width dimension (reference letters L, H and W, respectively, in  FIG. 7 ). 
     Acoustic barrier  42  is inserted into the foam core  28  during manufacture of the ear seal. With reference to  FIGS. 2 ,  3  and  4 , a circumferential slit  44  is formed in the material used for foam core  28 —the slit  44  is preferably formed in the foam core after the core has been bonded to backing material  34 , but the foam core  28  could be slit beforehand, or the foam core could be provided in two annular pieces if desired. In  FIGS. 1 and 2 , slit  44  extends from the outermost or external portion  46  of foam core  28  toward the backing material  34 . The slit  44  may extend completely to the backing material  34 , but typically terminates a short distance before the backing material. The strip of acoustic barrier material is then inserted into slit  44 , preferably such that the outermost edge  50  of the acoustic barrier is embedded within foam core  28 , and spaced apart from the external portion  46  by a short distance. The height of the acoustic barrier  42  may be varied according to need. Generally speaking, the height of the acoustic barrier should be as close as possible to the height of the foam core  28  in order to achieve the best noise attenuation. As noted above, balanced against this need, of course, is the need to provide a comfortable fit for the ear cup. In  FIG. 2  the innermost edge  51  of acoustic barrier  42  is spaced a short distance from backing material  34 . If slit  44  extends completely to the backing material, the acoustic barrier may abut the backing material. 
     Once the acoustic barrier  42  is inserted into the slit  44 , the cover  30  may be applied to the foam core  28  and the ear seal  26  may be fully assembled with the other components described above. Because the outermost edge  50  of the acoustic barrier  42  resides in foam core  28 , there is a portion of foam shown generally at  52  that completely covers the barrier material. This helps insure the comfort of the headset. 
     A first illustrated alternative embodiment for the structure of acoustic barrier  42  is shown in  FIG. 3 . In this embodiment the acoustic barrier  42  is formed as a circumferential flange  43  extending from and around backing plate  36 —the flange is thus an extension of the ear shell, or backing plate  36 , that extends into the foam core  28 . A circumferential slit  45  is cut into foam core  28  and backing material  34 , and the flange  43  is inserted into the slit during assembly of the ear seal. The flange  43  is an integral part of backing plate  36 . This may be contrasted with the acoustic barrier  42  illustrated in  FIGS. 1 and 2 , which is essentially “floating” in the foam core  28  because it is surrounded by the foam core and is not physically attached to the backing plate. 
     An alternative to the embodiment shown in  FIG. 3  may be fabricated by forming the flange  43  as a part of the backing material  34  instead of forming the flange  43  as a part of backing plate  36 . 
     In  FIGS. 1 ,  2  and  3 , the slit in which the acoustic barrier resides and the acoustic barriers are shown in roughly the axial center of foam core  28 . That is, the acoustic barrier is embedded in the foam in a central location. In practice, this orientation will provide the most comfort since those portions of the denser acoustic barrier that could press against the wearer&#39;s head are surrounded by foam—the foam thus provides a cushion between the acoustic barrier and the wearer. It will nonetheless be appreciated that the acoustic barrier may be oriented in any position in the ear seal, even for example on the surface  54  of foam core  28  between the foam core and cover  30 , or the surface on the opposite side of the foam core. Alternately, the strip could be associated with the cover material, between the cover material and the foam core. Where the cushioning material is a gel or liquid, one edge of the acoustic barrier will typically be fixed to the backing material to prevent the strip from being dislodged. It will be appreciated therefore that the word “associated” is used herein to refer not only to the orientation shown in  FIGS. 2 and 3 , but to any orientation in which an acoustic barrier strip is used with a foam core or other cushioning material to attenuate noise having its origin in the external cell from entering the internal cell  25 . 
     An ear seal  26  incorporating an acoustic barrier  42  as described herein and as illustrated in the drawing figures defines an ear seal having a cushioning material with a first density in an outer region—that is, externally of the acoustic barrier, a cushioning material having a second density in an inner region—internally of the acoustic barrier, and a third region having a density higher than the first and second regions, i.e., the acoustic barrier. In most instances the acoustic density of the cushioning material in the inner and outer regions is the same, while the density of the barrier is relatively greater. 
     The relative size dimensions of the headset components may vary widely, depending upon the type of cushioning material used in the ear seal, the material used to fabricate the acoustic barrier, etc. Assuming that the ear seal uses a form core  28  for the cushioning material, a preferred height dimension for the acoustic barrier  42  (dimension H in  FIG. 7 ) is typically about ¼ inch, and the corresponding height of the foam core  28  (dimension H in  FIG. 2 ) is typically about ⅝ inch. As noted above, an acoustic barrier that has a relatively great height in relation to the height of the foam core provides the best noise attenuation. However, comfort concerns must be balanced against this. Accordingly, a preferred embodiment of an ear seal according to the present invention has an acoustic barrier that has a height that is between about 25 to about 85% of the height of the foam core. More preferably, the height of the acoustic barrier may be between about 30 to about 55% of the height of the foam core. It will be appreciated that these dimensions are provided as examples only, and the actual dimensions of the acoustic barrier and foam core will vary depending upon the specific construction for headset  10 . The width dimension of the acoustic barrier will vary depending upon factors such as the material selected for the barrier, and the type of cushioning material used. For example, where the acoustic barrier  42  is formed of copper and CON FOR foam is used for foam core  28 , it has been found that the preferred height of the barrier is about 40% of the height of the foam core, as good noise attenuation and comfort are achieved with these relative dimensions. 
     An ear seal fitted with an acoustic barrier as described herein provides significant and substantial noise attenuation. One direct result is that by incorporating an acoustic barrier in the ear seal, a relatively thinner ear seal (i.e., lower height) may be used, and the side pressure may be reduced. Thus, by using an acoustic strip as described herein, the same levels of noise attenuation may be attained with thinner ear seals and less side pressure than conventional devices that require thick ear seals and significantly more side pressure. As a result, the same or better levels of noise attenuation are achieved with better comfort. 
     As noted above, acoustic barrier  42  may be used in the form of an endless strip (e.g.,  FIGS. 4 ,  5 ,  6 ), or a strip that has opposite ends (e.g.,  FIG. 7 ). Testing has shown that the best noise attenuation is achieved with an acoustic barrier that is in the form of an endless strip that is embedded in the ear seal and extends completely around the ear seal. The actual shape of acoustic barrier  42  may also be varied widely. The ear seal  26  illustrated in  FIG. 1  is not circular. As a result, acoustic barrier  42  will of course not be circular; since the acoustic barrier  42  is flexible, the shape of the ear seal may be modified. The acoustic barrier may further be modified in its height dimension along the length of the strip. To provide a few examples, the acoustic barrier  42  shown in  FIG. 5  includes a cut out or sculpted portion  56  that is positioned to accommodate the arm of a pair of eyeglasses. Of course, if the user specified a headset  10  for use with eyeglasses, the acoustic barrier  42  in each ear seal  26  would be of the type shown in  FIG. 5 . The acoustic barrier  42  shown in  FIG. 6  has a sculpted portion  58  that could be used to increase comfort by increasing the ability of the ear seal to conform to some head shapes. That is, the sculpted portion  58  could be situated in the ear seal  26  such that it rests on the users head anteriorly of the pinna. In addition, the acoustic barrier may be custom designed to accommodate users having specific fitting needs. Lastly, the acoustic barrier  42  illustrated in  FIG. 7  shows one end of the strip having a tapered end  60 . 
     It will be appreciated that when a headset incorporating an acoustic barrier of the type illustrated herein is worn on the head of a user, the strip resides in foam core  28  such that the height dimension of the strip (dimension H,  FIG. 7 ) is generally transverse to the plane defined by the side of the wearer&#39;s head. As a result, the strip provides an effective physical barrier that attenuates the level of noise reaching the interior cell  25 . 
     It will be understood that the fixed flange  43  illustrated in  FIG. 3  may be combined with a floating barrier  42  in the same ear seal, and that an ear seal may incorporate more than one acoustic barrier, or more than one fixed flange  43 . As another alternative, an ear seal could be built with a flange extending partially around the circumference of the device, with a floating barrier extending around the remainder of the ear seal. Other combinations may also be built. 
     While the present invention has been described in terms of a preferred embodiment, it will be appreciated by one of ordinary skill that the spirit and scope of the invention is not limited to those embodiments, but extend to the various modifications and equivalents as defined in the appended claims.