Patent Publication Number: US-9900675-B2

Title: Packaging of acoustic volume increasing materials for loudspeaker devices

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 14/003,217, filed Sep. 4, 2013, which is a national stage of PCT/EP2012/053719, filed Mar. 5, 2012, which claims priority to European Patent Application No. 11157097.4 filed Mar. 4, 2011, the disclosures of which are incorporated in their entirety by reference herein. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to the field of loudspeaker devices and in particular to miniature loudspeaker devices. 
     ART BACKGROUND 
     In loudspeaker devices an acoustically active material may be placed in a back volume of the loudspeaker device so as to virtually enlarge the back volume. Such an acoustically active material may be an acoustic volume increasing material which virtually enlarges the back volume. Hence, by use of an acoustically active material the resonance frequency of the loudspeaker device is lowered to a value that can be achieved without acoustically active material only with an essentially larger back volume. 
     EP 2 003 924 A1 discloses a molded gas adsorber obtained by adding a binder to a porous material including a plurality of grains, thereby forming widened spaces among the grains of the porous material as compared to a conventional gas adsorber including no binder. The binder is provided in the form of a powdery resin material or a fibrous resin material. 
     Forming a molded gas adsorber that provides good adsorption/desorption characteristics from grains of porous material and powdery resin material or fibrous resin material may be difficult and expensive. 
     In view of the above described situation, there exists a need for an improved technique that enables to provide an acoustic element while substantially avoiding or at least reducing one or more of the above-identified problems. 
     SUMMARY OF THE INVENTION 
     According to a first aspect of the herein disclosed subject-matter, there is provided an acoustic element for placement in a sound path of a loudspeaker device, the acoustic element comprising a container and an acoustic volume increasing material located in the container. 
     This aspect of the herein disclosed subject-matter is based on the idea that providing an acoustic element that is capable of increasing the acoustic volume is facilitated by providing acoustic volume increasing material in a container. 
     It should be understood that the acoustic volume increasing material does not increase the space available in a device for acoustic purposes. Rather, the virtual volume sensed by the loudspeaker is increased as is well known in the art. The increased acoustic (virtual) volume leads to a decreased lower resonance frequency of the loudspeaker device compared to the loudspeaker device without volume increasing material. 
     A sound path may be any sound path extending from the loudspeaker, e.g. a backward sound path or a lateral sound path. For example a backward sound path in the sense of the herein disclosed subject matter is a sound path that extends from the back side of a loudspeaker mounted in the loudspeaker device. As usual, the back side of the loudspeaker is a side opposite the sound radiation side from which sound is radiated into the surrounding of the loudspeaker device. 
     According to an embodiment, the container comprises a first wall portion and a second wall portion having a characteristic, e.g. a physical characteristic, different from the respective characteristic of the first wall portion. For example, in an embodiment the sound transmissibility of the first wall portion is higher than the sound transmissibility of the second wall portion. For example, the first wall portion may be formed of a material that is sound-transparent, whereas the second wall portion may be formed of any other material which is suitable as wall material for a container as disclosed herein but which has a reduced sound transmissibility compared to the first wall portion. 
     According to other embodiments, the first wall portion and the second wall portion have similar or identical characteristics. 
     According to a further embodiment, the second wall portion is formed of a molded element. For example, in an embodiment, the molded element is a deep drawn element, a thermo-formed element, an injection-molded element, etc. In an embodiment, the first wall portion is attached to the molded element forming the second wall portion. 
     According to a further embodiment, the second wall portion is cup-shaped having an opening and the first wall portion closes the opening. Hence, in an embodiment the second wall portion determines the overall shape of the acoustic element. The first wall portion may be provided for a transfer of the sound to the acoustic volume increasing material. This provides flexibility in regard to the shape and the material of the second wall portion. 
     In fabrication, according to an embodiment, the acoustic volume increasing material is placed into the cup-shaped second wall portion and thereafter the opening of the second wall portion is closed by the first wall portion. In a further embodiment, the first wall portion seals the opening of the second wall portion. For example, in the case of a granular acoustic volume increasing material (i.e. an acoustic volume increasing material comprising or consisting of loose particles) the sealing first wall portion prevents falling out of the particles. It should however be mentioned that “sealing” in this regard means that the falling out of the particles is prevented, while transmission of the sound into the container and out of the container is still possible. 
     According to a further embodiment, the container has a predetermined three-dimensional shape. For example, such a predetermined three-dimensional shape may be provided by a cup-shaped wall portion as described above. According to other embodiments, the predetermined three-dimensional shape may also be obtained by using a single wall material by a respective cut of the wall material and appropriate joining of the edges of the cut wall material. 
     As mentioned, the container comprises a container wall that encloses a volume containing the acoustic volume increasing material, wherein the container wall is formed of a single wall material. Forming the container of a single wall material provides for a very cost-efficient and easy manufacturing process. For example, containers of this type can be produced using similar packaging technologies such as is known for tea bags, sugar bags, coffee pads and coffee tabs, etc. 
     For example, in an embodiment the container wall is formed of a single sheet of the wall material and the single sheet of the wall material is folded to form the container. 
     According to a further embodiment, the container is at least partially formed of a filter material e.g. a fiber material having passages between the fibers that allow for a gas exchange through the fiber material, or a sieve or a mesh. For example, in an embodiment the single sheet of wall material is formed of such a fiber material. In another embodiment, the first wall portion of the container is formed of the fiber material. The fiber material may be formed of a cloth formed of fibers or may be formed of metal ceramics, plastic, and may be e.g. a woven fabric or a fleece, paper, etc. For example, the filter material may be a material as disclosed in the European Patent Application No. 09 169 178.2 (corresponding to U.S. patent application Ser. No. 12/873,782). 
     According to an embodiment, the acoustic volume increasing material is an electrically insulating material. In this way, interference with electrical currents and electromagnetic fields, which are present in various devices, can be avoided or at least reduced. 
     According to an embodiment, the acoustic volume increasing material comprises or consists of the loose particles. In such a case, the container may provide for a predetermined spatial distribution of the particles, the distribution being determined by the shape of the container. For example, in an embodiment, the acoustic volume increasing material is a material as disclosed in the European patent application No. 10 173 765.8 (corresponding to U.S. patent application Ser. No. 13/818,374). 
     In an embodiment the fiber material is be adapted to the particle size, e.g. to provide a good sound transparency and a low sound resistance while still ensuring the containment of the acoustic volume increasing material. 
     According to other embodiments, the acoustic volume increasing material comprises or consists of fibers, a fleece, etc. of respective acoustically active materials. An advantage of embodiments of the container is the containment of the acoustic volume increasing material itself and/or the containment of abraded particles of the acoustic volume increasing material. 
     An acoustic volume increasing material in the form of an electrically insulating material has further advantages if the acoustic volume increasing material is provided in the form of loose particles. 
     However, according to other embodiments of the herein disclosed subject-matter the acoustic volume increasing material includes or consists of an electrically conducting material, such as activated carbon. 
     According to a second aspect of the herein disclosed subject-matter, a loudspeaker device is provided, the loudspeaker device comprising an acoustic element according to the first aspect or an embodiment thereof. 
     For example, according to an embodiment, the loudspeaker device comprises a housing, the housing having a loudspeaker receptacle for receiving a loudspeaker and a sound path, e.g. a back volume, extending from the loudspeaker receptacle, wherein the container is placed in the sound path. In a further embodiment, the loudspeaker device comprises a loudspeaker mounted in the loudspeaker receptacle. 
     In a further embodiment, the shape of the container matches the shape of the back volume. This allows for a maximum filling of the back volume with the acoustic volume increasing material. 
     According to a third aspect of the herein disclosed subject-matter, there is provided a method of placement of an acoustic element in a sound path of a loudspeaker device, the method comprising providing a container, filling the acoustic volume increasing material into the container; and placing the container in the sound path. 
     It should be understood, that the container and the acoustic volume increasing material may be configured in accordance with embodiments of the herein disclosed subject-matter. 
     In the above there have been described and in the following there will be described exemplary embodiments of the subject-matter disclosed herein with reference to an acoustic element, a loudspeaker device and a method of placing an acoustic element in a loudspeaker device. It has to be pointed out that of course any combination of features relating to different aspects of the herein disclosed subject-matter is also possible. In particular, some embodiments have been described or will be described with reference to an apparatus, whereas other embodiments have been or will be described with reference to a method. However, a skilled person will gather from the above and the following description that, unless otherwise notified, in addition to any combination of features belonging to one aspect also any combination between features relating to different aspects or embodiments, for example even between features relating to an apparatus and features relating to a method, is considered to be disclosed with this application. The aspects and embodiments defined above and further aspects and embodiments of the herein disclosed subject-matter are apparent from the examples to be described hereinafter and are explained with reference to the drawings but to which the invention is not limited. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a cross-sectional view of a loudspeaker device in accordance with embodiments of the herein disclosed subject-matter. 
         FIG. 2  shows a side view of an acoustic element in accordance with embodiments of the herein disclosed subject-matter. 
         FIG. 3  shows a top view of the acoustic element  102  viewed from line III-III in  FIG. 2 . 
         FIG. 4  shows a further acoustic element  102  in cross-sectional view in accordance with embodiments of the herein disclosed subject-matter. 
         FIG. 5  shows a top view of an acoustic element  102  in accordance with embodiments of the herein disclosed subject-matter. 
         FIG. 6  shows a further acoustic element  102  in accordance with embodiments of the herein disclosed subject-matter. 
     
    
    
     DETAILED DESCRIPTION 
     The illustration in the drawings is schematic. It is noted that in different figures, similar or identical elements are provided with the same reference signs or with reference signs which are different from the corresponding reference signs only within the first digit or an appended character. 
     Acoustically active materials, i.e. acoustic volume increasing materials, can be used in the back volume of a loudspeaker device to improve the sound, e.g. the wideband performance, and/or to increase the acoustic volume of the loudspeaker and save space. Such acoustically active materials include zeolite materials or zeolite-based materials. Such electrically isolating materials are superior to conventional acoustically active materials like activated carbon, because they are electrically non-conductive and hence do not influence an antenna, a battery effect or bear the risk of short circuits. Furthermore, packaging of these materials is much easier than in case of activated carbon woven fabrics. 
     A problem may arise in insertion of the materials consisting or at least comprising loose particles, in the back volume of the loudspeaker device. Furthermore, the back volume of a miniature loudspeaker, such as a loudspeaker device placed in mobile phones, headsets, etc., is often built up by the surrounding area of the loudspeaker and is not well-defined. A direct insertion of the acoustically active materials into the surrounding area is practically difficult. Furthermore, the acoustically active materials can enter into the different components of the device having included the loudspeaker device and also in the loudspeaker itself and can therefore damage the device or the loudspeaker. 
     Embodiments of the herein disclosed subject-matter overcome these disadvantages by enclosing acoustically active materials in a container. This simplifies mounting and provides additionally a protection of the loudspeaker and the remaining device. 
       FIG. 1  shows a loudspeaker device in accordance with embodiments of the herein disclosed subject-matter. The loudspeaker device  100  comprises an acoustic element  102  in accordance with embodiments of the herein disclosed subject-matter. The acoustic element  102  includes a container  104  and an acoustic volume increasing material  106  in the form of loose particles in the container  104 . It should be noted that only a few particles  106  are shown in  FIG. 1  and that usually the container will be filled to a large extent or may be completely filled with the acoustic volume increasing material. The loudspeaker device  100  further comprises a housing including a base plate  108  and a wall structure  110 . The wall structure  110  separates a loudspeaker receptacle  112  which has mounted thereon a loudspeaker  114 , and a microphone receptacle  116  which has mounted thereon a microphone  118 . 
     The wall structure  110  further defines a back volume  120  in which the acoustic element  102  is located. In an embodiment, the size and the shape of the acoustic element  102  matches the size and the shape of the back volume, thereby providing for a maximum filling level of the back volume. 
     It should however be noted, that the configuration shown in  FIG. 1  is only exemplary and that other loudspeaker devices may not include a microphone receptacle or a microphone. Further, the back volume is, in another embodiment, not defined by a wall structure but only by surrounding components which surround the loudspeaker  114  in a device in which the loudspeaker is mounted. Such a device may be for example a mobile phone, a headset, etc. In such applications, the loudspeaker device may be a miniature loudspeaker device. 
     The acoustic element  102  may be configured in accordance with one or more embodiments disclosed herein. 
       FIG. 2  shows a side view of an acoustic element in accordance with embodiments of the herein disclosed subject-matter. The acoustic element  102  is made of a container  104  which has a cup-shaped second wall portion  122  and, as a cover of the second wall portion  122 , a first wall portion  124  which has a high sound transmissibility. Hence, while in an embodiment the cup-shaped second wall portion  122  serves as a receptacle for receiving the acoustic volume increasing material (not shown in  FIG. 2 ), the first wall portion  124  serves to couple sound from the loudspeaker into the container and into the acoustic volume increasing material. For example, in an embodiment the second wall portion  122  is made of a plastic whereas the first wall portion  124  is made of for example a fiber material, such as a sound transparent fleece or a foam being capable of passing the sound through the first wall portion. 
     According to an embodiment, cup-shaped second wall portion  122  is a rigid structure. Such a rigid structure guaranties a good mounting ability and robustness. 
       FIG. 3  shows a top view of the acoustic element  102  viewed from line III-III in  FIG. 2 . The side view of  FIG. 2  in turn is obtained when viewing the acoustic element  102  from line II-II in  FIG. 3 . 
     As can be seen from  FIG. 3 , the container  104  may have a predetermined three-dimensional shape. According to an embodiment, a three dimensional (3D) container (bag) having on all sides the “sound transparent” material is provided. The shape of such a 3D geometry means that a more complex geometry is evident not only in the xy direction (drawing plane in  FIG. 3 ) but also in the z direction. The 3D container has the advantage that it can fill a complex shaped back cavity more efficiently than the simple rectangular bags, which are however also in the scope of exemplary embodiments of the herein disclosed subject matter. 
     In an alternative embodiment, the container  104  or at least a container wall is made from a single type of material. For example, the shape shown in  FIG. 2  and  FIG. 3  may also be obtained by only using a fiber material of suitable shape. 
       FIG. 4  shows a further acoustic element  102  in cross-sectional view in accordance with embodiments of the herein disclosed subject-matter. The acoustic element  102  in  FIG. 4  is made of a single type of wall material. In particular, the container  104  of the acoustic element  102  in  FIG. 4  is made of two wall portions  124 ,  122  which are both made of a wall material of the same type. To obtain the container  104 , an upper wall portion  124  and a lower wall portion  122  are attached together at overlapping edge sections  126  of the wall portions  124 ,  122 . The wall portions  124 ,  122  enclose a cavity  105  that is filled with the acoustic volume increasing material (not shown in  FIG. 4 ). 
       FIG. 5  shows a top view of an acoustic element  102  in accordance with embodiments of the herein disclosed subject-matter. As shown in  FIG. 5 , a container comprising container walls being formed of a single type of material may also be formed in more complicated shapes as shown in  FIG. 5 . Again an upper wall portion  124  and a lower wall portion  122  are attached to each other at an edge portion  126 . 
     However, the shape shown in  FIG. 5  may be realized by any other suitable configuration of the wall portions and attachment methods. 
     According to an embodiment, the upper wall portion  124  and the lower wall portion  122  as described herein may be attached to each other by gluing, crimping, stamping, embossing, heat sealing or the like. 
       FIG. 6  shows a further acoustic element  102  in accordance with embodiments of the herein disclosed subject-matter. The container  104  of the acoustic element  102  shown in  FIG. 6  is made of a single sheet  127  of wall material. The single sheet  127  of wall material is folded to form the container  104 . Hence, there is a vertical overlapping region  128  and two edge portions  126  where an upper wall portion overlaps a lower wall portion of the single sheet  127  of wall material. 
     The edge portions  126  of the containers  104  shown in  FIG. 4 ,  FIG. 5  and  FIG. 6  may have formed the edge portions  126  in the form of seams. The overlapping region  128  is preferably positioned at a side opposite a first side which faces the loudspeaker, since the overlapping region may have a reduced sound transparency. 
     Generally in accordance with embodiments of the herein disclosed subject matter, a single wall portion, two or more wall portions, or all wall portions of the container may be of sound transparent material. 
     It should be noted that any entity disclosed herein (e.g. the acoustic element, the container, the loudspeaker device, etc.) are not limited to a dedicated entity as described in some embodiments. Rather, the herein disclosed subject matter may be implemented in various ways and with arbitrary granularity on device level while still providing the desired functionality. Further, it should be noted that according to embodiments a separate entity may be provided for each of the functions disclosed herein. According to other embodiments, an entity is configured for providing two or more functions as disclosed herein. 
     It should be noted that the term “comprising” does not exclude other elements or steps and the “a” or “an” does not exclude a plurality. Also elements described in association with different embodiments may be combined. It should also be noted that reference signs in the claims should not be construed as limiting the scope of the claims. 
     In order to recapitulate the above described embodiments of the present invention one can state: 
     There is provided an acoustic element for placement in a sound path of a loudspeaker device, the acoustic element comprising a container and an acoustic volume increasing material located in the container. In an embodiment, the container comprises wall portions with different physical characteristics. In other embodiments, the walls of the container are made of the same material. 
     LIST OF REFERENCE SIGNS 
     
         
           100  loudspeaker device 
           102  acoustic element 
           104  container 
           105  cavity 
           106  acoustic volume increasing material 
           108  base plate 
           110  wall structure 
           112  loudspeaker receptacle 
           114  loudspeaker 
           116  microphone receptacle 
           118  microphone 
           120  back volume 
           122  second wall portion 
           124  first wall portion 
           126  edge portion 
           127  single sheet 
           128  overlapping region