Abstract:
The present disclosure relates to a slim acoustic transducer having a thin thickness a low-frequency reproduction capability and a sound pressure level in the entire frequency band of which may not be lowered. A slim acoustic transducer includes a diaphragm; a voice coil disposed at a peripheral portion of the diaphragm; and a permanent magnet disposed around the voice coil and configured to apply a magnetic field to the voice coil, wherein a maximum amplitude of the diaphragm is less than a thickness of the permanent magnet.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is based on and claims priority under 35 U.S.C. §119 to U.S. provisional application No. 62/334,692, filed May 11, 2016, in the United States Patent &amp; Trademark Office, and Korean Patent Application No. 10-2016-0104070 filed Aug. 17, 2016 in the Korean Intellectual Property Office, the disclosures of which are incorporated by reference herein in their entireties. 
     
    
     BACKGROUND 
     1. Field 
       [0002]    The present disclosure relates generally to an acoustic transducer capable of reproducing sound. For example, the present disclosure relates to a slim acoustic transducer that can be used in thin electronic devices and an image display apparatus having the same. 
       2. Description of Related Art 
       [0003]    With the development of electronic technology, a thickness of the TV becomes thinner, and now a slim TV, a thickness of which is thin, is becoming popular. In addition, a mobile device, such as a smartphone, a tablet computer, a notebook computer, etc., is required to be reduced in thickness for convenience of carrying. 
         [0004]    In order to reduce the thickness of a TV or a mobile device, it is necessary to reduce the thickness of an acoustic transducer such as a speaker for outputting sound as well as the thickness of a display portion such as a liquid crystal display for outputting videos. 
         [0005]    A slim acoustic transducer as illustrated in  FIG. 1  has been developed and used to reduce the thickness of the TV or the mobile device. 
         [0006]    Referring to  FIG. 1 , in the conventional slim acoustic transducer  1 , a permanent magnet  5  is disposed below a diaphragm  3  and a yoke  7  is provided around the permanent magnet  5 . A voice coil  9  disposed below the diaphragm  3  is positioned between the permanent magnet  5  and the yoke  7  so that a magnetic field of the permanent magnet  5  is applied to the voice coil  9 . The voice coil  9 , the permanent magnet  5 , and the yoke  7  constitute an electric motor system for driving the diaphragm  3 . Accordingly, the diaphragm  3  vibrates based on the change of the current flowing through the voice coil  9 , thereby reproducing sound. 
         [0007]    The conventional slim acoustic transducer  1  has a structure in which the electric motor system for driving the diaphragm  3 , in particular, the permanent magnet  5  is provided below the diaphragm  3  so that the electric motor system and the diaphragm  3  are overlapped. Accordingly, in order to reduce the thickness T of the acoustic transducer  1 , it is necessary to reduce the thickness of the electric motor system or to reduce an operating range of the diaphragm  3 , that is, an amplitude of the diaphragm  3 . 
         [0008]    However, when the thickness of the electric motor system is made thin, the magnetic flux density of the permanent magnet is reduced so that the magnetic force is decreased. As a result, there is a problem that the sound pressure level is greatly lowered in the entire frequency band. Further, when the operating range of the diaphragm is reduced, there is a problem that the low-frequency reproduction capability is largely lowered. 
         [0009]    Accordingly, development of a slim acoustic transducer that addresses the above-described problems and can reduce the thickness thereof has been required. 
       SUMMARY 
       [0010]    The present disclosure has been developed to address the above drawbacks and other problems associated with the conventional arrangement. An example aspect of the present disclosure relates to a slim acoustic transducer having a thin thickness a low-frequency reproduction capability and a sound pressure level in substantially the entire frequency band of which may not be lowered. 
         [0011]    According to an example aspect of the present disclosure, a slim acoustic transducer may include a diaphragm; a voice coil disposed at a rim (e.g., peripheral portion) of the diaphragm; and a permanent magnet disposed around the voice coil and configured to apply a magnetic field to the voice coil, wherein a maximum amplitude of the diaphragm is less than a thickness of the permanent magnet. 
         [0012]    The permanent magnet may include an intermediate plate provided around the voice coil; an upper permanent magnet provided on a top surface of the intermediate plate; and a lower permanent magnet provided on a bottom surface of the intermediate plate. 
         [0013]    The upper permanent magnet and the lower permanent magnet may be provided on the intermediate plate so that equal magnetic poles face each other. 
         [0014]    Each of the upper permanent magnet and the lower permanent magnet may be provided with a plurality of air passages disposed in a radial direction. Each of the upper permanent magnet and the lower permanent magnet may be comprised of a plurality of permanent magnet pieces, and the plurality of air passages may be provided between the plurality of permanent magnet pieces. 
         [0015]    The slim acoustic transducer may include a frame configured to support and fix the intermediate plate, the upper permanent magnet, and the lower permanent magnet. 
         [0016]    The slim acoustic transducer may include a surround connecting a top surface of the diaphragm and a top surface of the intermediate plate; and a suspension connecting a bottom surface of the diaphragm and a bottom surface of the intermediate plate. 
         [0017]    The slim acoustic transducer may include an enclosure provided to be in contact with a top surface of the upper permanent magnet and a bottom surface of the lower permanent magnet. 
         [0018]    A magnetic body may not be provided below the diaphragm. 
         [0019]    According to another example aspect of the present disclosure, a slim acoustic transducer may include a diaphragm; a voice coil disposed at a rim (e.g., peripheral portion) of the diaphragm; and a permanent magnet disposed around the voice coil and configured to apply a magnetic field to the voice coil, wherein the permanent magnet may include an intermediate plate provided around the voice coil; an upper permanent magnet disposed on a top surface of the intermediate plate; and a lower permanent magnet disposed on a bottom surface of the intermediate plate. 
         [0020]    When the diaphragm moves maximally upward, the diaphragm may not protrude above a top surface of the upper permanent magnet, and when the diaphragm moves maximally downward, the diaphragm may not protrude below a bottom surface of the lower permanent magnet. 
         [0021]    According to another example aspect of the present disclosure, an image display apparatus may include a flat display panel configured to output video; and a slim acoustic transducer provided at a side of the flat display panel and configured to output sound, wherein the slim acoustic transducer may include any one of the above-described features. 
         [0022]    Other objects, advantages and salient features of the present disclosure will become apparent from the following detailed description, which, taken in conjunction with the annexed drawings, discloses various example embodiments. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0023]    These and/or other aspects, features and advantages of the present disclosure will become apparent and more readily appreciated from the following detailed description, taken in conjunction with the accompanying drawings, in which like reference numerals refer to like elements, and wherein: 
           [0024]      FIG. 1  is a cross-sectional diagram illustrating a conventional acoustic transducer; 
           [0025]      FIG. 2  is a perspective view illustrating an example slim acoustic transducer according to an example embodiment of the present disclosure; 
           [0026]      FIG. 3  is a cross-sectional view illustrating the slim acoustic transducer of  FIG. 2  taken along a line of I-I; 
           [0027]      FIG. 4  is an exploded perspective view illustrating the slim acoustic transducer of  FIG. 2 ; 
           [0028]      FIG. 5  is a rear perspective view illustrating the slim acoustic transducer of  FIG. 2 ; 
           [0029]      FIG. 6  is a diagram illustrating a magnetic flux flow of an electric motor system of a slim acoustic transducer according to an example embodiment of the present disclosure; 
           [0030]      FIG. 7  is an image illustrating a result of computer simulation analysis of an electric motor system of a slim acoustic transducer according to an example embodiment of the present disclosure; 
           [0031]      FIG. 8  is a cross-sectional view illustrating an example slim acoustic transducer according to an example embodiment of the present disclosure disposed in an enclosure; 
           [0032]      FIG. 9  is a plan view illustrating an example slim acoustic transducer according to an example embodiment of the present disclosure disposed in an enclosure; 
           [0033]      FIG. 10  is a rear view illustrating an example slim acoustic transducer according to an example embodiment of the present disclosure disposed in an enclosure; 
           [0034]      FIG. 11  is a perspective view illustrating an example slim acoustic transducer according to another example embodiment of the present disclosure; 
           [0035]      FIG. 12  is a cross-sectional view illustrating the slim acoustic transducer of  FIG. 11  taken along a line of II-II; 
           [0036]      FIG. 13  is an exploded perspective view illustrating the slim acoustic transducer of  FIG. 11 ; 
           [0037]      FIG. 14  is a rear perspective view illustrating the slim acoustic transducer of  FIG. 11 ; 
           [0038]      FIG. 15  is a perspective view illustrating an example slim acoustic transducer having air passages according to another example embodiment of the present disclosure; 
           [0039]      FIG. 16  is a perspective view illustrating an example slim acoustic transducer having air passages according to another example embodiment of the present disclosure; 
           [0040]      FIG. 17  is a cross-sectional view illustrating an example slim acoustic transducer according to another example embodiment of the present disclosure; 
           [0041]      FIG. 18  is a perspective view illustrating an example slim television provided with a slim acoustic transducer according to an example embodiment of the present disclosure; 
           [0042]      FIG. 19  is a cross-sectional view illustrating the slim acoustic transducer provided in the slim television of  FIG. 18  taken along a line of III-III; 
           [0043]      FIG. 20  is a perspective view illustrating an example mobile device provided with an example slim acoustic transducer according to an example embodiment of the present disclosure; 
           [0044]      FIG. 21  is a cross-sectional view illustrating the slim acoustic transducer provided in the mobile device of  FIG. 20  taken along a line of IV-IV; 
           [0045]      FIG. 22  is a perspective view illustrating an example speaker implemented by a slim acoustic transducer according to an example embodiment of the present disclosure; 
           [0046]      FIG. 23  is a cross-sectional view illustrating the speaker of  FIG. 22  taken along a line of V-V; 
           [0047]      FIG. 24  is a perspective view illustrating an example speaker implemented by a slim acoustic transducer according to another example embodiment of the present disclosure; and 
           [0048]      FIG. 25  is a cross-sectional view illustrating the speaker of  FIG. 24  taken along a line of VI-VI. 
       
    
    
       [0049]    Throughout the drawings, like reference numerals will be understood to refer to like parts, components and structures. 
       DETAILED DESCRIPTION 
       [0050]    Hereinafter, various example embodiments of the present disclosure will be described in greater detail with reference to the accompanying drawings. 
         [0051]    The matters disclosed herein, such as a detailed construction and elements thereof, are provided to aid in a comprehensive understanding of this disclosure. Thus, it is apparent that various example embodiments may be carried out without those defined matters. Also, well-known functions or constructions may be omitted to provide a clear and concise description of various example embodiments. Further, dimensions of various elements in the accompanying drawings may be arbitrarily increased or decreased for assisting in a comprehensive understanding. 
         [0052]    The terms “first”, “second”, etc. may be used to describe diverse components, but the components are not limited by the terms. The terms are used to simply distinguish one component from the others. 
         [0053]    The terms used in the present application are only used to describe the various example embodiments, but are not intended to limit the scope of the disclosure. The singular expression also includes the plural meaning as long as it does not conflict with the meaning in context. In the present application, the terms “include” and “consist of” designate the presence of features, numbers, steps, operations, components, elements, or a combination thereof that are written in the disclosure, but do not exclude the presence or possibility of addition of one or more other features, numbers, steps, operations, components, elements, or a combination thereof. 
         [0054]      FIG. 2  is a perspective view illustrating an example slim acoustic transducer according to an example embodiment of the present disclosure.  FIG. 3  is a cross-sectional view illustrating the slim acoustic transducer of  FIG. 2  taken along a line of I-I.  FIG. 4  is an exploded perspective view illustrating the slim acoustic transducer of  FIG. 2 , and  FIG. 5  is a rear perspective view illustrating the slim acoustic transducer of  FIG. 2 . 
         [0055]    Referring to  FIGS. 2 to 5 , a slim acoustic transducer  10  according to an example embodiment of the present disclosure may include a diaphragm  11 , a voice coil  20 , and a permanent magnet  30 . 
         [0056]    The diaphragm  11  vibrates depending on the movement of the voice coil  20  to produce a compressional wave of air particles, thereby producing sound. The diaphragm  11  is formed in a thin plate shape. The diaphragm  11  may, for example, comprise cotton-fabric, compression-molded sponge, rubber, synthetic resin, metal, and the like. Depending on weight and area of the diaphragm  11 , a lower limit frequency may vary. 
         [0057]    The voice coil  20  is provided on the rim of the diaphragm  11 . At this time, only the voice coil  20  may be vertically provided on the rim of the diaphragm  11 . As another example, the voice coil  20  may be formed by providing a hollow bobbin  21  on the rim of the diaphragm  11  and winding wire on the outer circumferential surface of the hollow bobbin  21 . Accordingly, when the voice coil  20  vibrates, the diaphragm  11  is vibrated to reproduce sound. It will be understood that the terms rim and peripheral portion may be used interchangeably. 
         [0058]    The permanent magnet  30  is disposed around the voice coil  20  to surround the diaphragm  11  and the voice coil  20 . The permanent magnet  30  is configured to apply a magnetic field to the voice coil  20  so that the voice coil  20  can vibrate based on the change of the current flowing through the voice coil  20 . 
         [0059]    As illustrated in  FIGS. 3 and 4 , the permanent magnet  30  may include an intermediate plate  31 , an upper permanent magnet  33 , and a lower permanent magnet  35 . 
         [0060]    The intermediate plate  31  is disposed around the voice coil  20 . For example, the intermediate plate  31  may be formed in a thin donut shape, and the diaphragm  11  and the voice coil  20  are provided in the center of the intermediate plate  31 . The intermediate plate  31  may be formed of a magnetic material. For example, the intermediate plate  31  may be made of a steel plate cold commercial (SPCC). 
         [0061]    The upper permanent magnet  33  is disposed on the top surface of the intermediate plate  31 , and the lower permanent magnet  35  is disposed on the bottom surface of the intermediate plate  31 . Accordingly, the intermediate plate  31  is disposed to be sandwiched between the upper permanent magnet  33  and the lower permanent magnet  35 . In other words, the lower permanent magnet  35 , the intermediate plate  31 , and the upper permanent magnet  33  are stacked in this order. The thickness of the upper permanent magnet  33  and the lower permanent magnet  35  may be determined to be larger than the maximum displacement of the diaphragm  11 . For example, when the diaphragm  11  vibrates, the thickness of each of the upper permanent magnet  33  and the lower permanent magnet  35  may be configured so that the diaphragm  11  does not protrude above the upper permanent magnet  33  or below the lower permanent magnet  35 . 
         [0062]    As illustrated in  FIG. 6 , the upper permanent magnet  33  and the lower permanent magnet  35  are disposed on the intermediate plate  31  so that the same magnetic poles face each other. When the intermediate plate  31  is interposed between the upper permanent magnet  33  and the lower permanent magnet  35  the same magnetic poles of which face each other, a large magnetic flux may be obtained by minimizing and/or reducing the leakage magnetic flux by a repulsive magnetic field. 
         [0063]      FIG. 6  is a diagram illustrating an example magnetic flux flow of an electric motor system of a slim acoustic transducer according to an example embodiment of the present disclosure. For example, the electric motor system is configured to operate the diaphragm  11 , and includes the voice coil  20 , the upper permanent magnet  33 , the lower permanent magnet  35 , and the intermediate plate  31 . 
         [0064]    Referring to  FIG. 6 , the N-pole of the upper permanent magnet  33  is provided to be in contact with the top surface of the intermediate plate  31 , and the N-pole of the lower permanent magnet  35  is provided to be in contact with the bottom surface of the intermediate plate  31 . Accordingly, the magnetic flux of each of the upper permanent magnet  33  and the lower permanent magnet  35  is concentrated on the voice coil  20  through the intermediate plate  31 . Accordingly, a large magnetic flux may be applied to the voice coil  20  by minimizing and/or reducing the leakage magnetic flux without providing a magnet or a magnetic body below the diaphragm  11 . 
         [0065]    The inventors performed magnetic field analysis to confirm whether that the electric motor system of the slim acoustic transducer  10  according to an example embodiment of the present disclosure having the above-described configuration forms a closed magnetic flux path and the magnetic flux is concentrated in the voice coil  20 . 
         [0066]    Physical properties of NdFeB-48H is applied to the upper permanent magnet  33  and the lower permanent magnet  35 , SPCC is applied to the intermediate plate  31 , and then computer simulation analysis is performed.  FIG. 7  is an image illustrating a result of computer simulation analysis of an electric motor system of a slim acoustic transducer  10  according to an example embodiment of the present disclosure. 
         [0067]    Referring to  FIG. 7 , it can be seen that the closed magnetic flux path of the electric motor system of the slim acoustic transducer  10  is formed to spread upward and downward from the intermediate plate  31 , and the magnetic flux F is concentrated to the voice coil  20  as much as possible by the repulsive magnetic field. Accordingly, it can be seen that when the electric motor system is configured by applying the repulsive magnetic field, the magnetic force loss due to the leakage magnetic flux may be minimized and/or substantially reduced. 
         [0068]    In  FIG. 6 , the upper permanent magnet  33  and the lower permanent magnet  35  are provided on the intermediate plate  31  so that the N-poles face each other, but they may be provided in the opposite manner. Although not illustrated, the upper permanent magnet  33  and the lower permanent magnet  35  may be provided on the intermediate plate  31  so that the S-poles face each other. 
         [0069]    The upper permanent magnet  33  may be formed of a plurality of permanent magnet pieces  33   a . For example, the upper permanent magnet  33 , as illustrated in  FIGS. 2 and 4 , may be formed of the plurality of permanent magnet pieces  33   a  having a shape in which a donut-shaped permanent magnet is cut into several pieces. Accordingly, the upper permanent magnet  33  may be formed by arranging the plurality of permanent magnet pieces  33   a  in a substantially circular shape at substantially regular intervals on the top surface of the intermediate plate  31 . A gap between two adjacent permanent magnet pieces  33   a  forms an air passage  41  through which air passes. Accordingly, the upper permanent magnet  33  includes a plurality of air passages  41  provided between the plurality of permanent magnet pieces  33   a . The plurality of air passages  41  are formed in a radial direction from the center of the upper permanent magnet  33 , for example, the center C of the diaphragm  11 . The plurality of air passages  41  as described above are paths through which the air moves when the diaphragm  11  vibrates. 
         [0070]    As illustrated in  FIGS. 2 and 4 , the upper permanent magnet  33  includes eight permanent magnet pieces  33   a  and eight air passages  41 . However, the number of the permanent magnet pieces  33   a  and the number of the air passages  41  are not limited thereto. Depending on the characteristics of the acoustic transducer  10  in need, the number of each of the permanent magnet pieces  33   a  and the air passages  41  of the upper permanent magnet  33  may be variously determined. 
         [0071]    The lower permanent magnet  35  also may be formed of a plurality of permanent magnet pieces  35   a . For example, the lower permanent magnet  35 , as illustrated in  FIGS. 4 and 5 , may be formed of a plurality of permanent magnet pieces  35   a  having a shape in which a donut-shaped permanent magnet is cut into several pieces. Accordingly, the lower permanent magnet  35  may be formed by arranging the plurality of permanent magnet pieces  35   a  in a substantially circular shape at substantially regular intervals on the bottom surface of the intermediate plate  31 . A gap between two adjacent permanent magnet pieces  35   a  forms an air passage  42  through which air passes. Accordingly, the lower permanent magnet  35  includes a plurality of air passages  42  provided between the plurality of permanent magnet pieces  35   a . The plurality of air passages  42  are formed in a radial direction from the center of the lower permanent magnet  35 , for example, the center C of the diaphragm  11 . The plurality of air passages  42  as described above are paths through which the air moves when the diaphragm  11  vibrates. 
         [0072]    In  FIGS. 4 and 5 , the lower permanent magnet  35  includes eight permanent magnet pieces  35   a  and eight air passages  42 . However, the number of the permanent magnet pieces  35   a  and the number of the air passages  42  are not limited thereto. Depending on the characteristics of the acoustic transducer  10  in need, the number of each of the permanent magnet pieces  35   a  and the air passages  42  of the lower permanent magnet  35  may be variously determined. Also, the number of the plurality of permanent magnet pieces  35   a  and the air passages  42  constituting the lower permanent magnet  35  may be determined differently from the number of the plurality of permanent magnet pieces  33   a  and the plurality of air passages  41  constituting the upper permanent magnet  33 . 
         [0073]    Further, referring to  FIGS. 2 and 5 , the plurality of air passages  41  of the upper permanent magnet  33  and the plurality of air passages  41  of the lower permanent magnet  35  are provided to coincide with each other in the vertical direction, but this is only an example. Although not illustrated, the plurality of air passages  41  of the upper permanent magnet  33  and the plurality of air passages  41  of the lower permanent magnet  35  are provided to be offset from each other in the vertical direction. 
         [0074]    The intermediate plate  31  may be fixed to a frame  50  and supports the diaphragm  11 . For this purpose, the top surface of the diaphragm  11  and the top surface of the intermediate plate  31  are connected by a surround  60 . For example, the rim or peripheral portion of the top surface of the diaphragm  11  and the inner rim or peripheral portion of the top surface of the intermediate plate  31  are connected by the surround  60  so that the diaphragm  11  is fixed to the intermediate plate  31 . At this time, the surround  60  is provided all around the rim of the top surface of the diaphragm  11 . The surround  60  is formed of an elastic material such as rubber so that the diaphragm  11  can vibrate up and down integrally with the voice coil  20 . The surround structure described above and hereinafter may also be referred to as a surround structure. 
         [0075]    Further, the bottom surface of the diaphragm  11  and the bottom surface of the intermediate plate  31  are connected by a suspension structure  70 . For example, the rim of the bottom surface of the diaphragm  11  and the inner rim of the bottom surface of the intermediate plate  31  are connected by the suspension structure  70  (hereinafter referred to as a suspension). The suspension  70  may, for example, be formed of a thin metal plate, and is provided to transmit current to the voice coil  20 . In other words, the suspension  70  is formed to perform a function of a lead wire that transmits current to the voice coil  20  together with a function of supporting the diaphragm  11 . 
         [0076]    For this purpose, as illustrated in  FIG. 4 , the suspension  70  may be comprised of two separate suspensions, for example, a first suspension  71  and a second suspension  72 , which can support the rim of the bottom surface of the diaphragm  11 . The first suspension  71  and the second suspension  72  may be configured to support half of the rim of the bottom surface of the diaphragm  11 , respectively. 
         [0077]    For example, the first suspension  71  may include a fixing portion  71   a  fixed to the intermediate plate  31  and a supporting portion  71   b  fixed to the diaphragm  11 . The supporting portion  71   b  is formed in a shape corresponding to the rim of the diaphragm  11 , the fixing portion  71   a  is bent along the supporting portion  71   b , and a distal end  71   c  of the fixing portion  71   a  is bent in the radial direction. Two fixing portions  71   a  are provided, and the distal end  71   c  of the fixing portion  71   a  may be formed to be inserted into the air passage  42  of the lower permanent magnet  35 . The second suspension  72  may be formed in the same manner as the first suspension  71 , and thus a detailed description thereof is omitted. Although  FIG. 4  illustrates and describes the case in which two fixing portions  71   a  are formed, the number of the fixing portions  71   a  is not limited thereto. The fixing portion  71   a  may be provided in three or more as necessary. 
         [0078]    An end of the voice coil  20  is connected to the first suspension  71 , and the other end of the voice coil  20  is connected to the second suspension  72 . Accordingly, the voice coil  20  may be connected to an electric circuit (not illustrated) that outputs current corresponding to a voice signal through the suspension  70 . 
         [0079]    The intermediate plate  31 , the upper permanent magnet  33 , and the lower permanent magnet  35  as described above may be fixed to and supported by the frame  50 . For example, the frame  50  may be formed in a shape corresponding to the upper permanent magnet  33  and the lower permanent magnet  35 . In the present example embodiment, since each of the upper permanent magnet  33  and the lower permanent magnet  35  is formed in a substantially circular shape, the frame  50  is also formed in a substantially circular shape. The frame  50  may be provided with a plurality of openings  51  and  52  corresponding to the plurality of air passages  41  and  42  of each of the upper permanent magnet  33  and the lower permanent magnet  35 . Accordingly, spaces above and below the diaphragm  11  and the outside of the slim acoustic transducer  10  are in fluid communication with each other through the plurality of openings  51  and  52  of the frame  50  and the plurality of air passages  41  and  42  of the permanent magnet  30 . 
         [0080]    A plurality of seating portions  53  may be formed on the inner circumferential surface of the frame  50 . The plurality of seating portions  53  are formed to protrude toward the center from the inner surface of the frame  50 . The plurality of permanent magnet pieces  33   a  comprising the upper permanent magnet  33  are placed on the top surfaces of the plurality of seating portions  53 , and the plurality of permanent magnet pieces  35   a  constituting the lower permanent magnet  35  are placed on the bottom surfaces of the plurality of seating portions  53 . The thickness of the plurality of seating portions  53  may be formed in the same as the thickness of the intermediate plate  31 . A plurality of fixing protrusions  55  for fixing the intermediate plate  31  are provided between the plurality of seating portions  53 . 
         [0081]    As described above, in the slim acoustic transducer  10  according to an example embodiment of the present disclosure, since the permanent magnet  30  is provided around the diaphragm  11 , the size of the permanent magnet  30  is not limited by the diaphragm  11 . For example, when the thickness T of the slim acoustic transducer  10  is limited, the permanent magnet  30  may be made larger in diameter to increase the magnetic force. 
         [0082]    The slim acoustic transducer  10  according to the present example embodiment may be received in an enclosure  80  (illustrated, for example, in  FIGS. 8 to 10 ). The enclosure  80  may be formed in such a shape that the upper side of the diaphragm  11  is opened and the lower side of the diaphragm  11  is enclosed. In order to reduce the height (or thickness) H of the enclosure  80 , the top and bottom surfaces of the slim acoustic transducer  10  may be formed to be in contact with upper and lower walls  81  and  82  of the enclosure  80 , respectively. 
         [0083]    Hereinafter, an enclosure in which a slim acoustic transducer according to an example embodiment of the present disclosure is disposed will be described with reference to  FIGS. 8 to 10 . 
         [0084]      FIG. 8  is a cross-sectional view illustrating an example slim acoustic transducer according to an example embodiment of the present disclosure disposed in an enclosure.  FIG. 9  is a plan view illustrating an example slim acoustic transducer according to an example embodiment of the present disclosure disposed in an enclosure, and  FIG. 10  is a rear view illustrating an example slim acoustic transducer according to an example embodiment of the present disclosure disposed in an enclosure. For reference,  FIG. 9  illustrates a state in which an upper wall  81  of the enclosure  80  covering the upper permanent magnet  33  is removed, and  FIG. 10  illustrates a state in which a lower wall  82  of the enclosure  80  covering the lower permanent magnet  35  is removed. 
         [0085]    Referring to  FIG. 8 , the top and bottom surfaces of the slim acoustic transducer  10  according to an example embodiment of the present disclosure are covered by the upper wall  81  and the lower wall  82  of the enclosure  80 , respectively. For example, the top surface of the upper permanent magnet  33  of the slim acoustic transducer  10  is in contact with the upper wall  81  of the enclosure  80 , and the bottom surface of the lower permanent magnet  35  is in contact with the lower wall  82  of the enclosure  80 . 
         [0086]    Accordingly, the upper side of the diaphragm  11  of the slim acoustic transducer  10  is covered by the upper wall  81  of the enclosure  80  so that an upper space  91  of the diaphragm  11  is formed between the top surface of the diaphragm  11  surrounded by the upper permanent magnet  33  and the upper wall  81  of the enclosure  80 . Since the thickness of the upper permanent magnet  33  is determined to be larger than the maximum displacement of the diaphragm  11 , when the diaphragm  11  is vibrated up and down by the voice coil  20 , the diaphragm  11  and the surround  60  are not in contact with the upper wall  81  of the enclosure  80 . Further, a side wall of the enclosure  80  is provided with an upper opening  83  in fluid communication with the upper space  91  of the diaphragm  11 . 
         [0087]    The lower side of the diaphragm  11  of the slim acoustic transducer  10  is covered by the lower wall  82  of the enclosure  80  so that an lower space  92  of the diaphragm  11  is formed between the bottom surface of the diaphragm  11  surrounded by the lower permanent magnet  35  and the lower wall  82  of the enclosure  80 . Since the thickness of the lower permanent magnet  35  is determined to be larger than the maximum displacement of the diaphragm  11 , when the diaphragm  11  is vibrated up and down by the voice coil  20 , the diaphragm  11  and the suspension  70  are not in contact with the lower wall  82  of the enclosure  80 . Further, the other side wall of the enclosure  80  is provided with a lower opening  84  in fluid communication with the lower space  92  of the diaphragm  11 . The lower opening  84  is in fluid communication with an inner space  87  of the enclosure  80  provided at one side of the slim acoustic transducer  10 . The inner space  87  of the enclosure  80  may be formed as a closed space formed by the upper wall  81 , the lower wall  82 , and the side wall  86  of the enclosure  80 . 
         [0088]    Also, the upper space  91  and the lower space  92  of the diaphragm  11  are separated from each other by a middle wall  85 . Accordingly, the upper space  91  of the diaphragm  11  is not in fluid communication with the inner space  87  of the enclosure  80 . 
         [0089]    Accordingly, when a voice signal corresponding to the sound to be reproduced is input to the voice coil  20  through the suspension  70 , the voice coil  20  is vibrated by the magnetic field applied by the upper permanent magnet  33  and the lower permanent magnet  35 . Thus, the diaphragm  11  provided integrally with the voice coil  20  vibrates to generate sound. When the diaphragm  11  vibrates to generate sound, the volume of each of the upper space  91  and the lower space  92  of the diaphragm  11  changes so that a flow of air may be generated. 
         [0090]    For example, as illustrated in  FIG. 8 , when the diaphragm  11  moves upward, the volume of the upper space  91  of the diaphragm  11  is reduced, so that the air in the upper space  91  is discharged to the outside of the upper permanent magnet  33  through the plurality of air passages  41  provided in the upper permanent magnet  33 . As illustrated in  FIG. 8 , since only one side surface of the upper permanent magnet  33  is opened and the other side surfaces of the upper permanent magnet  33  are surrounded by the enclosure  80 , the air discharged through the plurality of air passages  41  is discharged to the outside of the enclosure  80  through the upper opening  83  (see arrow of  FIG. 9 ). 
         [0091]    On the other hand, as illustrated in  FIG. 8 , when the diaphragm  11  moves upward, the volume of the lower space  92  of the diaphragm  11  becomes larger, so that the air in the inner space  87  of the enclosure  80  flows into the lower space  92  of the diaphragm  11  through the plurality of air passages  42  provided in the lower permanent magnet  35 . As illustrated in  FIG. 10 , since only one side surface of the lower permanent magnet  35  is opened and the other side surfaces of the lower permanent magnet  35  are surrounded by the enclosure  80 , the air in the inner space  87  of the enclosure  80  is drawn through the lower opening  84  and moved to the lower space  92  of the diaphragm  11  through the plurality of air passages  42  of the lower permanent magnet  35  (see arrow of  FIG. 10 ). 
         [0092]    Although not illustrated, when the diaphragm  11  moves downward, the volume of the upper space  91  of the diaphragm  11  becomes larger, and the volume of the lower space  92  becomes smaller, so that the air moves inversely to the above description. 
         [0093]    In the above description, the slim acoustic transducer  10  has the suspension  70  that is formed to perform both the function to support the diaphragm  11  and the function to transmit a voice signal to the voice coil  20 . However, the slim acoustic transducer may be formed so that a suspension only performs the function of supporting the diaphragm. 
         [0094]    Hereinafter, a slim acoustic transducer according to another example embodiment of the present disclosure will be described with reference to  FIGS. 11 to 14 . 
         [0095]      FIG. 11  is a perspective view illustrating an example slim acoustic transducer according to another example embodiment of the present disclosure.  FIG. 12  is a cross-sectional view illustrating the slim acoustic transducer of  FIG. 11  taken along a line of  FIG. 13  is an exploded perspective view illustrating the slim acoustic transducer of  FIG. 11 , and  FIG. 14  is a rear perspective view illustrating the slim acoustic transducer of  FIG. 11 . 
         [0096]    Referring to  FIGS. 11 to 14 , a slim acoustic transducer  10 ′ according to another example embodiment of the present disclosure may include a diaphragm  11 , a voice coil  20 , a permanent magnet  30 , a surround  60 ′, a suspension  90 , and a frame  50 ′. 
         [0097]    The diaphragm  11 , the voice coil  20 , and the permanent magnet  30  of the slim acoustic transducer  10 ′ according to the present embodiment are substantially the same as the diaphragm  11 , the voice coil  20 , and the permanent magnet  30  of the slim acoustic transducer  10  according to the above-described embodiment, and the surround  60 ′, the suspension  90 , and the frame  50 ′ of the slim acoustic transducer  10 ′ according to the present embodiment are different from the surround  60 , the suspension  70 , and the frame  50  of the slim acoustic transducer  10  according to the above-described embodiment. 
         [0098]    Accordingly, hereinafter, detailed descriptions of the diaphragm  11 , the voice coil  20 , and the permanent magnet  30  are omitted, and the surround  60 ′, the suspension  90 , and the frame  50 ′ will be described. Components having the same function will be described with the same reference numerals. 
         [0099]    The surround  60 ′ is provided to support the diaphragm  11  with respect to the frame  50 ′ so that the diaphragm  11  can vibrate up and down with respect to the permanent magnet  30 , and connects the top surface of the diaphragm  11  with the top surface of the frame  50 ′. For example, the rim of the top surface of the diaphragm  11  and the inner rim of the top surface of the frame  50 ′ are connected by the surround  60 ′ so that the diaphragm  11  is fixed to the frame  50 ′. The surround  60 ′ is provided all around the verge of the top surface of the diaphragm  11 . The surround  60 ′ may be formed of an elastic material such as rubber so that the diaphragm  11  can vibrate up and down integrally with the voice coil  20 . In the present example embodiment, since the frame  50 ′ is formed to cover the top surface and the bottom surface of the intermediate plate  31 , the surround  60 ′ is fixed to the top surface of the frame  50 ′. However, in the case where the intermediate plate  31  is exposed to the inside from the frame  50 ′ as in the above-described example embodiment, the surround  60 ′ may be fixed to the top surface of the intermediate plate  31 . 
         [0100]    The suspension  90  is provided to support the bottom surface of the diaphragm  11  with respect to the frame  50 ′ so that the diaphragm  11  can vibrate up and down with respect to the permanent magnet  30 . The suspension  90  connects the bottom surface of the diaphragm  11  with the bottom surface of the frame  50 ′. For example, the rim of the bottom surface of the diaphragm  11  and the inner rim of the bottom surface of the frame  50 ′ are connected by the suspension  90  so that the diaphragm  11  is supported by the frame  50 ′. The suspension  90  is provided all around the rim of the bottom surface of the diaphragm  11 . Accordingly, the suspension  90  may be formed in the same or similar shape as the above-described surround  60 ′. Further, the suspension  90  may be formed of an elastic material such as rubber so that the diaphragm  11  can vibrate up and down integrally with the voice coil  20 . In the present example embodiment, since the frame  50 ′ is formed to cover the bottom surface of the intermediate plate  31 , the suspension  90  is fixed to the bottom surface of the frame  50 ′. However, in the case where the intermediate plate  31  is exposed to the inside from the frame  50 ′ as in the above-described example embodiment, the suspension  90  may be fixed to the bottom surface of the intermediate plate  31 . 
         [0101]    The frame  50 ′ may be formed to fix and support the intermediate plate  31 , and the upper permanent magnet  33  and the lower permanent magnet  35  comprising the permanent magnet  30 . For example, the frame  50 ′ is formed in a shape corresponding to the upper permanent magnet  33  and the lower permanent magnet  35 . In the present example embodiment, since each of the upper permanent magnet  33  and the lower permanent magnet  35  is formed in a substantially circular shape, the frame  50 ′ is also formed in a substantially circular shape. The frame  50 ′ is provided with a plurality of openings  51  and  52  corresponding to the plurality of air passages  41  and  42  of each of the upper permanent magnet  33  and the lower permanent magnet  35 . Accordingly, spaces above and below the diaphragm  11  and the outside of the slim acoustic transducer  10 ′ are in fluid communication with each other through the plurality of openings  51  and  52  of the frame  50 ′ and the plurality of air passages  41  and  42  of the permanent magnet  30 . 
         [0102]    A plurality of seating portions  53  are formed on the inner circumferential surface of the frame  50 ′. The plurality of seating portions  53  are formed to protrude toward the center from the inner surface of the frame  50 ′. The plurality of permanent magnet pieces  33   a  constituting the upper permanent magnet  33  are placed on the top surfaces of the plurality of seating portions  53 , and the plurality of permanent magnet pieces  35   a  constituting the lower permanent magnet  35  are placed on the bottom surfaces of the plurality of seating portions  53 . The thickness of the plurality of seating portions  53  may be formed in the same as the thickness of the intermediate plate  31 . A support ring  57  for supporting the intermediate plate  31  is provided in the inside of the plurality of seating portions  53 . The above-described surround  60 ′ is disposed on the top surface of the support ring  57  of the frame  50 ′, and the suspension  90  is disposed on the bottom surface of the support ring  57  of the frame  50 ′. A plurality of fixing protrusions  55 ′ for fixing the support ring  57  with respect to the frame  50 ′ are provided between the plurality of seating portions  53 . 
         [0103]    In the present example embodiment, since the suspension  90  is not formed of metal, the suspension  90  does not perform the function of transmitting a voice signal to the voice coil  20 . Accordingly, wires  23  extending from opposite ends of the voice coil  20  are directly connected to an external electric circuit (not illustrated). For this purpose, the frame  50 ′ may be provided with a groove (not illustrated) through which the wires  23  of the voice coil  20  can pass. 
         [0104]    In the slim acoustic transducer  10  and  10 ′ as described above, the upper permanent magnet  33  and the lower permanent magnet  35  may be formed of a plurality of permanent magnet pieces  33   a  and  35   a  to provide the plurality of air passages  41  and  42 . However, the structure of each of the upper permanent magnet  33  and the lower permanent magnet  35  is not limited thereto. As another example embodiment, each of the upper permanent magnet and the lower permanent magnet may be formed in a single body. 
         [0105]    Hereinafter, a slim acoustic transducer having an upper permanent magnet and a lower permanent magnet that is formed in a single body will be described with reference to  FIGS. 15 and 16 . 
         [0106]      FIG. 15  is a perspective view illustrating an example slim acoustic transducer having air passages according to another example embodiment of the present disclosure. 
         [0107]    Referring to  FIG. 15 , a slim acoustic transducer  100  according to an example embodiment of the present disclosure may include a diaphragm  11 , a voice coil, a surround  160 , and a suspension that are substantially the same as the diaphragm  11 , the voice coil  20 , the surround  60 , and the suspension  70  of the slim acoustic transducer  10  according to the above-described example embodiment. A permanent magnet  130  and a frame  150  of the slim acoustic transducer  100  are different from the permanent magnet  30  and the frame  50  of the slim acoustic transducer  10  according to the above-described example embodiment. 
         [0108]    Accordingly, hereinafter, descriptions of the diaphragm  111 , the voice coil, the surround  160 , and the suspension are omitted, and both the permanent magnet  130  and the frame  150  will be described. 
         [0109]    The permanent magnet  130  may include an upper permanent magnet  133  and a lower permanent magnet  135 . Each of the upper permanent magnet  133  and the lower permanent magnet  135  may be formed in a donut shape. The upper permanent magnet  133  is provided with a plurality of through holes  141  in a radial direction. Also, the lower permanent magnet  135  is provided with a plurality of through holes  142  in the radial direction. An upper space and a lower space of the diaphragm  111  are in fluid communication with the outside through the plurality of through holes  141  and  142 . Accordingly, the plurality of through holes  141  and  142  may form the plurality of air passages  41  and  42  of the slim acoustic transducer  10  according to the above-described example embodiment. 
         [0110]    The frame  150  may be formed to fix the upper permanent magnet  133  and the lower permanent magnet  135  that are formed in a single body, and support an intermediate plate (not illustrated) provided between the upper permanent magnet  133  and the lower permanent magnet  135 . The frame  150  is provided with a plurality of openings  151  and  152  corresponding to the plurality of through holes  141  and  142 . 
         [0111]      FIG. 16  is a perspective view illustrating an example slim acoustic transducer having an air passage according to another example embodiment of the present disclosure. 
         [0112]    Referring to  FIG. 16 , a slim acoustic transducer  200  according to an example embodiment of the present disclosure may include a diaphragm  211 , a voice coil, a surround  260 , and a suspension that are substantially the same as the diaphragm  11 , the voice coil  20 , the surround  60 , and the suspension  70  of the slim acoustic transducer  10  according to the above-described example embodiment. A permanent magnet  230  and a frame  250  of the slim acoustic transducer  200  are different from the permanent magnet  30  and the frame  50  of the slim acoustic transducer  10  according to the above-described embodiment. 
         [0113]    Accordingly, hereinafter, descriptions of the diaphragm  211 , the voice coil, the surround  260 , and the suspension are omitted, and both the permanent magnet  230  and the frame  250  will be described. 
         [0114]    The permanent magnet  230  may include an upper permanent magnet  233  and a lower permanent magnet  235 . Each of the upper permanent magnet  233  and the lower permanent magnet  235  is formed in a donut shape. The top surface of the upper permanent magnet  233  is provided with a plurality of elongate grooves  241  in a radial direction. Also, the bottom surface of the lower permanent magnet  235  is provided with a plurality of elongate grooves  242  in the radial direction. An upper space and a lower space of the diaphragm  211  are in fluid communication with the outside through the plurality of elongate grooves  241  and  242 . Accordingly, the plurality of elongate grooves  241  and  242  may form the plurality of air passages  41  and  42  of the slim acoustic transducer  10  according to the above-described example embodiment. 
         [0115]    The frame  250  may be formed to fix the upper permanent magnet  233  and the lower permanent magnet  235  that are formed in a single body, and support an intermediate plate (not illustrated) provided between the upper permanent magnet  233  and the lower permanent magnet  235 . The frame  250  is provided with a plurality of openings  251  and  252  corresponding to the plurality of elongate grooves  241  and  242 . 
         [0116]    As described above, in the slim acoustic transducer  10 ,  10 ′,  100 , and  200  according to an example embodiment of the present disclosure, the permanent magnet  30 ,  130 , and  230  is not disposed below and overlapping the diaphragm  11 ,  111 , and  211  but is provided around the diaphragm  11 ,  111 , and  211 . Accordingly, the slim acoustic transducer  10 ,  10 ′,  100 , and  200  according to an example embodiment of the present disclosure may have a thickness smaller than that of the conventional acoustic transducer  1  in which the permanent magnet  5  and the yoke  7 , which is a magnetic body, are provided below the diaphragm  3 . 
         [0117]    Also, since the slim acoustic transducer  10 ,  10 ′,  100 , and  200  according to an example embodiment of the present disclosure does not have a structure in which the diaphragm  11 ,  111 , and  211  and the permanent magnet  30 ,  130 , and  230  are stacked, the amplitude of the diaphragm may be made larger than that of the conventional acoustic transducer even when the thickness of the slim acoustic transducer is reduced. Accordingly, when the thickness of the slim acoustic transducer according to an example embodiment of the present disclosure is made equal to the thickness of the acoustic transducer according to the prior art, there is an advantage that bass performance can be improved as compared with the acoustic transducer according to the prior art. 
         [0118]    Accordingly, by using the slim acoustic transducer  10 ,  10 ′,  100 , and  200  according to an example embodiment of the present disclosure, an ultrathin woofer capable of low-frequency reproduction may be implemented. 
         [0119]    In the above description, the permanent magnet is comprised of the upper permanent magnet and the lower permanent magnet; however, the structure of the permanent magnet is not limited thereto. The permanent magnet may be formed of one magnet. 
         [0120]    Hereinafter, a slim acoustic transducer having a permanent magnet formed of one magnet will be described with reference to  FIG. 17 . 
         [0121]      FIG. 17  is a cross-sectional view illustrating an example slim acoustic transducer according to another example embodiment of the present disclosure. 
         [0122]    Referring to  FIG. 17 , a slim acoustic transducer  300  according to an example embodiment of the present disclosure may include a diaphragm  311 , a voice coil  320 , a surround  360 , and a suspension  370  that are substantially the same as or similar to the diaphragm  11 , the voice coil  20 , the surround  60 , and the suspension  70  of the slim acoustic transducer  10  according to the above-described example embodiment. A permanent magnet  330  of the slim acoustic transducer  300  is different from the permanent magnet  30  of the slim acoustic transducer  10  according to the above-described embodiment. 
         [0123]    Accordingly, hereinafter, descriptions of the diaphragm  311 , the voice coil  320 , the surround  360 , and the suspension  370  are omitted, and only the permanent magnet  330  will be described. 
         [0124]    The permanent magnet  330  is formed in a donut shape. Each of the top surface and the bottom surface of the permanent magnet  330  may be provided with a plurality of air passages  341  and  342 . The plurality of air passages  341  and  342  may be formed in a plurality of elongated grooves on the top surface and the bottom surface of the permanent magnet  330 . 
         [0125]    The surround  360  and the suspension  370  may be fixed to the top surface and the bottom surface of a fixing ring  350  provided in the inner surface of the permanent magnet  330  to support the diaphragm  311 . 
         [0126]    The slim acoustic transducer  300  according to an example embodiment of the present disclosure having the configuration as described above may reproduce sound by vibrating the diaphragm  311  up and down when a voice signal flows through the voice coil  320 . 
         [0127]    In the above description of the slim acoustic transducer  10 ,  10 ′,  100 ,  200 , and  300  according to an example embodiment of the present disclosure, the diaphragm  11 ,  111 ,  211 , and  311  has a substantially circular shape; however, the shape of the diaphragm  11  is not limited thereto. Although not illustrated, the diaphragm may be formed in a rectangular shape, an elliptical shape, a track shape, or the like. In this case, the permanent magnet may also be formed in a shape corresponding to the diaphragm. 
         [0128]    Hereinafter, an image display apparatus having a slim acoustic transducer according to an example embodiment of the present disclosure will be described with reference to  FIGS. 18 to 21 . A slim television and a mobile device will be described as examples of the image display apparatus. However, the image display apparatus to which the slim acoustic transducer according to an example embodiment of the present disclosure can be applied is not limited thereto. 
         [0129]    A slim television in which a slim acoustic transducer according to an example embodiment of the present disclosure is provided will be described with reference to  FIGS. 18 and 19 . 
         [0130]      FIG. 18  is a perspective view illustrating a slim television provided with a slim acoustic transducer according to an example embodiment of the present disclosure, and  FIG. 19  is a cross-sectional view illustrating the slim acoustic transducer provided in the slim television of  FIG. 18  taken along a line of III-III. 
         [0131]    Referring to  FIG. 18 , two slim acoustic transducers  10  according to an example embodiment of the present disclosure are provided on the left and right sides of a slim television  400 . In this example two slim acoustic transducers  10  are provided to emit sound toward the bottom. However, the disclosure is not limited thereto 
         [0132]    For example, referring to  FIG. 19 , the slim acoustic transducer  10  is disposed behind a flat display panel  410 , and is provided inside an enclosure  80 . A first opening  83  of the enclosure  80 , which is in fluid communication with the outside, is provided on the lower surface  401  of the slim television  400 , so that sound reproduced by the slim acoustic transducer  10  is output to the outside of the slim television  400  through the first opening  83 . Also, a second opening  84  of the enclosure  80  is provided to be in fluid communication with the inner space  87  of the enclosure  80  opposite to the first opening  83 . 
         [0133]    Accordingly, when the slim television  400  outputs video, the sound is reproduced by the two slim acoustic transducers  10  provided on the lower portions of the left and right sides of the slim television  400 . 
         [0134]    As described above, since the slim acoustic transducer  10  according to an example embodiment of the present disclosure is very thin, the thickness of the slim television  400  may be reduced even if the flat display panel  410  and the slim acoustic transducer  10  are stacked. 
         [0135]    In the slim television  400  as illustrated in  FIGS. 18 and 19 , the slim acoustic transducer  10  is provided to emit sound toward the bottom; however, a direction in which the slim acoustic transducer  10  emits sound is not limited thereto. For example, the slim acoustic transducer  10  may be provided to emit sound to the left and right of the slim television  400 . Alternatively, a waveguide (not illustrated) may be provided so that the slim acoustic transducer  10  emits sound toward the front of the slim television  400 . 
         [0136]    Hereinafter, a mobile device in which a slim acoustic transducer according to an example embodiment of the present disclosure is provided will be described with reference to  FIGS. 20 and 21 . 
         [0137]      FIG. 20  is a perspective view illustrating a mobile device provided with an example slim acoustic transducer according to an example embodiment of the present disclosure, and  FIG. 21  is a cross-sectional view illustrating the slim acoustic transducer provided in the mobile device of  FIG. 20  taken along a line of IV-IV. 
         [0138]    Referring to  FIG. 20 , a slim acoustic transducer  10  according to an example embodiment of the present disclosure is provided in a side of a lower portion of a smartphone  500 . However, it will be understood that the placement of the slim acoustic transducer  10  is not limited thereto. 
         [0139]    For example, referring to  FIG. 21 , the slim acoustic transducer  10  is disposed behind a flat display panel  510 , and is provided inside of the enclosure  80 . A first opening  83  of the enclosure  80 , which is in fluid communication with the outside, is provided on a side surface  501  of the smartphone  500 , so that sound reproduced by the slim acoustic transducer  10  is output to the outside of the smartphone  500  through the first opening  83 . Also, a second opening  84  of the enclosure  80  is provided to be in fluid communication with the inner space  87  of the enclosure  80  opposite to the first opening  83 . 
         [0140]    Accordingly, when the smartphone  500  reproduces sound, the sound is reproduced by the slim acoustic transducer  10  provided on the side of the lower portion of the smartphone  500 . 
         [0141]    As described above, since the slim acoustic transducer  10  according to an example embodiment of the present disclosure is very thin, the thickness of the smartphone  500  may be reduced even if the flat display panel  510  and the slim acoustic transducer  10  are stacked. 
         [0142]    In the above description, the smartphone has been illustrated and described as an example of the mobile device; however, the mobile device in which the slim acoustic transducer according to an example embodiment of the present disclosure is used is not limited thereto. The slim acoustic transducer according to an example embodiment of the present disclosure may use in various mobile devices such as a tablet computer, a notebook computer, a portable gaming device, and the like. 
         [0143]    In the above description, a slim acoustic transducer according to an example embodiment of the present disclosure is used in an image display apparatus such as a slim television, a mobile device, etc. However, application of the slim acoustic transducer according to an example embodiment of the present disclosure is not limited thereto. The slim acoustic transducer according to an example embodiment of the present disclosure may be implemented as independent speakers or sound bars. 
         [0144]    Hereinafter, a slim acoustic transducer according to an example embodiment of the present disclosure implemented as an independent speaker or sound bar will be described with reference to  FIGS. 22 to 25 . 
         [0145]      FIG. 22  is a perspective view illustrating a speaker implemented by an example slim acoustic transducer according to an example embodiment of the present disclosure, and  FIG. 23  is a cross-sectional view illustrating the speaker of  FIG. 22  taken along a line of V-V. 
         [0146]    Referring to  FIGS. 22 and 23 , in a speaker according to an example embodiment of the present disclosure, a body  620  of the speaker  600  forms an enclosure. In other words, the enclosure  620  forms an outer appearance of the speaker  600 . A slim acoustic transducer  610  is provided inside the enclosure  620 . 
         [0147]    For example, the top surface and the bottom surface of the slim acoustic transducer  610  according to an example embodiment of the present disclosure are covered by an upper wall  621  and a lower wall  622  of the enclosure  620 , respectively. Accordingly, the upper side of a diaphragm  611  of the slim acoustic transducer  610  is covered by the upper wall  621  of the enclosure  620  so that an upper space  631  of the diaphragm  611  is formed between the top surface of the diaphragm  611  surrounded by the upper permanent magnet  612  and the upper wall  621  of the enclosure  620 . Further, one side wall of the enclosure  620  is provided with a first opening  623  that allows the upper space  631  of the diaphragm  11  to be in fluid communication with the outside. At this time, the upper wall  621  of the enclosure  620  may be provided to be in contact with or spaced apart from the top surface of the upper permanent magnet  612 . When the thickness of the speaker  600  is minimized, the upper wall  621  of the enclosure  620  and the top surface of the upper permanent magnet  612  are provided to be in contact with each other. 
         [0148]    The lower side of the diaphragm  611  of the slim acoustic transducer  610  is covered by the lower wall  622  of the enclosure  620  so that a lower space  632  of the diaphragm  611  is formed between the bottom surface of the diaphragm  611  surrounded by the lower permanent magnet  613  and the lower wall  622  of the enclosure  620 . The lower wall  622  of the enclosure  620  may be provided to be in contact with or spaced apart from the bottom surface of the lower permanent magnet  613 . When the thickness of the speaker  600  is minimized, the lower wall  622  of the enclosure  620  and the bottom surface of the lower permanent magnet  613  are provided to be in contact with each other. 
         [0149]    The upper space  631  and the lower space  632  of the diaphragm  611  are separated from each other by a middle wall  626  of the enclosure  620 . Other configurations of the slim acoustic transducer  610  are the same as those of the slim acoustic transducer  10  according to the above-described embodiment; therefore, detailed descriptions thereof are omitted. 
         [0150]    An inner space  633  is provided in a side of the slim acoustic transducer  610 . The inner space  633  of the enclosure  620  may be formed as a closed space formed by the upper wall  621 , the lower wall  622 , and the side wall  625  connecting the upper wall  621  and the lower wall  622 . The inner space  633  and the upper space  631  are separated by a partition wall  627  extending from the middle wall  626 , and the lower space  632  is in fluid communication with the inner space  633  through the second opening  624 . Accordingly, the upper space  631  of the enclosure  620  is not in fluid communication with the inner space  633 . The second opening  624  of the enclosure  620  may be provided opposite to the first opening  623 . 
         [0151]    Accordingly, the sound generated by the vibration of the diaphragm  611  caused due to the voice signal corresponding to the sound to be reproduced is output to the outside of the speaker  600  through the first opening  623  after colliding with the upper wall  621 . 
         [0152]      FIG. 24  is a perspective view illustrating a speaker implemented by an example slim acoustic transducer according to another example embodiment of the present disclosure, and  FIG. 25  is a cross-sectional view illustrating the speaker of  FIG. 24  taken along a line of VI-VI. 
         [0153]    Referring to  FIGS. 24 and 25 , in a speaker  700  according to an example embodiment of the present disclosure, a body  720  of the speaker  700  forms an enclosure. In other words, the enclosure  720  forms an outer appearance of the speaker  700 . A slim acoustic transducer  710  according to an example embodiment of the present disclosure is provided inside the enclosure  720 . However, the speaker  700  according to the present example embodiment is different in the output direction of sound from the speaker  600  as illustrated in  FIGS. 22 and 23 . 
         [0154]    For example, the top surface and the bottom surface of the slim acoustic transducer  710  according to an example embodiment of the present disclosure are covered by an upper wall  721  and a lower wall  722  of the enclosure  720 , respectively. The upper wall  721  is provided with a first opening  723  corresponding to the diaphragm  711 . Accordingly, an upper permanent magnet  712  of the slim acoustic transducer  710  is covered by the upper wall  721 , and an upper space  731  of the diaphragm  711  surrounded by the upper permanent magnet  712  is exposed to the outside. Since the upper space  731  of the diaphragm  711  is directly in fluid communication with the outside, the upper permanent magnet  712  is not provided with a plurality of air passages unlike the upper permanent magnet  33  of the slim acoustic transducer  10  according to the above-described embodiment. 
         [0155]    The lower side of the diaphragm  711  of the slim acoustic transducer  710  is covered by the lower wall  722  of the enclosure  720  so that a lower space  732  of the diaphragm  711  is formed between the bottom surface of the diaphragm  711  surrounded by the lower permanent magnet  713  and the lower wall  722  of the enclosure  720 . 
         [0156]    The upper space  731  and the lower space  732  of the diaphragm  711  are separated from each other by a middle wall  726  of the enclosure  720 . Other configurations of the slim acoustic transducer  710  are the same as those of the slim acoustic transducer  10  according to the above-described embodiment; therefore, detailed descriptions thereof are omitted. 
         [0157]    An inner space  733  is provided in a side of the slim acoustic transducer  710 . The inner space  733  of the enclosure  720  may be formed as a closed space formed by the upper wall  721 , the lower wall  722 , and the side wall  725 . The inner space  733  and the upper space  731  of the diaphragm  711  are separated by a partition wall  727  extending from the middle wall  726 , and the lower space  732  is in fluid communication with the inner space  733  through a second opening  724 . 
         [0158]    Accordingly, the sound generated by the vibration of the diaphragm  711  caused due to the voice signal corresponding to the sound to be reproduced is output to the outside of the speaker  700  through the first opening  723 . 
         [0159]    Speakers  600  and  700  or sound bars that are independently formed using a slim acoustic transducer according to an example embodiment of the present disclosure as illustrated in  FIGS. 22 to 25  may be fixed to a wall, furniture, or the like using a fixing device (not illustrated). 
         [0160]    While various example embodiments of the present disclosure have been described, additional variations and modifications of the embodiments may occur to those skilled in the art. Therefore, it is intended that the appended claims shall be understood to include both the above embodiments and all such variations and modifications that fall within the spirit and scope of the disclosure.