Patent Publication Number: US-2023152411-A1

Title: Directional acoustic sensor

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is based on and claims priority under 35 U.S.C. §119 to Korean Patent Application No. 10-2021-0155987, filed on Nov. 12, 2021, in the Korean Intellectual Property Office, the disclosure of which is incorporated by reference herein in its entirety. 
     BACKGROUND 
     1. Field 
     The present disclosure relates to directional acoustic sensors, and more particularly, to directional acoustic sensors including a resonator that reacts to a pressure difference in an acoustic sound. 
     2. Description of the Related Art 
     Utilization of acoustic sensors that are mounted on household appliances, video display devices, virtual reality devices, augmented reality devices, artificial intelligence speakers, etc., to detect a direction of a sound and recognize voices is increasing. Recently, a directional acoustic sensor for detecting an acoustic signal by converting a mechanical motion caused by a pressure difference into an electrical signal has been developed. 
     SUMMARY 
     Provided are directional acoustic sensors which may have improved sensitivity by increasing an acoustic resistance. 
     Additional aspects will be set forth in part in the description which follows and, in part, will be apparent from the description, or may be learned by practice of the presented embodiments of the disclosure. 
     According to an aspect of an example embodiment, a directional acoustic sensor includes: a support including a first support portion and a second support portion that are separated from each other and face each other; a plurality of first resonators extending in a length direction thereof from the first support portion of the support; and a plurality of second resonators extending in the length direction thereof from the second support portion of the support and facing the plurality of first resonators, wherein each first resonator of the plurality of first resonators has a first end, wherein each second resonator of the plurality of second resonators has a second end, and wherein, in a first resonator arrangement of a region where the plurality of first resonators and the plurality of second resonators face each other, the first ends of the plurality of first resonators and the second ends of the plurality of second resonators form an intersecting structure. 
     The first end of each first resonator of the plurality of first resonators may have a structure in which a partial width portion of each first resonator extends in the length direction thereof, the second end of each second resonator of the plurality of second resonators may have a structure in which a partial width portion of each second resonator that does not face the partial width portion of a corresponding first resonator extends in the length direction thereof, and a second resonator arrangement may be formed in a region where the plurality of first resonators and the plurality of second resonators face each other in a structure in which the first ends of the plurality of first resonators respectively intersect with the second ends of the plurality of second resonators. 
     The first ends of the plurality of first resonators and the second ends of the plurality of second resonators may respectively engage with each other. 
     The first ends of the plurality of first resonators and the second ends of the plurality of second resonators may respectively engage with each other in a male or female form. 
     The first ends of the plurality of first resonators and the second ends of the plurality of second resonators may respectively engage with each other in an edge shape. 
     Each first resonator of the plurality of first resonators and each second resonator of the plurality of second resonators may include a base, and a frame protruding from the base and extending in the length direction thereof. 
     The frame may be integrally formed with the base. 
     Each of the base and the frame may include silicon. 
     The frame may be provided on at least one of both sides and an inside of the base. 
     Each the first ends of the plurality of first resonators and the second ends of the plurality of second resonators may have a plate shape up to a height of the frame. 
     The base and the frame may extend to each of the first ends of the plurality of first resonators and each of the second ends of the plurality of second resonators. 
     The first end of each first resonator of the plurality of first resonators may have a structure in which a width portion of a first side of each first resonator extends in the length direction thereof, the second end of each second resonator of the plurality of second resonators may have a structure in which a width portion of a second side of each second resonator extends in the length direction thereof, and the frame may extend to end portions of the first end and the second end. 
     The first end of each first resonator of the plurality of first resonators may have a structure in which a width portion of a first side of each first resonator extends in the length direction thereof, the second end of each second resonator of the plurality of second resonators may have a structure in which a width portion of a second side of the second resonator that does not face the width portion of the first side of the first resonator extends in the length direction thereof, and the frame may extend to a circumference of the first end and the second end. 
     Each first resonator of the plurality of first resonators and each second resonator of the plurality of second resonators may include a base and a groove pattern formed in the base to a predetermined depth. 
     Each first resonator of the plurality of first resonators and each second resonator of the plurality of second resonators may include a base and a plurality of through holes formed in the base and having a size smaller than a wavelength of an audible frequency band. 
     The directional acoustic sensor may further include at least one third resonator extending in the length direction thereof from the first support portion or the second support portion of the support and not facing the plurality of first resonators or the plurality of second resonators. 
     The at least one third resonator may include a base and a frame protruding from the base and extending in the length direction thereof. 
     Each first resonator of the plurality of first resonators and each second resonator of the plurality of second resonators may include: a driving portion configured to move in response to an input sound signal; and a sensing portion configured to detect movement of the driving portion. 
     Each first resonator of the plurality of first resonators and each second resonator of the plurality of second resonators may include a cantilever beam having a first end fixed to the first support portion and the second support portion and a second end moving freely. 
     The plurality of first resonators and the plurality of second resonators may have resonant frequencies different from each other. 
     According to an aspect of an example embodiment, there is provided an electronic device including a directional acoustic sensor including: a support including a first support portion and a second support portion that are separated from each other and face each other; a plurality of first resonators extending in a length direction thereof from the first support portion of the support; and a plurality of second resonators extending in the length direction thereof from the second support portion of the support and facing the plurality of first resonators, wherein each first resonator of the plurality of first resonators has a first end, wherein each second resonator of the plurality of second resonators has a second end, and wherein, in a first resonator arrangement of a region where the plurality of first resonators and the plurality of second resonators face each other, the first ends of the plurality of first resonators and the second ends of the plurality of second resonators form an intersecting structure. 
     The directional acoustic sensor may further include at least one third resonator extending in the length direction thereof from the first support portion or the second support portion of the support and not facing the plurality of first resonators or the plurality of second resonators. 
     The at least one third resonator may include a base and a frame protruding from the base and extending in the length direction thereof. 
     Each first resonator of the plurality of first resonators and each second resonator of the plurality of second resonators may include: a driving portion configured to move in response to an input sound signal, and a sensing portion configured to detect movement of the driving portion. 
     Each first resonator of the plurality of first resonators and each second resonator of the plurality of second resonators may include a cantilever beam having a first end fixed to the first support portion and the second support portion and a second end moving freely. 
     The plurality of first resonators and the plurality of second resonators may have resonant frequencies different from each other. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other aspects, features, and advantages of certain example embodiments of the disclosure will be more apparent from the following description taken in conjunction with the accompanying drawings, in which: 
         FIG.  1    is a perspective view exemplarily illustrating a directional acoustic sensor according to an example embodiment; 
         FIG.  2    is a plan view of the directional acoustic sensor of  FIG.  1    according to an example embodiment; 
         FIGS.  3 A,  3 B and  3 C  are diagrams of resonators applicable to first and second resonators of  FIGS.  1  and  2    according to example embodiments; 
         FIG.  3 D  is a diagram of an example of a resonator applicable to a third resonator of  FIGS.  1  and  2    according to an example embodiment; 
         FIG.  4    is a cross-sectional view taken along line IV-IV of  FIG.  3 A  according to an embodiment; 
         FIG.  5 A  is a plan view of an intersecting portion when ends of two facing resonators have plate-shaped ends according to an example embodiment; 
         FIG.  5 B  is a cross-sectional view taken along line A-A* of  FIG.  5 A  according to an example embodiment; 
         FIG.  6 A  is a plan view of an intersecting portion when ends of two resonators facing each other have an end with a frame extending to the end according to an example embodiment; 
         FIG.  6 B  is a cross-sectional view taken along line B-B* of  FIG.  6 A  according to an example embodiment; 
         FIG.  7 A  is a plan view of an intersecting portion when ends of two resonators facing each other have an end with a frame extending to a circumference thereof according to an example embodiment; 
         FIG.  7 B  is a cross-sectional view taken along line C-C* of  FIG.  7 A  according to an example embodiment; 
         FIG.  8    is a diagram of an example of forming an intersecting structure in which ends of two resonators facing each other are engaged with each other in an edge shape according to an example embodiment; 
         FIG.  9    is a diagram of an example of forming an intersecting structure in which ends of two resonators facing each other are engaged with each other in a male/female form according to an example embodiment; 
         FIG.  10    is a schematic plan view illustrating a directional acoustic sensor according to a comparative example; 
         FIG.  11    is a diagram of a comparison of a layout size change of a resonator arrangement before and after the application of the intersecting structure of ends of two resonators facing each other according to an example embodiment; 
         FIG.  12    is a graph showing changes in the frequency response characteristics of resonators before and after the application of the intersecting structure of ends of two resonators facing each other according to an example embodiment; 
         FIG.  13    is a graph showing resonant frequency characteristics for each channel of the resonator arrangement before and after the application of the intersecting structure of the ends of two resonators facing each other according to an example embodiment; 
         FIG.  14    is a sample photograph after fabrication of a directional acoustic sensor according to an embodiment; 
         FIG.  15    is a photograph after packaging the directional acoustic sensor of  FIG.  14    according to an example embodiment; 
         FIG.  16    is a graph showing a result of measuring the frequency response characteristics of a directional acoustic sensor according to a manufactured example embodiment; 
         FIGS.  17 ,  18  and  19    are diagrams of resonators that may be applied to two resonators facing each other according to example embodiments; and 
         FIGS.  20 ,  21 ,  22 ,  23 ,  24  and  25    are diagrams of electronic devices to which the directional acoustic sensor according to an embodiment is applied as a voice interface device according to example embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to embodiments, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. In this regard, the present embodiments may have different forms and should not be construed as being limited to the descriptions set forth herein. Accordingly, the embodiments are merely described below, by referring to the figures, to explain aspects. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. Expressions such as “at least one of,” when preceding a list of elements, modify the entire list of elements and do not modify the individual elements of the list. 
     Reference will now be made in detail to embodiments, examples of which are illustrated in the accompanying drawings. In the drawings, like reference numerals refer to like elements, and the size of each component may be exaggerated for clarity and convenience of explanation. The embodiments of the inventive concept are capable of various modifications and may be embodied in many different forms. 
     When an element or layer is referred to as being “on” or “above” another element or layer, the element or layer may be directly on another element or layer or intervening elements or layers. The singular forms “a,” “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. When a part “comprises” or “includes” an element in the specification, unless otherwise defined, it is not excluding other elements but may further include other elements. 
     The term “above” and similar directional terms may be applied to both singular and plural. With respect to operations that constitute a method, the operations may be performed in any appropriate sequence unless the sequence of operations is clearly described or unless the context clearly indicates otherwise. The operations may not necessarily be performed in the order of sequence. 
     Also, in the specification, the term “units” or “...modules” denote units or modules that process at least one function or operation, and may be realized by hardware, software, or a combination of hardware and software. 
     The connections of lines and connection members between constituent elements depicted in the drawings are examples of functional connection and/or physical or circuitry connections, and thus, in practical devices, may be expressed as replicable or additional functional connections, physical connections, or circuitry connections. 
     The use of any and all examples, or exemplary language provided herein, is intended merely to better illuminate the inventive concept and does not pose a limitation on the scope of the inventive concept unless otherwise claimed. 
     A directional acoustic sensor according to an embodiment uses a principle of a resonator that responds to a pressure difference in an acoustic sound, and includes a combination of resonators having different resonant frequencies. Each of the resonators may be formed of a cantilever beam having one end fixed to a support and the other end moving freely, and the resonant frequency of each resonator may be determined by a length of the resonator or a concentration mass of the resonator. 
     The relationship between the characteristics of the cantilever-type resonator and the resonance frequency may be expressed as Equation (1). 
     
       
         
           
             
               w 
               0 
             
             = 
             
               
                 
                   
                     1.875 
                   
                   2 
                 
               
             
             
               
                 
                   
                     E 
                     l 
                   
                   
                     m 
                     
                       L 
                       2 
                     
                   
                 
               
             
           
         
       
     
     Here, w 0  indicates resonance frequency, E indicates effective modulus, l  
     
       
         
           
             
               l 
             
             = 
             
               
                 1 
                 
                   12 
                 
               
             
             
               
                 b 
                 
                   t 
                   3 
                 
               
             
           
         
       
     
      indicates moment of inertia, b indicates beam width, t is beam thickness, and m indicates effective mass, and L indicates beam length. 
     When a length of a resonator is the same and a mass is changed, a bandwidth of the resonator may be reduced. This is because if the mass is increased to lower a frequency, a Q-factor increases and the bandwidth decreases. Therefore, in order to implement the same bandwidth characteristics even though the frequencies are different from each other, the adjustment of a resonant frequency by changing the length of the resonator is suitable for designing a directional acoustic sensor with a wide frequency band. When a required resonance frequency is designed, the number and length of resonators may be determined and the size of a device may be determined. However, when resonators having lengths different from each other are arranged, a through hole may be generated. The through hole may reduce an acoustic resistance, thereby reducing a pressure difference in acoustic sound, and may be a factor of lowering sensitivity. 
     According to the directional acoustic sensor according to an embodiment, a through-hole portion of a cavity may be minimized by forming a resonator arrangement in which a plurality of resonators face each other, and forming the resonator arrangement in a structure in which ends of two facing resonators intersect each other. By reducing or almost eliminating a through-hole portion by such an arrangement of the resonator, a decrease in sensitivity due to a decrease in acoustic resistance may be prevented, and the element size of the directional acoustic sensor may also be reduced. 
       FIG.  1    is a perspective view illustrating a directional acoustic sensor according to an example embodiment.  FIG.  2    is a plan view of the directional acoustic sensor of  FIG.  1    according to an example embodiment. 
     Referring to  FIGS.  1  and  2   , the directional acoustic sensor  100  includes a support  101  and a plurality of first resonators  110  and a plurality of second resonators  130  provided on the support  101 . The directional acoustic sensor  100  according to the embodiment may include at least one third resonator  130 ′ provided on the support  101 , although in some embodiments, the at least one third resonator  130 ′ is not included. 
     The support  101  is formed to include a cavity that penetrates therethrough, and includes first and second support portions  103  and  105  facing each other with the cavity therebetween. A separation distance between the first and second support portions  103  and  105  may correspond to a width of the cavity in a length direction of the directional acoustic sensor  100 . 
     The support  101  may be, for example, a silicon substrate, but is not limited thereto. The plurality of first resonators  110  and the plurality of second resonators  130  may be arranged in the cavity of the support  101  in a predetermined shape. For example, the plurality of first resonators  110  and the plurality of second resonators  130  may be arranged to form a resonator arrangement to face each other in the cavity of the support  101 . The at least one third resonator  130 ′ may be arranged in a predetermined shape in the cavity of the support  101  so as not to face the first resonator  110  or the second resonator  130 . 
     One end of each of the plurality of first resonators  110  may be fixed to the first support portion  103  of the support  101  to form a planarly parallel arrangement in the cavity of the support  101 . One end of each the plurality of second resonators  130  may be fixed to the second support portion  105  of the support  101  to form the planarly parallel arrangement in the cavity of the support  101 . One end of the at least one third resonator  130 ′ may be fixed to, for example, the second support portion  105  of the support  101  to form the planarly parallel arrangement in the cavity of the support  101 . Here, one end of the third resonator  130 ′ may be fixed to the first support portion  103  of the support  101 . 
     Each of the plurality of first resonators  110  may extend in the length direction thereof from the first support portion  103  of the support  101 . Each of the plurality of second resonators  130  may extend in the length direction thereof with respect to the second support portion  105  of the support  101 , and may be arranged to face the plurality of first resonators  110 . The at least one third resonator  130 ′ may extend in the length direction thereof from the second support portion  105  towards the first support portion  103 . 
       FIGS.  1  and  2    show an example arrangement in which the plurality of first resonators  110  and the plurality of second resonators  130  face each other, and the third resonator  130 ′ that does not face the first resonator  110  is included. 
     As another example, the plurality of first resonators  110  and the plurality of second resonators  130  are arranged to face each other, and the at least one third resonator  130 ′ may be arranged not to face the second resonator  130 . As another example, the number of first resonators  110  is the same as the number of second resonators  130 , the plurality of first resonators  110  and the plurality of second resonators  130  are all arranged to face each other, and the at least one third resonator  130 ′ that does not face the first resonator  110  or the second resonator  130  is not included. Hereinafter, a case in which the directional acoustic sensor  100  according to an embodiment further includes the at least one third resonator  130 ′ that does not face the first resonator  110 , and the third resonator  130 ′ is arranged parallel to the second resonator  130  will be described as an example. 
     Here, the length direction is a direction corresponding to the length of each of the resonators, that is, the first resonator  110 , the second resonator  130 , and the third resonator  130 ′, may correspond to a direction from the first support portion  103  to the second support portion  105  or correspond to a direction from the second support portion  105  to the first support portion  103 . That is, the length direction may correspond to a direction (x-axis direction) crossing the first support portion  103  and the second support portion  105 . 
     Each of the plurality of first resonators  110  may constitute a cantilever beam in which one end is fixed to the first support portion  103  of the support  101  and the other end freely moves. Each of the plurality of second resonators  130  and the at least one third resonator  130 ′ may form a cantilever beam in which one end is fixed to the second support portion  105  of the support  101  and the other end freely moves. 
       FIGS.  1  and  2    illustrate a case in which the plurality of first resonators  110 , the plurality of second resonators  130 , and the at least one third resonator  130 ′ move in a z-axis direction.  FIG.  1    exemplarily illustrates a state in which some portion of the second resonator  130  are moved by an input acoustic sound. 
     Each of the plurality of first resonators  110  includes a driving portion  120  configured to vibrate in response to an input sound signal, and a sensing portion configured to detect a movement of the driving portion  120 . Each of the plurality of second resonators  130  includes a driving portion  140  configured to vibrate in response to an input sound signal, and a sensing portion configured to detect a movement of the driving portion  140 . The driving portions  120  and  140  of each of the plurality of first resonators  110  and the plurality of second resonators  130  may be configured as a cantilever beam. 
     One end of the driving portion  120  of each of the plurality of first resonators  110  may be fixed to the first support portion  103  of the support  101 , and extend in the length direction of the first resonator  110  from the first support portion  103  toward the cavity. The driving portion  120  may be integrally formed with the support  101 , and in this case, the driving portion  120  may include, for example, silicon. However, the present embodiment is not limited thereto, and the driving portion  120  may not be integrally formed with the support  101 . The driving portion  120  of each of the plurality of first resonators  110  may have a first end  125  at an end thereof. 
     One end of a driving portion  140  of each of the plurality of second resonators  130  and the at least one third resonator  130 ′ may be fixed to the second support portion  105  of the support  101 , and may extend in the length direction (an x-axis direction in  FIGS.  1  and  2   ) of the second and third resonators  130  and  130 ′ from the second support portion  105  toward the cavity. The driving portion  140  may be integrally formed with the support  101 , and in this case, the driving portion  140  may include, for example, silicon. However, the present embodiment is not limited thereto, and the driving portion  140  may not be integrally formed with the support  101 . The driving portion  140  of each of the plurality of second resonators  130  may have a second end  145  at the end thereof. 
     An effective length of the first resonator  110  is a vibrating length of the driving portion  120 , and may include a length of the first end  125 . An effective length of the second resonator  130  is a vibrating length of the driving portion  140 , and may include a length of the second end  145 . 
     The directional acoustic sensor  100  according to the embodiment is configured such that the first end  125  and the second end  145  of the first resonator  110  and the second resonator  130  that face each other form an intersecting structure. The length of each of the first end  125  and the second end  145  for the intersecting structure may be formed up to approximately half of the effective length of each of the first resonator  110  and the second resonator  130 . That is, the length of each of the first and second ends  125  and  145  forming the intersecting structure of the first and second resonators  110  and  130  facing each other may be up to about half the length of each of the first and second resonators  110  and  130 . 
     Sensing portions  111  and  131  may be provided on one surface of each of the driving portions  120  and  140  to detect the movement of the driving portions  120  and  140 . The sensing portions  111  and  131  may include, for example, a piezoelectric element that generates electric energy by deformation of the piezoelectric material. In this case, each of the sensing portions  111  and  131  may include two electrodes and a piezoelectric layer provided between the two electrodes. 
     The first end  125  of the first resonator  110  and the second end  145  of the second resonator  130  disposed to face each other may respectively correspond to the end of the cantilever beam, which is the driving portion  120  or  140 . 
     The directional acoustic sensor  100  according to the embodiment includes a resonator arrangement region in which the first resonator  110  and the second resonator  130  face each other, and in the resonator arrangement to face each other, the first resonator  110  and the second resonator  130  may be arranged to form a structure in which the first end  125  and the second end  145  intersect each other. 
     For example, the first resonator  110  and the second resonator  130  that face each other may have a resonator arrangement such that the first end  125  of the first resonator  110  has a structure in which a width portion of one side of the first resonator  110  extends in the length direction thereof, the second end  145  of the second resonator  130  has a structure in which a width portion of the other side of the second resonator  130  that does not face the width portion of the one side of the first resonator  110  extends in the length direction thereof, and the first end  125  of the first resonator  110  and the second end  145  of the second resonator  130  have an intersecting structure. 
     In this case, the first end  125  and the second end  145  may be engaged with each other. The first resonator  110  and the second resonator  130  may be arranged facing each other such that the first end  125  and the second end  145  are engaged with each other, but direct collision does not occur and a gap between them is minimized. In this way, when the first end  125  and the second end  145  of the first resonator  110  and the second resonator  130  that face each other form an intersecting structure engaged with each other, in the arrangement region where the first resonator  110  and the second resonator  130  face each other, a through-hole portion of the cavity may be reduced or almost absent, and thus, a decrease in sensitivity due to a decrease in an acoustic resistance may be prevented, the sensitivity for sensing acoustic sound may be improved, and the device size of the directional acoustic sensor  100  may be reduced. 
     The first end  125  of the first resonator  110  and the second end  145  of the second resonator  130  disposed to face each other may have the same length or different lengths, and a sum of widths of the first end  125  and the second end  145  may be less than half of a sum of a maximum width of the first resonator  110  and a maximum width of the second resonator  130 . 
     For example, consider a case in which the maximum width of the first resonator  110  and the second resonator  130  disposed to face each other is equal to W. In this case, when the first resonator  110  and the second resonator  130  facing each other are arranged to form an intersecting structure in which the first end  125  and the second end  145  are engaged with each other, the sum of the width of the first end  125  and the width of the second end  145  may be less than or equal to W such that a gap between the first end  125  and the second end  145  is minimized without collision between the first end  125  and the second end  145 . In this case, the first end  125  and the second end  145  of the first resonator  110  and the second resonator  130  facing each other may have the same length or different lengths, and the width of the first end  125  may be the same as or different from the width of the second end  145 . For example, the first end  125  and the second end  145  of the first resonator  110  and the second resonator  130  facing each other may be the same width, and may have a width equal to or less than W/2, respectively. When a gap between the first end  125  and the second end  145  intersecting each other is large, an acoustic resistance may be reduced, and thus, the shape, length, and width of the first end  125  of the first resonator  110  and the second end  145  of the second resonator  130  arranged to intersect each other may be determined such that the decrease in sensitivity is prevented by suppressing the decrease in acoustic resistance and a desired resonant frequency is realized without collision between the first end  125  and the second end  145  engaged with each other. 
       FIGS.  1  and  2    exemplarily illustrate an arrangement in which the plurality of first resonators  110  and the plurality of second resonators  130  are disposed to face each other, and the at least one third resonator  130 ′ does not face the first resonator  110 . In the case of the third resonator  130 ′ that does not face the first resonator  110 , the second end  145  having a different shape may not be provided as exemplarily shown in  FIGS.  1  and  2   . For example, the third resonator  130 ′ may be formed to have a constant width. As another example, similar to the second resonator  130  facing the first resonator  110 , even in the case of the third resonator  130 ′ not facing the first resonator  110 , the second end  145  having a different shape may be provided. 
     The plurality of first resonators  110 , the plurality of second resonators  130 , and the at least one third resonator  130 ′ may sense sound frequencies of different bands. That is, the plurality of first resonators  110  may be configured to have different resonance frequencies. To this end, the plurality of first resonators  110  may have dimensions different from each other. For example, the plurality of first resonators  110  may have lengths, widths, or thicknesses different from each other. Also, the plurality of second resonators  130  may be configured to have different resonance frequencies. To this end, the plurality of second resonators  130  may have dimensions different from each other. For example, the plurality of second resonators  130  may have lengths, widths, or thicknesses different from each other. In addition, the shapes, lengths, and widths of the first end  125  of the first resonator  110  and the second end  145  of the second resonator  130  arranged to intersect each other may be determined so as to realize a desired resonant frequency without collision between the first end  125  and the second end  145  that intersect each other. Also, the at least one third resonator  130 ′ may be configured to have a different resonance frequency. To this end, the at least one third resonator  130 ′ may have a different dimension. For example, the at least one third resonator  130 ′ may have a different length, width, or thickness. 
       FIGS.  1  and  2    illustrate, as an example, a case in which the plurality of first resonators  110  have different lengths from each other, the plurality of second resonators  130  have different lengths from each other, the maximum widths of the first resonator  110  and the second resonator  130  are equal to W, and the first end  125  and the second end  145  have the same width of W/2 or less. The directional acoustic sensor  100  according to the present embodiment may have a directivity, for example, bi-directionality in a z-axis direction. 
       FIGS.  3 A to  3 C  illustrate various examples of resonators  150 ,  160 ,  170  that may be applied as the first resonator  110  and the second resonator  130  facing each other in  FIGS.  1  and  2    according to embodiments.  FIG.  3 D  illustrates an example of a resonator  150 ′ that may be applied as the third resonator  130 ′ that does not face the first resonator  110  in  FIGS.  1  and  2    according to an embodiment.  FIG.  4    is a cross-sectional view taken along line IV-IV of  FIG.  3 A , which corresponds to a cross-sectional view of the resonators  150 ,  150 ′,  160 , and  170  of  FIGS.  3 A to  3 D  according to an embodiment. As a third resonator  130 ′ that does not face the first resonator  110 , the resonators  150 ,  160 , and  170  of  FIGS.  3 A to  3 C  may be applied instead of the resonator  150 ′ of  FIG.  3 D . 
     Referring to  FIGS.  3 A to  3 D , each of the resonators  150 ,  150 ′,  160 , and  170  includes a driving portion  180  that vibrates in response to an acoustic signal, and a sensing portion  190  detecting a movement of the driving portion  180 . 
     The driving portion  180  of each of the resonators  150 ,  150 ′,  160 , and  170  is configured of a cantilever beam, and may extend in a length direction (x-axis direction in  FIGS.  1  and  2   ) of the resonators  150 ,  150 ′,  160 ,  170  from a support  107  (corresponding to the first support portion  103  or the second support portion  105  in  FIGS.  1  and  2   ) toward a cavity. One end of the driving portion  180  may be fixed to the support portion  107  of a support. The driving portion  180  may be integrally formed with the support, and in this case, the driving portion  180  may include, for example, silicon. However, the present embodiment is not limited thereto, and the driving portion  180   may not be formed integrally with the support. The sensing portion  190  may be provided on one surface of the driving portion  180  to detect the movement of the driving portion  180 . The sensing portion  190  may include a piezoelectric element that generates electric energy by deformation of the piezoelectric material. In this case, the sensing portion  190  may include two electrodes and a piezoelectric layer provided between the two electrodes. 
     The driving portion  180  of the resonators  150 ,  160 ,  170  may include a base  181  and a frame  183  protruding from the base  181  and extending in the length direction thereof. The driving portion  180 ′ of the resonators  150 ′ may include a base  181  and a frame  183 ′ protruding from the base  181  and extending in the length direction thereof. 
     Referring to  FIGS.  3 A to  3 C , the driving portions  180  of the resonators  150 ,  160 , and  170  respectively have ends  155 ,  165 , and  175  at end portions thereof (corresponding to the first end  125  and the second end  145  in  FIGS.  1  and  2   ). Referring to  FIG.  3 D , the driving portion  180 ′ of the resonator  150 ′ may be formed such that the frame  183 ′ extends also to an end portion of the base  181 . In the driving portion  180 / 180 ′ of the resonators  150 ,  160 , and  170 / 150 ′, the frame  183 / 183 ′ may be integrally formed with the base  181 , and the ends  155 ,  165 , and  175  may also be integrally formed with the base  181  and the frame  183 . The base  181  and the frame  183 / 183 ′ may include silicon, and the ends  155 ,  165 , and  175  may also include silicon. 
     The frame  183 / 183 ′ may be provided on at least one of both sides and an inner side of the base  181 . The frame  183 / 183 ′, for example, as shown in  FIGS.  3 A to  3 D , may be provided on both sides of the base  181 . Here, the frame  183 / 183 ′ may be continuously provided in parallel to the length direction (x-axis direction in  FIGS.  1  and  2   ) of the resonators  150 ,  160 , and  170 / 150 ′. For example, the frame  183 / 183 ′ may be continuously provided along both edges of the base  181 . 
       FIG.  4    is a cross-sectional view taken along line IV-IV of  FIG.  3 A  as an example. Referring to  FIG.  4   , the base  181  may have a predetermined width W, and the frame  183  may have a predetermined width W1. In addition, the frame  183  may have a predetermined height t1, and the base  181  may have a predetermined thickness t2. The predetermined thickness t2 of the base  181  may be less than the height t1 of the frame  183 , but the present embodiment is not limited thereto. 
     By configuring the driving portion  180  of the resonator to include the base  181  and the frame  183  extending in the length direction thereof to protrude from the base  181 , compared with a plate-type resonator having a thickness corresponding to a sum of the thickness of the base  181  and the height of the frame  183 , a mass thereof may be reduced while maintaining the same resonant frequency of the resonator. Accordingly, a bandwidth may be widened by lowering the quality factor of the resonator, and a flatness characteristic and sound quality of the directional acoustic sensor  100  including the resonator arrangement may be improved. 
     Here, in order to implement a wide frequency range by using a limited number of resonators and to improve flatness characteristics, each of the resonators is required to have a wide bandwidth, and for this purpose, a quality factor of the resonators must be small. The quality factor Q of the resonator may be expressed by Equation (2) below. 
     
       
         
           
             Q =  
             
               
                 
                   
                     m 
                     × 
                     f 
                   
                 
               
               / 
               c 
             
           
         
       
     
     Here, m is an effective mass, f is a resonance frequency, and c is a damping coefficient. 
     Referring to Equation (2), in order to reduce the quality factor while maintaining the resonant frequency of the resonator constant, it is required to reduce the mass of the resonator. When the mass of the resonator is reduced by reducing the thickness of the resonator, the length of the resonator must also be reduced to maintain the resonant frequency, and accordingly, an area of a portion receiving pressure from the input sound signal is reduced, thereby reducing the sensitivity of the directional acoustic sensor  100 . 
     However, as in the directional acoustic sensor  100  according to the embodiment, by applying the resonators  150 ,  160 , and  170 / 150 ′ having the driving portion  180 / 180 ′ including the base  181  and the frame  183 / 183 ′ extending in the length direction thereof to protrude on the base  181  to the plurality of first resonators  110 , the plurality of second resonators  130 , and the at least one third resonator  130 ′, the mass of each resonator may be reduced while maintaining a resonance frequency constant, and accordingly, compared to a conventional plate-type resonator, the quality factor may be reduced and the bandwidth may be increased. 
     As described above, in the directional acoustic sensor  100  according to the embodiment, by configuring each of the plurality of first resonators  110 , the plurality of second resonators  130 , and the at least one third resonator  130 ′ to include a frame extending in the length direction thereof to protrude from the base, each resonator may have a wide bandwidth while maintaining a resonant frequency, thereby improving sensitivity and flatness characteristics, and as a result, the number of resonators may be reduced, thereby improving price competitiveness. In addition, sound quality may be improved due to the improvement of the flatness characteristic. 
     Referring to  FIGS.  3 A to  3 C  again, the ends  155 ,  165 , and  175  of the driving portion  180  of the resonators  150 ,  160 , and  170  (the first end  125  and the second end  145  in  FIGS.  1  and  2   ) may be formed in various shapes. 
     As exemplarily illustrated in  FIG.  3 A , the end  155  of the driving portion  180  may be formed such that a width portion of one side of the resonator  150  extends in the length direction thereof, and may be formed in a plate shape up to the thickness of the frame  183 . In the present embodiment, the end  155  may be formed to have a thickness t corresponding to a sum of a thickness t2 of the base  181  and a thickness t1 of the frame  183 , or may be formed to have a thickness greater than the thickness t2 of the base  181  and less than the thickness t. 
       FIG.  5 A  is a plan view of an intersecting portion when ends of two facing resonators have plate-shaped ends according to an embodiment.  FIG.  5 B  is a cross-sectional view taken along line A-A* of  FIG.  5 A  according to an embodiment. When the resonator  150  having the end  155  of the driving portion  180  is applied as the first resonator  110  and the second resonator  130  facing each other of the directional acoustic sensor  100  according to the embodiment, as exemplarily illustrated in  FIGS.  5 A and  5 B , the first end  125  of the first resonator  110  and the second end  145  of the second resonator  130  may be arranged in an intersecting structure in which the first end  125  and the second end  145  are engaged with each other. The first end  125  of the first resonator  110  extends in the length direction thereof to correspond to a width portion of one side of the first resonator  110 , and the second end  145  of the second resonator  130  extends in the length direction thereof to correspond to a width portion of the other side of the second resonator  130  that does not face the width portion of one side of the first resonator  110 .  FIG.  5 A  is a plan view showing a portion where the first end  125  and the second end  145  intersect each other when the first end  125  of the first resonator  110  and the second end  145  of the second resonator  130  are provided with the end  155  having a plate shape as in  FIG.  3 A , and  FIG.  5 B  is a cross-sectional view taken along line A-A* of  FIG.  5 A . 
     As exemplarily illustrated in  FIG.  3 B , the end  165  of the driving portion  180  may be formed in a structure in which a width portion of one side of the resonator  160  extends in the length direction thereof, and the frame  183  extends to the end of the extended width portion of the one side. 
       FIG.  6 A  is a plan view of an intersecting portion when ends of two resonators facing each other have an end with a frame extending to the end according to an embodiment.  FIG.  6 B  is a cross-sectional view taken along line B-B* of  FIG.  6 A  according to an embodiment. When the resonator  160  having the end  165  of the driving portion  180  is applied as the first resonator  110  and the second resonator  130  facing each other of the directional acoustic sensor  100  according to the embodiment, as exemplarily illustrated in  FIGS.  6 A and  6 B , the first end  125  of the first resonator  110  and the second end  145  of the second resonator  130  may be arranged in an intersecting structure in which the first end  125  and the second end  145  are engaged with each other. The first end  125  of the first resonator  110  may have a structure in which a width portion of one side of the first end  125  of the first resonator  110  extends in the length direction thereof, and the second end  145  of the second resonator  130  may have a structure in which a width portion of other side of the second end  145  of the second resonator  130  that does not face the width portion of the one side of the first resonator  110  extends in the length direction thereof, and frames  127  and  147  may be formed to extend to the end portions of the first and second ends  125  and  145 . 
       FIG.  6 A  is a plan view showing an intersecting portion of the first end  125  and the second end  145  when the first end  125  of the first resonator  110  and the second end  145  of the second resonator  130  facing each other include the end  165  formed by extending the frame  183  to the end as in  FIG.  3 B , and  FIG.  6 B  is a cross-sectional view taken along line B-B* of  FIG.  6 A . 
     As exemplarily illustrated in  FIG.  3 C , the end  175  of the driving portion  180  may be formed in a structure in which a width portion of one side of the resonator  170  extends in the length direction thereof, and the frame  183  extends to a circumference of the extended end  175 . 
       FIG.  7 A  is a plan view of an intersecting portion when ends of two resonators facing each other have an end with a frame extending to a circumference thereof according to an embodiment.  FIG.  7 B  is a cross-sectional view taken along line C-C* of  FIG.  7 A  according to an embodiment. When the resonator  170  having the end  175  of the driving portion  180  is applied as the first resonator  110  and the second resonator  130  facing each other of the directional acoustic sensor  100  according to the embodiment, the first end  125  of the first resonator  110  and the second end  145  of the second resonator  130  facing each other may be arranged in an intersecting structure in which the first and second ends  125  and  145  are engaged with each other as exemplarily illustrated in  FIGS.  7 A and  7 B . The first end  125  of the first resonator  110  may have a structure in which a width portion of one side of the first resonator  110  extends in the length direction thereof, and the second end  145  of the second resonator  130  may have a structure in which a width portion of other side of the second resonator  130  that does not face the width portion of one side of the first resonator  110  extends in the length direction of the second resonator  130 , and the frames  127  and  147  may extend to the circumference of the first end  125  and the second end  145 . 
       FIG.  7 A  is a plan view showing an intersecting portion of the first end  125  and the second end  145  when the first end  125  of the first resonator  110  and the second end  145  of the second resonator  130  facing each other include the end  175  in which the frame  183  is formed by extending to a circumference of the end  175  as shown in  FIG.  3 C , and  FIG.  7 B  is a cross-sectional view taken along line C-C* of  FIG.  7 A . 
     When the resonators  150 ,  160 , and  170  having the ends  155 ,  165 , and  175  of the shape as exemplarily illustrated in  FIGS.  3 A to  3 C  are applied to the first resonator  110  and the second resonator  130  facing each other of the directional acoustic sensor  100  according to the embodiment, the intersecting structure in which the first and second ends  125  and  145  are engaged with each other may be formed to a thickness reaching a height of the frame as in  FIGS.  5 A and  5 B , or the frames  127  and  147  may be formed to extend to at least a portion of the engaged intersecting portion of the first and second ends  125  and  145  as in  FIGS.  6 A and  6 B  and as in  FIGS.  7 A and  7 B . 
       FIGS.  1  and  2    illustrate an example in which the structure of  FIGS.  5 A and  5 B  is applied as an intersecting structure of the first and second ends  125  and  145  engaged each other. Alternatively, the structure of  FIGS.  6 A and  6 B  or the structure of  FIGS.  7 A and  7 B  may be applied as the intersecting structure of the first and second ends  125  and  145  engaged each other. 
     In  FIGS.  1 ,  2 ,  3 A,  3 B, and  3 C , it is illustrated that the frame  183  does not extend to the end of the base  181  where the first end  125  of the driving portion  120  of the first resonator  110  and the second end  145  of the driving portion  140  of the second resonator  130  are not located, but this is merely an example, and the embodiment is not limited thereto. That is, the frame  183  may extend to the end of the base  181  where the first end  125  and the second end  145  are not located. 
     In addition, in  FIGS.  1 ,  2 ,  3 A,  3 B, and  3 C , it has been described and illustrated that the driving portions  120  and  140  of the first resonator  110  and the second resonator  130  have a structure including the base  181  and the frame  183  protruding from the base  181 , but this is merely an example, and the embodiment is not limited thereto. For example, the driving portions  120  and  140  of the first resonator  110  and the second resonator  130  may be formed in a structure without the frame  183 . 
       FIG.  8    is a diagram of an example of forming an intersecting structure in which ends of two resonators facing each other are engaged with each other in an edge shape according to an embodiment.  FIG.  9    is a diagram of an example of forming an intersecting structure in which ends of two resonators facing each other are engaged with each other in a male/female form according to an embodiment. In the above description, it has been described a case in which, at the intersecting portion of the first end  125  and the second end  145 , the width portion of the one side of the first resonator  110  and the width portion of the other side of the second resonator  130  that face each other extend in the length direction thereof to form an intersecting structure in which the first end  125  and the second end  145  are engaged with each other, but the embodiment is not limited thereto. For example, as shown in  FIG.  8   , the first end  125  and the second end  145  may be formed in an intersecting structure that engages with each other in an edge shape. In addition, an intersecting portion where the first and second ends  125  and  145  are engaged with each other may be formed to have an intersecting structure in which the first end  125  and the second end  145  are engaged with each other in a male/female shape, as shown in  FIG.  9   . The male/female shape of the first end  125  and the second end  145  may be formed opposite to that in  FIG.  9   . Also, in  FIGS.  8  and  9   , the first end  125  and the second end  145  may be formed in a plate-shape with a thickness reaching the height of the frame, or may be formed in a structure in which the frame extends to at least a portion of the intersecting portions of the first and second ends  125  and  145 . In  FIGS.  8  and  9   , the specific structure of the intersecting portions of the first end  125  and the second end  145  engaged with each other may be inferred from  FIGS.  5 A and  5 B ,  FIGS.  6 A and  6 B , and  FIGS.  7 A and  7 B , and thus, repeated descriptions and illustrations thereof are omitted. 
     In the embodiment described above, as an example, it is depicted that the directional acoustic sensor  100  according to the embodiment has a resonator arrangement including a plurality of first resonators  110 , a plurality of second resonators  130 , and at least one third resonator  130 ′, and in  FIGS.  1  and  2   , the directional acoustic sensor  100  includes a total of 16 resonators by including seven first and second resonators  110  and  130  respectively forming a resonator arrangement to face each other, respectively, and two third resonator  130 ′ that does not face the first resonator  110 , and the embodiment is not limited thereto. 
     According to the directional acoustic sensor  100  according to the embodiment as described above, the first end  125  of the first resonator  110  and the second end  145  of the second resonator  130  that face each other in the resonator arrangement form an intersecting structure in which the first end  125  and the second end  145  are engaged with each other, and thus, a through-hole in the cavity may be minimized or virtually eliminated in an arrangement region where the resonators face each other. Accordingly, in the directional acoustic sensor  100  according to the embodiment, a decrease in acoustic resistance may be suppressed, such that sensitivity may be improved, and a layout size of a resonator arrangement may be reduced, such that a device size may be reduced. 
     On the other hand, when the ends of the resonators facing each other are disposed without an intersecting structure, there may be a through-hole between the two facing resonators, whereby the acoustic resistance is reduced, and as a result, the sensitivity may be reduced than that of the directional acoustic sensor  100  according to the embodiment. 
       FIG.  10    is a schematic plan view illustrating a directional acoustic sensor according to a comparative example.  FIG.  10    shows an example in which the directional acoustic sensor  200  according to the comparative example is provided to compare to the directional acoustic sensor  100  according to the embodiment of  FIG.  2   . 
     Referring to  FIG.  10   , the directional acoustic sensor  200  of the comparative example includes a support  201 , and a plurality of first resonators  210  and a plurality of second resonators  230  provided on the support  201 . The plurality of first resonators  210  and the plurality of second resonators  230  are arranged to form a resonator arrangement in which at least some of them face each other in a cavity of the support  201 . 
     One end of each of the plurality of first resonators  210  is fixed to the first support portion  203  of the support  201  to form a planarly parallel arrangement in the cavity of the support  201 . One end of each of the plurality of second resonators  230  is fixed to the second support  205  of the support  201  to form a planarly parallel arrangement in the cavity of the support  201 . 
     When compared with the directional acoustic sensor  100  according to the embodiment shown in  FIG.  2   , the directional acoustic sensor  200  of the comparative example does not have an intersecting structure of ends of the first resonator  210  and the second resonator  230  facing each other. In  FIG.  10   , reference numeral  230 ′ denotes a second resonator that does not face the first resonator  210 . 
     Each of the plurality of first resonators  210  and the plurality of second resonators  230  include bases  211  and  231  and frames  213  and  233  extending in a length direction thereof to protrude from the bases  211  and  231 , and the frames  213  and  233  extend to end portions of the first resonator  210  and the second resonator  230 . 
     In the directional acoustic sensor  200  of the comparative example, the first resonator  210  and the second resonator  230  facing each other do not have an intersecting structure of ends, there may be a through hole  240  of the cavity between the first resonator  210  and the second resonator  230  facing each other. 
       FIG.  11    is a diagram of a comparison of a change of a layout size of a resonator arrangement before (comparative example) and after (embodiment example) application of the intersecting structure of ends of two resonators facing each other according to an embodiment. In  FIG.  11   , when the resonant frequency change before (comparative example) and after (embodiment example) a change of the shape of the ends of the two facing resonators is limited to about 5% or less, a design example in which the size of device in the length direction thereof is reduced from approximately 2950 µm to approximately 2700 µm is shown. When not limiting the resonant frequency change, the ends that constitute an intersecting structure may be formed up to approximately half the length of the resonator. 
     In  FIG.  11   , a layout of the resonator arrangement before applying the intersecting structure of the two facing resonators corresponds to the directional acoustic sensor  200  of the comparative example shown in  FIG.  10   , and a layout of the resonator arrangement after the application of the intersecting structure of the ends of the two facing resonators corresponds to the directional acoustic sensor  100  according to the embodiment shown in  FIG.  2   . 
     As shown in  FIG.  11   , the directional acoustic sensor  100  according to the embodiment to which an intersecting structure of the ends of the two resonators facing each other is applied has a reduced layout size of the resonator arrangement by about 10% compared to the directional acoustic sensor  200  of the comparative example to which the intersecting structure of the ends is not applied. Therefore, according to the directional acoustic sensor  100  according to the embodiment, the size of the device may be reduced, and thus, price competitiveness may be improved. 
       FIG.  12    is a graph showing the change in frequency response characteristics of resonators before (comparative example) and after (embodiment example) application of an intersecting structure of ends of two resonators facing each other according to an embodiment. 
     As shown in  FIG.  12   , it may be seen that the sensitivity increases by about 2.4 dB when the intersecting structure of the ends of the two resonators facing each other is applied. As such, according to the directional acoustic sensor  100  according to the embodiment, due to the intersecting structure of the ends of the two facing resonators, there is almost no through-hole between the two facing resonators, and thus, the decrease in acoustic resistance is suppressed, thereby increasing the sensitivity. 
       FIG.  13    is a graph showing resonant frequency characteristics for each channel of a resonator arrangement before (comparative example) and after (embodiment example) the application of an intersecting structure of ends of two resonators facing each other. The channel represents each resonator, and when width, thickness, and mass conditions are the same, the resonant frequency of each channel (resonator) is approximately proportional to the square root of a beam length of the resonator. The resonance frequency graph of  FIG.  13    is a result obtained through COMSOL simulation. 
     As shown in  FIG.  13   , it may be seen that, even when an intersecting structure of ends of two resonators facing each other is applied, a directional acoustic sensor with almost no change in primary and secondary resonant frequencies may be implemented. 
     From the difference in layout size of the resonator arrangement before (comparative example) and after (embodiment example) application of the intersecting structure of the ends of the two resonators facing each other as in  FIG.  11   , the frequency response characteristics of the resonator in  FIG.  12   , and the resonant frequency characteristics for each channel of  FIG.  13   , by applying an intersecting structure of ends of two resonators facing each other to a directional acoustic sensor, it may be seen that a directional acoustic sensor having good sensitivity and desired resonant frequency characteristics for each channel may be implemented, and a device size may be reduced.  FIGS.  11  to  13    are only illustrative, and the embodiment is not limited thereto. 
     The directional acoustic sensor  100  according to the embodiment may be manufactured, for example, as shown in  FIG.  14   , and may be packaged as shown in  FIG.  15   . 
       FIG.  14    is a photograph after manufacturing the directional acoustic sensor  100  according to the embodiment.  FIG.  15    is a photograph after packaging the directional acoustic sensor  100  of  FIG.  14    according to an embodiment.  FIG.  15    shows an example in which holes are formed in a packaging case such that acoustic sound is transmitted to the directional acoustic sensor  100 .  FIG.  16    is a graph showing a result of measuring a frequency response characteristic of the directional acoustic sensor  100  according to the manufactured embodiment. It may be confirmed from the measurement result of  FIG.  16    that the device size may be reduced without decreasing in sensitivity. Here,  FIGS.  14  to  16    are only illustrative, and the present embodiment is not limited thereto, and the directional acoustic sensor  100  according to the embodiment may be modified to have various frequency response characteristics. 
     In the above, a resonator having a structure including a base and a frame extending along both edges of the base in the length direction thereof to protrude from the base has been described as the first resonator  110  and the second resonator  130  facing each other in the directional acoustic sensor  100  according to the embodiment, but the embodiment is not limited thereto, and resonators having various structures may be applied. 
       FIGS.  17 ,  18  and  19    are diagrams of other examples of resonators that may be applied to two resonators facing each other according to an embodiment.  FIGS.  17  to  19    illustrate other examples of resonators  250 ,  270 , and  290  that may be applied as the first resonator  110  and the second resonator  130  facing each other in  FIGS.  1  and  2   . 
     Referring to  FIG.  17   , a driving portion  260  of the resonator  250  may include a base  181  and a frame  183  protruding from the base  181  and extending in the length direction thereof. Also, the driving portion  260  of the resonator  250  may have an end  155  (e.g., corresponding to the first end  125  and the second end  145  in  FIGS.  1  and  2   ) at the end thereof. 
     The frame  183  may be continuously provided parallel to the length direction of the resonator  250  inside the base  181 . In  FIG.  17   , a case in which only one frame  183  is provided is illustrated as an example, but the embodiment is not limited thereto, and a plurality of frames  183  may be provided inside the base  181 . 
     Referring to  FIG.  18   , a driving portion  280  of the resonator  270  may include a base  281  and a groove pattern  282  having a predetermined depth in the base  281 . Also, the driving portion  280  of the resonator  270  may have an end  155  (corresponding to the first end  125  and the second end  145  in  FIGS.  1  and  2   ) at the end thereof. 
     The groove pattern  282  may be formed in a regular shape on the base  281 . Here, the groove pattern  282  is formed in the base  281  to a predetermined depth, thereby reducing the mass of the resonator compared to a resonator having only the base without the groove pattern. 
     The resonator  270  according to the present embodiment includes the groove pattern  282  formed to a predetermined depth in the base  281 , thereby reducing the mass of the resonator  270  while maintaining the resonant frequency constant, and accordingly, a quality factor may be reduced and a bandwidth may be increased compared to a resonator including only a base without a groove pattern. 
     Referring to  FIG.  19   , a driving portion  295  of a resonator  290  may include a base  296  and a plurality of through holes  297  formed through the base  296 . The plurality of through-holes  297  may be formed in a regular shape in the base  296 . In addition, the driving portion  295  of the resonator  290  may have an end  155  (corresponding to the first end  125  and the second end  145  in  FIGS.  1  and  2   ) at the end thereof. 
     The resonator  290  shown in  FIG.  19    may have the same resonant frequency as a resonator in which a plurality of through holes are not formed. To this end, each through hole  297  may be formed to have a size smaller than the wavelength of an audible frequency band. 
     In the present embodiment, the resonator  290  includes a plurality of through-holes  297  having a size smaller than a wavelength of an audible frequency band formed in the base  296 , thereby reducing the mass of the resonator while maintaining the resonant frequency constant, and accordingly, compared to a resonator that does not include a plurality of through-holes, a quality factor may be reduced and a bandwidth may be increased. 
     In  FIGS.  17 ,  18 , and  19   , the resonators  250 ,  270 , and  290  are illustrated as having plate-shaped ends  155  at the ends of the driving portions  260 ,  280 , and  295 , but the embodiment is not limited thereto, and the shapes of the ends may be modified in various forms as described above. 
     On the other hand, the resonators  250 ,  270 , and  290  of  FIGS.  17 ,  18 , and  19    may also be applied to the third resonator  130 ′ that does not face the first resonator  110  in  FIGS.  1  and  2   , and in this case, the structure may be changed to a structure without the end  155 , or a structure including the end  155  may be applied as it is. 
     The directional acoustic sensor  100  according to the embodiment as described above may reduce or eliminate through-holes caused by the arrangement of the resonators having different lengths from each other by forming ends of two facing resonators to an intersecting structure engaged each other, thereby, improving the acoustic sensitivity and reducing the device size. 
     The directional acoustic sensor  100  according to the embodiment described above may be applied to various electronic devices to which a voice interface technology is applied, for example, a smart phone, a foldable phone, an AI speaker, AR glasses, wearable devices, robots, TVs, etc. 
       FIGS.  20 ,  21 ,  22 ,  23 ,  24  and  25    are diagrams of examples of electronic devices to which the directional acoustic sensor according to an embodiment is applied as a voice interface device according to an embodiment. For example, the directional acoustic sensor  100  according to the embodiment may be applied to AR glasses  1000 , earbuds  1100 , smart phones  1200 , TVs  1300 , artificial intelligent speakers  1400 , and the like as shown in  FIGS.  20  to  24   . Also, the directional acoustic sensor  100  according to the embodiment may be applied to a vehicle  1500  as shown in  FIG.  25   .  FIG.  25    shows an example in which the directional acoustic sensor  1510  according to the embodiment is provided on an upper side of the windshield, and besides above, the directional acoustic sensor  1510  according to the embodiment may be mounted at various positions inside and outside the vehicle  1500 . In addition, the directional acoustic sensor  100  according to the embodiment may be applied to various electronic devices including household appliances, such as air conditioners, refrigerators, and air purifiers. Although the embodiments have been described above, this is merely examples, and various modifications are possible to those skilled in the art from the above description. 
     According to the directional acoustic sensor according to the embodiment, by forming ends of two facing resonators in an intersecting structure, a through-hole of a cavity in an arrangement region facing resonators may be minimized, and thus a directional acoustic sensor with improved sensitivity may be realized. 
     In addition, by forming the ends of the two resonators in an intersecting structure, the size of the resonator arrangement region may be reduced, thereby reducing the device size. 
     It should be understood that embodiments described herein should be considered in a descriptive sense only and not for purposes of limitation. Descriptions of features or aspects within each embodiment should typically be considered as available for other similar features or aspects in other embodiments. While one or more embodiments have been described with reference to the figures, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope as defined by the following claims.