Patent Publication Number: US-2022214211-A1

Title: Acoustic sensor assembly and method of sensing sound using the same

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. 10-2021-0001062, filed on Jan. 5, 2021, in the Korean Intellectual Property Office, the disclosure of which is incorporated by reference herein in its entirety. 
     BACKGROUND 
     1. Field 
     The disclosure relates to acoustic sensor assemblies and methods of sensing sound by using the same. 
     2. Description of Related Art 
     dAcoustic sensors are mounted in household appliances, image display devices, virtual reality devices, augmented reality devices, artificial intelligence speakers, and the like, to detect a direction from which sounds are coming from and recognize voices. Such acoustic sensors are being used in increasingly more areas. Recently, a directional acoustic sensor that detects sound by converting a mechanical movement due to a pressure difference into an electrical signal has been developed. 
     SUMMARY 
     Provided are acoustic sensor assemblies and methods of sensing sound using the same. 
     Additional aspects will be set forth in part in the description that follows and, in part, will be apparent from the description, or may be learned by practice of the presented example embodiments of the disclosure. 
     According to an aspect of embodiments, an acoustic sensor assembly includes a non-directional acoustic sensor having a first directional pattern, a plurality of directional acoustic sensors surrounding the non-directional acoustic sensor and including a plurality of resonators having different resonance frequencies from each other, each of the plurality of directional acoustic sensors having a second directional pattern, and a processor configured to obtain output signals from the non-directional acoustic sensor and the plurality of directional acoustic sensors. The processor is further configured to calculate an acoustic signal having directivity by selecting any one or any combination of the obtained output signals or selectively combining the obtained output signals, and obtain sound around the acoustic sensor assembly, using the calculated acoustic signal. 
     Each of the plurality of directional acoustic sensors may be disposed such that the second directional pattern is in a radial direction with respect to the non-directional acoustic sensor. 
     Each of the plurality of directional acoustic sensors may be configured to sense, in a direction of the second directional pattern, a sound that is in-phase with a phase of a sound that is sensed by the non-directional acoustic sensor, and sense, in a direction opposite to the direction of the second directional pattern, a sound that is anti-phase with the phase of the sound sensed by the non-directional acoustic sensor. 
     The processor may be further configured to calculate the acoustic signal having a third directional pattern different from the first directional pattern and the second directional pattern. 
     The first directional pattern may be omnidirectional, the second directional pattern may be bi-directional, and the third directional pattern may be uni-directional. 
     The processor may be further configured to calculate a plurality of acoustic signals having third directional patterns oriented in different directions from each other, and obtain the sound around the acoustic sensor assembly, using the calculated plurality of acoustic signals. 
     The processor may be further configured to calculate the acoustic signal by calculating a sum of or a difference between ratios of a first output signal of the non-directional acoustic sensor and a second output signal of each of the plurality of directional acoustic sensors, among the obtained output signals. 
     The processor may be further configured to calculate the acoustic signal having a third directional pattern in a front direction of one of the plurality of directional acoustic sensors corresponding to the second output signal, by calculating the sum of the ratios of the first output signal and the second output signal. 
     The processor may be further configured to calculate the acoustic signal having a third directional pattern in a rear side direction of one of the plurality of directional acoustic sensor corresponding to the second output signal, by calculating the difference between the ratios of the first output signal and the second output signal. 
     Each of the plurality of directional acoustic sensors may further include a support, and the plurality of resonators may extend from the support in a length direction. 
     Each of the plurality of resonators may include a driver moving based on input sound, and a sensor detecting movement of the driver. 
     An electronic device includes the acoustic sensor assembly. 
     According to an aspect of embodiments, a method of sensing sound includes obtaining output signals from a non-directional acoustic sensor having a first directional pattern and a plurality of directional acoustic sensors, the plurality of directional acoustic sensors surrounding the non-directional acoustic sensor, and including a plurality of resonators having different resonance frequencies from each other, and each of the plurality of directional acoustic sensors having a second directional pattern. The method further includes calculating an acoustic signal having directivity by selecting any one or any combination of the obtained output signals or selectively combining the obtained output signals, and obtaining sound around an acoustic sensor assembly, using the acoustic calculated signal. 
     Each of the plurality of directional acoustic sensors may be disposed such that the second directional pattern is in a radial direction with respect to the non-directional acoustic sensor. 
     The obtaining of the output signals may include sensing, in a direction of the second directional pattern, a sound that is in-phase with a phase of a sound that is sensed by the non-directional acoustic sensor, and sensing, in a direction opposite to the direction of the second directional pattern, a sound that is anti-phase with the phase of the sound sensed by the non-directional acoustic sensor. 
     The calculating of the acoustic signal may include calculating a plurality of acoustic signals having third directional patterns oriented in different directions from each other, and the obtaining of the sound includes obtaining the sound, using the calculated plurality of acoustic signals. 
     The calculating of the acoustic signal may include calculating the acoustic signal by calculating a sum of or a difference between ratios of a first output signal of the non-directional acoustic sensor and a second output signal of each of the plurality of directional acoustic sensors, among the obtained output signals. 
     The calculating of the acoustic signal may further include calculating the acoustic signal having a third directional pattern in a front direction of one of the plurality of directional acoustic sensors corresponding to the second output signal, by calculating the sum of the ratios of the first output signal and the second output signal. 
     The calculating of the acoustic signal may further include calculating the acoustic signal having a third directional pattern in a rear side direction of one of the plurality of directional acoustic sensors corresponding to the second output signal, by calculating the difference between the ratios of the first output signal and the second output signal. 
     A non-transitory computer-readable storage medium stores instructions that, when executed by at least one processor, cause the at least one processor to perform the method. 
     According to an aspect of embodiments, an acoustic sensor assembly includes a non-directional acoustic sensor configured to sense sound in all directions, a plurality of directional acoustic sensors surrounding the non-directional acoustic sensor, each of the plurality of directional acoustic sensors being configured to sense sound in a front direction and a rear side direction, and a processor configured to obtain output signals from the non-directional acoustic sensor and the plurality of directional acoustic sensors. The processor is further configured to calculate an acoustic signal in the front direction or the rear side direction of each of the plurality of directional acoustic sensors by calculating a sum of or difference between ratios of a first one of the output signals from the non-directional acoustic sensor and a second one of the output signals from a respective one of the plurality of directional acoustic sensors, and obtain sound around the acoustic sensor assembly, using the calculated acoustic signal of each of the plurality of directional acoustic sensors. 
     Each of the plurality of directional acoustic sensors may be disposed such that the front direction or the rear side direction is in a radial direction with respect to the non-directional acoustic sensor. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other aspects, features, and advantages of 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 of a directional acoustic sensor according to embodiments; 
         FIG. 2  is a cross-sectional view of a resonator illustrated in  FIG. 1 ; 
         FIG. 3  is a diagram for describing a method of adjusting directivity by using a plurality of acoustic sensors, according to a comparative example; 
         FIG. 4  is a block diagram of an acoustic sensor assembly according to embodiments; 
         FIG. 5  is a diagram for describing a directional acoustic sensor according to embodiments and a directional pattern of the directional acoustic sensor, according to embodiments; 
         FIG. 6  is a graph showing results of measurement of frequency response characteristics of a directional acoustic sensor according to embodiments; 
         FIG. 7  is a diagram of results of measurement of a directional pattern of a directional acoustic sensor according to embodiments; 
         FIGS. 8A and 8B  are diagrams for describing signal processing of an acoustic sensor assembly according to embodiments; 
         FIG. 9A  is a graph showing a result of sensing sound transmitted from a front direction, by acoustic sensors, according to embodiments; 
         FIG. 9B  is a graph showing a result of sensing sound transmitted from a rear side direction, by acoustic sensors, according to embodiments; 
         FIG. 10A  is a graph showing measurement of directional patterns of acoustic sensors according to embodiments; 
         FIG. 10B  is a graph showing measurement of a directional pattern of an acoustic signal calculated by summing output signals, according to embodiments; 
         FIG. 11A  is a diagram for describing an arrangement of an acoustic sensor assembly including a directional acoustic sensor according to embodiments; 
         FIG. 11B  is a plan view for describing a directional pattern of an acoustic sensor assembly including a directional acoustic sensor according to embodiments; 
         FIG. 12A  is a diagram for describing an arrangement of an acoustic sensor assembly including a directional acoustic sensor according to other embodiments; 
         FIG. 12B  is a plan view for describing a directional pattern of an acoustic sensor assembly including a directional acoustic sensor according to other embodiments; 
         FIG. 13A  is a diagram for describing an arrangement of an acoustic sensor assembly including a directional acoustic sensor according to other embodiments; 
         FIG. 13B  is a plan view for describing a directional pattern of an acoustic sensor assembly including a directional acoustic sensor according to other embodiments; 
         FIG. 14  is a diagram illustrating an acoustic sensor assembly according to embodiments, mounted in an electronic device; and 
         FIG. 15  is a flowchart of a method of sensing sound, according to 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 may not be construed as being limited to the descriptions set forth herein. Accordingly, the embodiments are 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. 
     The terms used in the embodiments below are those general terms currently widely used in the art in consideration of functions in regard to the present embodiments, but the terms may vary according to the intention of those of ordinary skill in the art, precedents, or new technology in the art. Also, specified terms may be selected by the applicant, and in this case, the detailed meaning thereof will be described in the detailed description of the relevant embodiment. Thus, the terms used in the specification may be understood not as simple names but based on the meaning of the terms and the overall description of the embodiments. 
     In the description of the embodiments, it will also be understood that when an element is referred to as being “above” or “on” another element, it can be directly on, under, on the left of, or on the right of the other element, or intervening elements may also be present. The singular forms include the plural forms unless the context clearly indicates otherwise. 
     In the description of the embodiments, it will also be understood that when an element is referred to as being “connected to” another element, it can be directly connected to the other element, or it can be electrically connected to the other element and intervening elements may be present. 
     The terms such as “comprise” or “include” may not be construed as necessarily including various elements or processes described in the specification, and it may be construed that some of the elements or the processes may not be included, or additional elements or processes may be further included. 
     Herein, terms including ordinal numbers such as ‘first’, ‘second’, etc. are used to describe various elements, but the elements may not be defined by these terms. The terms are used only for distinguishing one element from another element. 
     The present embodiments relate to an acoustic sensor assembly, and description of details that are well known to those of ordinary skill in the art may be omitted. 
     Description of the following embodiments may not be construed as limiting or defining the scope of the disclosure, and details that are easily derivable by one of ordinary skill in the art to which the disclosure pertains are construed as being in the scope of the embodiments. Hereinafter, the embodiments that are just for illustration will be described in detail with reference to the attached drawings. 
       FIG. 1  is a perspective view of a directional acoustic sensor  10  according to embodiments.  FIG. 2  is a cross-sectional view of a resonator  102  illustrated in  FIG. 1 . 
     Referring to  FIGS. 1 and 2 , the directional acoustic sensor  10  may include a support  101  and a plurality of resonators  102 . A cavity  105  may be formed in the support  101  to pass through the support  101 . As the support  101 , for example, a silicon substrate may be used, but is not limited thereto. 
     The plurality of resonators  102  may be arranged in the cavity  105  of the support  101  in a form. The resonators  102  may be arranged two-dimensionally without overlapping each other. As illustrated in  FIG. 2 , an end of each of the resonators  102  may be fixed to the support  101 , and the other end thereof may extend toward the cavity  105 . Each of the resonators  102  may include a driver  108  moving by reacting to an input sound and a sensor  107  sensing a movement of the driver  108 . Also, the resonators  102  may further include a mass body  109  for providing a mass to the driver  108 . 
     The resonators  102  may be provided to sense, for example, acoustic frequencies of different bands. That is, the resonators  102  may be provided to have different center frequencies or resonance frequencies. To this end, the resonators  102  may be provided to have different dimensions from each other. For example, the resonators  102  may be provided to have different lengths, widths or thicknesses from each other. 
     Dimensions such as widths or thicknesses of the resonators  102  may be set by considering a desired resonance frequency with respect to the resonators  102 . For example, the resonators  102  may have dimensions such as a width from about several pm to several hundreds of μm, a thickness of several μm or less, and a length of about several mm or less. The resonators  102  having fine sizes may be manufactured in a Micro Electro Mechanical System (MEMS) process. 
       FIG. 3  is a diagram for describing a method of adjusting directivity by using a plurality of acoustic sensors  31 , according to a comparative example. 
     Referring to  FIG. 3 , in a method of adjusting directivity by using the plurality of acoustic sensors  31 , the plurality of acoustic sensors  31  may be used to hear a sound in a direction louder. The plurality of acoustic sensors  31  may be arranged at a distance D, and a time or phase delay that sound reaches each acoustic sensor  31  is caused due to the distance D, and the overall directivity may be adjusted by differentiating a degree of compensating for the time or phase delay. The method of adjusting directivity as described above may be referred to as Time Difference of Arrival (TDOA). 
     However, the above method is based on the assumption that there is a difference in times that sound reaches each acoustic sensor. Thus, there may be a restriction on setting a distance between acoustic sensors as the distance may need to be set by considering a wavelength of an audible frequency band. The restriction on setting a distance between acoustic sensors may also limit providing a compact size of a device performing the above method. As a low frequency has a longer wavelength, to distinguish a sound of a low frequency, a distance between acoustic sensors may need to be relatively broad and a signal-to-noise ratio (SNR) of each acoustic sensor may need to be relatively high. 
     Moreover, as phases differ according to frequency bands of sound sensed by each acoustic sensor in the above-described method, the phases may have to be compensated for with respect to each frequency band. To compensate for the phase of each frequency, a complex signal processing process of applying an appropriate weight for each frequency may be necessary in the above-described method. 
     According to the disclosure, there may be provided an acoustic sensor assembly in which there is no restriction on distances between acoustic sensors and whereby ambient sound may be obtained by distinguishing a direction with only a relatively simple operation and without complex signal processing. Hereinafter, an efficient structure and operation of the acoustic sensor assembly according to the disclosure will be described in detail with reference to the drawings. 
       FIG. 4  is a block diagram of an acoustic sensor assembly  4  according to embodiments. 
     Referring to  FIG. 4 , the acoustic sensor assembly  4  may include a processor  41 , a non-directional acoustic sensor  42 , and a plurality of directional acoustic sensors  43   a ,  43   b , . . . ,  43   n . The acoustic sensor assembly  4  may obtain sound around the acoustic sensor assembly  4  by using the processor  41 , the non-directional acoustic sensor  42 , and the plurality of directional acoustic sensors  43   a ,  43   b , . . . ,  43   n.    
     The non-directional acoustic sensor  42  may sense sound in all directions surrounding the non-directional acoustic sensor  42 . The non-directional acoustic sensor  42  may have directivity for uniformly sensing sound in all directions. For example, the directivity for uniformly sensing sound in all directions may be omni-directional or non-directional. 
     The sound sensed using the non-directional acoustic sensor  42  may be output as a same output signal from the non-directional acoustic sensor  42 , regardless of a direction in which the sound is input. Accordingly, a sound source reproduced based on the output signal of the non-directional acoustic sensor  42  may not include information on direction. 
     A directivity of an acoustic sensor may be expressed using a directional pattern, and the directional pattern may refer to a pattern indicating a direction in which an acoustic sensor may receive a sound source. 
     A directional pattern may be illustrated to identify sensitivity of an acoustic sensor according to a direction in which sound is transmitted based on a 360° space surrounding the acoustic sensor having the directional pattern. For example, a directional pattern of the non-directional acoustic sensor  42  may be illustrated in a circle to indicate that the non-directional acoustic sensor  42  has the same sensitivity to sounds transmitted 360° omni-directionally. An application of the directional pattern of the non-directional acoustic sensor  42  will be described later with reference to  FIGS. 8A and 8B . 
     Each of the plurality of directional acoustic sensors  43   a ,  43   b , . . . ,  43   n  may have a same configuration as the directional acoustic sensor  10  illustrated in  FIG. 1  described above. The plurality of directional acoustic sensors  43   a ,  43   b , . . . ,  43   n  may sense sound from a front (e.g., +z direction in  FIG. 1 ) and a rear side (e.g., −z direction of  FIG. 1 ). Each of the plurality of directional acoustic sensors  43   a ,  43   b , . . . ,  43   n  may have directivity of sensing sounds from the front and the rear side. For example, directivity for sensing sounds from a front direction and a rear side direction may be bi-directional. 
     The plurality of directional acoustic sensors  43   a ,  43   b , . . . ,  43   n  may be arranged to surround the non-directional acoustic sensor  42 . An arrangement structure of the plurality of directional acoustic sensors  43   a ,  43   b , . . . ,  43   n  will be described later in detail with reference to  FIGS. 11A through 13B . 
     The processor  41  controls the overall operation of the acoustic sensor assembly  4  and performs signal processing. The processor  41  may select any one or any combination of output signals of acoustic sensors having different directivities, thereby calculating an acoustic signal having a same directivity as those of the acoustic sensors  42 ,  43   a ,  43   b , . . . ,  43   n . An acoustic signal having a directional pattern of an acoustic sensor corresponding to an output signal selected by the processor  41  may be calculated based on the output signal selected by the processor  41 . For example, the selected output signal may be identical to the acoustic signal. The processor  41  may adjust directivity by selecting a directional pattern of the acoustic sensor assembly  4  as a directional pattern of an acoustic sensor corresponding to the selected output signal, and may reduce or loudly sense sound transmitted in a direction according to situations. 
     An acoustic signal refers to a signal including information about directivity, like output signals of the acoustic sensors  42 ,  43   a ,  43   b , . . . ,  43   n , and some of the output signals may be selected and determined as acoustic signals or may be newly calculated based on calculation of some of the output signals. A directional pattern of an acoustic signal may be in a same shape as directional patterns of the acoustic sensors  42 ,  43   a ,  43   b , . . . ,  43   n  or in a different shape, and have a same or different directivity. That is, there is no limitation on a directional pattern or directivity of an acoustic signal. 
     The processor  41  may obtain output signals of the non-directional acoustic sensor  42  and/or the plurality of directional acoustic sensors  43   a ,  43   b , . . . ,  43   n , and may calculate an acoustic signal having a different directivity from those of the acoustic sensors  42 ,  43   a ,  43   b , . . . ,  43   n  included in the acoustic sensor assembly  4  by selectively combining the obtained output signals. For example, the processor  41  may calculate an acoustic signal having a different directional pattern from directional patterns of the acoustic sensors  42 ,  43   a ,  43   b , . . . ,  43   n . The processor  41  may calculate an acoustic signal having a directional pattern oriented toward a front of a directional acoustic sensor (e.g.,  43   a ), depending on the situation. 
     The processor  41  may calculate an acoustic signal by calculating any one or any combination of a sum of and a difference between ratios of an output signal of the non-directional acoustic sensor  42  and output signals of the plurality of directional acoustic sensors  43   a ,  43   b , . . . ,  43   n.    
     The processor  41  may obtain sound around the acoustic sensor assembly  4  by using an acoustic signal. The processor  41  may obtain ambient sound by distinguishing a direction of a sound transmitted to the acoustic sensor assembly  4  by using an acoustic signal. For example, when the processor  41  records a sound source transmitted from the right side of the acoustic sensor assembly  4  and provides the recorded sound source to a user, the user may hear the sound source as if it is coming from the right side of the user; when the processor  41  records a sound source circling the acoustic sensor assembly  4  and provides the recorded sound source to the user, the user may hear the sound source as if it is circling the user. 
     The processor  41  may include a single processor core (single-core) or a plurality of processor cores (multi-core). The processor  41  may process or execute programs and/or data stored in a memory. In some embodiments, the processor  41  may control a function of the acoustic sensor assembly  4  by executing programs stored in a memory. The processor  41  may be implemented as a central processing unit (CPU), a graphic processing unit (GPU), an application processor (AP), or the like. 
       FIG. 5  is a diagram for describing the directional acoustic sensor  10  according to embodiments and a directional pattern  51  or  52  of the directional acoustic sensor  10 . 
     Referring to  FIG. 5 , the directional acoustic sensor  10  may include the bi-directional patterns  51  and  52 . For example, the bi-directional patterns  51  and  52  may be a figure-8 type directional pattern including a front portion  51  oriented toward a front of the directional acoustic sensor  10  (+z direction) and a rear side portion  52  oriented toward a rear side (−z direction) of the directional acoustic sensor  10 . 
       FIG. 6  is a graph showing results of measurement of frequency response characteristics of a directional acoustic sensor according to embodiments. 
     Referring to  FIG. 6 , the directional acoustic sensor  10  has uniform sensitivity to various frequencies. In a frequency range from 0 Hz to 8000 Hz, sensitivity marked by a dashed line is uniformly at −40 dB, and noise marked by a solid line is at −80 dB. The directional acoustic sensor  10  has uniform sensitivity with respect to various frequencies, and may thus uniformly sense sounds of the various frequencies. 
       FIG. 7  is a diagram of results of measurement of a directional pattern of a directional acoustic sensor according to embodiments. 
     As illustrated in  FIG. 7 , the directional acoustic sensor  10  has a uniform, bi-directional pattern with respect to various frequencies. That is, the directional acoustic sensor  10  has directivity in a +z axis direction and a −z axis direction of  FIG. 1 , which are respectively a 0-degree direction and a 180-degree direction. 
       FIGS. 8A and 8B  are diagrams for describing signal processing of an acoustic sensor assembly according to embodiments. 
     Referring to  FIG. 8A , the processor  41  may calculate an acoustic signal by calculating any one or any combination of a sum of and a difference between ratios of an output signal of the non-directional acoustic sensor  42  and an output signal of the directional acoustic sensor  10 . An acoustic signal may be a digital signal calculated based on output signals to be in a different shape or have a different directivity from those of direction patterns (a bi-directional pattern  81  and an omni-directional pattern  82 ) of the directional acoustic sensor  10  and the non-directional acoustic sensor  42 . 
     For example, in a calculation to calculate an acoustic signal, when an output signal of the non-directional acoustic sensor  42  is G1, and an output signal of the directional acoustic sensor  10  is G2, and a ratio of the output signal G2 of the directional acoustic sensor  10  to the acoustic signal G1 of the non-directional acoustic sensor  42  is 1:k, a sum of ratios of the output signals G1 and G2 may be calculated using a formula of G1+kG2, and a difference between the ratios of the output signals G1 and G2 may be calculated using a formula of G1-kG2. A ratio of each of the output signals may be preset according to a shape or directivity of an appropriate directional pattern used by the acoustic sensor assembly  4  ( FIG. 4 ). 
     The processor  41  may calculate an acoustic signal having a directional pattern oriented toward the front direction of the directional acoustic sensor  10  (e.g., +z direction of  FIG. 5 ) by calculating a sum of ratios of the output signal of the non-directional acoustic sensor  42  and the output signal of the directional acoustic sensor  10 . 
     The non-directional acoustic sensor  42  is oriented in all directions, and thus, there may be no difference in output signals regardless of a direction in which sound is transmitted. However, for convenience of description below, the front direction of the directional acoustic sensor  10  will be assumed to be identical to a front direction of the non-directional acoustic sensor  42 . 
     For example, the processor  41  may calculate an acoustic signal having a uni-directional pattern  83  by calculating a sum of 1:1 ratios of an output signal of the non-directional acoustic sensor  42  and an output signal of the directional acoustic sensor  10 . The uni-directional pattern  83  may have a directivity facing the front of the directional acoustic sensor  10 . However, the uni-directional pattern  83  may be a directional pattern covering a broader range to the left and the right, compared to a front portion of the bi-directional pattern  81 . For example, the uni-directional pattern  83  may be a cardioid directional pattern. 
     The directional acoustic sensor  10  may include the bi-directional pattern  81 , and the non-directional acoustic sensor  42  may include the omni-directional pattern  82 . The directional acoustic sensor  10  may sense a sound that is in-phase with a phase of a sound sensed by the non-directional acoustic sensor  42  from a front direction of the bi-directional pattern  81  (e.g., +z direction of  FIG. 5 ), and a sound that is anti-phase with a phase of a sound sensed by the non-directional acoustic sensor  42  from a rear side direction of the bi-directional pattern  81  (e.g., −z direction of  FIG. 5 ). 
       FIG. 9A  is a graph showing a result of sensing sound transmitted from a front direction, by acoustic sensors, according to embodiments.  FIG. 9B  is a graph showing a result of sensing sound transmitted from a rear side direction, by acoustic sensors, according to embodiments. 
     Referring to  FIGS. 9A and 9B , a sound transmitted from the front direction of the directional acoustic sensor  10  and a sound transmitted from the front direction of the non-directional acoustic sensor  42  are in-phase with each other, and the sound transmitted from the front direction of the directional acoustic sensor  10  and sound transmitted from the rear side direction of the non-directional acoustic sensor  42  have a phase difference of 180° from each other such that peaks and troughs alternately cross each other. 
     Referring back to  FIG. 8A , sounds transmitted from the front direction are in-phase with each other, and sounds transmitted from the rear side direction are in anti-phase with each other, and thus, some of the output signals are added and some others are offset and an acoustic signal having the uni-directional pattern  83  oriented in the front direction may be calculated. 
     Referring to  FIG. 8B , the processor  41  may calculate an acoustic signal having a directional pattern oriented toward the rear side direction of the directional acoustic sensor  10  (e.g., −z direction of  FIG. 5 ) by calculating a difference between ratios of an output signal of the non-directional acoustic sensor  42  and an output signal of the directional acoustic sensor  10 . 
     For example, the processor  41  may calculate an acoustic signal having a uni-directional pattern  84  by calculating a difference between 1:1 ratios of an output signal of the non-directional acoustic sensor  42  and an output signal of the directional acoustic sensor  10 . The uni-directional pattern  84  may have a directivity facing a rear surface of the directional acoustic sensor  10 , opposite to the uni-directional pattern  83  of  FIG. 8B . The uni-directional pattern  84  may be a directional pattern covering a broader range to the left and the right, compared to a rear side portion of the bi-directional pattern  81 . For example, the uni-directional pattern  83  may be a cardioid directional pattern. 
     While a method of calculating an acoustic signal having a uni-directional pattern by calculating a sum of or a difference between an output of the directional acoustic sensor  10  and an output of the non-directional acoustic sensor  42  is described above, this is an example, and the control of directivity of the acoustic sensor assembly  4  by using output signals of acoustic sensors is not limited to the above-described method. 
     The processor  41  may calculate an acoustic signal having a new bi-directional pattern differing from bi-directivity of directional acoustic sensors by selecting only a non-directional pattern, or selecting only a bi-directional pattern of a directional acoustic sensor oriented toward a direction, or calculating output signals of directional acoustic sensors, according to situations. 
       FIG. 10A  is a graph showing measurement of directional patterns of acoustic sensors according to embodiments.  FIG. 10B  is a graph showing measurement of a directional pattern of an acoustic signal calculated by summing output signals, according to embodiments. 
     Referring to  FIG. 10A , the directional acoustic sensor  10  has a bi-directional pattern, and the non-directional acoustic sensor  42  has an omni-directional pattern. In detail, the directional acoustic sensor  10  may sense a sound transmitted from a region from 315 degrees to 45 degrees corresponding to the front (+z direction of  FIG. 5 ) and a sound transmitted from a region from 135 degrees to 225 degrees corresponding to the rear side (+z direction of  FIG. 5 ). The non-directional acoustic sensor  42  may sense a sound transmitted from all directions of a 360-degree region in the surroundings. 
     Referring to  FIG. 10B , an acoustic signal calculated by summing an output signal of the directional acoustic sensor  10  and an output signal of the non-directional acoustic sensor  42  may have a uni-directional pattern. By using only the directional acoustic sensor  10 , only a sound transmitted from the region in the front from 315 degrees to 45 degrees may be sensed, whereas the acoustic sensor assembly  4  ( FIG. 4 ) may sense a sound transmitted from a region from 300 degrees to 60 degrees, which is a broader range than the region from 315 degrees to 45 degrees. As described above, the processor  41  may adjust a directivity of the acoustic sensor assembly  4  by forming a directional pattern that is different from directional patterns of acoustic sensors by a relatively simple calculation using output signals of the non-directional acoustic sensor  42  and the directional acoustic sensor  10 . 
     While a result of a single frequency is illustrated in  FIGS. 10A and 10B , as described above with reference to  FIGS. 6 and 7 , the directional acoustic sensor  10  is uniformly sensitive to various frequencies, and thus, a directional pattern having a same shape may be formed from results with respect to various frequencies. For example, the various frequencies may be in audible frequency ranges, and an acoustic signal may form a directional pattern of a same shape regardless of the level of frequency. 
       FIG. 11A  is a diagram for describing an arrangement of an acoustic sensor assembly  11  including a directional acoustic sensor according to embodiments.  FIG. 11B  is a plan view for describing a directional pattern of the acoustic sensor assembly  11  including a directional acoustic sensor according to embodiments. 
     Referring to  FIGS. 11A and 11B , the acoustic sensor assembly  11  may include four (first through fourth) directional acoustic sensors  1110 ,  1112 ,  1114 , and  1116 , the non-directional acoustic sensor  42 , and a fixing unit  1120 . Each of the plurality of directional acoustic sensors  1110 ,  1112 ,  1114 , and  1116  may have a same configuration as the directional acoustic sensor  10  described above and illustrated in  FIG. 1 . 
     The plurality of directional acoustic sensors  1110 ,  1112 ,  1114 , and  1116  and the non-directional acoustic sensor  42  may be arranged on the fixing unit  1120 , and the plurality of directional acoustic sensors  1110 ,  1112 ,  1114 , and  1116  may be arranged to have different directivities. The plurality of directional acoustic sensors  1110 ,  1112 ,  1114 , and  1116  may be arranged to surround the non-directional acoustic sensor  42 . 
     The plurality of directional acoustic sensors  1110 ,  1112 ,  1114 , and  1116  may be arranged at an angle from each other with respect to the non-directional acoustic sensor  42 . The first directional acoustic sensor  1110  and the second directional acoustic sensor  1112  may be arranged at an angle of θ 1  from each other with respect to the non-directional acoustic sensor  42 . The second directional acoustic sensor  1112  and the third directional acoustic sensor  1114  may be at an angle of θ 2  from each other, and the third directional acoustic sensor  1114  and the fourth directional acoustic sensor  1116  may be at an angle of θ 3  from each other, and the fourth directional acoustic sensor  1116  and the first directional acoustic sensor  1110  may be at an angle of θ 4  from each other. 
     For example, the angles of θ 1 , θ 2 , θ 3 , and θ 4  may be 90 degrees. However, this is an example, and the angles of θ 1 , θ 2 , θ 3 , and θ 4  may be modified. 
     A distance between each of the plurality of directional acoustic sensors  1110 ,  1112 ,  1114 , and  1116  and the non-directional acoustic sensor  42  is not limited, and a distance between each of the directional acoustic sensors  1110 ,  1112 ,  1114 , and  1116  is also not limited. For example, the directional acoustic sensors  1110 ,  1112 ,  1114 , and  1116  may be arranged equidistantly from the non-directional acoustic sensor  42 , or at different distances, or some of them may be equidistantly arranged, and some others may be arranged at different distances from each other. 
     The plurality of directional acoustic sensors  1110 ,  1112 ,  1114 , and  1116  may be arranged such that directional patterns of the directional acoustic sensors  1110 ,  1112 ,  1114 , and  1116  are in a radial direction with respect to the non-directional acoustic sensor  42 . As each directional pattern is arranged in a radial direction with respect to the non-directional acoustic sensor  42 , sounds transmitted from each direction around the acoustic sensor assembly  11  may be obtained while distinguishing which direction the sounds came from. 
     As described above with reference to  FIG. 5 , the directional patterns of the directional acoustic sensor  10  ( FIG. 5 ) and the directional acoustic sensors  1110 ,  1112 ,  1114 , and  1116  are oriented towards the front (+z direction of  FIG. 5 ) and the rear side (−z direction of  FIG. 5 ) of each of the directional acoustic sensor  10  ( FIG. 5 ) and the directional acoustic sensors  1110 ,  1112 ,  1114 , and  1116 , and thus, a direction in which a directional pattern faces may be a direction that the front or the rear side of the directional acoustic sensors  1110 ,  1112 ,  1114 , and  1116  faces. 
     In other words, the plurality of directional acoustic sensors  1110 ,  1112 ,  1114 , and  1116  may be arranged such that the front or the rear side of each of the directional acoustic sensors  1110 ,  1112 ,  1114 , and  1116  is in a radial direction with respect to the non-directional acoustic sensor  42 . 
     The processor  41  ( FIG. 4 ) may calculate a plurality of acoustic signals. For example, the processor  41  may calculate a plurality of acoustic signals by using output signals of the non-directional acoustic sensor  42  and the directional acoustic sensors  1110 ,  1112 ,  1114 , and  1116 . The processor  41  may calculate an acoustic signal having a first uni-directional pattern  1130  based on output signals of the first directional acoustic sensor  1110  and the non-directional acoustic sensor  42 , and an acoustic signal having a second uni-directional pattern  1132  based on output signals of the second directional acoustic sensor  1112  and the non-directional acoustic sensor  42 , and an acoustic signal having a third uni-directional pattern  1134  based on output signals of the third directional acoustic sensor  1114  and the non-directional acoustic sensor  42 , and an acoustic signal having a third uni-directional pattern  1136  based on output signals of the fourth directional acoustic sensor  1116  and the non-directional acoustic sensor  42 . 
     The plurality of uni-directional patterns  1130 ,  1132 ,  1134 , and  1136  may oriented in different directions. For example, each of the plurality of uni-directional patterns  1130 ,  1132 ,  1134 , and  1136  may be oriented in different directions among the radial directions in which they are oriented with respect to the non-directional acoustic sensor  42 . As the plurality of uni-directional patterns  1130 ,  1132 ,  1134 , and  1136  are formed to cover all directions around the acoustic sensor assembly  11 , the acoustic sensor assembly  11  may evenly sense surround sound that allows spatial awareness in all directions around the acoustic sensor assembly  11 . 
       FIG. 12A  is a diagram for describing an arrangement of an acoustic sensor assembly  12  including a directional acoustic sensor according to other embodiments.  FIG. 12B  is a plan view for describing a directional pattern of the acoustic sensor assembly  12  including a directional acoustic sensor according to other embodiments. 
       FIGS. 12A and 12B  may include the description provided above with reference to  FIGS. 11A and 11B . 
     Referring to  FIGS. 12A and 12B , the acoustic sensor assembly  12  may include three (first through third) directional acoustic sensors  1210 ,  1212 , and  1214 , the non-directional acoustic sensor  42 , and a fixing unit  1220 . Each of the plurality of directional acoustic sensors  1210 ,  1212 , and  1214  may have a same configuration as the directional acoustic sensor  10  illustrated in  FIG. 1  described above. 
     The plurality of directional acoustic sensors  1210 ,  1212 , and  1214  and the non-directional acoustic sensor  42  may be arranged on the fixing unit  1220 , and the plurality of directional acoustic sensors  1210 ,  1212 , and  1214  may be arranged to have different directivities. 
     The plurality of directional acoustic sensors  1210 ,  1212 , and  1214  may be arranged to be at an angle from each other with respect to the non-directional acoustic sensor  42 . The first directional acoustic sensor  1210  and the second directional acoustic sensor  1212  may be arranged at an angle of θ 1  from each other with respect to the non-directional acoustic sensor  42 . The second directional acoustic sensor  1212  and the third directional acoustic sensor  1214  may be at an angle of θ 2  with respect to each other, and the third directional acoustic sensor  1214  and the first directional acoustic sensor  1210  may be at an angle of θ 3  with respect to each other. 
     For example, the angles of θ 1 , θ 2 , and θ 3  may be 120 degrees. However, this is an example, and the angles of θ 1 , θ 2 , and θ 3  may be modified. 
     The processor  41  ( FIG. 4 ) may calculate a plurality of acoustic signals. For example, the processor  41  may calculate a plurality of acoustic signals by using output signals of the non-directional acoustic sensor  42  and the \directional acoustic sensors  1210 ,  1212 , and  1214 . The processor  41  may calculate an acoustic signal having a first uni-directional pattern  1230  based on output signals of the first directional acoustic sensor  1210  and the non-directional acoustic sensor  42 , and an acoustic signal having a second uni-directional pattern  1232  based on output signals of the second directional acoustic sensor  1212  and the non-directional acoustic sensor  42 , and an acoustic signal having a third uni-directional pattern  1234  based on output signals of the third directional acoustic sensor  1214  and the non-directional acoustic sensor  42 . 
     The plurality of uni-directional patterns  1230 ,  1232 , and  1234  may be oriented in different directions. For example, each of the plurality of uni-directional patterns  1230 ,  1232 , and  1234  may be oriented in different directions among the radial directions in which they are oriented with respect to the non-directional acoustic sensor  42 . As the plurality of uni-directional patterns  1230 ,  1232 , and  1234  are formed to cover all directions around the acoustic sensor assembly  12 , the acoustic sensor assembly  12  may evenly sense surround sound that allows spatial awareness in all directions around the acoustic sensor assembly  12 . 
     While calculation of acoustic signals having four and three uni-directional patterns is respectively described with reference to  FIGS. 11B and 12B , the number of calculated acoustic signals and a type of directional patterns are not limited to the above description, and various combinations of the number of calculated acoustic signals or a type of the directional patterns may be made by the processor  41 . 
       FIG. 13A  is a diagram for describing an arrangement of an acoustic sensor assembly  13  including a directional acoustic sensor according to other embodiments.  FIG. 13B  is a plan view for describing a directional pattern of the acoustic sensor assembly  13  including a directional acoustic sensor according to other embodiments. 
       FIGS. 13A and 13B  may include the description provided above with reference to  FIGS. 11A through 12B . 
     Referring to  FIGS. 13A and 13B , the acoustic sensor assembly  13  may include two (first and second) directional acoustic sensors  1310  and  1312 , the non-directional acoustic sensor  42 , and a fixing unit  1320 . Each of the plurality of directional acoustic sensors  1310  and  1312  may have a same configuration as the directional acoustic sensor  10  illustrated in  FIG. 1  described above. 
     The plurality of directional acoustic sensors  1310  and  1312  and the non-directional acoustic sensor  42  may be arranged on the fixing unit  1320 , and the plurality of directional acoustic sensors  1310  and  1312 may be arranged to have different directivities. 
     The plurality of directional acoustic sensors  1310  and  1312  may be arranged to be at an angle from each other with respect to the non-directional acoustic sensor  42 . The first directional acoustic sensor  1310  and the second directional acoustic sensor  1312  may be arranged at an angle of θ 1  from each other with respect to the non-directional acoustic sensor  42 . For example, the angle of θ 1  may be 90 degrees. However, this is an example, and the angle of θ 1  may be modified. 
     The processor  41  ( FIG. 4 ) may calculate a plurality of acoustic signals. The plurality of acoustic signals may include an acoustic signal having a directional pattern oriented toward the rear side direction (e.g., −z direction of  FIG. 5 ) of the directional acoustic sensor  10  described above with reference to  FIG. 8A . For example, the processor  41  may calculate an acoustic signal having a first uni-directional pattern  1330  oriented toward a front direction of the first directional acoustic sensor  1310  and an acoustic signal having a second uni-directional pattern  1332  oriented toward a rear surface of the first directional acoustic sensor  1310  based on output signals of the first directional acoustic sensor  1310  and the omni-directional acoustic sensor  42 . The processor  41  may calculate an acoustic signal having a third uni-directional pattern  1334  oriented toward a front direction of the first directional acoustic sensor  1334  and an acoustic signal having a fourth uni-directional pattern  1336  oriented toward a rear side direction of the second directional acoustic sensor  1312  based on output signals of the second directional acoustic sensor  1312  and the omni-directional acoustic sensor  42 . 
     Unlike the acoustic sensor assembly  11  of  FIG. 11A , the acoustic sensor assembly  13  of  FIG. 13A  may calculate acoustic signals having the uni-directional patterns  1330 ,  1332 ,  1334  and  1336  having different directivities, by using the two directional acoustic sensors  1310  and  1312 . As the uni-directional patterns  1330 ,  1332 ,  1334  and  1336  are configured to obtain sounds transmitted from all directions of the surroundings by distinguishing from which direction the sounds came, the acoustic sensor assembly  13  may evenly sense surround sound that allows spatial awareness in all directions around the acoustic sensor assembly  13 . As the two directional acoustic sensors  1310  and  1312  are used, a size of the acoustic sensor assembly  13  may be further reduced, and the complexity of circuitry structure for connecting elements of the acoustic sensor assembly  13  may be reduced. 
       FIG. 14  is a diagram illustrating the acoustic sensor assembly  11  according to embodiments, mounted in an electronic device  14 . 
     Referring to  FIG. 14 , the acoustic sensor assembly  11  may be mounted in the electronic device  14  that may need to acquire ambient sound. For example, the electronic device  14  may be a sensor device, a smart speaker, a mobile phone, a vehicle assistance device, a TV, an Internet of Things (IoT) smart device, a mobile device, an augmented reality (AR) device, or a virtual reality (VR) device. Hereinafter, the acoustic sensor assembly  11  of  FIG. 11A  is mounted (in the electronic device  14 ) for description, but the disclosure is not limited thereto, and any acoustic sensor assembly (the acoustic sensor assembly  4  of  FIG. 4 , the acoustic sensor assembly  12  of  FIG. 12A , or the acoustic sensor assembly  13  of  FIG. 13A ) may also be mounted in the electronic device  14 . 
     By including the acoustic sensor assembly  11 , the electronic device  14  may obtain sound by using a directional pattern in a direction, detect a direction of transmitted sound, or obtain sound around the electronic device  14  in such a way that allows spatial awareness based on various combinations of directional patterns. 
     For example, when a first user  141  and a second user  142  have a conversation around the electronic device  14 , the electronic device  14  may detect each direction in which each user is located or sense only the voice of the first user  141  by using a directional pattern oriented toward the first user  141 , or sense only the voice of the second user  142  by using a directional pattern oriented toward the second user  142 , or simultaneously sense the voices of both the first and second users  141  and  142  while distinguishing which directions the voices come from. 
     The acoustic sensor assembly  11  mounted in the electronic device  14  has a uniform sensitivity to various frequencies of sounds sensed, and is easy to be reduced in size because there is no restriction on the distances between each acoustic sensor. Also, the degree of freedom of operation of the acoustic sensor assembly  11  is high as various directional patterns may be selected or used in combination according to a location of the acoustic sensor assembly  11  or conditions around the acoustic sensor assembly  11 . In addition, only relatively simple calculations such as summation or subtraction are used to control the acoustic sensor assembly  11 , and accordingly, calculation resources may be used efficiently. 
       FIG. 15  is a flowchart of a method of sensing sound, according to embodiments. 
     Referring to  FIG. 15 , the method of sensing sound includes operations processed in time series in the acoustic sensor assemblies described above (the acoustic sensor assembly  4  of  FIG. 4 , the acoustic sensor assembly  11  of  FIG. 11A , the acoustic sensor assembly  12  of  FIG. 12A , or the acoustic sensor assembly  13  of  FIG. 13A ) described above. Thus, details that may be omitted below but provided above in relation to the acoustic sensor assemblies of the drawings described above (the acoustic sensor assembly  4  of  FIG. 4 , the acoustic sensor assembly  11  of  FIG. 11A , the acoustic sensor assembly  12  of  FIG. 12A , or the acoustic sensor assembly  13  of  FIG. 13A ) may apply to the method of  FIG. 15 . 
     In operation  151 , the processor (the processor  41  of  FIG. 4 ) may obtain output signals from the non-directional acoustic sensor  42  having a first directional pattern and the plurality of directional acoustic sensors  43   a ,  43   b , . . . ,  43   n  that are arranged to surround the non-directional acoustic sensor  42 , include a plurality of resonators having different resonance frequencies from each other, and respectively have a second directional pattern. 
     The processor ( 41  in  FIG. 4 ) may obtain output signals from the plurality of directional acoustic sensors  43   a ,  43   b , . . . ,  43   n  arranged such that the second directional pattern of each of the directional acoustic sensors  43   a ,  43   b , . . . ,  43   n  is in a radial direction with respect to the non-directional acoustic sensor  42 . 
     The processor  41  may obtain an output signal that is output by the plurality of directional acoustic sensors  43   a ,  43   b , . . . ,  43   n  by sensing, in a direction, a sound that is in-phase with a phase of a sound sensed by a non-directional acoustic sensor, and an output signal that is output by sensing, in an opposite direction to the above direction, a sound that is in anti-phase with the phase of the sound sensed by the non-directional acoustic sensor. 
     In operation  152 , the processor ( 41  of  FIG. 4 ) may calculate an acoustic signal having a directivity by selecting at least one of the output signals or selectively combining the output signals. 
     The processor  41  may calculate a plurality of acoustic signals having third directional patterns oriented in different directions. 
     The processor  41  may calculate an acoustic signal by calculating any one or any combination of a sum of and a difference between ratios of a first output signal of the non-directional acoustic sensor  42  and second output signals of the plurality of directional acoustic sensors  43   a ,  43   b , . . . ,  43   n.    
     The processor  41  may calculate an acoustic signal having a third directional pattern facing the front direction of the directional acoustic sensors  43   a ,  43   b , . . . ,  43   n  corresponding to the second output signal, by calculating a sum of ratios of the first output signal and the second output signals. 
     The processor  41  may calculate an acoustic signal having the third directional pattern facing the rear side direction of the directional acoustic sensors  43   a ,  43   b , . . . ,  43   n  corresponding to the second output signal, by calculating a difference between ratios of the first output signal and the second output signals. 
     In operation  153 , the processor ( 41  of  FIG. 4 ) may obtain surround sound by using the acoustic signal. 
     The processor  41  may acquire surround sound by using a plurality of acoustic signals. 
     The embodiments described above can be written as computer programs that can be implemented in general-use digital computers that execute the programs using a computer readable recording medium. Also, data structures used in the embodiments described above may be written to the computer readable recording medium using various means. Examples of the computer readable recording medium include magnetic storage media (e.g., ROM, floppy disks, hard disks, etc.) and optical recording media (e.g., CD-ROMs, or DVDs). 
     It may be understood that embodiments described herein may be considered in a descriptive sense only and not for purposes of limitation. Descriptions of features or aspects within each embodiment may 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 and their equivalents.