Patent Publication Number: US-2015085615-A1

Title: Motion modified steering vector

Description:
FIELD 
     The subject matter disclosed herein relates to steering vectors and more particularly relates to motion modified steering vectors. 
     BACKGROUND 
     Description of the Related Art 
     A steering vector may be calculated to an audible source so that a spatial filter based on the steering vector may be applied to audible signals from the source to enhance the audible signals. Unfortunately, a microphone array receiving the audible signals may move, reducing the effectiveness of the steering vector. 
     BRIEF SUMMARY 
     An apparatus for motion modified steering vector is disclosed. The apparatus includes a microphone array, a motion sensor, a processor, and a memory. The memory stores computer readable code that includes a motion module and a steering module. The motion module modifies a prior steering vector with a motion vector. The steering module spatially filters audio signals using the modified steering vector. A method and computer program product also perform the functions of the apparatus. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A more particular description of the embodiments briefly described above will be rendered by reference to specific embodiments that are illustrated in the appended drawings. Understanding that these drawings depict only some embodiments and are not therefore to be considered to be limiting of scope, the embodiments will be described and explained with additional specificity and detail through the use of the accompanying drawings, in which: 
         FIG. 1  is a schematic block diagram illustrating one embodiment of a microphone array; 
         FIGS. 2A-C  are schematic block diagrams illustrating embodiments of microphone arrays; 
         FIGS. 3A-B  are perspective drawings illustrating embodiments of electronic devices; 
         FIG. 4  is a schematic diagram illustrating one embodiment of spatial filtering; 
         FIGS. 5A-B  are schematic diagrams illustrating embodiments of moving microphone arrays; 
         FIG. 6  is a schematic block diagram illustrating one embodiment of an audio channel; 
         FIG. 7  is a perspective drawing illustrating one embodiment of microphone array and audible source geometries; 
         FIG. 8  is a schematic block diagram illustrating one embodiment of an electronic device; 
         FIG. 9  is a schematic block diagram illustrating one embodiment of the steering vector apparatus; 
         FIG. 10  is a schematic flow chart diagram illustrating one embodiment of a steering vector modification method; and 
         FIG. 11  is a schematic flow chart diagram illustrating one alternate embodiment of a steering vector modification method. 
     
    
    
     DETAILED DESCRIPTION 
     As will be appreciated by one skilled in the art, aspects of the embodiments may be embodied as a system, method or program product. Accordingly, embodiments may take the form of an entirely hardware embodiment, an entirely software embodiment (including firmware, resident software, micro-code, etc.) or an embodiment combining software and hardware aspects that may all generally be referred to herein as a “circuit,” “module” or “system.” Furthermore, embodiments may take the form of a program product embodied in one or more computer readable storage devices storing computer readable code. The storage devices may be tangible, non-transitory, and/or non-transmission. 
     Many of the functional units described in this specification have been labeled as modules, in order to more particularly emphasize their implementation independence. For example, a module may be implemented as a hardware circuit comprising custom VLSI circuits or gate arrays, off-the-shelf semiconductors such as logic chips, transistors, or other discrete components. A module may also be implemented in programmable hardware devices such as field programmable gate arrays, programmable array logic, programmable logic devices or the like. 
     Modules may also be implemented in computer readable code and/or software for execution by various types of processors. An identified module of computer readable code may, for instance, comprise one or more physical or logical blocks of executable code which may, for instance, be organized as an object, procedure, or function. Nevertheless, the executables of an identified module need not be physically located together, but may comprise disparate instructions stored in different locations which, when joined logically together, comprise the module and achieve the stated purpose for the module. 
     Indeed, a module of computer readable code may be a single instruction, or many instructions, and may even be distributed over several different code segments, among different programs, and across several memory devices. Similarly, operational data may be identified and illustrated herein within modules, and may be embodied in any suitable form and organized within any suitable type of data structure. The operational data may be collected as a single data set, or may be distributed over different locations including over different computer readable storage devices, and may exist, at least partially, merely as electronic signals on a system or network. Where a module or portions of a module are implemented in software, the software portions are stored on one or more computer readable storage devices. 
     Any combination of one or more computer readable medium may be utilized. The computer readable medium may be a computer readable signal medium or a storage device. The computer readable medium may be a storage device storing the computer readable code. The storage device may be, for example, but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, holographic, micromechanical, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. 
     More specific examples (a non-exhaustive list) of the storage device would include the following: an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing. In the context of this document, a computer readable storage medium may be any tangible medium that can contain, or store a program for use by or in connection with an instruction execution system, apparatus, or device. 
     A computer readable signal medium may include a propagated data signal with computer readable code embodied therein, for example, in baseband or as part of a carrier wave. Such a propagated signal may take any of a variety of forms, including, but not limited to, electro-magnetic, optical, or any suitable combination thereof. A computer readable signal medium may be any storage device that is not a computer readable storage medium and that can communicate, propagate, or transport a program for use by or in connection with an instruction execution system, apparatus, or device. Computer readable code embodied on a storage device may be transmitted using any appropriate medium, including but not limited to wireless, wire line, optical fiber cable, Radio Frequency (RF), etc., or any suitable combination of the foregoing. 
     Computer readable code for carrying out operations for embodiments may be written in any combination of one or more programming languages, including an object oriented programming language such as Java, Smalltalk, C++ or the like and conventional procedural programming languages, such as the “C” programming language or similar programming languages. The computer readable code may execute entirely on the user&#39;s computer, partly on the user&#39;s computer, as a stand-alone software package, partly on the user&#39;s computer and partly on a remote computer or entirely on the remote computer or server. In the latter scenario, the remote computer may be connected to the user&#39;s computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or the connection may be made to an external computer (for example, through the Internet using an Internet Service Provider). 
     Reference throughout this specification to “one embodiment,” “an embodiment,” or similar language means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, appearances of the phrases “in one embodiment,” “in an embodiment,” and similar language throughout this specification may, but do not necessarily, all refer to the same embodiment, but mean “one or more but not all embodiments” unless expressly specified otherwise. The terms “including,” “comprising,” “having,” and variations thereof mean “including but not limited to,” unless expressly specified otherwise. An enumerated listing of items does not imply that any or all of the items are mutually exclusive, unless expressly specified otherwise. The terms “a,” “an,” and “the” also refer to “one or more” unless expressly specified otherwise. 
     Furthermore, the described features, structures, or characteristics of the embodiments may be combined in any suitable manner. In the following description, numerous specific details are provided, such as examples of programming, software modules, user selections, network transactions, database queries, database structures, hardware modules, hardware circuits, hardware chips, etc., to provide a thorough understanding of embodiments. One skilled in the relevant art will recognize, however, that embodiments may be practiced without one or more of the specific details, or with other methods, components, materials, and so forth. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of an embodiment. 
     Aspects of the embodiments are described below with reference to schematic flowchart diagrams and/or schematic block diagrams of methods, apparatuses, systems, and program products according to embodiments. It will be understood that each block of the schematic flowchart diagrams and/or schematic block diagrams, and combinations of blocks in the schematic flowchart diagrams and/or schematic block diagrams, can be implemented by computer readable code. These computer readable code may be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions/acts specified in the schematic flowchart diagrams and/or schematic block diagrams block or blocks. 
     The computer readable code may also be stored in a storage device that can direct a computer, other programmable data processing apparatus, or other devices to function in a particular manner, such that the instructions stored in the storage device produce an article of manufacture including instructions which implement the function/act specified in the schematic flowchart diagrams and/or schematic block diagrams block or blocks. 
     The computer readable code may also be loaded onto a computer, other programmable data processing apparatus, or other devices to cause a series of operational steps to be performed on the computer, other programmable apparatus or other devices to produce a computer implemented process such that the program code which execute on the computer or other programmable apparatus provide processes for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks. 
     The schematic flowchart diagrams and/or schematic block diagrams in the Figures illustrate the architecture, functionality, and operation of possible implementations of apparatuses, systems, methods and program products according to various embodiments. In this regard, each block in the schematic flowchart diagrams and/or schematic block diagrams may represent a module, segment, or portion of code, which comprises one or more executable instructions of the program code for implementing the specified logical function(s). 
     It should also be noted that, in some alternative implementations, the functions noted in the block may occur out of the order noted in the Figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. Other steps and methods may be conceived that are equivalent in function, logic, or effect to one or more blocks, or portions thereof, of the illustrated Figures. 
     Although various arrow types and line types may be employed in the flowchart and/or block diagrams, they are understood not to limit the scope of the corresponding embodiments. Indeed, some arrows or other connectors may be used to indicate only the logical flow of the depicted embodiment. For instance, an arrow may indicate a waiting or monitoring period of unspecified duration between enumerated steps of the depicted embodiment. It will also be noted that each block of the block diagrams and/or flowchart diagrams, and combinations of blocks in the block diagrams and/or flowchart diagrams, can be implemented by special purpose hardware-based systems that perform the specified functions or acts, or combinations of special purpose hardware and computer readable code. 
     Descriptions of Figures may refer to elements described in previous Figures, like numbers referring to like elements. 
       FIG. 1  is a schematic block diagram illustrating one embodiment of a microphone array  100 . The microphone array  100  may include two or more microphones  105 . In one embodiment, the microphones  105  are organized in a planar array. 
       FIGS. 2A-C  are schematic block diagrams illustrating embodiments of microphone arrays  100   a - c . The microphone arrays  100   a - c  include two to four microphones  105  and are organized in various geometries, including a square geometry as in  FIG. 2A , a triangular geometry as in  FIG. 2B , and a linear geometry as in  FIG. 2C . In one embodiment, the microphones  105  are disposed along a common axis  102 . 
       FIGS. 3A-B  are perspective drawings illustrating embodiments of electronic devices  190 .  FIG. 3A  depicts a laptop computer electronic device  190   a  with a microphone array  100 .  FIG. 3B  shows a mobile telephone electronic device  190   b  with a microphone array  100 . One of skill in the art will recognize that the embodiments may be practiced with other electronic devices  190  including but not limited to computer workstations, tablet computers, eyeglass computers, wearable computers, and the like. 
       FIG. 4  is a schematic diagram illustrating one embodiment of spatial filtering  101 . Spatial filtering, as referred to as beamforming, is applied to the audio signals from a microphone array  100  to produce a plurality of receiving gain areas  110 . Within the receiving gain area  110 , the signal-to-noise ratio of an audible signal received by the microphone array  100  is increased. A steering vector for the spatial filtering is adjusted to define the direction of the spatial filtering and the receiving gain area  110 . In the depicted embodiment, the steering vector for a second receiving gain area  110   b  is selected to enhance the signal-to-noise ratio of an audible signal received from an audible source  115 . 
       FIGS. 5A-B  are schematic diagrams illustrating embodiments of moving microphone arrays  100 . In  FIG. 5A  a first steering vector  120   a  is directed from the microphone array  100  to the audible source  115 .  FIG. 5B  depicts the microphone array  100  and the audible source  115  of  FIG. 5A  after the microphone array  100  has moved. The first steering vector  120   a  is no longer directed to the audible source  115 . As a result, spatial filtering using the first steering vector  120   a  would be much less efficient to increase the signal-to-noise ratio for the audible signals from the audible source  115  than a second steering vector  120   b  that is directed more accurately to the audible source  115 . 
     The embodiments described herein modify a prior steering vector with a motion vector to generate a modified steering vector  120 . The modified steering vector  120  may then be employed to more effectively spatially filter audible signals from an audible source  115  as will be described hereafter. 
       FIG. 6  is a schematic block diagram illustrating one embodiment of an audio channel  160 . The audio channel  160  includes audible signals  195 , audio signals  135 , the steering vector  120 , output signals  155 , a motion vector  140 , and a prior steering vector  125 . The audible signals  195  are received by the microphone array  100 . The audible signals  195  are converted into electrical audio signals  135 . The audio signals  135  may be digital audio signals  135  or analog audio signals  135 . The steering vector  120  may be applied to the audio signals  135  as part of a spatial filter to generate output signals  155 . 
     Unfortunately as was illustrated in  FIGS. 5A-B , when the microphone array  100  moves, either in translation, rotation, or combinations thereof, the steering vector  120  is less effective for spatial filtering. However, the present embodiments apply the motion vector  140  for the microphone array  100  to the prior steering vector  125  to generate a modified steering vector  120 . As a result, the steering vector  120  is adjusted for the motion of the microphone array  100 , so that spatial filtering is more effective despite the motion of the microphone array  100 . 
       FIG. 7  is a perspective drawing illustrating one embodiment of microphone array  100  and audible source  115  geometries. A steering vector k  120  is shown from an audible source  115  to a microphone array  100 . The microphone array  100  is depicted at an origin of mutually orthogonal axes  114 . The steering vector k  120  is defined by two angles, θ  145  and φ  150 , relative to the origin of the mutually orthogonal axes  114 , where the steering vector k  120  is given by Equation 1. 
     
       
         
           
             
               
                 
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                   Equation 
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     A first microphone  105   a  of the microphone array  100  is disposed at vector m 1    136   a  and the second microphone  105   b  is disposed at vector m 2    136   b . The delays d for spatial filtering for the microphones  105  may be calculated using Equation 2. 
         d =( m   2   −m   1 ) T   k   Equation 2
 
     When the microphone array  100  is moved, the microphone array  100  may be rotated relative to the audible source  115 . The rotation of the microphone array  100  is calculated using the matrices of Equation 3, where α  137   a  is rotation about a first axis  114   a , β  137   b  is a rotation about a second axis  114   b , and γ  137   c  is a rotation about a third axis  114   c . 
     
       
         
           
             
               
                 
                   
                     
                       
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     A rotation matrix R may be defined as shown in Equation 4. The rotation matrix R may be the motion vector MV  140 . 
         R=R   x (α) R   y (β) R   z (γ)  Equation 4
 
     The motion vector  140  may be applied to the steering vector  120  to adjust the delays for the microphones  105  of the microphone array  100  and shown in Equation 5. 
         d=MV ( m   2   −m   1 ) T   k   Equation 5
 
     Alternatively, the motion vector  140  may be applied to the prior steering vector  125  to calculate a modified steering vector  120  as shown in Equation 6 
         MS=MV*SV 0  Equation 6
 
     Thus the audio signals  135  are filtered with the modified steering vector  120  that more accurately reflects the position of the audible source  115 . 
       FIG. 8  is a schematic block diagram illustrating one embodiment of an electronic device  190 . The electronic device  190  includes a processor  305 , a memory  310 , and communication hardware  315 . The processor  305  may be a digital signal processor. The memory  310  may be a semiconductor storage device, a hard disk drive, an optical storage device, a micromechanical storage device, or combinations thereof. The memory  310  stores computer readable code. The processor  305  may execute the computer readable code. The communication hardware  315  may communicate with other devices. 
       FIG. 9  is a schematic block diagram illustrating one embodiment of the steering vector apparatus  400 . The apparatus  400  may be embodied in the electronic device  190 . The apparatus  400  includes the microphone array  100 , a motion sensor  405 , a motion module  410 , and a steering module  415 . The motion module  410  and the steering module  415  may be embodied in a computer readable storage medium such as the memory  310 . 
     The motion sensor  405  may be an accelerometer measuring accelerations in one or more axes. Alternatively, the motion sensor  405  may be a gyroscope measuring changes in orientation. The rotation matrix R may be calculated from the changes in orientation and/or from the accelerations. 
     The motion module  410  may modify the prior steering vector  125  with the motion vector  140 . The steering module  415  may spatially filter the audio signals  135  using the modified steering vector  120 . 
       FIG. 10  is a schematic flow chart diagram illustrating one embodiment of a steering vector modification method  500 . The method  500  may perform the functions of the apparatus  400  and electronic device  190 . The method  500  may be performed by the processor  305 . Alternatively, the method  500  may be performed by a program product. The program product may include a computer readable storage medium such as the memory  310  storing computer readable code that is executed by the processor  305 . 
     The method  500  starts, and in one embodiment, the motion module  410  calculates  505  the steering vector  120 . In one embodiment, the motion module  410  may calculate a signal strength for the audio signals  135  at each of a plurality of trial steering vectors  120 . For example, the motion module  410  may generate trial steering vectors  120  for a sphere of θ 145 plus 0 to 360° and φ 150 plus 0 to 180°. The motion module  410  may select the trial steering vector  120  with the greatest signal strength as the steering vector  120 . 
     The motion module  410  may further generate  510  the motion vector  140 . The motion vector  140  may estimate all motion of the microphone array  100  since the last calculation  505  of the steering vector  120 . In one embodiment, the motion module  410  receives signals encoding the changes in orientation and/or acceleration from the motion sensor  405 . The motion module  410  may further calculate the rotation matrix R using Equations 3 and 4. The rotation matrix R may be the motion vector  140 . 
     The motion module  410  may further modify  515  the prior steering vector  125  with the motion vector to generate the modified steering vector  120 . In one embodiment, the motion module  410  may employ Equation 6 to generate the modified steering vector  120 . 
     The steering module  415  may spatially filter  520  the audio signals  135  using the modified steering vector  120  and the method  500  ends. In one embodiment, the steering module  415  spatially filters  520  the audio signals  135  using Equation 2, where k is the modified steering vector  120 . 
     By modifying the prior steering vector  125  with the motion vector  140 , the steering vector  120  is better oriented towards the audible source  115 . As a result, the steering vector  120  may provide better spatial filtering for the audible signals  195  received from the audible source  115 . 
       FIG. 11  is a schematic flow chart diagram illustrating one alternate embodiment of a steering vector modification method  501 . The method  501  may perform the functions of the apparatus  400  and electronic device  190 . The method  501  may be performed by the processor  305 . Alternatively, the method  501  may be performed by a program product. The program product may include a computer readable storage medium such as the memory  310  storing computer readable code executable by the processor  305 . 
     The method  501  starts, and in one embodiment, the microphone array  100  receives  550  audible signals  195 . The microphone array  100  may further generate  555  audio signals  135  from the audible signals  195 . In one embodiment, the audio signals  135  comprises an array of digitized audio values. 
     The motion module  410  may generate  560  the motion vector  140 . In one embodiment, the motion vector  140  the rotation matrix R and may be calculated using Equations 3 and 4. 
     The motion module  410  may further modify  565  the prior steering vector  125  with the motion vector  140 . In one embodiment, the motion module  410  may employ Equation 6 to generate the modified steering vector  120 . 
     In one embodiment, the motion module  410  calculates one or more trial steering vectors  120 . The trial steering vectors  120  may each be an angular variation of the modified steering vector  120 . For example, the motion module  410  may generate trial steering vectors  120  for a hemisphere about the prior steering vector  125 , for θ  145  plus 0 to 180° and φ  150  plus 0 to 90° . . . . 
     The motion module  410  may determine  575  which of the trial steering vectors  120  correlates with the audio signal  135 . If a first trial steering vector  120  does not correlate  575  of the audio signal  135 , the motion module  410  may calculate 570 another trial steering vector  120 . 
     In one embodiment, a trial steering vector  120  that when applied to the audio signals  135  results in the highest signal strength may correlate with the audio signals  135 . The trial steering vector  120  that correlates with the audio signals  135  may have a greatest effect when applied to the audio signals  135  among the plurality of trial steering vectors  120 . 
     The motion module  410  may select  580  the trial steering vector  120  that correlates with the audio signals  135  as the steering vector  120 . The steering module  415  may further spatially filter  585  the audio signals  135  with the steering vector  120 . The method  501  may further loop to the microphone array  100  receiving  550  the audible signals  195 . 
     By modifying the prior steering vector  125  with the motion vector  140  to use as the basis for calculating the trial steering vectors  120 , the motion module  410  calculates  570  trial steering vectors  120  that are likely closer to the ultimate value that will be determined for the steering vector  120 . As a result, the motion module  410  may more rapidly, and with fewer computational resources, select  580  the steering vector  120 . Therefore, the steering vector  120  the more rapidly and accurately track the audible source  115 . 
     Embodiments may be practiced in other specific forms. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.