PATENT DOCUMENT

Publication Number: US-10154339-B2
Application Number: US-201715583949-A
Country: US
Kind Code: B2

Title: Rotationally symmetric speaker array

Abstract:
A multi-way speaker array is disclosed that includes rings of transducers of different types. The rings of transducers may encircle the cabinet of the speaker array such that the speaker array is rotationally symmetric. The distance between rings of transducers may be based on a logarithmic scale. By separating rings of transducers using logarithmic spacing, denser transducer spacing at short wavelengths is achieved while limiting the number of transducers needed for longer wavelengths by spacing them in larger and larger logarithmic increments. Transducers with overlapping frequency ranges may be used in the speaker array to avoid initial dips or shortfalls in directivity for corresponding beam patterns.

Claims:
What is claimed is: 
     
       1. A multi-way speaker array, comprising:
 a cylindrical cabinet for holding a plurality of transducers, wherein the cylindrical cabinet is rotationally symmetric about a center axis; 
 a first ring of transducers arranged along a surface of the cylindrical cabinet around the center axis; 
 a second ring of transducers arranged along the surface of the cylindrical cabinet around the center axis; and 
 an end transducer arranged on an end of the cylindrical cabinet and facing a direction of the center axis; 
 wherein a first spacing between the first ring of transducers and the second ring of transducers in the direction of the center axis is different than a second spacing between the second ring of transducers and the end transducer in the direction of the center axis. 
 
     
     
       2. The multi-way speaker array of  claim 1 , further comprising:
 a third set of third transducers arranged in a third set of rings along the surface of the cylindrical cabinet around the center axis and surrounding the second ring of transducers such that an equal number of rings of the third set of rings are positioned on each side of the second ring of transducers. 
 
     
     
       3. The multi-way speaker array of  claim 1 , further comprising:
 a third set of third transducers arranged on one or more ends of the cylindrical cabinet and including the end transducer pointed perpendicular to the first and second rings of transducers. 
 
     
     
       4. The multi-way speaker array of  claim 3 , wherein the first ring of transducers is selected to produce audio frequencies in a first frequency range, the second ring of transducers is selected to produce audio frequencies in a second frequency range, and the end transducer is selected to produce audio frequencies in a third frequency range. 
     
     
       5. The multi-way speaker array of  claim 4 ,
 wherein the audio frequencies in the first frequency range overlap with the audio frequencies in the second frequency range; and 
 wherein the audio frequencies in the second frequency range overlap with the audio frequencies in the third frequency range. 
 
     
     
       6. The multi-way speaker array of  claim 1 , wherein a center of each transducer in the first ring of transducers is aligned with a center of a transducer in the second ring of transducers to form N uniform columns of transducers, wherein the uniform columns of transducers encircle the cylindrical cabinet such that the multi-way speaker array is rotationally symmetric on an order of N. 
     
     
       7. A method for driving one or more types of transducers in a speaker array, comprising:
 receiving, by the speaker array, a first segment of an audio signal during a first time period, wherein the first segment has a frequency range; 
 detecting that the frequency range includes a first frequency; 
 determining that the first frequency falls within a frequency overlap between a first frequency range of a first transducer and a second frequency range of a second transducer within the speaker array, wherein the second frequency range of the second transducer is different than the first frequency range of the first transducer, wherein the first transducer is in a first ring of transducers arranged around a center axis and the second transducer is in a second ring of transducers arranged around the center axis, and wherein a first spacing between the first ring of transducers and the second ring of transducers in a direction of the center axis is different than a second spacing between the second ring of transducers and the end transducer in the direction of the center axis; and 
 driving, in response to determining that the first frequency falls within the frequency overlap, the speaker array to generate a first beam pattern using the first transducer and the second transducer. 
 
     
     
       8. The method of  claim 7 , further comprising:
 receiving, by the speaker array, a second segment of the audio signal during a second time period, wherein the second segment includes a respective frequency range; 
 detecting that the respective frequency range includes a second frequency; 
 determining that the second frequency falls within the first frequency range of the first transducer and not within the second frequency range of the second transducer; and 
 driving, in response to determining that the second frequency falls outside the frequency overlap, the speaker array to continue to generate the first beam pattern using the first transducer and not the second transducer. 
 
     
     
       9. A multi-way speaker array, comprising:
 a cylindrical cabinet for holding a plurality of transducers, wherein the cylindrical cabinet is rotationally symmetric about a center axis; 
 a first set of first transducers arranged in a first ring along an outer surface of the cylindrical cabinet around the center axis, wherein each of the first transducers has a first frequency range; and 
 a second set of second transducers arranged in a second ring along the outer surface of the cylindrical cabinet around the center axis, wherein each of the second transducers has a second frequency range different than the first frequency range, and wherein the second ring is spaced from the first ring in a direction of the center axis by a first vertical distance; and 
 a third transducer having a third frequency range different than the first frequency range and the second frequency range, wherein the third transducer is spaced from the second ring in the direction of the center axis by a second vertical distance greater than the first vertical distance. 
 
     
     
       10. The multi-way speaker array of  claim 9 , wherein each of the first transducers is spaced relative to adjacent transducers in the first ring by a first distance along the outer surface of the cylindrical cabinet, wherein each of the second transducers is spaced relative to adjacent transducers in the second ring by a second distance along the outer surface of the cylindrical cabinet, wherein the second distance is greater than the first distance, wherein the second set of second transducers is arranged in a second set of rings including the second ring and surrounding the first ring such that an equal number of rings of the second set of second transducers are positioned on each side of the first ring, and further comprising:
 a third set of third transducers including the third transducer and arranged in a third set of rings along the outer surface of the cylindrical cabinet around the center axis and surrounding the second set of rings such that an equal number of rings of the third set of transducers are positioned on each side of the second set of rings. 
 
     
     
       11. The multi-way speaker array of  claim 9 , wherein the third transducer is arranged on an end of the cylindrical cabinet and pointed in the direction of the center axis perpendicular to the first and second sets of transducers. 
     
     
       12. The multi-way speaker array of  claim 11 , wherein the first set of first transducers are selected to produce audio frequencies in the first frequency range, the second set of second transducers are selected to produce audio frequencies in the second frequency range, and the third transducer is selected to produce audio frequencies in the third frequency range. 
     
     
       13. The multi-way speaker array of  claim 12 ,
 wherein the audio frequencies in the first frequency range of audio frequencies overlap with the audio frequencies in the second frequency range of audio frequencies; and 
 wherein the audio frequencies in the second frequency range of audio frequencies overlap with the audio frequencies in the third frequency range of audio frequencies. 
 
     
     
       14. The multi-way speaker array of  claim 9 , wherein a center of each transducer in the first ring is aligned with a center of a transducer in the second ring to form N uniform columns of transducers, wherein the uniform columns of transducers encircle the cylindrical cabinet such that the speaker array is rotationally symmetric on an order of N. 
     
     
       15. The multi-way speaker array of  claim 9 , wherein each first transducer in the first ring is evenly spaced relative to adjacent first transducers in the first ring, and wherein each second transducer in the second ring is evenly spaced relative to adjacent second transducers in the second ring.

Description:
This application is a continuation of U.S. patent application Ser. No. 15/504,312, filed Feb. 15, 2017, which is a U.S. National Phase Application under 35 U.S.C. § 371 of International Application No. PCT/US2014/051554, filed Aug. 18, 2014. 
    
    
     FIELD 
     A rotationally symmetric speaker array, which includes multiple types of transducers symmetrically arranged in rings around an enclosure is disclosed. Other embodiments are also described. 
     BACKGROUND 
     Speaker arrays are often used by computers and home electronics for outputting sound into a listening area. Each speaker array may be composed of multiple transducers that are arranged on a single plane or surface of an associated cabinet or casing. Since the transducers are arranged on a single surface, these speaker arrays must be manually oriented such that sound produced by each array is aimed at a particular target (e.g., a listener). For example, a speaker array may be initially oriented to directly face a listener. However, any movement of the speaker array and/or the listener may require manual adjustment of the array such that generated sound is again properly aimed at the target listener. This repeated adjustment and configuration may become time consuming and may provide a poor user experience. 
     SUMMARY 
     A multi-way speaker array is disclosed that includes one or more rings of transducers of different types. In one embodiment, the rings of transducers encircle the cabinet of the speaker array such that the speaker array is rotationally symmetric. This rotational symmetry allows the speaker array to be easily adapted to any placement within the listening area. In particular, since the speaker array is rotationally symmetric, the same number and type of transducers are pointed in each direction. Once the orientation of the speaker array is known, the speaker array may be driven according to this orientation to produce one or more channels of audio without the need for movement and/or physical adjustment of the speaker array. 
     In some embodiments, the distance between rings of transducers may be based on a logarithmic scale. By separating rings of transducers using logarithmic spacing, denser transducer spacing at short wavelengths is achieved while limiting the number of transducers needed for longer wavelengths by spacing them in larger and larger logarithmic increments. 
     In one embodiment, the selection of types of transducers may be made based on desired frequency coverage for the speaker array. In some embodiments, the frequency ranges covered by separate types of transducers may overlap. In these embodiments, multiple types of transducers may be used to generate beam patterns. By utilizing multiple transducers with overlapping frequency ranges, the speaker array may avoid initial dips or shortfalls in directivity for corresponding beam patterns. 
     The above summary does not include an exhaustive list of all aspects of the present invention. It is contemplated that the invention includes all systems and methods that can be practiced from all suitable combinations of the various aspects summarized above, as well as those disclosed in the Detailed Description below and particularly pointed out in the claims filed with the application. Such combinations have particular advantages not specifically recited in the above summary. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The embodiments of the invention are illustrated by way of example and not by way of limitation in the figures of the accompanying drawings in which like references indicate similar elements. It should be noted that references to “an” or “one” embodiment of the invention in this disclosure are not necessarily to the same embodiment, and they mean at least one. 
         FIG. 1  shows a view of a listening area with an audio receiver, a rotationally symmetric speaker array, and a listener according to one embodiment. 
         FIG. 2A  shows a component diagram of the audio receiver according to one embodiment. 
         FIG. 2B  shows a component diagram and signal flow in the speaker array according to one embodiment. 
         FIG. 3  shows an overhead, cutaway view of the speaker array according to one embodiment. 
         FIG. 4  shows example beam patterns with varied directivity indices (DIs) that may be generated by the speaker array according to one embodiment. 
         FIG. 5A  shows a view of the speaker array with two rings of transducers of a first type, two rings of transducers of a second type, and two rings of transducers of a third type according to one embodiment. 
         FIG. 5B  shows a view of the speaker array with two rings of transducers of a first type, two rings of transducers of a second type, and three rings of transducers of a third type according to one embodiment. 
         FIG. 5C  shows a view of the speaker array with two rings of transducers of a first type, two rings of transducers of a second type, and one ring of transducers of a third type according to one embodiment. 
         FIG. 6A  shows the distance between transducers within a ring according to one embodiment. 
         FIG. 6B  shows transducer placement in a speaker array with a conically shaped cabinet according to one embodiment. 
         FIG. 7A  shows transducers arranged in uniform columns according to one embodiment. 
         FIG. 7B  shows transducers offset between rings according to one embodiment. 
         FIG. 8  shows the speaker array rotationally symmetric about a center axis according to one embodiment. 
         FIG. 9  shows a set of transducers of a first type arranged on the top and bottom surface of the cabinet and perpendicular to a set of transducers of a second type and a set of transducers of a third type according to one embodiment. 
         FIG. 10A  shows equal spacing amongst rings of transducers according to one embodiment. 
         FIG. 10B  shows varied spacing amongst rings of transducers according to one embodiment. 
         FIG. 10C  shows logarithmic spacing amongst rings of transducers according to one embodiment. 
         FIG. 11A  shows a graph of frequency to directivity for a transducer of a first type according to one embodiment. 
         FIG. 11B  shows a graph of frequency to directivity for a transducer of a second type according to one embodiment. 
         FIG. 11C  shows a graph of frequency to directivity for a transducer of a third type according to one embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Several embodiments are described with reference to the appended drawings are now explained. While numerous details are set forth, it is understood that some embodiments of the invention may be practiced without these details. In other instances, well-known circuits, structures, and techniques have not been shown in detail so as not to obscure the understanding of this description. 
       FIG. 1  shows a view of a listening area  101  with an audio receiver  103 , a rotationally symmetric speaker array  105 , and a listener  107 . The audio receiver  103  may be coupled to the speaker array  105  to drive individual transducers  109  in the speaker array  105  to emit various sound beam patterns into the listening area  101 . In one embodiment, the speaker array  105  may be configured to generate beam patterns that represent individual channels of a piece of sound program content. For example, the speaker array  105  may generate beam patterns that represent front left, front right, and front center channels of a piece of sound program content (e.g., a musical composition or an audio track for a movie). 
       FIG. 2A  shows a component diagram of the audio receiver  103  according to one embodiment. The audio receiver  103  may be any electronic device that is capable of driving one or more transducers  109  in the speaker array  105 . For example, the audio receiver  103  may be a desktop computer, a laptop computer, a tablet computer, a home theater receiver, a set-top box, and/or a mobile device (e.g., a smartphone). The audio receiver  103  may include a hardware processor  201  and a memory unit  203 . 
     The processor  201  and the memory unit  203  are generically used here to refer to any suitable combination of programmable data processing components and data storage that conduct the operations needed to implement the various functions and operations of the audio receiver  103 . The processor  201  may be an applications processor typically found in a smart phone, while the memory unit  203  may refer to microelectronic, non-volatile random access memory. An operating system may be stored in the memory unit  203  along with application programs specific to the various functions of the audio receiver  103 , which are to be run or executed by the processor  201  to perform the various functions of the audio receiver  103 . 
     The audio receiver  103  may include one or more audio inputs  205  for receiving audio signals from an external and/or a remote device. For example, the audio receiver  103  may receive audio signals from a streaming media service and/or a remote server. The audio signals may represent one or more channels of a piece of sound program content (e.g., a musical composition or an audio track for a movie). For example, a single signal corresponding to a single channel of a piece of multichannel sound program content may be received by an input  205  of the audio receiver  103 . In another example, a single signal may correspond to multiple channels of a piece of sound program content, which are multiplexed onto the single signal. 
     In one embodiment, the audio receiver  103  may include a digital audio input  205 A that receives digital audio signals from an external device and/or a remote device. For example, the audio input  205 A may be a TOSLINK connector or a digital wireless interface (e.g., a wireless local area network (WLAN) adapter or a Bluetooth receiver). In one embodiment, the audio receiver  103  may include an analog audio input  205 B that receives analog audio signals from an external device. For example, the audio input  205 B may be a binding post, a Fahnestock clip, or a phono plug that is designed to receive a wire or conduit and a corresponding analog signal. 
     In one embodiment, the audio receiver  103  may include an interface  207  for communicating with the speaker array  105 . The interface  207  may utilize wired mediums (e.g., conduit or wire) to communicate with the speaker array  105 , as shown in  FIG. 1 . In another embodiment, the interface  207  may communicate with the speaker array  105  through a wireless connection. For example, the network interface  207  may utilize one or more wireless protocols and standards for communicating with the speaker array  105 , including the IEEE 802.11 suite of standards, IEEE 802.3, cellular Global System for Mobile Communications (GSM) standards, cellular Code Division Multiple Access (CDMA) standards, Long Term Evolution (LTE) standards, and/or Bluetooth standards. 
     As shown in  FIG. 2B , the speaker array  105  may receive drive signals from the audio receiver  103  and drive each of the transducers  109  in the array  105  through a corresponding interface  213 . As with the interface  207 , the interface  213  may utilize wired protocols and standards and/or one or more wireless protocols and standards, including the IEEE 802.11 suite of standards, IEEE 802.3, cellular Global System for Mobile Communications (GSM) standards, cellular Code Division Multiple Access (CDMA) standards, Long Term Evolution (LTE) standards, and/or Bluetooth standards. In some embodiment, the speaker array  105  may include digital-to-analog converters  209  and power amplifiers  211  for driving each transducer  109  in the speaker array  105 . 
     Although described and shown as being separate from the audio receiver  103 , in some embodiments, one or more components of the audio receiver  103  may be integrated within the speaker array  105 . For example, the speaker array  105  may include the hardware processor  201 , the memory unit  203 , and the one or more audio inputs  205 . 
     As shown in  FIG. 1 , the speaker array  105  houses multiple transducers  109  in a curved cabinet  111 . As shown, the cabinet  111  is cylindrical; however, in other embodiments the cabinet may be in any shape, including a polyhedron, a frustum, a cone, a pyramid, a triangular prism, a hexagonal prism, a sphere, or a frusto conical shape. 
       FIG. 3  shows an overhead, cutaway view of the speaker array  105 . As shown in  FIGS. 1 and 3 , the transducers  109  in the speaker array  105  encircle the cabinet  111  such that transducers  109  cover the curved face of the cabinet  111 . The transducers  109  may be any combination of full-range drivers, mid-range drivers, subwoofers, woofers, and tweeters. Each of the transducers  109  may use a lightweight diaphragm, or cone, connected to a rigid basket, or frame, via a flexible suspension that constrains a coil of wire (e.g., a voice coil) to move axially through a cylindrical magnetic gap. When an electrical audio signal is applied to the voice coil, a magnetic field is created by the electric current in the voice coil, making it a variable electromagnet. The coil and the transducers&#39;  109  magnetic system interact, generating a mechanical force that causes the coil (and thus, the attached cone) to move back and forth, thereby reproducing sound under the control of the applied electrical audio signal coming from an audio source, such as the audio receiver  103 . Although electromagnetic dynamic loudspeaker drivers are described for use as the transducers  109 , those skilled in the art will recognize that other types of loudspeaker drivers, such as piezoelectric, planar electromagnetic and electrostatic drivers are possible. 
     Each transducer  109  may be individually and separately driven to produce sound in response to separate and discrete audio signals received from an audio source (e.g., the audio receiver  103 ). By allowing the transducers  109  in the speaker array  105  to be individually and separately driven according to different parameters and settings (including delays and energy levels), the speaker array  105  may produce numerous directivity/beam patterns that accurately represent each channel of a piece of sound program content output by the audio receiver  103 . For example, in one embodiment, the speaker array  105  may produce one or more of the directivity patterns shown in  FIG. 4 . The directivity patterns produced by the speaker array  105  may not only differ in shape, but may also differ in direction. For example, a directivity pattern may be adjusted to point in various directions in the listening area  101  and/or different directivity patterns may be pointed in different directions. 
     In one embodiment, the speaker array  105  may include multiple types of transducers  109  aligned in rings  113  around the cabinet  111  as shown in  FIG. 5A . The different types of transducers  109  may be selected based on sound frequencies intended to be used by each transducer  109 . For example, the speaker array  105  shown in  FIG. 5A  may include three separate types of transducers  109 A- 109 C arranged in groups of rings  113 . In this example, the transducers  109 A in the rings  113 A 1  and  113 A 2  may be selected to ideally play low-frequency sounds (e.g., sounds in the range of 20 Hz to 200 Hz); the transducers  109 B in the rings  113 B 1  and  113 B 2  may be selected to ideally play mid-frequency sounds (e.g., sounds in the range of 201 Hz to 2,000 Hz); and the transducers  109 C in the rings  113 C 1  and  113 C 2  may be selected to ideally play high-frequency sounds (e.g., sounds in the range of 2,001 Hz to 20,000 Hz). A set of crossover filters may be used within the speaker array  105  for splitting an audio signal into separate frequency bands and driving each type of transducer  109  with a corresponding band. Although the example frequency ranges provided above are non-overlapping between the different types of transducers  109 A- 109 C, in other embodiments, as will be described below, the frequency ranges of the different types of transducers  109 A- 109 C within the speaker array  105  may be overlapping. 
     As shown in  FIG. 5A  and described above, each of the transducers  109  are arranged in rings  113  based on type. For instance, the transducers  109 A may be arranged in two outer rings  113 A 1  and  113 A 2 , the transducers  109 B may be arranged in two rings  113 B 1  and  113 B 2  between the rings  113 A 1  and  113 A 2 , and the transducers  109 C may be arranged in two rings  113 C 1  and  113 C 2  between the rings  113 B 1  and  113 B 2 . In other embodiments, the configuration of the transducers  109  may be different. For example, as shown in  FIG. 5B , the speaker array  105  may include three rings  113 C 1 ,  113 C 2 , and  113 C 3  of the transducers  109 C. In another example embodiment shown in  FIG. 5C , the speaker array  105  may include a single ring  113 C 1  of the transducers  109 C. 
     In one embodiment, the number of rings  113  and type of transducers  109  in each ring  113  maintains horizontal symmetry for the speaker array  105  about a horizontal axis. In this embodiment, there are an even number of outer rings  113  of each type that symmetrically surround more inner rings  113 . For example, in  FIG. 5C  there are an even number of rings  113 A that surround the more inner rings  113 B and  113 C. Similarly, there are an even number of rings  113 B that surround the ring  113 C. The speaker arrays  105  shown in  FIGS. 5A and 5C  maintain similar symmetry about a horizontal access through the center of the array  105 . By maintaining horizontal symmetry in this fashion, the speaker array  105  allows sound produced from each type of transducer  109  and each frequency of sound produced by this complimentary arrangement of transducers  109  to appear to originate from the same origin point. In particular, since low frequency sounds may be produced from the transducers  109 A in the ring  113 A 1  and the transducers  109 A in the ring  113 A 2 , these low frequency sounds will appear to emanate from the center of the speaker array  105  instead of from a top or bottom portion of the speaker array. Similarly, mid and high frequency sounds produced by the transducers  109 B and  109 C, respectively, will also appear to emanate from the center of the speaker array  105  based on this horizontal symmetry. 
     In one embodiment, each transducer  109  in each ring  113  may be evenly spaced relative to adjacent transducers  109  in the same ring  113 . For example, as shown in  FIG. 6A , the distance between the outer rim of adjacent transducers  109 A in the rings  113 A 1  and  113 A 2  may be X 1 , the distance between the outer rim of each of adjacent transducers  109 B in the rings  113 B 1  and  113 B 2  may be X 2 , and the distance between the outer rim of adjacent transducers  109 C in the rings  113 C 1  and  113 C 2  may be X 3 . In this embodiment, each transducer  109  is evenly spaced relative to each other transducer  109  in a corresponding ring  113 . However, since the diameters of each of the different types of transducers  109 A- 109 C may be different, the distance between each type of transducer  109 A- 109 C may also be different (i.e., X 1 ≠X 2 ≠X 3 ). 
     Although described and shown in relation to multiple rings  113 , in some embodiments, the speaker array  105  may include a single ring  113  of transducers  109 . In this embodiment, the single ring  113  of transducers  109  may be of a single type. 
     Although shown as including the same number of transducers  109  in each of the rings  113 , in some embodiments the number of transducers  109  in each ring  113  may be different/not constant. For example, in an embodiment in which a speaker array  105  has rings  113  with different types of transducers  109 , the number of transducers  109  in each ring  113  may be different. More specifically, in a speaker array  105  with rings  113 A 1  and  113 A 2  with transducers  109 A, rings  113 B 1  and  113 B 2  with transducers  109 B, and rings  113 C 1  and  113 C 2  with transducers  109 C, the number of transducers  109 C in the rings  113 C 1  and  113 C 2  may be greater than the number of transducers  109 B in the rings  113 B 1  and  113 B 2 . Further, the number of transducers  109 B in the rings  113 B 1  and  113 B 2  may be greater than the number of transducers  109 A in the rings  113 A 1  and  113 A 2 . This difference in the number of transducers  109  in each ring  113  may accommodate the difference in diameter of each type of transducer  109 . 
     In some embodiments, the number of transducers  109  in each ring  113  may be constant even when the diameters of the different types of transducers  109  in each ring are different. For example, in some embodiments, a speaker array  105  with a cabinet  111  having a conical shape may be used. In this embodiment, the larger transducers  109  may be placed at the bottom of the conically shaped cabinet  111  while the smaller transducers  109  may be placed at the top of the conically shaped cabinet  111  as shown in  FIG. 6B . 
     In one embodiment, transducers  109  between rings  113  may be evenly aligned as shown in  FIGS. 5A-5C  and  FIG. 7A . In this embodiment, as shown in  FIG. 7A , the centers of each transducer  109  are aligned with the centers of transducers  109  in other rings  113  to form uniform columns  115  of transducers  109 . The uniform columns  115  of transducers  109  may encircle the cabinet  111  of the speaker array  105 . Based on this configuration, the number of uniform columns  115  is equal to the number of transducers  109  in any ring  113  within the speaker array  105 . 
     In other embodiments, the separate rings  113  of transducers  109  may be offset from adjacent rings  113  as shown in  FIG. 7B . In these embodiments, the center of each transducer  109  in the speaker array  105  is aligned directly between transducers  109  in adjacent rings  113 . For example, as shown in  FIG. 7B , the transducers  109 A and  109 C are aligned between the transducers  109 B and consequently the transducers  109 B are aligned between the transducers  109 A and  109 C. 
     Using the configurations discussed above, the speaker array  105  is rotationally symmetric about the center axis R as shown in  FIG. 8  such that rotating the speaker array  105  around the axis R a prescribed amount/degree does not change how the speaker array  105  looks relative to a defined perspective. For example, the speaker array  105  may be rotationally symmetric on the order of N, where N is the number of transducers  109  in each ring  113  of transducers  109 . By the speaker array  105  being rotationally symmetric on the order of N, rotating the speaker array  105  about the axis R at an angle of 360/n, where n is an integer between 1 and N, does not change how the speaker array  105  looks relative to a defined perspective. 
     This rotational symmetry allows the speaker array  105  to be easily adapted to any placement within the listening area  101 . For example, the speaker array  105  may be associated with one or more sensors and logic circuits for detecting the orientation of the speaker array  105  relative to the listener  107  and/or one or more objects in the listening area  101  (e.g., walls in the listening area  101 ). For instance, the sensors may include microphones, cameras, accelerometers, or other similar devices. These sensors and logic circuits may be integrated with the speaker array  105  and/or separate from the array  105  (e.g., the sensors and logic circuits may be within or coupled to the audio receiver  103 ). For example, one or more transducers  109  in the speaker array  105  may be driven to output a series of test sounds into the listening area  101 . These test sounds may be detected by a set of microphones within the listening area  101 . Based on the detected sounds, the orientation of the speaker array  105  may be determined relative to one or more of the microphones, the listener  107 , and/or one or more objects in the listening area  101 . Since the speaker array  105  is rotationally symmetric, the same number and type of transducers  109  are pointed in all directions. Accordingly, once the orientation of the speaker array  105  is known, the speaker array  105  may be driven according to this orientation to produce one or more channels of audio without the need for movement and/or physical adjustment of the speaker array  105 . 
     Although described above and shown in  FIGS. 5A-5C  as each transducer  109  located in a ring around the cabinet  111  of the speaker array  105 , in some embodiments one or more of the transducers  109  may be placed on top and/or bottoms surfaces of the cabinet  111 . For example, as shown in  FIG. 9 , the transducers  109 A may be respectively placed on the top and bottom surfaces of the cabinet  111  and faced outward relative to the cabinet  111 . In this configuration, the transducers  109 A are faced perpendicular to the transducers  109 B and  109 C, but the arrangement of all the transducers  109  in the speaker array  105  remains rotationally and horizontally symmetric. 
     In one embodiment, the rings  113  of transducers  109  may be evenly spaced. For example, the outer rims of the transducers  109  in any ring  113  may be separated from the outer rims of any other ring  113  of transducers  109  by the distance Z as shown in the example column  115  of transducers  109  in  FIG. 10A . For example, the distance Z may be in the range of 10 mm to 500 mm. 
     In other embodiments, the spacing between rings  113  of transducers  109  may be varied. For example, in the column  115  shown in  FIG. 10B  the outer rims of the transducers  109 A in the ring  113 A 1  may be separated from the outer rims of the transducers  109 B in the ring  113 B 1  by the distance Z 1  while the outer rims of the transducers  109 B in the ring  113 B 1  may be separated from the outer rims of the transducers  109 C in the ring  113 C 1  by the distance Z 2 , where Z 1 ≠Z 2 . Further, the outer rims of the transducers  109 C in the ring  113 C 1  may be separated from the outer rims of the transducers  109 C in the ring  113 C 2  by the distance Z 3 , where Z 1 ≠Z 3  and/or Z 2 ≠Z 3 . 
     In some embodiments, the distance between rings  113  of transducers  109  may be based on a logarithmic scale. For example, as shown in the example column  115  in  FIG. 10C , starting from the center-most ring  113  in the speaker array  105  and moving outward along each column in both directions, the distances between each ring  113  may be a logarithmic factor of the distance, where is a real number greater than one. Accordingly, the spacing between each ring  113  may be represented by  N , wherein N is an integer greater than or equal to zero. For example, the outer rims of the transducers  109 C in the ring  113 C 1  may be separated from the outer rims of the transducers  109 B in the ring  113 B 1  by the distance  0  and the outer rims of the transducers  109 B in the ring  113 B 1  may be separated from the outer rims of the transducers  109 A in the ring  113 A 1  by the distance  1 . Similarly, the outer rims of the transducers  109 C in the ring  113 C 1  may be separated from the outer rims of the transducers  109 B in the ring  113 B 2  by the distance  1  and the outer rims of the transducers  109 B in the ring  113 B 2  may be separated from the outer rims of the transducers  109 A in the ring  113 A 2  by the distance  2 . By separate rings  113  of transducers  109  using logarithmic spacing, denser transducer  109  spacing at short wavelengths is achieved while limiting the number of transducers  109  needed for longer wavelengths by spacing them in larger and larger logarithmic increments. In one embodiment, the distance H may be in the range of 10 mm to 500 mm. 
     As noted above, the selection of types of transducers  109  may be made based on desired frequency coverage for the speaker array  105 . In some embodiments, the frequency ranges covered by separate types of transducers  109  may overlap. For example, the transducers  109 A may be designed to have frequency coverage between 20 to 200 Hz, the transducers  109 B may be designed to have frequency coverage between 100 Hz to 3,000 Hz, and the transducers  109 C may be designed to have frequency coverage between 2,000 Hz to 20,000 Hz. Accordingly, in this example the transducers  109 B overlap frequency coverage with both the transducers  109 A and  109 C. In one embodiment, the above frequency limits may correspond to cutoff frequencies for audio crossover filters associated with each transducer  109  in the speaker array  105 . 
     As discussed above, one or more of the transducers  109  in the speaker array  105  may be used to generate one or more beam patterns. For example, one or more of the transducers  109  may be used to generate one or more of the beam patterns shown in  FIG. 4 . The beam patterns may represent separate channels for a piece of sound program content (e.g., a musical composition or an audio track for a movie). 
     As shown in  FIGS. 11A-11C , the directivity of a transducer  109  typically rises with the frequency of a drive signal. Accordingly, as shown in  FIG. 11A  for the transducer  109 A, the directivity index at the beginning end of a transducer  109 A with the frequency range (e.g., 20 Hz) is low, but the directivity index increases as the frequency of a corresponding signal approaches the far end of the transducer  109 A&#39;s frequency range (e.g., 200 Hz). Similar behavior can also be seen for the transducers  109 B and  109 C as shown in  FIGS. 11B and 11C , respectively. 
     Accordingly, based on these initial dips or shortfalls in directivity, blindly/abruptly switching between types of transducers  109  based on signal frequency may result in a poor beam pattern production. Namely, switching from the transducers  109 A to the transducers  109 B as a signal reaches 100 Hz may generate a low directivity beam pattern as shown in  FIG. 11B . Similarly, switching from the transducers  109 B to the transducers  109 B as a signal reached 2,000 Hz may generate a low directivity beam pattern as shown in  FIG. 11C . When a higher directivity beam pattern is desired, these low directivity beam patterns, which are caused by abrupt switches between transducers  109  of different types, may provide undesirable or unintended sounds. 
     To overcome these directivity and switching issues, in one embodiment, as described above, the transducers  109  selected for the speaker array  105  have overlapping frequency ranges. In this embodiment, strict switching between transducers  109  of different types may be avoided. Instead, gradual transitions between transducers  109  of different types may be used to generate beam patterns. For example, when a drive signal is used that falls into the frequency overlap between the transducers  109 A and  109 B (e.g., 100 Hz to 200 Hz), the audio receiver  103  and/or the speaker array  105  may utilize both types of transducers  109 A and  109 B to produce an associated beam pattern. As the drive signal moves out of the frequency overlap (e.g., above 200 Hz), the audio receiver  103  and/or the speaker array  105  may transition to only utilize the transducers  109 B. At this frequency, the transducers  109 B may be capable of generating a sufficiently directed beam pattern as shown in  FIG. 11B . 
     Similar transitions may be performed between the transducers  109 B and  109 C. For example, when a drive signal is used that falls into the frequency overlap between the transducers  109 B and  109 C (e.g., 2,000 Hz to 3,000 Hz), the audio receiver  103  and/or the speaker array  105  may utilize both types of transducers  109 B and  109 C to produce an associated beam pattern. As the drive signal moves out of the frequency overlap (e.g., above 3,000 Hz), the audio receiver  103  and/or the speaker array  105  may transition to only utilize the transducers  109 C. At this frequency, the transducers  109 C may be capable of generating a sufficiently directed beam pattern as shown in  FIG. 11C . 
     As described above, a gradual transition between different types of transducers  109  may be performed based on the frequency of an associated drive signal. This gradual transition may allow the speaker array  105  to produce beam patterns with high directivity indexes, even at the cutoff frequencies of transducers  109 . In one embodiment, the transitions are implemented using one or more crossover filters in the speaker array  105  while in other embodiments the transitions are implemented by the audio receiver  103  through the adjustment of beam settings by the hardware processor  201 . 
     As explained above, an embodiment of the invention may be an article of manufacture in which a machine-readable medium (such as microelectronic memory) has stored thereon instructions which program one or more data processing components (generically referred to here as a “processor”) to perform the operations described above. In other embodiments, some of these operations might be performed by specific hardware components that contain hardwired logic (e.g., dedicated digital filter blocks and state machines). Those operations might alternatively be performed by any combination of programmed data processing components and fixed hardwired circuit components. 
     While certain embodiments have been described and shown in the accompanying drawings, it is to be understood that such embodiments are merely illustrative of and not restrictive on the broad invention, and that the invention is not limited to the specific constructions and arrangements shown and described, since various other modifications may occur to those of ordinary skill in the art. The description is thus to be regarded as illustrative instead of limiting.

Metadata:
Filing Date: 20170501
Publication Date: 20181211
Grant Date: 20181211
Priority Date: 20140818
Inventors: JOHNSON, MARTIN E.
DIX, GORDON R.
Howes, Michael B.
GEAVES, Gary P.
SAUX, TOM-DAVY WILLIAM JENDRIK
Assignee: APPLE INC
CPC Classifications: [{"code": "H04R5/02", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04R1/403", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04R2201/401", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04R2201/401", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04R5/02", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04R1/403", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04R1/403", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04R2201/401", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04R5/02", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 59561883