Patent Publication Number: US-2023145713-A1

Title: System and method for omnidirectional adaptive loudspeaker

Description:
TECHNICAL FIELD 
     Aspects disclosed herein generally relate to an omnidirectional adaptive loudspeaker assembly. This aspect and others will be discussed in more detail below. 
     BACKGROUND 
     Conventional loudspeakers were designed to be directional based on its transducer radiation pattern and speaker positioning. The loudspeaker has no prior knowledge of the number of listeners will be listening and what their respective relative positioning in the space will be. In recent years, due to the advancement of voice assistance, smart homes, and working from home; loudspeakers are shifting from corners of the room into portable omnidirectional usage. Hence, the industry has started seeing a new form factor of 360-degree audio speaker emerging. This form factor may deliver 360-degree sound for consistent, uniform coverage. Namely, by placing the loudspeaker in a middle of a room where everyone may be able to perceive remarkably similar sound experience. Furthermore, in some configurations, this form factor may also be able to simulate 3D sound and perform better sound effect than a conventional Bluetooth stereo speaker. 
     SUMMARY 
     In at least one embodiment, a system for providing an adaptive loudspeaker assembly is provided. The system includes a loudspeaker array, a microphone array, and at least one controller. The loudspeaker array transmits an audio output signal in an omnidirectional sound mode in a room having a plurality of walls. The microphone array is coupled to the loudspeaker array to capture the audio output signal in the room. The at least one controller is programmed to receive the captured audio output signal and to determine that at least one first wall of the plurality of walls is closest to the loudspeaker array based on the captured audio output signal. The at least one controller is further programmed to change a sound mode of the loudspeaker array from transmitting the audio output signal in the omnidirectional mode into a beamforming sound mode to transmit the audio output signal away from the at least one first wall of the plurality walls. 
     In at least one embodiment, a method for providing an adaptive loudspeaker assembly is provided. The method includes transmitting, a loudspeaker array, an audio output signal in an omnidirectional sound mode in a room having a plurality of walls and capturing, via a microphone array, the audio output signal in the room. The method further includes determining with at least one controller that at least one first wall of the plurality of walls is closest to the loudspeaker array based on the captured audio output signal and changing a sound mode of the loudspeaker array from transmitting the audio output signal in the omnidirectional mode into a beamforming sound mode to transmit the audio output signal away from the at least one first wall of the plurality walls. 
     In at least one embodiment, a system for providing an adaptive loudspeaker assembly is provided. The system includes a circular loudspeaker array, a microphone array, and at least one controller. The circular loudspeaker array transmits an audio output signal in an omnidirectional sound mode in a room having a plurality of walls. The circular microphone array is coupled to the circular loudspeaker array to capture the audio output signal in the room. The at least one controller programmed to receive the captured audio output signal indicating a plurality of sound reflections from the plurality of walls and to determine that at least one first wall of the plurality of walls is closest to the circular loudspeaker array based on a first sound reflection from the at least one first wall being the strongest reflection out of the plurality of sound reflections. The at least one controller is further programmed to change a sound mode of the loudspeaker array from transmitting the audio output signal in the omnidirectional mode into a beamforming sound mode to transmit the audio output signal away from the at least one first wall of the plurality walls. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The embodiments of the present disclosure are pointed out with particularity in the appended claims. However, other features of the various embodiments will become more apparent and will be best understood by referring to the following detailed description in conjunction with the accompanying drawings in which: 
         FIG.  1    depicts a system for providing an omnidirectional adaptive loudspeaker assembly in accordance with one embodiment; 
         FIG.  2    depicts one example of a circular loudspeaker array that forms a portion of the system of  FIG.  1    in accordance with one embodiment; 
         FIG.  3    depicts one example of a six-element microphone array along with the circular loudspeaker array that forms a portion of the system of  FIG.  1    in accordance with one embodiment; 
         FIG.  4    depicts a waveform that illustrates direct sound and reflections; 
         FIG.  5    depicts another example of a microphone array in accordance with one embodiment; and 
         FIG.  6    depicts a schematic diagram of a digital signal processing (DSP) implementation that is implemented by the system of  FIG.  1    in accordance with one embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention that may be embodied in various and alternative forms. The figures are not necessarily to scale; some features may be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention. 
     It is recognized that the controllers as disclosed herein may include various microprocessors, integrated circuits, memory devices (e.g., FLASH, random access memory (RAM), read only memory (ROM), electrically programmable read only memory (EPROM), electrically erasable programmable read only memory (EEPROM), or other suitable variants thereof), and software which co-act with one another to perform operation(s) disclosed herein. In addition, such controllers as disclosed utilizes one or more microprocessors to execute a computer-program that is embodied in a non-transitory computer readable medium that is programmed to perform any number of the functions as disclosed. Further, the controller(s) as provided herein includes a housing and the various number of microprocessors, integrated circuits, and memory devices ((e.g., FLASH, random access memory (RAM), read only memory (ROM), electrically programmable read only memory (EPROM), electrically erasable programmable read only memory (EEPROM)) positioned within the housing. The controller(s) as disclosed also include hardware-based inputs and outputs for receiving and transmitting data, respectively from and to other hardware-based devices as discussed herein. 
     In general, there may be two types of structures of the loudspeaker speaker product that can be claimed as 360-loudspeaker. One is an upward loudspeaker and the other is a downward loudspeaker with a waveguide design such as a reflector. While the mechanical design may be able to achieve an omnidirectional radiation pattern, when the loudspeaker is placed close to a wall or other obstacles, it may sound unnatural or colored. This may be due to near field interaction around the loudspeaker such as the reflected sound interfered with the direct sound and thus lead to frequency response alternations. 
     Another configuration is to position multiple transducers around a unit circle in the horizontal plane such as distributing full range drivers uniformly around the circle. This configuration enables different transducers to run different processing based on the environment and hence alleviate the coloration problem. However, the current existing market solutions are either controlled manually or fixed while on the factory floor. It makes the form factor loses its flexibility and inconvenience to the end users. 
       FIG.  1    depicts a system  100  for providing an omnidirectional adaptive loudspeaker assembly  102  in accordance with one embodiment. The system  100  includes the loudspeaker assembly  102 , a controller  104 , and a microphone array  106 . In general, the controller  104  includes any number of digital signal processors  109  (hereafter “digital signal processor” or “DSP”  109 ) and is programmed to receive an audio input signal. The controller  104  is programmed to process the audio input signal and to provide a processed audio output signal to the loudspeaker assembly  102  (or loudspeaker array  102 ) into a room  108  having one or more walls  110 . The controller  104  may change a sound mode of the loudspeaker array  102  from an omnidirectional mode to a beamforming mode based on a location the loudspeaker array  102  relative to the closest wall  110 . In the beamforming mode, the controller  104  controls the loudspeaker array  102  to radiate the processed audio output signal in a direction that is opposite to the closest wall  110 . In this case, the loudspeaker array  102  may be placed anywhere in the room  108  and its relative sound mode may be adjusted automatically based on the environment of the room  108  and may still demonstrate ideal and robust audio performance. 
     In general, the microphone array  106  may detect audio that is being output by the loudspeaker array  102  and transmit the detected audio back to the controller  104 . In turn, the controller  104  (e.g., the DSP  109 ) may then determine the distance (e.g., location) of the closest wall  110  to the loudspeaker array  102  and then control the sound mode of the loudspeaker array  102 . This may entail transmitting the processed audio output signal from the omnidirectional mode to the beamforming mode. In general, the controller  104  determines the strongest reflection of audio from the wall  110  (i.e., the closest wall) to then either deactivate one or more loudspeakers in the array  102  that is closest to the wall  110  or apply beamforming to direct the audio output in a desired direction. 
     It is recognized that the loudspeaker array  102  may be implemented as a circular array of m loudspeakers that are uniformly distributed on a horizontal plane. It is also recognized that the microphone array  106  may also be implemented as a circular array of n microphones. The microphone array  106  may be positioned parallel with the loudspeaker array  102 . 
       FIG.  2    depicts one example of the circular loudspeaker array  102  that forms a portion of the system  100  of  FIG.  1    in accordance with one embodiment. The example circular loudspeaker array  102  as shown in connection with  FIG.  2    includes a total of 8 loudspeakers  120   a - 120   h . However, it is recognized that any number of loudspeakers may be utilized in the array  102 . The loudspeakers  120   a - 120   h  are uniformly distributed along a horizontal plane  122 . In general, each loudspeaker  120   a - 120   h  may radiate a similar amount of sound energy all forward facing direction when the loudspeaker array  102  is in the omnidirectional sound mode. In the beamforming mode, any one or more of the loudspeakers  120   a - 120   h  may be controlled to play the audio output at different volumes, delay the audio output thereof or be completely shut off while transmitting the processed audio output. It is recognized that the arrangement and structure of the loudspeakers  120   a - 120   h  need to be strategically positioned, since the sound radiation of the loudspeakers  120   a - 120   h  are often interfered with each other and a combing filtering will hence appear in the frequency response. Additionally, the sound field may not be spatially uniform and omnidirectional. To avoid these issues, some special acoustics structure may be required, such as horn structure, to smooth the transition of the frequency response of the adjacent loudspeakers  120   a - 120   h.    
       FIG.  3    depicts one example of a six-element microphone array  106  along with the circular loudspeaker array  102  that forms a portion of the system  100  of  FIG.  1    in accordance with one embodiment. The microphone array  106  may be positioned on top of the loudspeaker array  102 . The array  106  as illustrated in  FIG.  3    may include, for example, 6 microphones  130   a - 130   f  that are positioned on an outer perimeter of the array  106 . As for sound reflection detection as performed by the system  100 , the microphone array  106  may need to be implemented in a circular array and uniformly distributed as generally shown in  FIG.  3    to record sound from the loudspeakers  120   a - 120   h  and the reflections. The microphone array  106  is generally configured to record all of the sound output by the loudspeaker array  102  including direct sound and reflection sound. The direct sound is distinguishable from reflection sound (i.e., reflections). This is shown in reference to  FIG.  4    where direct sound is clearly distinguishable from the reflection. 
     Referring back to  FIG.  3   , while in some cases it may be desirable to distribute the microphones  130   a - 130   f  uniformly, it is recognized that this may be optional and that non-uniform implementations may be pursued as well. When the loudspeaker array  102  is powered on, or sound detection is triggered via the controller  104 , the loudspeaker array  102  is generally placed in the omnidirectional sound mode. The microphone array  106  captures the audio and the controller  104  records the audio. The controller  104  converts the captured audio into a multi-channel signal which is then provided to the DSP  109  for signal processing. 
     The loudspeaker array  102  may include any number of loudspeakers  120 , M that is greater than, or equal to two. Similarly, the microphone array  106  may include any number of microphones, N that is greater than, or equal to two. Thus, the combination of M loudspeakers  120  and N microphones  130  will be able to form K direction of microphone beams where K is greater than 1. For the example illustrated in  FIG.  3   , K=12 twelve beams or vectors. In general, K is arbitrary and can be set to a value that is most desired. The greater the number of beams K, the greater the computational needs may be required by the DSP  109 . 
       FIG.  5    depicts another example of the microphone array  106 ′ in accordance with one embodiment. The microphone array  106 ′ may, for example, include 5 microphones  130   a ′- 130   e ′. In particular, the microphone  130   e ′ may be positioned generally in a center of the array  106 ′ and the microphone  130   e ′ may be surrounded by microphones  130   a ′- 130   e ′. In this regard, all of the microphones  130   a ′- 130   e ′ may not be radially formed on an outer perimeter of the array  106  when compared to the array  106  as illustrated in  FIG.  3   . 
       FIG.  6    depicts a schematic diagram of the controller  104  and more specifically to the DSP  109  that is implemented by the system  100  of  FIG.  1    in accordance with one embodiment. The DSP  109  generally includes a first processing stage  202  and a second processing stage  204 . The first processing stage  202  may be implemented as an acoustic echo canceller (AEC) block. The second processing stage  204  may be implemented as a minimum variance distortion less response (MVDR) block. The second processing stage  204  may also be implemented as, but not limited to, a General Sidelobe Canceler (GSC) block). The controller  104  generally includes any number of microprocessors to execute the first processing stage  202 , the second processing stage  204 , the equalization/limiter block  206 , and the loudspeaker beamforming block  208 . 
     The equalization/limiter block  206  receives the incoming audio signal and equalizes the same to generate a reference signal that is provided to the loudspeaker beamforming block  208  and the first processing stage  202 . The first processing stage  202  also receives an output signal from the microphone array  106  (i.e., received signal) which corresponds to the captured audio output in the room  108 . In general, the first processing stage  202  may extract acoustic impulse responses from the reference signal and the received signal as provided by the loudspeaker array  102 . 
     For example, the reference signal may be defined by r(n)), a j th  microphone input signal m j (n) containing a background signal ν(n) (as received from the microphone array  106  via the received signal), and speaker playing signal (or the reference signal as provided by the equalization limiter block  206 ), the first processing stage  202  (e.g., the AEC block) may compute the j th  unknown impulse responses h j (n) based on the following equation, 
         m   j ( n )= r ( n )* h   j ( n )+ν( n )  (1)
 
     where * is the convolution operator. Since the background signal and the reference signal is usually uncorrelated, it is possible to reduce the background signal while obtaining the impulse responses h j (n) by using an adaptive algorithm, such as, for example, a Normalized Least-Mean-Square (NLMS) algorithm as expressed as, 
     
       
         
           
             
               
                 
                   
                     
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     where e j (n), ĥ j (n), μ NLMS  and δ NLMS  are the instantaneous estimation error, NLMS adaptively estimated impulse response, step size with the range 0 to 2 and a small positive constant used to avoid division by zero, respectively. 
     The first processing stage  202  may then transmit the impulse responses e.g.,  (n) to the second processing stage  204 . As noted above, the second processing stage  204  may employ MVDR that is provided by, 
         w   opt   =R   hh   −1   f ( f   H   R   hh   −1   f ) −1   (4)
 
     where R hh  is an autocorrelation matrix of the impulse responses, and f is a desired response vector, which is determined by the detected angles of the sound in 360 degrees. The second processing stage  204  is generally configured to minimize a variance of the received signal. When the controller  104  is programmed or set to a target detection angle, the MVDR block (or the second processing stage  204 ) may maximize the signal received from the programmed direction while minimizing the signal from other directions. If there is a wall  110  in this direction with respect to the microphone array  106  (or the loudspeaker array  102  since the microphone array  106  is attached thereto), the sound reflection may be stronger, and the second processing stage  204  (or the MVDR block) may detect and distinguish this reflection signal. Therefore, we can determine which direction the wall  110  is most likely to be. Speaker beamforming may be bypassed at this point until the location (e.g., distance, angle, etc.) of the wall  110  relative to the array  102  is known. The target detection angle may also be known as the microphone beamforming angle which is determined by the performance of the DSP  109  and/or criteria. The target detection angle is pre-defined and different from the desired response vector, f as set forth in equation (4) above. In general, microphone beamforming may be like a probe that requires instruction with respect to which direction to detect and analyze. 
     After the second processing stage  204  detects wall directions (e.g., distance, angle) relative to the 360 degrees circular array of loudspeakers (or the loudspeaker array  102 ), the controller  104  then ceases to perform wall detection and waits for a next detection trigger event to initiate performing wall detection in the event this operation is being requested again by a user. After wall detection, the controller  104  activates the loudspeaker beamforming block  208  to set a beamforming target angle according to the direction of the wall  110  that is closest to the loudspeaker array  102 . For example, the loudspeaker beamformer block  208  may execute a speaker beamforming algorithm and utilize a weighted delay-and-sum approach which is given by, 
         y ( n )=Σ i=0   N-1   w   i   x ( n−τ   i )  (5)
 
     where N, w i , x, y and τ i  are the number of microphones, weight of the i th  speaker, input signal, output signal and the delay for the i th  microphone, respectively. 
     Hence, if the controller  104  detects the wall  110  or other obstacle at 0 degrees, the controller  104  may select the beamforming target angle at 180 degrees to avoid reflection causing the sound coloration. On the other hand, if the controller  104  detects the wall  110  or other obstacle at a far distance from the microphone array  106  (or from the loudspeaker array  102 ), the controller  104  may bypass the beamforming mode and control the audio output from the loudspeaker array  102  to remain in the omnidirectional sound mode, as a 360-degree loudspeaker. In one example, a distance that is less than one meter to the wall  110  may be adequate to transition the sound mode of the system  100  from the omnidirectional mode into the beamforming mode. Otherwise, the system  100  remains in the omnidirectional mode. 
     For the sake of clarification, it is recognized that the controller  104  may determine the location of any one or more walls  110  with respect to the loudspeaker array  102  and also enter into the beamforming mode to transmit the audio from any number of the walls  110  that are closest to the loudspeaker array  102 . Assuming, for example, that the controller  104  determines that both a first wall  110   a  and a second wall  110   b  are positioned within a predetermined distance (e.g., one meter) of the loudspeaker array  102 , the controller  104  enters into the beamforming mode and transmits the audio output signal away from each of the first wall  110   a  and the second wall  110   b . In this case, the controller  104  provides a first beamforming pattern to direct the audio output signal away from the first wall  110   a  and also provides a second beamforming pattern to direct the audio output signal away from the second wall  110   b.    
     While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms of the invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention. Additionally, the features of various implementing embodiments may be combined to form further embodiments of the invention.