SYSTEM AND METHOD FOR PERFORMING AUTOMATIC SWEET SPOT CALIBRATION FOR BEAMFORMING LOUDSPEAKERS - Patent application

Abstract

To provide a system and method for performing automatic sweet spot calibration for beamforming loudspeakers.SOLUTION: In an audio playback system 100 including a beamforming loudspeaker system realizing sweet spots for a listener, an audio source (device) 101 transmits a first stimulus signal to one of a left loudspeaker assembly 102a and a right loudspeaker assembly 102b to play back an audio output, and receives the audio output from the one of the left loudspeaker assembly 102a and the right loudspeaker assembly 102b. The audio source 101 determines a first distance between the left loudspeaker assembly 102a and the right loudspeaker assembly 102b, and second and third distances from the audio source 101 to the left loudspeaker assembly 102a and the right loudspeaker assembly 102b.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] Aspects disclosed herein generally relate to systems and methods for performing automatic sweet-spot calibration for beamforming loudspeakers. These aspects and others are discussed in more detail herein. [Background technology]

[0002] In U.S. Patent Application Publication No. 2018 / 0242097 to Kriegel et al., an audio receiver is provided that receives one or more input audio signals representing one or more channels of sound content and applies a first beam pattern to the input audio signals to generate a set of first beamformed audio signals. The audio receiver determines a second beam pattern that is less directional than the first beam pattern. The audio receiver determines that driving a loudspeaker array with the set of first beamformed audio signals causes one or more transducers of the loudspeaker array to operate above an operating threshold. In response, the audio receiver applies a second beam pattern to the input audio signals to generate a set of second beamformed audio signals. The audio receiver drives the loudspeaker array with the set of second beamformed audio signals. Summary of the Invention [Means for solving the problem]

[0003] In at least one embodiment, a system is provided for determining a location to which a beamforming loudspeaker system sends an audio output. The system includes a memory device and an audio source including the memory device. The audio source is configured to transmit a first stimulus signal to one of the first beamforming loudspeaker assembly and the second beamforming loudspeaker assembly for playing an audio output, and to receive an audio output from one of the first beamforming loudspeaker assembly and the second beamforming loudspeaker assembly. The audio source is further configured to determine a first distance between the first beamforming loudspeaker assembly and the second beamforming loudspeaker assembly, and to determine a second distance between the audio source and the first beamforming loudspeaker assembly. The audio source is further configured to determine a third distance between the audio source and the second beamforming loudspeaker assembly, and to determine a location for sending the audio output from each of the first beamforming loudspeaker assembly and the second beamforming loudspeaker assembly based at least on the first distance, the second distance, and the third distance.

[0004] In at least another embodiment, a computer program product embodied in a non-transitory computer-readable medium is provided that is programmed to determine a location to which a beamforming loudspeaker system sends an audio output. The computer program product includes instructions for transmitting a first stimulus signal to one of the first and second beamforming loudspeaker assemblies for playing an audio output and receiving an audio output from one of the first and second beamforming loudspeaker assemblies. The computer program product includes instructions for determining a first distance between the first and second beamforming loudspeaker assemblies and determining a second distance between an audio source and the first beamforming loudspeaker assemblies. The computer program product includes instructions for determining a third distance between the audio source and the second beamforming loudspeaker assemblies and determining a location to send the audio output from each of the first and second beamforming loudspeaker assemblies based at least on the first distance, the second distance, and the third distance.

[0005] In at least another embodiment, a method is provided for a beamforming loudspeaker system to determine a location to which to send an audio output. The method includes receiving an audio output from one of a first beamforming loudspeaker assembly and a second beamforming loudspeaker assembly. The method further includes determining a first distance between the first beamforming loudspeaker assembly and the second beamforming loudspeaker assembly and determining a second distance between an audio source and the first beamforming loudspeaker assembly. The method further includes determining a third distance between the audio source and the second beamforming loudspeaker assembly and determining a location for sending the audio output from each of the first beamforming loudspeaker assembly and the second beamforming loudspeaker assembly based at least on the first distance, the second distance, and the third distance. The locations correspond to positions where the audio output from the first beamforming loudspeaker assembly and the second beamforming loudspeaker assembly are perceived by a listener as having similar loudness and acoustic delay. For example, the present application provides the following: (Item 1) 1. A system for determining a location to which a beamforming loudspeaker system should deliver an audio output, comprising: A memory device; an audio source including the memory device; The audio source includes: transmitting a first stimulus signal to one of the first beamforming loudspeaker assembly and the second beamforming loudspeaker assembly for reproducing an audio output; receiving the audio output from the one of the first beamforming loudspeaker assembly and the second beamforming loudspeaker assembly; determining a first distance between the first beamforming loudspeaker assembly and the second beamforming loudspeaker assembly; determining a second distance between said audio source and said first beamforming loudspeaker assembly; determining a third distance between said audio source and said second beamforming loudspeaker assembly; determining a location for transmitting the audio output from each of the first beamforming loudspeaker assembly and the second beamforming loudspeaker assembly based at least on the first distance, the second distance, and the third distance; The above system is configured as follows. (Item 2) The system described in the above item, wherein the audio source is further configured to determine a first angle from which the first beamforming loudspeaker assembly will emit the audio output based at least on the first distance, the second distance, and the third distance before determining the location of the audio output. (Item 3) 2. The system of claim 1, wherein the audio source is further configured to transmit the first angle via a control signal to the first beamforming loudspeaker assembly to cause the first beamforming loudspeaker assembly to emit the audio output in a narrow directional field responsive to the first angle and within a first predetermined frequency range. (Item 4) The system according to any one of the preceding claims, wherein the first predetermined frequency range is 250 Hz to 1.5 kHz. (Item 5) The system of any one of the preceding claims, wherein the audio source is further configured to determine a second angle from which the second beamforming loudspeaker assembly will emit the audio output based at least on the first distance, the second distance, and the third distance before determining the location of the audio output. (Item 6) 2. The system of claim 1, wherein the audio source is further configured to transmit the second angle via a control signal to the second beamforming loudspeaker assembly to cause the second beamforming loudspeaker assembly to emit the audio output in a narrow directional field responsive to the second angle and within a predetermined frequency range. (Item 7) The system according to any one of the preceding claims, wherein the predetermined frequency range is 250 Hz to 1.5 kHz. (Item 8) 13. The system of claim 12, wherein the audio source is further configured to measure a first peak amplitude of the audio output from the first beamforming loudspeaker assembly after the first beamforming loudspeaker assembly delivers the audio output at the first angle. (Item 9) 2. The system of claim 1, wherein the audio source is further configured to measure a second peak amplitude of the audio output from the second beamforming loudspeaker assembly after the second beamforming loudspeaker assembly delivers the audio output at the second angle. (Item 10) The system of any one of the preceding claims, wherein the audio source compares the first peak amplitude to the second peak amplitude to determine the location for sending the audio output from each of the first beamforming loudspeaker assembly and the second beamforming loudspeaker assembly. (Item 11) The system of any one of the preceding claims, wherein the location corresponds to a position where the audio output from the first beamforming loudspeaker assembly and the second beamforming loudspeaker assembly are perceived by a listener as having similar loudness and acoustic delay. (Item 12) 1. A computer program product embodied in a non-transitory computer readable medium programmed to determine a location to which a beamforming loudspeaker system should deliver an audio output, the computer program product comprising: transmitting a first stimulus signal to one of the first beamforming loudspeaker assembly and the second beamforming loudspeaker assembly for reproducing an audio output; receiving the audio output from the one of the first beamforming loudspeaker assembly and the second beamforming loudspeaker assembly; determining a first distance between the first beamforming loudspeaker assembly and the second beamforming loudspeaker assembly; determining a second distance between said audio source and said first beamforming loudspeaker assembly; determining a third distance between said audio source and said second beamforming loudspeaker assembly; determining a location for transmitting the audio output from each of the first beamforming loudspeaker assembly and the second beamforming loudspeaker assembly based at least on the first distance, the second distance, and the third distance; The computer program product as described above, comprising instructions for: (Item 13) 20. The computer program product of claim 19, further comprising instructions for determining a first angle from which the first beamforming loudspeaker assembly will emit the audio output based at least on the first distance, the second distance, and the third distance prior to determining the location of the audio output. (Item 14) 20. The computer program product of claim 19, further comprising instructions for transmitting the first angle via a control signal to the first beamforming loudspeaker assembly to deliver the audio output in a narrow directional field responsive to the first angle and within a first predetermined frequency range. (Item 15) 23. The computer program product of claim 22, further comprising instructions for determining a second angle from which the second beamforming loudspeaker assembly will deliver the audio output based at least on the first distance, the second distance, and the third distance prior to determining the location of the audio output. (Item 16) 23. The computer program product of claim 22, further comprising instructions for transmitting the second angle via a control signal to the second beamforming loudspeaker assembly to deliver the audio output in a narrow directional field responsive to the second angle and within a predetermined frequency range. (Item 17) 20. The computer program product of any one of the preceding claims, further comprising instructions for measuring a first peak amplitude of the audio output from the first beamforming loudspeaker assembly after the first beamforming loudspeaker assembly delivers the audio output at the first angle. (Item 18) 20. The computer program product of claim 19, further comprising instructions for measuring a second peak amplitude of the audio output from the second beamforming loudspeaker assembly after the second beamforming loudspeaker assembly delivers the audio output at the second angle. (Item 19) 20. The computer program product of claim 19, further comprising instructions for comparing the first peak amplitude to the second peak amplitude to determine the location for sending the audio output from each of the first beamforming loudspeaker assembly and the second beamforming loudspeaker assembly. (Item 20) 1. A method for determining a location to which a beamforming loudspeaker system should deliver an audio output, comprising: receiving an audio output from one of the first beamforming loudspeaker assembly and the second beamforming loudspeaker assembly; determining a first distance between the first beamforming loudspeaker assembly and the second beamforming loudspeaker assembly; determining a second distance between an audio source and the first beamforming loudspeaker assembly; determining a third distance between the audio source and the second beamforming loudspeaker assembly; determining a location for transmitting the audio output from each of the first beamforming loudspeaker assembly and the second beamforming loudspeaker assembly based at least on the first distance, the second distance, and the third distance; Including, The method, wherein the location corresponds to a position where the audio output from the first beamforming loudspeaker assembly and the second beamforming loudspeaker assembly are perceived by a listener as having similar loudness and acoustic delay. (Summary) 1. A system including an audio source configured to transmit a first stimulus signal to one of a first beamforming loudspeaker assembly and a second beamforming loudspeaker assembly for reproducing an audio output, and to receive an audio output from one of the first beamforming loudspeaker assembly and the second beamforming loudspeaker assembly, the audio source configured to determine a first distance between the first beamforming loudspeaker assembly and the second beamforming loudspeaker assembly, and to determine a second distance between the audio source and the first beamforming loudspeaker assembly, the audio source configured to determine a third distance between the audio source and the second beamforming loudspeaker assembly, and to determine a location for sending the audio output from each of the first beamforming loudspeaker assembly and the second beamforming loudspeaker assembly based at least on the first distance, the second distance, and the third distance.

[0006] While embodiments of the present disclosure are pointed out with particularity in the appended claims, other features of the various embodiments will become more apparent and will be best understood by reference to the following detailed description taken in conjunction with the accompanying drawings, in which: [Brief description of the drawings]

[0007] [Figure 1] 1 illustrates a schematic diagram of an embodiment of an audio reproduction system that provides a sweet spot listening experience to a listener. [Diagram 2] 1 illustrates a schematic diagram of an example of an audio system that provides a dynamic sweet spot listening experience to a listener, according to one embodiment. [Diagram 3] 1 illustrates generally one embodiment for calibrating a loudspeaker system to an audio source to achieve a sweet spot. [Figure 4] 1 illustrates a schematic of an audio system for performing sweet-spot calibration for a beamforming loudspeaker system according to one embodiment. [Diagram 5] 2 illustrates generally a first aspect implemented by an audio system to perform sweet-spot calibration for a beamforming loudspeaker system, according to one embodiment; [Figure 6] 6 shows a schematic signal contour of the audio output of a left or right beamforming loudspeaker associated with the first embodiment shown in FIG. 5; [Figure 7] 1 illustrates a schematic of an audio system having corresponding system latency associated with a stimulus signal, according to one embodiment. [Figure 8] 4A-4C are schematic diagrams illustrating corresponding system latency, distance between first and second loudspeaker assemblies, and time of flight of a stimulus signal according to one embodiment; [Figure 9] 13 illustrates generally a second aspect implemented by an audio system to perform sweet-spot calibration for a beamforming loudspeaker system, according to one embodiment; [Figure 10] 1 illustrates a schematic diagram of an example of how an audio source determines the angles of the left and right loudspeaker assemblies, according to one embodiment. [Figure 11A] 4A illustrates a schematic diagram of the peak amplitude and its measurement for the left loudspeaker assembly according to one embodiment. [Figure 11B] 13A illustrates a schematic diagram of the peak amplitude and its measurement for the right loudspeaker assembly according to one embodiment. [Figure 12] 4 illustrates generally one embodiment of how ambiguity in an audio system is resolved and how the system determines a sweet spot according to a third aspect; [Figure 13A] 4A illustrates a schematic diagram of the peak amplitude and its measurement for the left loudspeaker assembly according to one embodiment. [Figure 13B] 13A illustrates a schematic diagram of the peak amplitude and its measurement for the right loudspeaker assembly according to one embodiment. [Figure 14] 13A and 13B show schematic signal contours of the output of a left or right beamforming loudspeaker assembly associated with the third embodiment shown in FIG. [Figure 15] 1 illustrates generally a method for performing sweet-spot calibration for a beamforming loudspeaker system according to one embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Where necessary, detailed embodiments of the present invention are disclosed herein, but it should be understood that the disclosed embodiments are merely illustrative of the invention that may be embodied in various and alternative forms. The figures are not necessarily to scale, and some features may be exaggerated or minimized to show details of specific components. Therefore, specific structural and functional details disclosed herein are not intended to be limiting, but should be construed as merely a representative basis for teaching those skilled in the art to variously utilize the present invention.

[0009] It is recognized that the controllers 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 variations thereof), and software that cooperate with one another to perform the operation(s) disclosed herein. Also, such controllers disclosed use one or more microprocessors to execute computer programs embodied in non-transitory computer-readable media that are programmed to perform any number of functions disclosed herein. Furthermore, the controller(s) provided herein include a housing and various numbers 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)) disposed within the housing. Also, the disclosed controller(s) include hardware-based inputs and outputs for transmitting and receiving data, respectively, to and from other hardware-based devices discussed herein.

[0010] 1 illustrates generally one embodiment of an audio reproduction system 100 including a device 101 and a beamforming loudspeaker system 102 that provides a sweet spot for a listener 104. The device 101 may be, for example, an audio source (hereinafter 101) that provides an audio input signal to the loudspeaker system 102. It is recognized that the audio source 101 may be a mobile device, a laptop, a tablet, or other suitable variations thereof. The audio source 101 may transmit the audio input signal wirelessly (or via a hardwired connection) to the loudspeaker system 102. The loudspeaker system 102 reproduces the audio input signal for the listener 104. The loudspeaker system 102 generally includes a left beamforming loudspeaker assembly (hereinafter "left loudspeaker assembly") 102a and a right beamforming loudspeaker assembly (hereinafter "right loudspeaker assembly") 102b. However, it is recognized that the loudspeaker system 102 may include any number of loudspeaker assemblies that reproduce an audio input signal to the listener 104 .

[0011] The left and right loudspeaker assemblies 102a, 102b may be implemented as beamforming loudspeakers, with each assembly 102a, 102b including an array of loudspeakers. In one embodiment, each beamforming loudspeaker assembly may include an array of loudspeakers including a total of 33 speaker drivers. For example, the 33 speaker drivers may include, for example, 12 ¾ inch (19 mm) tweeters, 16 2 inch (50 mm) midrange speakers, four 5.25 inch (50 mm) woofers, and one 10 inch (250 mm) integrated subwoofer. In this case, such a beamforming loudspeaker assembly may be implemented, for example, as a Lexicon SL-1™ loudspeaker assembly. It is recognized that the number and size of the tweeters, midrange speakers, woofers, and subwoofers may vary based on the desired criteria of a particular implementation.

[0012] Each array of loudspeakers in a given loudspeaker assembly 102a, 102b may be controlled by a number of digital sound processors (DSPs) (not shown). In one embodiment, the DSPs may utilize finite impulse response (FIR) filters and various signal processing algorithms to control the audio output from the assembly 102a, 102b. For example, the DSPs may control the phase (or angle) and volume of the audio signals being output from the loudspeaker assemblies 102a, 102b to achieve high directionality of the audio output to the intended target (i.e., the intended listener 104). In general, a DSP may be located in each loudspeaker assembly 102a, 102b and generally receives a stimulus signal from an audio source 101. The stimulus signal is discussed in more detail below. The DSPs receive audio input signals from the audio source 101 and control beamforming operations to reproduce the audio input signals as audio output to the listener 104.

[0013] 1, the left and right loudspeaker assemblies 102a, 102b provide a listening sweet spot to the listener 104. For example, the sweet spot may be generally defined as the left and right loudspeaker assemblies 102a, 102b providing audio output of the same loudness and time of flight (e.g., delay) to the listener 104. Alternatively, the audio output from the left and right loudspeaker assemblies 102a, 102b arrives at the same time and at the same level to the listener 104.

[0014] Figure 2 shows a schematic of an example of system 100 in relation to a dynamic sweet spot, according to one embodiment. In comparison to Figure 1, Figure 2 shows that the distance between the sound source 101 and the left loudspeaker assembly 102a is different than the distance between the sound source 101 and the right loudspeaker assembly 102b. However, system 10 can be calibrated to control the sound output so that it arrives at the left loudspeaker assembly 102a and the right loudspeaker assembly 102b at the same time and at the same level.

[0015] Without sweet spot calibration, it is known that because the left loudspeaker assembly 102a is closer to the audio source 101 than the right loudspeaker assembly 102b, the audio source 101 will provide audio output to the left loudspeaker assembly 102a before the audio output is received by the right loudspeaker assembly 102b. To account for the difference between the distance between the audio source 101 and the left loudspeaker assembly 102a and the distance between the audio source 101 and the right loudspeaker assembly 102b, the system 100 is calibrated to vary the delay and gain of the audio that the audio source 101 transmits to the nearest loudspeaker assembly (i.e., the left loudspeaker assembly 102a). In this case, the audio source 101 may use a longer delay for transmitting audio output to the left loudspeaker assembly 102a than the delay applied to transmitting audio output to the right loudspeaker assembly 102b.

[0016] For example, the audio source 101 may be calibrated such that audio transmitted from it is received simultaneously by both the left loudspeaker assembly 102a and the right loudspeaker assembly 102b, and audio transmitted from the audio source 101 is provided to the left loudspeaker assembly 102a and the right loudspeaker assembly 102b at the same amplitude. The left and right loudspeaker assemblies 102a and 102b may then focus (i.e., steer) audio beams towards the listener 104 as part of the beamforming functionality provided by these devices.

[0017] 3 shows a schematic representation of an embodiment of an audio system 200 for calibrating a loudspeaker system 202 to achieve a sweet spot for a listener. For example, the system 200 includes an audio source 204, which may be in the form of a tablet with a built-in microphone (not shown). The audio source 204 includes a user interface 206 that allows a user to specify the distance of each speaker (see, for example, reference elements 208a and 208b, which correspond to the visual representations of the left and right loudspeaker assemblies, respectively) relative to a visual representation of the audio source 204 on the user interface 206 (see, for example, reference element 210), as shown diagrammatically on a display of the user interface 206. The audio source 204 stores information corresponding to the distance settings entered by the user and adjusts the delay of the transmission of audio signals to the loudspeaker system 200 accordingly.

[0018] 4 shows a schematic diagram of an audio system 100 for performing sweet-spot calibration for a beamforming loudspeaker system, according to one embodiment. An audio source 101 is typically equipped with at least one microphone 106 (hereinafter "microphone 106") for performing the calibration. In general, the audio source 101 may wirelessly transmit a stimulus signal for reproducing sound to the left and right loudspeaker assemblies 102a, 102b. In response to receiving the stimulus signal, the left and right loudspeaker assemblies 102a, 102b send out an audio output. It is recognized that the stimulus signal is not audible.

[0019] The microphone 106 captures the audio output provided by the left and right loudspeaker assemblies 102a, 102b. In general, a stable round-trip latency may be required between transmitting the stimulus signal, receiving it, playing the audio output, and finally recording the audio output at the microphone 106. For example, the jitter associated with the round-trip latency must be stable, and the jitter should be within ±145 microseconds, roughly equivalent to 7 samples of audio data for a 48 kHz audio output. This may allow the audio source 101 to ensure that the distance of each of the left and right loudspeaker assemblies 102a, 102b from itself is within ±5 centimeters. The aspects required to perform sweet spot calibration are discussed in more detail below.

[0020] FIG. 5 illustrates a schematic diagram of a first aspect implemented by the system 100 to perform sweet spot calibration for the beamforming loudspeaker system 102, according to an embodiment. In the first aspect, the audio source 101 determines the distance between the loudspeaker assemblies 102a, 102b after a first stimulus signal is sent. In general, the user may place the audio source 101 close to the left or right loudspeaker assembly 102a, 102b. In one embodiment, the user may place the audio source 101 within 5 cm of the left or right loudspeaker assembly 102a, 102b. The user may also activate the left or right loudspeaker assembly 102a, 102b to send audio output to the audio source 101 as an omnidirectional beam rather than a directional beam (i.e., a beamforming beam with a predetermined directivity) in response to the stimulus signal.

[0021] In this case, the left or right loudspeaker assembly 102a, 102b emits audio signals at a large horizontal angle extending from -180 degrees to +180 degrees (e.g., omnidirectional) as shown in the signal contour block 300 of Fig. 6 (e.g., see axis 302 of Fig. 6). The left and / or right loudspeaker assemblies 102a and 102b emit audio signals within a frequency range (i.e., a predetermined frequency range) from 250 Hz to about 1.5 kHz (see axis 304 of Fig. 6). The axis 306 provided in Fig. 6 corresponds to the attenuation of the signal at various decibel levels. The stimulus signal has a bandwidth from 250 Hz to about 1.5 kHz, so that the loudspeaker assemblies 102a, 102b reproduce sound in this frequency range. The stimulus signal includes a bandwidth from 250 Hz to 1.5 kHz, allowing the left or right loudspeaker assemblies 102a and 102b to have sophisticated control over their directivity in this frequency range. When the audio source 101 is placed near either the left or right loudspeaker assemblies 102a, 102b, the system latency and distance between such loudspeaker assemblies 102a, 102b are calibrated. For example, the audio source 101 performs a time-of-flight calculation to determine the distance between the left or right loudspeaker assemblies 102a, 102b.

[0022] 7 shows the system 100 including the distance between the left loudspeaker assembly 102a and the right loudspeaker assembly 102b. The system latency s associated with the stimulus signal t In one embodiment, the system latency s t may be 30 milliseconds. Figures 7 and 8 provide additional information regarding how the distance is determined.

[0023] From FIG. 7 and FIG. 8, it can be defined as follows:

[0024] s t = System Latency

[0025] d t = speaker distance (flight time) (sec)

[0026] d = loudspeaker distance (m)

[0027] c = speed of sound (i.e., 343 m / s)

[0028] Here, dt' (i.e., the time of flight) and d (i.e., the loudspeaker distance (i.e., the distance between the loudspeakers)) are given by the following equations, respectively:

[0029] d t =d' t -s t Formula (1)

[0030] d=d t *c formula (2)

[0031] 9 illustrates a schematic of a second aspect implemented by the audio system 100 to perform a sweet-spot calibration for the beamforming loudspeaker system 102, according to one embodiment. In the second aspect, the audio source 101 transmits a second stimulus signal, which may be omnidirectional, to determine the distance of each loudspeaker assembly 102a, 102b relative to the audio source 101. However, ambiguity arises because the location (e.g., angle) of each loudspeaker assembly 102a, 102b may be unknown. As described above in connection with FIG. 5, once the audio source 101 determines the distance to the left and / or right loudspeaker assemblies 102a, 102b, the audio source 101 needs to resolve the ambiguity regarding the location of the left and / or right loudspeaker assemblies 102a, 102b relative to the audio source 101. For example, an audio source 101 may determine the distance to the left and / or right loudspeaker assemblies 102a, 102b, but it is unknown whether the left and / or right loudspeaker assemblies 102a, 102b are located in front of the audio source 101 or behind (or rear of) the audio source 101. The distance between the audio source 101 and the left loudspeaker assembly 102a is generally defined by a variable L, and the distance between the audio source 101 and the right loudspeaker assembly 102b is generally defined by a variable R. The relationship between L and R will be discussed in more detail in connection with FIG. 10.

[0032] The embodiment shown in Fig. 9 is not intended to imply that two sound sources 101 are actually present in the system 100. Instead, Fig. 9 shows that the sound source 101 may be located at a location 320 that may be in front of the left and right loudspeaker assemblies 102a, 102b, or that the sound source 101 may be located at a location 322 that may be behind or rear of the left and right loudspeaker assemblies 102a, 102b. In this case, an ambiguity exists that needs to be resolved. Thus, depending on the location of the left and right loudspeaker assemblies 102a, 102b, the sweet spot may be located in front of the left and / or right loudspeaker assemblies 102a, 102b, or behind (or rear of) the left and / or right loudspeaker assemblies 102a, 102b.

[0033] To resolve this ambiguity, the audio source 101 transmits a stimulus signal to the left and right loudspeaker assemblies 102a, 102b. In response to the stimulus signal, the left and right loudspeaker assemblies 102a, 102b transmit directional (e.g., not as an omnidirectional beam as transmitted in relation to FIG. 5) audio output according to a unidirectional beamforming principle to the audio source 101. For example, the audio source 101 transmits separate control signals (different from the stimulus signal) instructing the loudspeakers to transmit audio output in a directional field (not the omnidirectional field as described above in relation to FIGS. 4 and 6). The control signals transmitted by the audio source 101 to the left and right loudspeaker assemblies 102a, 102b further provide corresponding angles (e.g., α for the left loudspeaker assembly 102a and β for the right loudspeaker assembly 102b) for the left and right loudspeaker assemblies 102a, 102b to transmit the audio output signals to resolve the ambiguity. These angles α, β must be determined before providing control signals having corresponding angles α, β, this aspect will be discussed in more detail in conjunction with FIG.

[0034] FIG. 10 illustrates one embodiment of how the audio source 101 determines angles α and β of the left and right loudspeaker assemblies 102a, 102b, respectively. The audio source 101 also determines a distance L between the audio source 101 and the left loudspeaker assembly 102a and a distance R between the audio source 101 and the right loudspeaker assembly 102b. These aspects are discussed in more detail below. The system 100 illustrated in connection with FIG. 10 includes a number of delay blocks 110a-110c. The delay block 110a generally corresponds to a signal delay (or delay latency) associated with the transmission of control signals from the audio source 101 to the left and right loudspeaker assemblies 102a, 102b. The delay block 110b generally corresponds to a signal delay associated with the delivery of an audio output signal from the left loudspeaker assembly 102a to the microphone 106 of the audio source 101 (e.g., an acoustic delay for the left loudspeaker assembly 102a). The delay block 110c generally corresponds to a signal delay associated with the delivery of the audio output signal from the right loudspeaker assembly 102b to the microphone 106 of the audio source 101 (eg, the acoustic delay of the left loudspeaker assembly 102a).

[0035] As discussed above, the audio source 101 determines the distance d between the left and right loudspeaker assemblies 102a and 102b, respectively, as well as the distance L between the audio source 101 and the left loudspeaker assembly 102a and the distance R between the audio source 101 and the right loudspeaker assembly 102b, as discussed above in connection with Equation 2, and the audio source 101 uses the distances d, L, and R to determine the corresponding angles α and β. The audio source 101 transmits stimulus signals to the left and right loudspeaker assemblies 102a, 102b such that the assemblies 102a, 102b emit audio output signals in an omnidirectional range, as also shown above in connection with Figures 5 and 6.

[0036] 11A illustrates an example of measurements performed by audio source 101 on the audio output from the left loudspeaker assembly 102a. In general, audio source 101 measures the peak amplitude L' of the audio output from the left loudspeaker assembly 102a. t Identify the peak amplitude L' t corresponds to the length of time it takes for the audio output from the left loudspeaker assembly 102a to reach a peak value. The audio source 101 determines the time of flight l for the audio output from the left loudspeaker assembly 102a. t The audio source 101 determines the time of flight L for the audio output from the left loudspeaker assembly 102a. t and the distance between the audio source 101 and the left loudspeaker assembly 102a is calculated by:

[0037] L t =L' t -s t (Formula 3)

[0038] L=L t *c[m] (Formula 4)

[0039] 11B illustrates an example of measurements performed by audio source 101 on the audio output from the right loudspeaker assembly 102b. In general, audio source 101 measures the peak amplitude R' of the audio output from the right loudspeaker assembly 102b. t Identify the peak amplitude R' t corresponds to the length of time it takes for the audio output from the right loudspeaker assembly 102b to reach a peak value. The audio source 101 determines the time of flight R t and the distance between the audio source 101 and the right loudspeaker assembly 102b is determined by the following equation:

[0040] R t =R' t -s t (Formula 5)

[0041] R=R t *c[m] (Equation 6)

[0042] Knowing L, R, and d, audio source 101 may determine angles α and β using the following equations:

[0043] α = acos(L 2 +d 2 -R 2 ) / 2Ld Equation (7)

[0044] β = acos(R 2 +d 2 -L 2 ) / 2Rd Formula (8)

[0045] As described above, the audio source 101 includes information corresponding to the angles α and β in the control signals sent to the left and right loudspeaker assemblies 102a, 102b, such that the left and right loudspeaker assemblies 102a, 102b, respectively, emit audio data into a directional field (e.g., a narrow sound field that is not omnidirectional) at their corresponding angles α and β.

[0046] To remove the above-mentioned ambiguity, the audio source 101 determines which of the audio data received from the left loudspeaker assembly 102a and the right loudspeaker assembly 102b is loudest, an aspect of which is discussed in more detail below.

[0047] 12 shows a schematic diagram of an example of how the system 100 resolves ambiguities and determines the sweet spot (S1 or S2) for the listener 104 according to the third aspect. As described above, once the audio source 101 determines the corresponding angle (e.g., α for the left loudspeaker assembly 102a and β for the right loudspeaker assembly 102b), the audio source 101 transmits information corresponding to the angles α and β to the left and right loudspeaker assemblies 102a and 102b, respectively. FIG. 12 shows the relationship between the two corresponding angles (e.g., α 1 , α 2), only one of these angles may be transmitted by the control signal for the left loudspeaker assembly 102a to emit an audio output signal for determining the location of the sweet spot. 1 or α 2 It is recognized that the angle α can be positive or negative. For example, 1 can be defined as -α, and the angle α 2 can be defined as +α. Similarly, β 1 or β 2 It is recognized that angle β can be positive or negative. For example, 1 can be defined as -β, and the angle β 2 can be defined as +β.

[0048] In the example shown in FIG. 12, two audio sources 101 are shown for illustrative purposes. However, in an embodiment, in practice only one of these audio sources 101 may be provided. In general, it is unknown where the audio source 101 is located relative to the left and right loudspeaker assemblies 102a and 102b, which is why two audio sources 101 are shown. In general, the audio source 101 provides a control signal (having directionality) having information corresponding to an angle −α to the left loudspeaker assembly 102a, and the audio source 101 provides a control signal having information corresponding to an angle +β to the right loudspeaker assembly 102b (e.g., angle −α 1 (where +β and +β are determined based on Equations 7 and 8 above.) In this manner, the left loudspeaker assembly 102a directs its audio output signal toward sweet spot S2, and the right loudspeaker assembly 102b directs its audio output signal toward sweet spot S1. At this point, we do not know where the actual sweet spot is, only that it may correspond to the location of S1 or S2.

[0049] The audio source 101 performs measurements of the peak amplitudes of the audio output signals received from the left loudspeaker assembly 102a and the right loudspeaker assembly 102b in response to such assemblies 102a and 102b transmitting audio output signals at angles -α and +β, respectively. Figures 13A and 13B show the peak amplitudes of the audio output from the left loudspeaker assembly 102a and the right loudspeaker assembly 102b. In this case, the audio source 101 determines which peak amplitudes (i.e., a R ) is largest (see, for example, FIG. 13B).

[0050] Generally, the a of the audio output from the left loudspeaker assembly 102b R (e.g., the measured peak amplitude) is a L (e.g., the measured peak amplitude output from the left loudspeaker assembly 102a), then the sweet spot is determined to be at location S1. Figures 13a and 13b correspond to this situation, with the peak amplitude a R The measured peak amplitude a L Since the sweet spot S1 is greater than the angle S1, it is determined that S1 is the sweet spot. In this case, the audio source 101 is located at the bottom of FIG. 12 (i.e., in front of the left and right loudspeaker assemblies 102a-102b). Once the audio source 101 determines that the sweet spot is located at S1, it sends another control signal to cause the left loudspeaker assembly 102a to emit audio output at an angle +α (note that this is the inverse of the angle -α mentioned immediately above that was used to determine the location of the sweet spot S1), and the right loudspeaker assembly 102b continues to emit audio output at an angle +β such that the audio output from each of the left and right loudspeaker assemblies 102a and 102b is directed toward the sweet spot S1.

[0051] Alternatively, the audio output from the left loudspeaker assembly 102a may be L(e.g., the measured peak amplitude) is a R (e.g., the measured peak amplitude output from the left loudspeaker assembly 102b), then the sweet spot is determined to be at location S2. In this case, the audio source 101 is located at the top of FIG. 12 (i.e., behind the left and right loudspeaker assemblies 102a-102b). Once the audio source 101 determines that the sweet spot is located at S2, it sends another control signal to cause the left loudspeaker assembly 102a to continue to emit audio output at angle -α and the right loudspeaker assembly 102b to emit audio output at angle -β (note that this is the inverse of the angle +β, discussed immediately above, that was used to determine the location of sweet spot S1), such that the audio output from each of the left loudspeaker assembly 102a and the right loudspeaker assembly 102b is directed toward the sweet spot S2.

[0052] Fig. 14 shows a schematic signal contour 500 of the output of the left or right beamforming loudspeaker assembly 102a, 102b in relation to the third embodiment shown in Fig. 12. In the embodiment shown in relation to Fig. 8, the left or right loudspeaker assembly 102a, 102b emits audio signals at a small horizontal angle extending from -50 degrees to +50 degrees as shown in the signal contour block 300 in Fig. 9 (see, for example, axis 502 in Fig. 6). The left and / or right loudspeaker assemblies 102a and 102b emit audio signals within a frequency range from 250 Hz to about 1.5 kHz (see, for example, axis 504 in Fig. 9). In this case, the frequency is controlled so that the audio output (e.g., from the left and right loudspeaker assemblies 102a, 102b) is appropriately received at the audio source 101 to determine the loudness of the left and right loudspeaker assemblies 102a, 102b. By controlling the directivity (e.g., omnidirectional or narrow beam beamforming) within this frequency range (e.g., 250 Hz to 1.5 KHz), it becomes possible to detect amplitude differences due to beamforming. In general, the audio output signals from the left and right loudspeaker assemblies 102a, 102b are narrowly directional (e.g., not omnidirectional) and are within the above frequency range. These aspects provide advantageous results in that the directivity and frequency are well controlled and the measurement tone of the audio output signal is not at a very high frequency that may annoy the listener.

[0053] FIG. 15 illustrates generally a method 600 for performing sweet-spot calibration for a beamforming loudspeaker system, according to one embodiment.

[0054] In operation 602, the audio source 101 receives a stable round trip latency (e.g., s t) to the left and right loudspeaker assemblies 102a and 102b. As mentioned above, the jitter associated with the round trip latency must be stable, and the jitter should be between ±145 microseconds, which roughly corresponds to 7 samples of audio for a 48 kHz audio output provided by the left and right loudspeaker assemblies 102a and 102b. For example, a stable round trip latency may be 30 milliseconds. This aspect is described in more detail above in connection with FIG. 4.

[0055] In operation 604, the audio source 101 determines the distance d between the left and right loudspeaker assemblies 102a, 102b. As described above in connection with FIG. 7, the audio source 101 determines the speaker distance or the time of flight corresponding to that distance (e.g., d t ) and calculate the distance d based on the above equation (2).

[0056] In operation 606, the audio source 101 determines the distance L between the audio source 101 and the left loudspeaker assembly 102a. The audio source 101 also determines the distance R between the audio source 101 and the right loudspeaker assembly based on Equations 4 and 6 above.

[0057] In operation 608, the audio source 101 determines the angle α of the left loudspeaker assembly and the angle β of the right loudspeaker assembly based on equations 7 and 8 above.

[0058] In operation 610, the audio source 101 transmits information corresponding to an angle (e.g., α) to the left loudspeaker assembly 102a and information corresponding to an angle (e.g., β) to the right loudspeaker assembly 102b to determine the location of the sweet spot.

[0059] At operation 612, the audio source 101 adjusts the amplitude (e.g., a L) and measure the amplitude of the audio output from the right loudspeaker assembly (for example, a R ) is measured.

[0060] In operation 614, the audio source 101 L A R to determine the location of the sweet spot. As mentioned above, the sweet spot generally corresponds to the location or position where the sound output from the left loudspeaker assembly 102a and the right loudspeaker assembly 102b are perceived by a listener as having similar loudness and similar acoustic delay.

[0061] In operation 616, the audio source 101 adjusts the angle information of either the left loudspeaker assembly 102a or the right loudspeaker assembly 102b to deliver the audio output to the sweet spot location, as described above in connection with FIG. 12.

[0062] Although exemplary embodiments have been described above, it is not intended that these embodiments describe every possible form of the present invention. Rather, the words used herein 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 present invention. Moreover, features of the various implementation embodiments may be combined to form further embodiments of the present invention.

Claims

1. 1. A system for determining a location to which a beamforming loudspeaker system should deliver an audio output, the system comprising: A memory device; an audio source including the memory device; the audio source comprising: transmitting a first stimulus signal to a first beamforming loudspeaker assembly and a second beamforming loudspeaker assembly for reproducing an audio output; receiving the audio output from the first beamforming loudspeaker assembly and the second beamforming loudspeaker assembly; determining a first distance between a first beamforming loudspeaker assembly and a second beamforming loudspeaker assembly; determining a second distance between the sound source and the first beamforming loudspeaker assembly; determining a third distance between the audio source and the second beamforming loudspeaker assembly; determining a location for transmitting the audio output from each of the first beamforming loudspeaker assembly and the second beamforming loudspeaker assembly based at least on the first distance, the second distance, and the third distance; A system configured to run

2. 2. The system of claim 1, wherein the audio source is further configured to determine a first angle from which the first beamforming loudspeaker assembly will emit the audio output based at least on the first distance, the second distance, and the third distance prior to determining the location of the audio output.

3. 3. The system of claim 2, wherein the audio source is further configured to transmit the first angle via a control signal to the first beamforming loudspeaker assembly to cause the first beamforming loudspeaker assembly to emit the audio output in a narrow directional field responsive to the first angle and within a first predetermined frequency range.

4. The system of claim 3 , wherein the first predetermined frequency range is from 250 Hz to 1.5 kHz.

5. 3. The system of claim 2, wherein the audio source is further configured to determine a second angle from which the second beamforming loudspeaker assembly will emit the audio output based at least on the first distance, the second distance, and the third distance prior to determining the location of the audio output.

6. 6. The system of claim 5, wherein the audio source is further configured to transmit the second angle via a control signal to the second beamforming loudspeaker assembly to cause the second beamforming loudspeaker assembly to emit the audio output in a narrow directional field responsive to the second angle and within a predetermined frequency range.

7. The system of claim 6, wherein the predetermined frequency range is from 250 Hz to 1.5 kHz.

8. 6. The system of claim 5, wherein the audio source is further configured to measure a first peak amplitude of the audio output from the first beamforming loudspeaker assembly after the first beamforming loudspeaker assembly delivers the audio output at the first angle.

9. 9. The system of claim 8, wherein the audio source is further configured to measure a second peak amplitude of the audio output from the second beamforming loudspeaker assembly after the second beamforming loudspeaker assembly delivers the audio output at the second angle.

10. 10. The system of claim 9, wherein the audio source compares the first peak amplitude to the second peak amplitude to determine the location for sending the audio output from each of the first beamforming loudspeaker assembly and the second beamforming loudspeaker assembly.

11. 2. The system of claim 1, wherein the location corresponds to a position where the audio output from the first beamforming loudspeaker assembly and the second beamforming loudspeaker assembly are perceived by a listener as having similar loudness and acoustic delay.

12. 1. A computer program product embodied in a non-transitory computer readable medium programmed to determine a location to which a beamforming loudspeaker system should send an audio output, the computer program product including: transmitting a first stimulus signal to a first beamforming loudspeaker assembly and a second beamforming loudspeaker assembly for reproducing an audio output; receiving the audio output from the first beamforming loudspeaker assembly and the second beamforming loudspeaker assembly; determining a first distance between a first beamforming loudspeaker assembly and a second beamforming loudspeaker assembly; determining a second distance between the sound source and the first beamforming loudspeaker assembly; determining a third distance between the audio source and the second beamforming loudspeaker assembly; determining a location for transmitting the audio output from each of the first beamforming loudspeaker assembly and the second beamforming loudspeaker assembly based at least on the first distance, the second distance, and the third distance; A computer program product comprising instructions for executing the

13. 13. The computer program product of claim 12, further comprising instructions for, prior to determining the location of the audio output, determining a first angle from which the first beamforming loudspeaker assembly will deliver the audio output based at least on the first distance, the second distance, and the third distance.

14. 14. The computer program product of claim 13, further comprising instructions for transmitting the first angle via a control signal to the first beamforming loudspeaker assembly to deliver the audio output in a narrow directional field responsive to the first angle and within a first predetermined frequency range.

15. 15. The computer program product of claim 14, further comprising instructions for, prior to determining the location of the audio output, determining a second angle from which the second beamforming loudspeaker assembly will deliver the audio output based at least on the first distance, the second distance, and the third distance.

16. 16. The computer program product of claim 15, further comprising instructions for transmitting the second angle via a control signal to the second beamforming loudspeaker assembly to deliver the audio output in a narrow directional field responsive to the second angle and within a predetermined frequency range.

17. 17. The computer program product of claim 16, further comprising instructions for measuring a first peak amplitude of the audio output from the first beamforming loudspeaker assembly after the first beamforming loudspeaker assembly delivers the audio output at the first angle.

18. 20. The computer program product of claim 17, further comprising instructions for measuring a second peak amplitude of the audio output from the second beamforming loudspeaker assembly after the second beamforming loudspeaker assembly delivers the audio output at the second angle.

19. 20. The computer program product of claim 18, further comprising instructions for comparing the first peak amplitude to the second peak amplitude to determine the location for sending the audio output from each of the first beamforming loudspeaker assembly and the second beamforming loudspeaker assembly.

20. 1. A method for determining a location to which a beamforming loudspeaker system should deliver an audio output, the method comprising: an audio source receiving audio output from a first beamforming loudspeaker assembly and a second beamforming loudspeaker assembly; determining a first distance between the first beamforming loudspeaker assembly and the second beamforming loudspeaker assembly; determining a second distance between the sound source and the first beamforming loudspeaker assembly; determining a third distance between the audio source and the second beamforming loudspeaker assembly; determining a location for transmitting the audio output from each of the first beamforming loudspeaker assembly and the second beamforming loudspeaker assembly based at least on the first distance, the second distance, and the third distance; Including, The method, wherein the location corresponds to a position where the audio output from the first beamforming loudspeaker assembly and the second beamforming loudspeaker assembly are perceived by a listener as having similar loudness and acoustic delay.

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