Patent Description:
Options for accessing and listening to digital audio in an out-loud setting were limited until in <NUM>, when SONOS, Inc. filed for one of its first patent applications, entitled "Method for Synchronizing Audio Playback between Multiple Networked Devices," and began offering a media playback system for sale in <NUM>. The Sonos Wireless HiFi System enables people to experience music from many sources via one or more networked playback devices. Through a software control application installed on a smartphone, tablet, or computer, one can play what he or she wants in any room that has a networked playback device. Additionally, using the controller, for example, different songs can be streamed to each room with a playback device, rooms can be grouped together for synchronous playback, or the same song can be heard in all rooms synchronously.

Given the ever growing interest in digital media, there continues to be a need to develop consumer-accessible technologies to further enhance the listening experience. <CIT> describes a method for processing a multichannel audio signal including mounting electroacoustical transducers in a low frequency augmenting device. <CIT> describes a sound system processor for converting left and right channel signals from an audio source into composite left and right signals
According to a first aspect of the invention, there is provided a method according to appended claim <NUM>. According to a second aspect of the invention, there is provided a method according to claim <NUM>. According to a third aspect of the invention, there is provided a computer-readable medium according to claim <NUM>. According to a fourth aspect of the invention, there is provided a playback system according to claim <NUM>.

The drawings are for the purpose of illustrating example embodiments, but it is understood that the inventions are not limited to the arrangements and instrumentality shown in the drawings.

Multi-channel playback of audio content may enhance a listener's experience by causing the listener to perceive a "wideness effect" when the audio content is played back. In some examples, multi-channel playback of the audio content may be facilitated by multiple groups of one or more audio drivers included as part of one or more playback devices that make up a playback system. In some cases, the wideness effect produced by a playback system performing multi-channel playback might only be perceivable at limited locations within the environment of the playback system. The locations at which a listener could perceive the wideness effect during playback may be increased by manipulating input signals provided to the various groups of audio drivers of the playback system.

In situations where the playback system is in a small room or the listener is close to the playback system, the listener may benefit from a less pronounced wideness effect. But, in situations where the playback system is in a large room or the listener is far from the playback system, the listener may benefit from a more pronounced wideness effect.

Regardless of whether multi-channel playback is facilitated via a playback system that includes a single playback device or multiple playback devices, the playback system may include at least a first group of one or more audio drivers and a second group of one or more audio drivers. In some cases, the playback system may also include a third group of one or more audio drivers. Each group of audio driver(s) may be configured to generate sound waves according to a particular radiation pattern. Such radiation patterns may define a direction-dependent amplitude of sound waves produced by the corresponding group of audio drivers (i) at a given audio frequency (or range of audio frequencies), (ii) at a given radius from the audio driver, (iii) for a given amplitude of input signal. A radiation pattern corresponding to a group of audio driver(s) may be dependent on the audio drivers' construction, structure, geometry, materials, and/or orientation and position within an enclosure of a playback device, for example.

In some instances, the playback system provides a center channel of the audio content to the first group, the second group, and if applicable, the third group. The first, second, and/or third groups may generate sound waves corresponding to the center channel according to a first radiation pattern having a maximum along a first direction (e.g. , a center line of the playback system). The playback system may also provide a first side channel to the first group so that the first group may generate sound waves corresponding to the first side channel according to a second radiation pattern having a maximum along a second direction. The first radiation pattern and the second radiation pattern may combine via superposition to form a first response lobe that has a maximum along a third direction between the first and second directions. Since the first radiation pattern represents the center channel and the second radiation pattern represents the center channel and the first side channel, the first response lobe represents playback of both the center channel and the first side channel with a perceived wideness that is dependent on the relative input amplitudes of the center channel and the first side channel. That is, by increasing the amplitude of the center channel with respect to the first side channel, the maximum of the first response lobe is shifted toward the first direction, resulting in a "narrowed" multi-channel audio "image. " Similarly, by decreasing the amplitude of the center channel with respect to the first side channel, the maximum of the first response lobe is shifted toward the second direction, resulting in a "widened" multi-channel audio "image.

In some applications, the playback system provides the center channel and a second side channel to the third group, causing the third group to generate sound waves corresponding to both the center channel and the second side channel according to a third radiation pattern having a maximum along a fourth direction. The first radiation pattern and the third radiation pattern may combine to form a second response lobe that has a maximum along a fifth direction between the first and fourth directions. Since the first radiation pattern represents the center channel and the third radiation pattern represents the center channel and the second side channel, the second response lobe represents playback of both the center channel and the second side channel with a perceived wideness that is dependent on the relative input amplitudes of the center channel and the second side channel. That is, by increasing the amplitude of the center channel with respect to the second side channel, the maximum of the second response lobe is shifted toward the first direction, resulting in a "narrowed" multi-channel audio "image. " Similarly, by decreasing the amplitude of the center channel with respect to the second side channel, the maximum of the second response lobe is shifted toward the fourth direction, resulting in a "widened" multi-channel audio "image.

Using the above techniques, the wideness of the multi-channel audio image may be adjusted in accordance with the environment of the playback system. For example, the playback system may receive, via a user interface, input indicating (i) a size of a room that the playback system is located in and/or (ii) locations of walls or other sound barriers within the room. The playback system may use the received input to determine an appropriate wideness for the multi-channel audio image, and adjust the respective amplitudes of the center channel, first side channel, and/or second side channel accordingly. In some examples, a playback device of the playback system may be placed near a corner of a room, and for the sake of efficiency, it may be useful for that playback device to reproduce only the center channel and the first (or alternatively the second) side channel.

Accordingly, some examples described herein include, among other things, a playback device (i) providing a center channel of audio content to one or more first audio drivers and one or more second audio drivers so that the center channel is reproduced according to a first radiation pattern and (ii) providing a side channel of audio content to the one or more first audio drivers so that the side channel is reproduced according to a second radiation pattern. The first and second radiation patterns may combine to form a response lobe that has a maximum between the respective maxima of the first and second radiation patterns. Other aspects of the examples will be made apparent in the remainder of the description herein.

In a first aspect, a method is performed by a playback device comprising one or more first audio drivers and one or more second audio drivers. The method includes (a) receiving a left channel of audio content and a right channel of the audio content, (b) generating a center channel of the audio content comprising a combination of the left and right channels, (c) providing the generated center channel to (i) the one or more first audio drivers and (ii) the one or more second audio drivers for playback of the center channel according to a first radiation pattern that has a maximum along a first direction, (d) generating a side channel comprising a combination of (i) the center channel and (ii) a difference between the left channel and the right channel, and (e) providing the generated side channel to the one or more first audio drivers for playback of the side channel according to a second radiation pattern that has a maximum along a second direction. The first radiation pattern and the second radiation pattern combine to form a first response lobe that has a maximum along a third direction between the first and second directions.

The method may further comprise changing the third direction by amplifying or attenuating the center channel relative to the side channel, wherein providing the generated center channel to (i) the one or more first audio drivers and (ii) the one or more second audio drivers comprises providing the amplified or attenuated center channel.

The method may further comprise changing the third direction by amplifying or attenuating the side channel relative to the center channel, wherein providing the generated side channel to the one or more first audio drivers comprises providing the amplified or attenuated side channel.

The playback device may further comprise one or more third audio drivers, wherein the side channel is a first side channel, and wherein the method further comprises: providing the generated center channel to the one or more third audio drivers; generating a second side channel comprising a combination of (i) the center channel and (ii) an inverse of the difference between the left channel and the right channel; and providing the generated second side channel to the one or more third audio drivers for playback of the second side channel according to a third radiation pattern that has a maximum along a fourth direction, wherein the first radiation pattern and the third radiation pattern combine to form a second response lobe that has a maximum along a fifth direction between the first and fourth directions.

The method may further comprise changing the fifth direction by amplifying or attenuating the center channel relative to the second side channel, wherein providing the generated center channel to (i) the one or more first audio drivers, (ii) the one or more second audio drivers, and (iii) the one or more third audio drivers comprises providing the amplified or attenuated center channel.

The method may further comprise changing the fifth direction by amplifying or attenuating the second side channel relative to the center channel, wherein providing the generated second side channel to the one or more third audio drivers comprises providing the amplified or attenuated second side channel.

The method may further comprise determining a physical orientation of the playback device at a first point in time; after the first point in time, determining that the physical orientation of the playback device has changed relative to the physical orientation at the first point in time by more than a threshold amount of change; and in response to determining that the physical orientation of the playback device has changed relative to the physical orientation at the first point in time by more than the threshold amount of change, (i) providing the generated first side channel to the one or more third audio drivers and (ii) providing the generated second side channel to the one or more first audio drivers.

The method may further comprise: attenuating a range of audio frequencies of the side channel; and amplifying the range of audio frequencies of the center channel, wherein providing the generated side channel to the one or more first audio drivers comprises providing the attenuated side channel, and wherein providing the generated center channel to (i) the one or more first audio drivers and (ii) the one or more second audio drivers comprises providing the amplified center channel. The range of audio frequencies may be defined at least in part by a cutoff frequency. The method may further comprise receiving a command to increase a volume at which the playback device plays the audio content and increasing the cutoff frequency in response to receiving the command to increase the volume. The method may further comprise receiving a command to decrease a volume at which the playback device plays the audio content and decreasing the cutoff frequency in response to receiving the command to decrease the volume.

The method may further comprise: determining a degree to which the left channel or the right channel exceeds a threshold amplitude within the range of audio frequencies; and based on the determined degree, determining a factor by which to (i) attenuate the range of audio frequencies of the side channel and (ii) amplify the range of audio frequencies of the center channel, wherein attenuating the range of audio frequencies of the side channel comprises attenuating the range of audio frequencies of the side channel by the determined factor, and wherein amplifying the range of audio frequencies of the center channel comprises amplifying the range of audio frequencies of the center channel by the determined factor.

In a second aspect, a method is performed by a playback device comprising one or more first audio drivers, one or more second audio drivers, and one or more third audio drivers. The method includes (a) receiving a center channel of audio content and a side channel of the audio content, (b) providing the center channel of the audio content to (i) the one or more first audio drivers, (ii) the one or more second audio drivers, and (iii) the one or more third audio drivers for playback of the center channel according to a first radiation pattern that has a maximum along a first direction, (c) providing the side channel to the one or more first audio drivers for playback of the side channel according to a second radiation pattern that has a maximum along a second direction. The first radiation pattern and the second radiation pattern combine to form a first response lobe that has a maximum along a third direction between the first and second directions. The functions further include (d) generating an inverted side channel comprising an inverse of the side channel and (e) providing the inverted side channel to the one or more third audio drivers for playback of the inverted side channel according to a third radiation pattern that has a maximum along a fourth direction. The first radiation pattern and the third radiation pattern combine to form a second response lobe that has a maximum along a fifth direction between the first and fourth directions.

In another aspect a non-transitory computer-readable medium stores instructions that, when executed by a playback device, cause the playback device to perform the method of the above-described first and second aspects. The playback device includes one or more first audio drivers and one or more second audio drivers.

In another aspect a playback device is provided. The playback device comprises one or more processors, one or more first audio drivers, one or more second audio drivers, and one or more processors configured to execute the method of the above-described first and second aspects. The playback device may also comprise one or more third audio drivers.

In another aspect, a playback device includes one or more processors, one or more first audio drivers, one or more second audio drivers, and a non-transitory computer-readable medium storing instructions that, when executed by the one or more processors, cause the playback device to perform functions. The functions include (a) receiving a left channel of audio content and a right channel of the audio content, (b) generating a center channel of the audio content comprising a combination of the left and right channels, (c) providing the generated center channel to (i) the one or more first audio drivers and (ii) the one or more second audio drivers for playback of the center channel according to a first radiation pattern that has a maximum along a first direction, (d) generating a side channel comprising a combination of (i) the center channel and (ii) a difference between the left channel and the right channel, and (e) providing the generated side channel to the one or more first audio drivers for playback of the side channel according to a second radiation pattern that has a maximum along a second direction. The first radiation pattern and the second radiation pattern combine to form a first response lobe that has a maximum along a third direction between the first and second directions.

In another aspect, a non-transitory computer-readable medium stores instructions that, when executed by a playback device, cause the playback device to perform functions. The playback device includes one or more first audio drivers and one or more second audio drivers. The functions include (a) receiving a left channel of audio content and a right channel of the audio content, (b) generating a center channel of the audio content comprising a combination of the left and right channels, (c) providing the generated center channel to (i) the one or more first audio drivers and (ii) the one or more second audio drivers for playback of the center channel according to a first radiation pattern that has a maximum along a first direction, (d) generating a side channel comprising a combination of (i) the center channel and (ii) a difference between the left channel and the right channel, and (e) providing the generated side channel to the one or more first audio drivers for playback of the side channel according to a second radiation pattern that has a maximum along a second direction. The first radiation pattern and the second radiation pattern combine to form a first response lobe that has a maximum along a third direction between the first and second directions.

In yet another aspect, a playback device includes one or more processors, one or more first audio drivers, one or more second audio drivers, one or more third audio drivers, and a non-transitory computer-readable medium storing instructions that, when executed by the one or more processors, cause the playback device to perform functions. The functions include (a) receiving a center channel of audio content and a side channel of the audio content, (b) providing the center channel of the audio content to (i) the one or more first audio drivers, (ii) the one or more second audio drivers, and (iii) the one or more third audio drivers for playback of the center channel according to a first radiation pattern that has a maximum along a first direction, (c) providing the side channel to the one or more first audio drivers for playback of the side channel according to a second radiation pattern that has a maximum along a second direction. The first radiation pattern and the second radiation pattern combine to form a first response lobe that has a maximum along a third direction between the first and second directions. The functions further include (d) generating an inverted side channel comprising an inverse of the side channel and (e) providing the inverted side channel to the one or more third audio drivers for playback of the inverted side channel according to a third radiation pattern that has a maximum along a fourth direction. The first radiation pattern and the third radiation pattern combine to form a second response lobe that has a maximum along a fifth direction between the first and fourth directions.

In yet another aspect, a non-transitory computer-readable medium stores instructions that, when executed by a playback device, cause the playback device to perform functions. The playback device includes one or more first audio drivers, one or more second audio drivers, and one or more third audio drivers. The functions include (a) receiving a center channel of audio content and a side channel of the audio content, (b) providing the center channel of the audio content to (i) the one or more first audio drivers, (ii) the one or more second audio drivers, and (iii) the one or more third audio drivers for playback of the center channel according to a first radiation pattern that has a maximum along a first direction, (c) providing the side channel to the one or more first audio drivers for playback of the side channel according to a second radiation pattern that has a maximum along a second direction. The first radiation pattern and the second radiation pattern combine to form a first response lobe that has a maximum along a third direction between the first and second directions. The functions further include (d) generating an inverted side channel comprising an inverse of the side channel and (e) providing the inverted side channel to the one or more third audio drivers for playback of the inverted side channel according to a third radiation pattern that has a maximum along a fourth direction. The first radiation pattern and the third radiation pattern combine to form a second response lobe that has a maximum along a fifth direction between the first and fourth directions.

It will be understood by one of ordinary skill in the art that this disclosure includes numerous other embodiments. While some examples described herein may refer to functions performed by given actors such as "users" and/or other entities, it should be understood that this is for purposes of explanation only. The claims should not be interpreted to require action by any such example actor unless explicitly required by the language of the claims themselves.

<FIG> shows an example configuration of a media playback system <NUM> in which one or more embodiments disclosed herein may be practiced or implemented. The media playback system <NUM> as shown is associated with an example home environment having several rooms and spaces, such as for example, a master bedroom, an office, a dining room, and a living room. As shown in the example of <FIG>, the media playback system <NUM> includes playback devices <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>, control devices <NUM> and <NUM>, and a wired or wireless network router <NUM>.

<FIG> shows a functional block diagram of an example playback device <NUM> that may be configured to be one or more of the playback devices <NUM>-<NUM> of the media playback system <NUM> of <FIG>. The playback device <NUM> may include a processor <NUM>, software components <NUM>, memory <NUM>, audio processing components <NUM>, audio amplifier(s) <NUM>, speaker(s) <NUM>, and a network interface <NUM> including wireless interface(s) <NUM> and wired interface(s) <NUM>. In one case, the playback device <NUM> might not include the speaker(s) <NUM>, but rather a speaker interface for connecting the playback device <NUM> to external speakers. In another case, the playback device <NUM> may include neither the speaker(s) <NUM> nor the audio amplifier(s) <NUM>, but rather an audio interface for connecting the playback device <NUM> to an external audio amplifier or audio-visual receiver.

In one example, the processor <NUM> may be a clock-driven computing component configured to process input data according to instructions stored in the memory <NUM>. The memory <NUM> may be a tangible computer-readable medium configured to store instructions executable by the processor <NUM>. For instance, the memory <NUM> may be data storage that can be loaded with one or more of the software components <NUM> executable by the processor <NUM> to achieve certain functions. In one example, the functions may involve the playback device <NUM> retrieving audio data from an audio source or another playback device. In another example, the functions may involve the playback device <NUM> sending audio data to another device or playback device on a network. In yet another example, the functions may involve pairing of the playback device <NUM> with one or more playback devices to create a multi-channel audio environment.

Certain functions may involve the playback device <NUM> synchronizing playback of audio content with one or more other playback devices. During synchronous playback, a listener will preferably not be able to perceive time-delay differences between playback of the audio content by the playback device <NUM> and the one or more other playback devices. <CIT> entitled, "System and method for synchronizing operations among a plurality of independently clocked digital data processing devices," provides in more detail some examples for audio playback synchronization among playback devices.

The memory <NUM> may further be configured to store data associated with the playback device <NUM>, such as one or more zones and/or zone groups the playback device <NUM> is a part of, audio sources accessible by the playback device <NUM>, or a playback queue that the playback device <NUM> (or some other playback device) may be associated with. The data may be stored as one or more state variables that are periodically updated and used to describe the state of the playback device <NUM>. The memory <NUM> may also include the data associated with the state of the other devices of the media system, and shared from time to time among the devices so that one or more of the devices have the most recent data associated with the system. Other embodiments are also possible.

The audio processing components <NUM> may include one or more digital-to-analog converters (DAC), an audio preprocessing component, an audio enhancement component or a digital signal processor (DSP), and so on. In one embodiment, one or more of the audio processing components <NUM> may be a subcomponent of the processor <NUM>. In one example, audio content may be processed and/or intentionally altered by the audio processing components <NUM> to produce audio signals. The produced audio signals may then be provided to the audio amplifier(s) <NUM> for amplification and playback through speaker(s) <NUM>. Particularly, the audio amplifier(s) <NUM> may include devices configured to amplify audio signals to a level for driving one or more of the speakers <NUM>. The speaker(s) <NUM> may include an individual transducer (e.g. , a "driver") or a complete speaker system involving an enclosure with one or more drivers. A particular driver of the speaker(s) <NUM> may include, for example, a subwoofer (e.g. , for low frequencies), a mid-range driver (e.g. , for middle frequencies), and/or a tweeter (e.g. , for high frequencies). In some cases, each transducer in the one or more speakers <NUM> may be driven by an individual corresponding audio amplifier of the audio amplifier(s) <NUM>. In addition to producing analog signals for playback by the playback device <NUM>, the audio processing components <NUM> may be configured to process audio content to be sent to one or more other playback devices for playback.

Audio content to be processed and/or played back by the playback device <NUM> may be received from an external source, such as via an audio line-in input connection (e.g. , an auto-detecting <NUM> audio line-in connection) or the network interface <NUM>.

The microphone(s) <NUM> may include an audio sensor configured to convert detected sounds into electrical signals. The electrical signal may be processed by the audio processing components <NUM> and/or the processor <NUM>. The microphone(s) <NUM> may be positioned in one or more orientations at one or more locations on the playback device <NUM>. The microphone(s) <NUM> may be configured to detect sound within one or more frequency ranges. In one case, one or more of the microphone(s) <NUM> may be configured to detect sound within a frequency range of audio that the playback device <NUM> is capable or rendering. In another case, one or more of the microphone(s) <NUM> may be configured to detect sound within a frequency range audible to humans.

The network interface <NUM> may be configured to facilitate a data flow between the playback device <NUM> and one or more other devices on a data network. As such, the playback device <NUM> may be configured to receive audio content over the data network from one or more other playback devices in communication with the playback device <NUM>, network devices within a local area network, or audio content sources over a wide area network such as the Internet. In one example, the audio content and other signals transmitted and received by the playback device <NUM> may be transmitted in the form of digital packet data containing an Internet Protocol (IP)-based source address and IP-based destination addresses. In such a case, the network interface <NUM> may be configured to parse the digital packet data such that the data destined for the playback device <NUM> is properly received and processed by the playback device <NUM>.

As shown, the network interface <NUM> may include wireless interface(s) <NUM> and wired interface(s) <NUM>. The wireless interface(s) <NUM> may provide network interface functions for the playback device <NUM> to wirelessly communicate with other devices (e.g. , other playback device(s), speaker(s), receiver(s), network device(s), control device(s) within a data network the playback device <NUM> is associated with) in accordance with a communication protocol (e.g. , any wireless standard including IEEE <NUM>. 11a, <NUM>. 11b, <NUM>. <NUM>, <NUM>. 11η, <NUM>. 11ac, <NUM>, <NUM> mobile communication standard, and so on). The wired interface(s) <NUM> may provide network interface functions for the playback device <NUM> to communicate over a wired connection with other devices in accordance with a communication protocol (e.g. , IEEE <NUM>). While the network interface <NUM> shown in <FIG> includes both wireless interface(s) <NUM> and wired interface(s) <NUM>, the network interface <NUM> may in some embodiments include only wireless interface(s) or only wired interface(s).

In one example, the playback device <NUM> and one other playback device may be paired to play two separate audio components of audio content. For instance, playback device <NUM> may be configured to play a left channel audio component, while the other playback device may be configured to play a right channel audio component, thereby producing or enhancing a stereo effect of the audio content. The paired playback devices (also referred to as "bonded playback devices") may further play audio content in synchrony with other playback devices.

In another example, the playback device <NUM> may be sonically consolidated with one or more other playback devices to form a single, consolidated playback device. A consolidated playback device may be configured to process and reproduce sound differently than an unconsolidated playback device or playback devices that are paired, because a consolidated playback device may have additional speaker drivers through which audio content may be rendered. For instance, if the playback device <NUM> is a playback device designed to render low frequency range audio content (i.e. a subwoofer), the playback device <NUM> may be consolidated with a playback device designed to render full frequency range audio content. In such a case, the full frequency range playback device, when consolidated with the low frequency playback device <NUM>, may be configured to render only the mid and high frequency components of audio content, while the low frequency range playback device <NUM> renders the low frequency component of the audio content. The consolidated playback device may further be paired with a single playback device or yet another consolidated playback device.

By way of illustration, SONOS, Inc. presently offers (or has offered) for sale certain playback devices including a "PLAY:<NUM>," "PLAY:<NUM>," "PLAY:<NUM>," "PLAYBAR," "CONNECT:AMP," "CONNECT," and "SUB. " Any other past, present, and/or future playback devices may additionally or alternatively be used to implement the playback devices of example embodiments disclosed herein. Additionally, it is understood that a playback device is not limited to the example illustrated in <FIG> or to the SONOS product offerings. For example, a playback device may include a wired or wireless headphone. In another example, a playback device may include or interact with a docking station for personal mobile media playback devices. In yet another example, a playback device may be integral to another device or component such as a television, a lighting fixture, or some other device for indoor or outdoor use.

Referring back to the media playback system <NUM> of <FIG>, the environment may have one or more playback zones, each with one or more playback devices. The media playback system <NUM> may be established with one or more playback zones, after which one or more zones may be added, or removed to arrive at the example configuration shown in <FIG>. Each zone may be given a name according to a different room or space such as an office, bathroom, master bedroom, bedroom, kitchen, dining room, living room, and/or balcony. In one case, a single playback zone may include multiple rooms or spaces. In another case, a single room or space may include multiple playback zones.

As shown in <FIG>, the balcony, dining room, kitchen, bathroom, office, and bedroom zones each have one playback device, while the living room and master bedroom zones each have multiple playback devices. In the living room zone, playback devices <NUM>, <NUM>, <NUM>, and <NUM> may be configured to play audio content in synchrony as individual playback devices, as one or more bonded playback devices, as one or more consolidated playback devices, or any combination thereof. Similarly, in the case of the master bedroom, playback devices <NUM> and <NUM> may be configured to play audio content in synchrony as individual playback devices, as a bonded playback device, or as a consolidated playback device.

In one example, one or more playback zones in the environment of <FIG> may each be playing different audio content. For instance, the user may be grilling in the balcony zone and listening to hip hop music being played by the playback device <NUM> while another user may be preparing food in the kitchen zone and listening to classical music being played by the playback device <NUM>. In another example, a playback zone may play the same audio content in synchrony with another playback zone. For instance, the user may be in the office zone where the playback device <NUM> is playing the same rock music that is being played by playback device <NUM> in the balcony zone. In such a case, playback devices <NUM> and <NUM> may be playing the rock music in synchrony such that the user may seamlessly (or at least substantially seamlessly) enjoy the audio content that is being played out-loud while moving between different playback zones. Synchronization among playback zones may be achieved in a manner similar to that of synchronization among playback devices, as described in previously referenced <CIT>.

Further, different playback zones of the media playback system <NUM> may be dynamically combined into zone groups or split up into individual playback zones. For instance, the dining room zone and the kitchen zone <NUM> may be combined into a zone group for a dinner party such that playback devices <NUM> and <NUM> may render audio content in synchrony. On the other hand, the living room zone may be split into a television zone including playback device <NUM>, and a listening zone including playback devices <NUM>, <NUM>, and <NUM>, if the user wishes to listen to music in the living room space while another user wishes to watch television.

<FIG> shows a functional block diagram of an example control device <NUM> that may be configured to be one or both of the control devices <NUM> and <NUM> of the media playback system <NUM>. As shown, the control device <NUM> may include a processor <NUM>, memory <NUM>, a network interface <NUM>, and a user interface <NUM>. In one example, the control device <NUM> may be a dedicated controller for the media playback system <NUM>. In another example, the control device <NUM> may be a network device on which media playback system controller application software may be installed, such as for example, an iPhone™, iPad™ or any other smart phone, tablet or network device (e.g. , a networked computer such as a PC or Mac™).

The processor <NUM> may be configured to perform functions relevant to facilitating user access, control, and configuration of the media playback system <NUM>. The memory <NUM> may be configured to store instructions executable by the processor <NUM> to perform those functions. The memory <NUM> may also be configured to store the media playback system controller application software and other data associated with the media playback system <NUM> and the user.

The microphone(s) <NUM> may include an audio sensor configured to convert detected sounds into electrical signals. The electrical signal may be processed by the processor <NUM>. In one case, if the control device <NUM> is a device that may also be used as a means for voice communication or voice recording, one or more of the microphone(s) <NUM> may be a microphone for facilitating those functions. For instance, the one or more of the microphone(s) <NUM> may be configured to detect sound within a frequency range that a human is capable of producing and/or a frequency range audible to humans.

In one example, the network interface <NUM> may be based on an industry standard (e.g. , infrared, radio, wired standards including IEEE <NUM>, wireless standards including IEEE <NUM>. 11a, <NUM>. 11b, <NUM>. <NUM>, <NUM>. 11η, <NUM>. 11ac, <NUM>, <NUM> mobile communication standard, and so on). The network interface <NUM> may provide a means for the control device <NUM> to communicate with other devices in the media playback system <NUM>. In one example, data and information (e.g. , such as a state variable) may be communicated between control device <NUM> and other devices via the network interface <NUM>. For instance, playback zone and zone group configurations in the media playback system <NUM> may be received by the control device <NUM> from a playback device or another network device, or transmitted by the control device <NUM> to another playback device or network device via the network interface <NUM>. In some cases, the other network device may be another control device.

Playback device control commands such as volume control and audio playback control may also be communicated from the control device <NUM> to a playback device via the network interface <NUM>. As suggested above, changes to configurations of the media playback system <NUM> may also be performed by a user using the control device <NUM>. The configuration changes may include adding/removing one or more playback devices to/from a zone, adding/removing one or more zones to/from a zone group, forming a bonded or consolidated player, separating one or more playback devices from a bonded or consolidated player, among others. Accordingly, the control device <NUM> may sometimes be referred to as a controller, whether the control device <NUM> is a dedicated controller or a network device on which media playback system controller application software is installed.

The user interface <NUM> of the control device <NUM> may be configured to facilitate user access and control of the media playback system <NUM>, by providing a controller interface such as the controller interface <NUM> shown in <FIG>. The controller interface <NUM> includes a playback control region <NUM>, a playback zone region <NUM>, a playback status region <NUM>, a playback queue region <NUM>, and an audio content sources region <NUM>. The user interface <NUM> as shown is just one example of a user interface that may be provided on a network device such as the control device <NUM> of <FIG> (and/or the control devices <NUM> and <NUM> of <FIG>) and accessed by users to control a media playback system such as the media playback system <NUM>. Other user interfaces of varying formats, styles, and interactive sequences may alternatively be implemented on one or more network devices to provide comparable control access to a media playback system.

For example, as shown, a "group" icon may be provided within each of the graphical representations of playback zones. The "group" icon provided within a graphical representation of a particular zone may be selectable to bring up options to select one or more other zones in the media playback system to be grouped with the particular zone. Once grouped, playback devices in the zones that have been grouped with the particular zone will be configured to play audio content in synchrony with the playback device(s) in the particular zone. Analogously, a "group" icon may be provided within a graphical representation of a zone group. In this case, the "group" icon may be selectable to bring up options to deselect one or more zones in the zone group to be removed from the zone group. Other interactions and implementations for grouping and ungrouping zones via a user interface such as the user interface <NUM> are also possible. The representations of playback zones in the playback zone region <NUM> may be dynamically updated as playback zone or zone group configurations are modified.

The playback status region <NUM> may include graphical representations of audio content that is presently being played, previously played, or scheduled to play next in the selected playback zone or zone group. The selected playback zone or zone group may be visually distinguished on the user interface, such as within the playback zone region <NUM> and/or the playback status region <NUM>. The graphical representations may include track title, artist name, album name, album year, track length, and other relevant information that may be useful for the user to know when controlling the media playback system via the user interface <NUM>.

Referring back to the user interface <NUM> of <FIG>, the graphical representations of audio content in the playback queue region <NUM> may include track titles, artist names, track lengths, and other relevant information associated with the audio content in the playback queue. In one example, graphical representations of audio content may be selectable to bring up additional selectable icons to manage and/or manipulate the playback queue and/or audio content represented in the playback queue. For instance, a represented audio content may be removed from the playback queue, moved to a different position within the playback queue, or selected to be played immediately, or after any currently playing audio content, among other possibilities. A playback queue associated with a playback zone or zone group may be stored in a memory on one or more playback devices in the playback zone or zone group, on a playback device that is not in the playback zone or zone group, and/or some other designated device.

As indicated previously, one or more playback devices in a zone or zone group may be configured to retrieve for playback audio content (e.g. according to a corresponding URI or URL for the audio content) from a variety of available audio content sources. In one example, audio content may be retrieved by a playback device directly from a corresponding audio content source (e.g., a line-in connection). In another example, audio content may be provided to a playback device over a network via one or more other playback devices or network devices.

Example audio content sources may include a memory of one or more playback devices in a media playback system such as the media playback system <NUM> of <FIG>, local music libraries on one or more network devices (such as a control device, a network-enabled personal computer, or a networked-attached storage (NAS), for example), streaming audio services providing audio content via the Internet (e.g. , the cloud), or audio sources connected to the media playback system via a line-in input connection on a playback device or network devise, among other possibilities.

Indexing of audio items may involve scanning for identifiable audio items in all folders/directory shared over a network accessible by playback devices in the media playback system, and generating or updating an audio content database containing metadata (e.g. , title, artist, album, track length, among others) and other associated information, such as a URI or URL for each identifiable audio item found.

As discussed above, some examples described herein include, among other things, a playback device (i) providing a center channel of audio content to one or more first audio drivers and one or more second audio drivers so that the center channel is reproduced according to a first radiation pattern and (ii) providing a side channel of audio content to the one or more first audio drivers so that the side channel is reproduced according to a second radiation pattern. The first and second radiation patterns may combine to form a response lobe that has a maximum between the respective maxima of the first and second radiation patterns. Other aspects of the examples will be made apparent in the remainder of the description herein.

<FIG> shows an example playback device <NUM>. The playback device <NUM> includes audio drivers 511A, 511B, 511C, 513A, 513B, and 513C. The audio drivers 511A-C may comprise woofers configured to reproduce low-range and/or mid-range audio frequencies whereas the audio drivers 513A-C may comprise tweeters configured to reproduce high-range frequencies. Other audio driver configurations are possible.

The playback device <NUM> may also include an acoustic filter <NUM> placed in front of the audio driver 513B that is configured to attenuate sound waves generated by the audio driver 513B. In other examples, the acoustic filter <NUM> may be placed in front of another audio driver of the playback device <NUM> for attenuation of sound waves generated by the other audio driver. More detailed examples of the acoustic filter <NUM> are included in <CIT>.

<FIG> shows a simplified block diagram of playback devices <NUM> and <NUM>. The playback device <NUM> includes audio drivers 561A, 561B, 563A, and 563B. The playback device <NUM> includes audio drivers 581A, 581B, 583A, and 583B. In some examples, the audio drivers 561A, 561B, 581A, and 581B may comprise woofers configured to reproduce low-range and/or mid-range audio frequencies whereas the audio drivers 563A, 563B, 583A, and 583B may comprise tweeters configured to reproduce high-range frequencies, but other audio driver configurations are possible.

Methods <NUM> and <NUM> respectively shown in <FIG> and <FIG> present example methods that can be implemented within an operating environment including, for example, one or more of the media playback system <NUM> of <FIG>, one or more of the playback device <NUM> of <FIG>, one or more of the control device <NUM> of <FIG>, one or more of the playback device <NUM> of <FIG>, and one or more of the playback devices <NUM> and/or <NUM> of <FIG>. Methods <NUM> and <NUM> may include one or more operations, functions, or actions as illustrated by one or more of blocks <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>. Although the blocks are illustrated in sequential order, these blocks may also be performed in parallel, and/or in a different order than those described herein. Also, the various blocks may be combined into fewer blocks, divided into additional blocks, and/or removed based upon the desired implementation.

In addition, for the methods <NUM> and <NUM> and other processes and methods disclosed herein, the flowcharts show functionality and operation of one possible implementation of present embodiments. In this regard, each block may represent a module, a segment, or a portion of program code, which includes one or more instructions executable by a processor for implementing specific logical functions or steps in the process. The program code may be stored on any type of computer-readable medium, for example, such as a storage device including a disk(s) or hard drive(s). In some embodiments, the program code may be stored in memory (e.g. , disks or disk arrays) associated with and/or connected to a server system that makes the program code available for download (e.g. , an application store or other type of server system) to desktop/laptop computers, smart phones, tablet computers, or other types of computing devices. The computer-readable medium may include non-transitory computer-readable media, for example, such as computer-readable media that stores data for short periods of time like register memory, processor cache, and Random Access Memory (RAM). The computer-readable medium may also include non-transitory media, such as secondary or persistent long-term storage, like read-only memory (ROM), optical or magnetic disks, compact-disc read-only memory (CD-ROM), for example. The computer-readable media may also be any other volatile or non-volatile storage systems. The computer-readable medium may be considered a computer-readable storage medium, for example, or a tangible storage device. In addition, for the methods <NUM> and <NUM> and other processes and methods disclosed herein, each block in <FIG> and <FIG> may represent circuitry that is wired to perform the specific logical functions in the process.

In some examples, the method <NUM> is performed by a playback device comprising one or more first audio drivers and one or more second audio drivers (e.g. , playback devices <NUM>, <NUM>, or <NUM>). At block <NUM>, the method <NUM> includes receiving a left channel of audio content and a right channel of the audio content. For example, any of the playback devices <NUM>, <NUM>, or <NUM> may receive the left channel and/or the right channel from one or more other playback devices, from one or more network locations, or from any audio content source described in section Il. The playback device may receive the left and right channels from other sources as well. The left and right channels may be received as an analog signal or a digital data stream, for example.

At block <NUM>, the method <NUM> includes generating a center channel of the audio content comprising a combination of the left and right channels. For instance, any of the playback devices <NUM>, <NUM>, or <NUM> may add amplitudes corresponding to various times (e.g. , track time) and audio frequencies of the left channel with respective amplitudes corresponding to various times and audio frequencies of the right channel. In a specific example, the playback device may add a first amplitude "x" corresponding to t=<NUM> second (s) and f=<NUM> of the left channel with a second amplitude "y" corresponding to t=l s and f=<NUM> of the right channel, resulting in an amplitude of (x+y) corresponding to t=l s and f=<NUM> of the center channel. In some examples, the amplitude of the center channel may be adjusted (e.g. , averaged) to avoid volume distortion. Accordingly, the amplitude of the center channel corresponding to t=l s and f=<NUM> may be (x+y)/<NUM>. Other example combinations of the left and right channels are also possible. Block <NUM> may be repeated for any or all of the times and frequencies represented by the left and right channels to generate the center channel.

At block <NUM>, the method <NUM> includes providing the generated center channel to (i) the one or more first audio drivers and (ii) the one or more second audio drivers for playback of the center channel according to a first radiation pattern that has a maximum along a first direction. (In various examples described below, the generated center channel is also provided to one or more third audio drivers of the playback device. ) For example, any of the playback devices <NUM>, <NUM>, or <NUM> may provide a digital data stream representing the center channel to a digital-to-analog converter (DAC) of the corresponding playback device so that the DAC may provide an analog signal representing the center channel to (i) the one or more first audio drivers of the corresponding playback device and (ii) the one or more second audio drivers of the corresponding playback device.

In some examples, the playback device <NUM> may provide multi-channel playback of the audio content independently (e.g. , without coordination with other playback devices). In such an instance, the playback device <NUM> may provide the generated center channel to first audio drivers 511A and 513A, second audio drivers 511B and 513B, and third audio drivers 511C and 513C. The audio drivers 511A-C and 513A-C may play the center channel according to a first radiation pattern <NUM> depicted in <FIG>. The first radiation pattern <NUM> may have a maximum aligned with axis <NUM>. In such an example, the playback device <NUM> may be located at the intersection of axes <NUM> and <NUM>. The intersection of axes <NUM> and <NUM> may also be referred to as an acoustic center of the playback device <NUM>.

In other examples, the playback device <NUM> may provide multi-channel playback of the audio content in coordination with the playback device <NUM>. In such an instance, the playback device <NUM> may provide the center channel to first audio drivers 561A and 563A and second audio drivers 561B and 563B, and the playback device <NUM> may provide the center channel to the audio drivers 581A, 58IB, 583A, and 583B. The audio drivers 561A, 561B, 563A, 563B, 581A, 581B, 583A, and 583B may play the center channel in coordination according to the first radiation pattern <NUM>. In such an example, the playback devices <NUM> and <NUM> may both be on the axis <NUM> and be spaced symmetrically with respect to axis <NUM>. The intersection of axes <NUM> and <NUM> may be referred to as an acoustic center of a playback system that includes playback devices <NUM> and <NUM>.

In some examples, providing the generated center channel to (i) the one or more first audio drivers, (ii) the one or more second audio drivers, and/or (iii) the one or more third audio drivers may include providing an amplified or attenuated center channel to (i) the one or more first audio drivers, (ii) the one or more second audio drivers, and/or (iii) the one or more third audio drivers.

For example, the playback device <NUM> may amplify or attenuate the center channel by a scaling factor of 'C before the playback device <NUM> provides the amplified or attenuated center channel to the first audio drivers 511A and 513A, the second audio drivers 511B and 513B, and/or the third audio drivers 511C and 513C. With reference to an example described above in which the amplitude of the generated center channel is (x+y)/<NUM> at t=l s and f=<NUM>, the amplified or attenuated center channel provided to the to the first audio drivers 511A and 513A, the second audio drivers <NUM>1IB and 513B, and the third audio drivers 511C and 513C may be represented as C(x+y)/<NUM> at t=l s and f=<NUM>. A scaling factor of 'C that is greater than <NUM> may correspond to an amplified center channel whereas a scaling factor of 'C that is less than <NUM> may correspond to an attenuated center channel.

In another example, the playback device <NUM> may amplify or attenuate the center channel by a scaling factor of 'C before the playback device <NUM> provides the amplified or attenuated center channel to the first audio drivers 561A and 563A and the second audio drivers 561B and 563B. The playback device <NUM> may also amplify or attenuate the center channel by a scaling factor of 'C before the playback device <NUM> provides the amplified or attenuated center channel to the audio drivers 581A, 583A, 581B, and 583B. With reference to an example described above in which the amplitude of the generated center channel is (x+y)/<NUM> at t=l s and f=<NUM>, the amplified or attenuated center channel provided to the to the first audio drivers 561A and 563A and the second audio drivers 561B and 563B may be represented as C(x+y)/<NUM>. The amplified or attenuated center channel provided to the audio drivers 581A, 583A, 581B, and 583B may also be represented as C(x+y)/<NUM> at t=l s and f=<NUM>.

Amplifying or attenuating the center channel may affect the perceived wideness of audio playback by the corresponding playback device, as described below. In some cases, the same scaling factor 'C may be used to amplify or attenuate all portions of the center channel, but in other cases different scaling factors may be used for various frequencies and/or times of the center channel.

At block <NUM>, the method <NUM> includes generating a first side channel comprising a combination of (i) the center channel and (ii) a difference between the left channel and the right channel. (In some examples described below, the method <NUM> may also involve generating a second side channel.

For instance, any of the playback devices <NUM>, <NUM>, or <NUM> may subtract amplitudes corresponding to various times and frequencies of the right channel from respective amplitudes corresponding to various times and frequencies of the left channel (or vice versa). In a specific example, the playback device may subtract a second amplitude "y" corresponding to t=l s and f=<NUM> of the right channel from a first amplitude "x" corresponding to t=l s and f=<NUM> of the left channel, resulting in an amplitude of (x-y) corresponding to t=l s and f=<NUM> of the difference between the left channel and the right channel. In some examples, amplitudes may be adjusted (e.g. , averaged) to avoid volume distortion. Accordingly, the amplitude of the difference between the left channel and the right channel corresponding to t=l s and f=<NUM> may be (x-y)/<NUM>.

In addition, any of the playback devices <NUM>, <NUM>, or <NUM> may add amplitudes corresponding to various times and audio frequencies of center channel with respective amplitudes corresponding to various times and audio frequencies of the difference between the left channel and the right channel. For example, an amplitude (x-y)/<NUM> of the difference between the left channel and the right channel corresponding to t=l s and f=<NUM> may be added to an amplitude (x+y)/<NUM> of the center channel corresponding to t=l s and f=<NUM>, resulting in an amplitude of the first side channel of (x+y)/<NUM>+(x-y)/<NUM>. In some cases, actual numeric summation of the amplitudes of the center channel and the amplitudes of the difference between the left and right channels may be deferred until the center channel and the difference between the left and right channels have been amplified or attenuated, as described below.

Block <NUM> may be repeated for any or all of the times and frequencies represented by the center channel and the difference between the left channel and the right channel to generate the first side channel.

At block <NUM>, the method <NUM> includes providing the generated first side channel to the one or more first audio drivers for playback of the first side channel according to a second radiation pattern that has a maximum along a second direction. (In various examples described below, a generated second side channel is also provided to one or more third audio drivers of the playback device. ) For example, any of the playback devices <NUM>, <NUM>, or <NUM> may provide a digital data stream representing the first side channel to a digital-to-analog converter (DAC) of the corresponding playback device so that the DAC may provide an analog signal representing the first side channel to the one or more first audio drivers of the corresponding playback device.

The first radiation pattern corresponding to the center channel and the second radiation pattern corresponding to the first side channel may combine to form a first response lobe that has a maximum along a third direction between the first and second directions. The first response lobe may represent audio information from both the center channel and the first side channel. A listener may perceive audio corresponding to the first response lobe as having a wideness that is dependent on the relative amplitudes of (i) the center channel provided to the one or more first audio drivers, the one or more second audio drivers, and/or the one or more third audio drivers, and (ii) the first side channel provided to the one or more first audio drivers.

Accordingly, in some examples providing the generated first side channel to the one or more first audio drivers may include providing an amplified or attenuated first side channel to the one or more first audio drivers.

In an example where the playback device <NUM> provides multi-channel playback of the audio content independently (e.g. , without coordination with other playback devices), the playback device <NUM> may amplify or attenuate the first side channel by scaling factors of 'C and/or 'S' before the amplified or attenuated first side channel is provided to the first audio drivers 511A and 513A. With reference to examples described above, the amplified or attenuated first side channel (e.g. , at t=l s and f=<NUM>) provided to the first audio drivers 511A and 513A may be represented as C(x+y)/<NUM>+S(x-y)/<NUM>.

The audio drivers 511A and 513A may play the first side channel according to a second radiation pattern <NUM> depicted in <FIG>. The second radiation pattern <NUM> may have a maximum along the axis <NUM>. The first radiation pattern <NUM> and the second radiation pattern <NUM> may combine to form a first response lobe 805A having a maximum along a third direction between the respective maxima of the first radiation pattern <NUM> and the second radiation pattern <NUM>. The first response lobe 805A may represent audio information from both the center channel and the first side channel. A listener may hear audio corresponding to the first response lobe 805A as having a wideness that is dependent on the relative amplitudes of (i) the center channel provided to the audio drivers 511A, 513A, 511B, 513B, 511C, and 513C and (ii) the first side channel provided to the audio drivers 511A and 513A. As discussed below, the perceived wideness may be proportional to S/C as determined by the selected values of 'S' and 'C.

In an example where the playback device <NUM> provides multi-channel playback of the audio content in coordination with the playback device <NUM>, the playback device <NUM> may amplify or attenuate the first side channel by scaling factors of 'C and 'S' before the amplified or attenuated first side channel is provided to the first audio drivers 561A and 563A. With reference to examples described above, the amplified or attenuated first side channel (e.g. , at t=l s and f=<NUM>) provided to the audio drivers 561A and 563A may be represented as C(x+y)/<NUM>+S(x-y)/<NUM>.

In some cases, the same scaling factor 'C and/or 'S' may be used to amplify or attenuate all portions of the first side channel, but in other cases different scaling factors may be used for various frequencies and/or times of the center channel.

The audio drivers 561A and 563A may play the first side channel according to the second radiation pattern <NUM>. The first radiation pattern <NUM> and the second radiation pattern <NUM> may combine to form a first response lobe 805A having a maximum along a third direction between the respective maxima of the first radiation pattern <NUM> and the second radiation pattern <NUM>. The first response lobe 805A may represent audio information from both the center channel and the first side channel. A listener may hear audio corresponding to the first response lobe 805A as having a wideness that is dependent on the relative amplitudes of (i) the center channel provided to the audio drivers <NUM> A, 563A, 561B, 563B, 581A, 583A, 58IB, and 583B and (ii) the first side channel provided to the audio drivers 561A and 563A. That is, the perceived wideness may be proportional to S/C as determined by the selected values of 'S' and 'C.

For purposes of illustration, assume that the first response lobe 805A represents playback of the center channel with a scaling factor C=<NUM> and playback of the first side channel with a scaling factor of S=l. Changing C=<NUM> to C=<NUM> may cause first response lobe 805A to realign so that the maximum of the first response lobe is more closely aligned with the axis <NUM> (e.g. , the maximum of the second radiation pattern <NUM>) as shown at first response lobe 805B of <FIG>. The alignment of the first response lobe 805B may be more suited for a large room listening environment when compared to the alignment of the first response lobe 805A. Similarly, changing to C=<NUM> to C=<NUM> may cause the first response lobe 805A to realign so that the maximum of the first response lobe is more closely aligned with the axis <NUM> (e.g. , the maximum of the first radiation pattern <NUM>) as shown at first response lobe 805C of <FIG>. The alignment of the first response lobe 805C may be more suited for a small room listening environment when compared to the alignment of the first response lobe 805A.

In another example, assume that the first response lobe 805A represents playback of the center channel with a scaling factor C=<NUM> and playback of the first side channel with a scaling factor of S=l. Changing S=l to S=<NUM> may cause first response lobe 805A to realign so that the maximum of the first response lobe is more closely aligned with the axis <NUM> (e.g. , the maximum of the second radiation pattern <NUM>) as shown at 805B of <FIG>. Similarly, changing S=l to S=<NUM> may cause the first response lobe 805A to realign so that the maximum of the first response lobe is more closely aligned with the axis <NUM> (e.g. , the maximum of the first radiation pattern <NUM>) as shown at first response lobe 805C of <FIG>.

The method <NUM> may further involve generating a second side channel comprising a combination of (i) the center channel and (ii) an inverse of the difference between the left channel and the right channel. For instance any of the playback devices <NUM>, <NUM>, or <NUM> may subtract amplitudes corresponding to various times and frequencies of the left channel from respective amplitudes corresponding to various times and frequencies of the right channel (or vice versa). In a specific example, the playback device may subtract a first amplitude "x" corresponding to t=l s and f=<NUM> of the left channel from a second amplitude "y" corresponding to t=l s and f=<NUM> of the right channel, resulting in an amplitude of (y-x) corresponding to t=l s and f=<NUM> of the inverse of the difference between the left channel and the right channel. In some cases, instead of performing a subtraction operation, the playback device may calculate an additive inverse of the difference between the left channel and the right channel. Amplitudes may be adjusted (e.g. , averaged) to avoid volume distortion. Accordingly, the amplitude of the inverse of the difference between the left channel and the right channel corresponding to t=l s and f=<NUM> may be (y-x)/<NUM>.

In addition, any of the playback devices <NUM>, <NUM>, or <NUM> may add amplitudes corresponding to various times and audio frequencies of the center channel with respective amplitudes corresponding to various times and audio frequencies of the inverse of the difference between the left channel and the right channel. For example, an amplitude (y-x)/<NUM> of the inverse of the difference between the left channel and the right channel corresponding to t=l s and f=<NUM> may be added to an amplitude (x+y)/<NUM> of the center channel corresponding to t=l s and f=<NUM>, resulting in an amplitude of the second side channel of (x+y)/<NUM>+(y-x)/<NUM>. In some cases, actual numeric summation of the amplitudes of the center channel and the amplitudes of the inverse of the difference between the left and right channels may be deferred until the center channel and the inverse of the difference between the left and right channels have been amplified or attenuated, as described below. This may be repeated for any or all of the times and frequencies represented by the center channel and the inverse of the difference between the left channel and the right channel to generate the second side channel.

The method <NUM> may further involve providing the generated second side channel to the one or more third audio drivers for playback of the second side channel according to a third radiation pattern that has a maximum along a fourth direction. In this context, the first radiation pattern and the third radiation pattern may combine to form a second response lobe that has a maximum along a fifth direction between the first and fourth directions. The second response lobe may represent audio information from both the center channel and the second side channel. A listener may perceive audio corresponding to the second response lobe as having a wideness that is dependent on the relative amplitudes of (i) the center channel provided to the one or more first audio drivers, the one or more second audio drivers, and/or the one or more third audio drivers, and (ii) the second side channel provided to the one or more third audio drivers.

For example, the playback device <NUM> may provide the center channel to the third audio drivers 511C and 513C, in addition to the first audio drivers 511A and 513A and the second audio drivers 51IB and 513B. The playback device <NUM> may also provide the generated second side channel to the audio drivers 511C and 513C. The audio drivers 5llC and 513C may play the second side channel according to a third radiation pattern <NUM> depicted in <FIG>. The first radiation pattern <NUM> and the third radiation pattern <NUM> may combine to form a second response lobe 806A having a maximum between the respective maxima of the first radiation pattern <NUM> and the third radiation pattern <NUM>. The second response lobe 806A may represent audio information from both the center channel and the second side channel. A listener may hear audio corresponding to the second response lobe 806A as having a wideness that is dependent on the relative amplitudes of (i) the center channel provided to the audio drivers 511A-C and 513A-C and (ii) the second side channel provided to the audio drivers 511C and 513C.

In an example where, the playback device <NUM> provides multi-channel playback of the audio content in coordination with the playback device <NUM>, the playback device <NUM> may provide the generated second side channel to the audio drivers 581B and 583B. The audio drivers 581B and 583B may play the second side channel according to the third radiation pattern <NUM>. The first radiation pattern <NUM> and the third radiation pattern <NUM> may combine to form a second response lobe 806A having a maximum between the respective maxima of the first radiation pattern <NUM> and the third radiation pattern <NUM>. The second response lobe 806A may represent audio information from both the center channel and the second side channel. A listener may hear audio corresponding to the second response lobe 806A as having a wideness that is dependent on the relative amplitudes of (i) the center channel provided to the audio drivers 561A, 561B, 581A, 581B, 563A, 563B, 583A, and 583B and (ii) the second side channel provided to the audio drivers 581B and 583B.

The method <NUM> may further involve changing the fifth direction by amplifying or attenuating the center channel relative to the second side channel. In this context, providing the generated center channel to (i) the one or more first audio drivers, (ii) the one or more second audio drivers, and/or (iii) the one or more third audio drivers may include providing the amplified or attenuated center channel.

For purposes of illustration, assume that the second response lobe 806A represents playback of the center channel with a scaling factor C=<NUM> and playback of the second side channel with a scaling factor of S=<NUM>. Changing C=<NUM> to C=<NUM> may cause second response lobe 806A to realign so that the maximum of the second response lobe is more closely aligned with the axis <NUM> (e.g. , the maximum of the third radiation pattern <NUM>) as shown at second response lobe 806B of <FIG>. The alignment of the second response lobe 806B may be more suited for a large room listening environment when compared to the alignment of the second response lobe 806A. Similarly, changing to C=<NUM> to C=<NUM> may cause the second response lobe 806A to realign so that the maximum of the second response lobe is more closely aligned with the axis <NUM> (e.g. , the maximum of the first radiation pattern <NUM>) as shown at second response lobe 806C of <FIG>. The alignment of the second response lobe 806C may be more suited for a small room listening environment when compared to the alignment of the second response lobe 806A.

The method <NUM> may further involve changing the fifth direction by amplifying or attenuating the second side channel relative to the center channel. In this context, providing the generated second side channel to the one or more third audio drivers may include providing the amplified or attenuated second side channel.

For purposes of illustration, assume that the second response lobe 806A represents playback of the center channel with a scaling factor C=<NUM> and playback of the second side channel with a scaling factor of S=<NUM>. Changing S=l to S=<NUM> may cause second response lobe 806A to realign so that the maximum of the second response lobe is more closely aligned with the axis <NUM> (e.g. , the maximum of the third radiation pattern <NUM>) as shown at second response lobe 806B of <FIG>. The alignment of the second response lobe 806B may be more suited for a large room listening environment when compared to the alignment of the second response lobe 806A. Similarly, changing S=l to S=<NUM> may cause the second response lobe 806A to realign so that the maximum of the second response lobe is more closely aligned with the axis <NUM> (e.g. , the maximum of the first radiation pattern <NUM>) as shown at second response lobe 806C of <FIG>. The alignment of the second response lobe 806C may be more suited for a small room listening environment when compared to the alignment of the second response lobe 806A.

The method <NUM> may further involve (a) determining a physical orientation of the playback device at a first point in time, (b) after the first point in time, determining that the physical orientation of the playback device has changed relative to the physical orientation at the first point in time by more than a threshold amount of change, and (c) in response to determining that the physical orientation of the playback device has changed relative to the physical orientation at the first point in time by more than the threshold amount of change, (i) providing the generated first side channel to the one or more third audio drivers and (ii) providing the generated second side channel to the one or more first audio drivers.

For example, the playback device <NUM> may determine, via an accelerometer or a gyroscope, that at a first point in time the playback device <NUM> is in an "upright" orientation similar to the orientation of playback device <NUM> of <FIG>. In one instance, the upright orientation may be defined as a <NUM>° rotation with respect to a rotational axis of symmetry (not shown) of the audio driver 51IB or the audio driver <NUM>1IB.

As shown in <FIG>, after the first point in time the playback device <NUM> has been moved into an "inverted" orientation, which may be defined as a <NUM>° rotation with respect to the rotational axis of symmetry of the audio driver <NUM>1IB. The playback device <NUM> may determine that the physical orientation of the playback device <NUM> has changed relative to the upright orientation depicted in <FIG> by more than a threshold amount of change. The threshold amount of change may be <NUM>° of rotation about the rotational axis of symmetry, but other examples are possible.

In response to determining that the physical orientation of the playback device <NUM> has changed relative to the upright orientation depicted in <FIG> by more than the threshold amount of change, the playback device <NUM> may operate in an "inverted" mode by providing the first side channel to the audio drivers 911A and 913A, providing the second side channel to the audio drivers 911C and 913C, and/or providing the center channel to the audio drivers 911A-C and 913A-C. In this way, the listener may perceive the same audio "image" regardless of whether the playback device is oriented as depicted in <FIG> or oriented as depicted in <FIG>.

The playback devices <NUM> and/or <NUM> may similarly be configured to detect changes in their respective orientations that exceed a threshold amount of change, and to operate in an "inverted" mode in response. For example, the playback device <NUM> may determine that the playback device <NUM> has undergone a <NUM>° rotation with respect to the orientation of playback device <NUM> depicted in <FIG>, and in response provide the first side channel to audio drivers 561B and 563B and provide the center channel to audio drivers 561A and 563A. Similarly, the the playback device <NUM> may determine that the playback device <NUM> has undergone a <NUM>° rotation with respect to the orientation of playback device <NUM> depicted in <FIG>, and in response provide the second side channel to audio drivers 58IB and 583B and provide the center channel to audio drivers 581A and 583A.

The method <NUM> may further involve attenuating a range of audio frequencies of the first side channel and/or the second side channel and amplifying the range of audio frequencies of the center channel. In this context, providing the generated first side channel to the one or more first audio drivers may include providing the attenuated first side channel. Providing the generated second side channel to the one or more third audio drivers may include providing the attenuated second side channel. Providing the generated center channel to (i) the one or more first audio drivers, (ii) the one or more second audio drivers, and/or (iii) the one or more third audio drivers may include providing the amplified center channel.

For example, the playback device <NUM> may adjust the amplitudes of the first and/or second side channels within a given audio frequency range. Due to potentially different construction and or configuration, the second audio drivers 51IB and 513B may be, as a group, more efficient at generating sound waves within the given audio frequency range than the first audio drivers 511A and 513A and the third audio drivers 511C and 513C. For example, the audio drivers 511B and 513B may be less likely to reproduce distorted output at a given input amplitude corresponding to the given audio frequency range than the audio drivers 511A, 513A, 511C, and 513C.

For instance, the playback device <NUM>, <NUM>, <NUM>, or <NUM> may, via an integrated low-pass filter, attenuate the first (or second) side channel (e.g. , by 3dB) with respect to the unattenuated first (or second) side channel. This is depicted by attenuation curve FSC of <FIG>. The attenuated range of audio frequencies may be defined at least in part by an adjustable cutoff frequency. As shown in <FIG>, the low-pass filter might not substantially attenuate frequencies of the first (or second) side channel that are much higher than the cutoff frequency (fci) of the low-pass filter (e.g. , frequencies greater than fH1). The low-pass filter may attenuate the first (or second) side channel by approximately <NUM> dB at fci. The low-pass filter may also attenuate frequencies of the first (or second) side channel that are much lower than fci (e.g. , frequencies less than fL1) by approximately 3dB. It should be noted that magnitudes of attenuation or amplification are presented herein for illustrative purposes only and are not intended to be limiting.

By further example, the playback device <NUM>, <NUM>, <NUM>, or <NUM> may, via an integrated amplifier, amplify the center channel (e.g. , by 3dB) with respect to the unamplified center channel. This is depicted by attenuation curve CC of <FIG>. As shown in <FIG>, the amplifier might not substantially amplify frequencies of the center channel that are much higher than the cutoff frequency (fci) of the amplifier (e.g. , frequencies greater than fm). The amplifier may amplify the center channel by approximately <NUM> dB at fci. The amplifier may also amplify frequencies of the center channel that are much lower than fci (e.g. , frequencies less than fL1) by approximately 3dB. As a specific example, the cutoff frequency fci may be <NUM>, but other examples are possible.

The playback device <NUM> may then provide the frequency-dependently attenuated first side channel to the audio drivers 511A and 513A and the frequency-dependently amplified center channel to the audio drivers 511A-C and 513A-C. The playback device <NUM> may also provide a frequency-dependently attenuated second side channel to the audio drivers 511C and 513C in a manner similar to generating and providing the frequency-dependently attenuated first side channel to the audio drivers 511A and 513A described above.

In another example, the playback device <NUM> may provide the frequency-dependently attenuated first side channel to the audio drivers 561A and 563A and the frequency-dependently amplified center channel to the audio drivers 561A-B and 563A-B. The playback device <NUM> may provide the frequency-dependently amplified center channel to the audio drivers 581A-B and 583A-B. The playback device <NUM> may also provide a frequency-dependently attenuated second side channel to the audio drivers 58IB and 583B in a manner similar to generating and providing the frequency-dependently attenuated first side channel described above.

In this context, the method <NUM> may further involve receiving a command to increase a volume at which the playback device plays the audio content and increasing the cutoff frequency in response to receiving the command to increase the volume.

For example, the playback device may receive an "increase volume" command from the control device <NUM> depicted in <FIG>. In other examples, the playback device receives the "increase volume" command via its own user input device(s) such as a button, dial, and/or touch screen. In response to receiving the "increase volume" command, the amplifier and/or the low-pass filter of the playback device may increase their respective cutoff frequencies from fci to fc2 as shown in Figure IOC. Accordingly, the playback device might not substantially attenuate frequencies of the first (or second) side channel greater than fm nor substantially amplify frequencies of the center channel greater than fm. The playback device may attenuate the first (or second) side channel by approximately <NUM> dB at fc2 and amplify the center channel by approximately <NUM> dB at ic2. The playback device may also attenuate frequencies of the first (or second) side channel that are much lower than fc2 (e.g., frequencies less than fL2) by approximately 3dB and amplify frequencies of the center channel that are much lower than fc2 (e.g., frequencies less than fL2) by approximately 3dB.

The method <NUM> may further involve receiving a command to decrease a volume at which the playback device plays the audio content and decreasing the cutoff frequency in response to receiving the command to decrease the volume.

For example, the playback device may receive a "decrease volume" command from the control device <NUM> depicted in <FIG>. In other examples, the playback device receives the "decrease volume" command via its own user input device(s) such as a button, dial, and/or touch screen. In response to receiving the "decrease volume" command, the amplifier and/or the low-pass filter of the playback device may decrease their respective cutoff frequencies from fci to fc3 as shown in <FIG>. Accordingly, the playback device might not substantially attenuate frequencies of the first (or second) side channel greater than fH3 nor substantially amplify frequencies of the center channel greater than fm-The playback device may attenuate the first (or second) side channel by approximately <NUM> dB at fc3 and amplify the center channel by approximately <NUM> dB at fc3. The playback device may also attenuate frequencies of the first (or second) side channel that are much lower than fc3 (e.g., frequencies less than fL3) by approximately 3dB and amplify frequencies of the center channel that are much lower than fc3 (e.g., frequencies less than fL3) by approximately 3dB.

The method <NUM> may further involve determining a degree to which the left channel or the right channel exceeds a threshold amplitude within the range of audio frequencies and based on the determined degree, determining a factor by which to (i) attenuate the range of audio frequencies of the first side channel and/or the second side channel and (ii) amplify the range of audio frequencies of the center channel. In this context, attenuating the range of audio frequencies of a side channel may include attenuating the range of audio frequencies of the side channel by the determined factor. Amplifying the range of audio frequencies of the center channel may include amplifying the range of audio frequencies of the center channel by the determined factor.

Accordingly, if the playback device <NUM> determines that an amplitude of the left or right channel exceeds a predetermined threshold amplitude within the given frequency range, the playback device <NUM> may attenuate the amplitudes of the first and/or second side channels and amplify the amplitude of the center channel so as to have the audio drivers 51IB and 513B handle more of the overall "load" of reproducing the audio content. In a sense, the playback device <NUM> may reallocate the overall audio power output reproduced by the playback device <NUM>. In some cases, this reallocation of audio power among audio drivers may be performed at the expense of a less perceivable wideness of the audio content reproduced by the playback device <NUM>.

For example, the playback device <NUM> may determine that the input amplitude of at least one portion of the left or right channel within the given frequency range (e.g. , f ≤ fci = <NUM>) exceeds the threshold amplitude by an amount such as <NUM> dB. In response, the playback device <NUM> may attenuate the first side channel and/or the second side channel by <NUM> dB (or another amount) and/or amplify the center channel by <NUM> dB (or another amount) as shown in <FIG>. In some examples, the first and/or second side channels may be attenuated by an amount different from the amount of amplification provided for the center channel.

Method <NUM> and related functionality described above may be related to instances in which audio content is provided to a playback system in a format that includes center, left, and right channels. On the other hand, the method <NUM> and related functionality described below may be related to instances in which audio content is provided to a playback system in a format that includes a center channel and a side channel. As such, the method <NUM> and related functions may be performed by a single playback device or perhaps a pair of playback devices, but other examples are possible. Generally, the method <NUM> is performed by a single playback device, but other examples are possible as well.

In some examples, the method <NUM> is performed by a playback device comprising one or more first audio drivers, one or more second audio drivers, and one or more third audio drivers, such as the playback device <NUM>. At block <NUM>, the method <NUM> includes receiving a center channel of audio content and a side channel of the audio content. For example, the playback device <NUM> may receive the center channel and/or the side channel in any manner described above at paragraph [<NUM>] with regard to block <NUM> of the method <NUM>.

At block <NUM>, the method <NUM> includes providing the center channel of the audio content to (i) the one or more first audio drivers, (ii) the one or more second audio drivers, and (iii) the one or more third audio drivers for playback of the center channel according to a first radiation pattern that has a maximum along a first direction. For example, the playback device <NUM> may provide the center channel to the audio drivers 511A-C and 513A-C in any manner described above at paragraphs [<NUM>]-[<NUM>], [<NUM>]-[<NUM>], and [<NUM>] with regard to block <NUM> of the method <NUM>.

At block <NUM>, the method <NUM> includes providing the side channel to the one or more first audio drivers for playback of the side channel according to a second radiation pattern that has a maximum along a second direction. In this context, the first radiation pattern and the second radiation pattern combine to form a first response lobe that has a maximum along a third direction between the first and second directions. The first response lobe may represent audio information from both the center channel and the side channel. A listener may perceive audio corresponding to the first response lobe as having a wideness that is dependent on the relative amplitudes of (i) the center channel provided to the one or more first audio drivers 511A and 513A, the one or more second audio drivers 511B and 513B, and the one or more third audio drivers 511C and 513C, and (ii) the side channel provided to the one or more first audio drivers <NUM>11A and 513B. The playback device <NUM> may provide the side channel in any manner described above at paragraphs [<NUM>], [103M105], [<NUM>], and [<NUM>]-[<NUM>] with regard to block <NUM> of the method <NUM>.

At block <NUM>, the method <NUM> includes generating an inverted side channel comprising an inverse of the side channel. For instance, the playback device <NUM> may compute or otherwise generate the inverted side channel by inverting the side channel and/or calculating additive inverses of amplitudes of the side channel. The inverted side channel may be generated in any manner described above at paragraphs [<NUM>]-[<NUM>].

At block <NUM>, the method <NUM> includes providing the inverted side channel to the one or more third audio drivers for playback of the inverted side channel according to a third radiation pattern that has a maximum along a fourth direction. In this context, the first radiation pattern and the third radiation pattern may combine to form a second response lobe that has a maximum along a fifth direction between the first and fourth directions. The second response lobe may represent audio information from both the center channel and the inverted side channel. A listener may perceive audio corresponding to the second response lobe as having a wideness that is dependent on the relative amplitudes of (i) the center channel provided to the one or more first audio drivers 511A and 513A, the one or more second audio drivers 51IB and 513B, and the one or more third audio drivers 511C and 513C, and (ii) the inverted side channel provided to the one or more third audio drivers 51IC and 513C. The playback device <NUM> may provide the inverted side channel in any manner described above at paragraphs [<NUM>]-[<NUM><NUM>].

In addition, one of skill in the art will recognize that the functionality related to the method <NUM> described at paragraphs [<NUM>]-[<NUM>] and [<NUM><NUM>]-[<NUM>] can also be incorporated into the method <NUM> in a variety of ways which are contemplated herein.

Additionally, references herein to "embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one example embodiment of an invention. The appearances of this phrase in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. As such, the embodiments described herein, explicitly and implicitly understood by one skilled in the art, can be combined with other embodiments.

The specification is presented largely in terms of illustrative environments, systems, procedures, steps, logic blocks, processing, and other symbolic representations that directly or indirectly resemble the operations of data processing devices coupled to networks. These process descriptions and representations are typically used by those skilled in the art to most effectively convey the substance of their work to others skilled in the art. Numerous specific details are set forth to provide a thorough understanding of the present disclosure. However, it is understood to those skilled in the art that certain embodiments of the present disclosure can be practiced without certain, specific details. In other instances, well known methods, procedures, components, and circuitry have not been described in detail to avoid unnecessarily obscuring aspects of the embodiments. Accordingly, the scope of the present disclosure is defined by the appended claims rather than the forgoing description of embodiments.

Claim 1:
A method for a playback system comprising a playback device (<NUM>; <NUM>; <NUM>; <NUM>; <NUM>) comprising one or more first audio drivers (511A, 513A; 561A, 563A; 581A, 583A; 911A, 913A) and one or more second audio drivers (511B, 513B; 561B, 563B; 581B, 583B; 911B, 913B), the method comprising:
receiving (<NUM>) audio content comprising center and side audio channels;
providing the center channel received in the audio content to (i) the one or more first audio drivers and (ii) the one or more second audio drivers for playback according to a first radiation pattern (<NUM>) that has a maximum along a first direction;
providing the side channel received in the audio content to the one or more first audio drivers for playback of the side channel according to a second radiation pattern (<NUM>) that has a maximum along a second direction, wherein the first radiation pattern and the second radiation pattern combine to form a first response lobe that has a maximum along a third direction between the first and second directions; and
changing the third direction to adjust a perceived audio image by amplifying or attenuating a frequency range of one of the center channel and the side channel relative to the other of the center channel and the side channel, wherein the frequency range is defined at least in part by a cutoff frequency.