Patent Publication Number: US-2023161550-A1

Title: Audio Response Playback

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of priority under 35 USC § 119(e) to U.S. Provisional Application Ser. No. 62/298,418 filed on Feb. 22, 2016 and entitled “AUDIO RESPONSE PLAYBACK”, U.S. Provisional Application Ser. No. 62/312,350 filed on Mar. 23, 2016 and entitled “VOICE CONTROL OF A MEDIA PLAYBACK SYSTEM”, U.S. Provisional Application Ser. No. 62/298,425 filed on Feb. 22, 2016 and entitled “MUSIC SERVICE SELECTION”, U.S. Provisional Application Ser. No. 62/298,350 filed on Feb. 22, 2016 and entitled “METADATA EXCHANGE INVOLVING A NETWORKED PLAYBACK SYSTEM AND A NETWORKED MICROPHONE SYSTEM”, U.S. Provisional Application Ser. No. 62/298,388 filed on Feb. 22, 2016 and entitled “HANDLING OF LOSS OF PAIRING BETWEEN NETWORKED DEVICES”, U.S. Provisional Application Ser. No. 62/298,410 filed on Feb. 22, 2016 and entitled “DEFAULT PLAYBACK DEVICE(S)”, and claims priority to, and is a continuation of, U.S. patent application Ser. No. 17/222,151, filed on Apr. 5, 2021, entitled “Audio Playback Response,” which is a continuation of U.S. patent application Ser. No. 16/539,843, filed on Aug. 13, 2019, entitled “Audio Playback Response,” which is a continuation of U.S. patent application Ser. No. 16/154,469, filed on Oct. 8, 2018, entitled “Audio Playback Response,” which is a continuation of U.S. patent application Ser. No. 15/237,133, filed on Aug. 15, 2016, entitled “Audio Playback Response,” the contents each of which are herein incorporated by reference in their entireties. 
     This application is also related to U.S. Provisional Application Ser. No. 62/298,439 filed on Feb. 22, 2016 and entitled “CONTENT MIXING”, U.S. Provisional Application Ser. No. 62/298,433 filed on Feb. 22, 2016 and entitled “ROOM-CORRECTED VOICE DETECTION”, and U.S. Provisional Application Ser. No. 62/298,393 filed on Feb. 22, 2016 and entitled “ACTION BASED ON USER ID”, the contents each of which are herein incorporated by reference in their entireties. 
    
    
     FIELD OF THE DISCLOSURE 
     The disclosure is related to consumer goods and, more particularly, to methods, systems, products, features, services, and other elements directed to media playback or some aspect thereof. 
     BACKGROUND 
     Options for accessing and listening to digital audio in an out-loud setting were limited until in 2003, 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 2005. 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. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Features, aspects, and advantages of the presently disclosed technology may be better understood with regard to the following description, appended claims, and accompanying drawings where: 
         FIG.  1    shows an example media playback system configuration in which certain embodiments may be practiced; 
         FIG.  2    shows a functional block diagram of an example playback device according to aspects described herein; 
         FIG.  3    shows a functional block diagram of an example control device according to aspects described herein; 
         FIG.  4    shows an example controller interface according to aspects described herein; 
         FIG.  5    shows an example plurality of network devices according to aspects described herein; 
         FIG.  6    shows a function block diagram of an example network microphone device according to aspects described herein; 
         FIG.  7    shows a flow diagram of an example method of playing an audio response according to aspects described herein; and 
         FIG.  8    shows a flow diagram of blocks  708  and  712  of  FIG.  7    in more detail according to aspects described herein. 
     
    
    
     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. 
     DETAILED DESCRIPTION 
     I. Overview 
     Some embodiments described herein involve playing an audio response to a voice command in a media playback system and selecting a response device or zone to play the audio response to the voice command. In one embodiment, the response device or zone may be predetermined, and in another embodiment, the response device or zone may be dynamically selected based on context information. 
     As indicated above, the examples provided herein involve determining one or more devices or zone(s) to play an audio response to a voice command in a media playback system. In one aspect, a method is provided. The method may involve receiving a voice command from a microphone device associated with a media playback system. The media playback system may include one or more zones. At least one playback device of the one or more playback devices or at least one zone may be selected to play the audio response based on at least one of pairing information or capabilities of the zone, and the selected at least one playback device or zone is caused to play the audio response. 
     In another aspect, a non-transitory computer-readable medium is provided. The non-transitory computer readable medium has stored thereon instructions executable by a computing device to cause the computing device to perform functions. The functions include receiving a voice command from a microphone device associated with a media playback system, and the media playback system may include one or more zones, selecting at least one playback device of the one or more playback devices or a zone to play the audio response based on context information, and causing the selected at least one playback device or zone to play the audio response. 
     In yet another aspect, an apparatus is provided. The apparatus includes a processor and a memory. The memory has stored thereon instructions executable by the apparatus to cause the apparatus to perform functions. The functions include receiving a voice command via a microphone device assigned to a zone which includes one or more playback devices, selecting at least one playback device of the one or more playback devices to play the audio response based on at least one of pairing information or capabilities of the zone, and causing the selected at least one playback device to play the audio response. 
     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. It will be understood by one of ordinary skill in the art that this disclosure includes numerous other embodiments. 
     II. Example Operating Environment 
       FIG.  1    shows an example configuration of a media playback system  100  in which one or more embodiments disclosed herein may be practiced or implemented. The media playback system  100  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.  1   , the media playback system  100  includes playback devices  102 - 124 , control devices  126  and  128 , and a wired or wireless network router  130 . 
     Further discussions relating to the different components of the example media playback system  100  and how the different components may interact to provide a user with a media experience may be found in the following sections. While discussions herein may generally refer to the example media playback system  100 , technologies described herein are not limited to applications within, among other things, the home environment as shown in  FIG.  1   . For instance, the technologies described herein may be useful in environments where multi-zone audio may be desired, such as, for example, a commercial setting like a restaurant, mall or airport, a vehicle like a sports utility vehicle (SUV), bus or car, a ship or boat, an airplane, and so on. 
     a. Example Playback Devices 
       FIG.  2    shows a functional block diagram of an example playback device  200  that may be configured to be one or more of the playback devices  102 - 124  of the media playback system  100  of  FIG.  1   . The playback device  200  may include a processor  202 , software components  204 , memory  206 , audio processing components  208 , audio amplifier(s)  210 , speaker(s)  212 , a network interface  214  including wireless interface(s)  216  and wired interface(s)  218 , and microphone(s)  220 . In one case, the playback device  200  may not include the speaker(s)  212 , but rather a speaker interface for connecting the playback device  200  to external speakers. In another case, the playback device  200  may include neither the speaker(s)  212  nor the audio amplifier(s)  210 , but rather an audio interface for connecting the playback device  200  to an external audio amplifier or audio-visual receiver. 
     In one example, the processor  202  may be a clock-driven computing component configured to process input data according to instructions stored in the memory  206 . The memory  206  may be a tangible computer-readable medium configured to store instructions executable by the processor  202 . For instance, the memory  206  may be data storage that can be loaded with one or more of the software components  204  executable by the processor  202  to achieve certain functions. In one example, the functions may involve the playback device  200  retrieving audio data from an audio source or another playback device. In another example, the functions may involve the playback device  200  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  200  with one or more playback devices to create a multi-channel audio environment. 
     Certain functions may involve the playback device  200  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  200  and the one or more other playback devices. U.S. Pat. No. 8,234,395 entitled, “System and method for synchronizing operations among a plurality of independently clocked digital data processing devices,” which is hereby incorporated by reference, provides in more detail some examples for audio playback synchronization among playback devices. 
     The memory  206  may further be configured to store data associated with the playback device  200 , such as one or more zones and/or zone groups the playback device  200  is a part of, audio sources accessible by the playback device  200 , or a playback queue that the playback device  200  (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  200 . The memory  206  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  208  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  208  may be a subcomponent of the processor  202 . In one example, audio content may be processed and/or intentionally altered by the audio processing components  208  to produce audio signals. The produced audio signals may then be provided to the audio amplifier(s)  210  for amplification and playback through speaker(s)  212 . Particularly, the audio amplifier(s)  210  may include devices configured to amplify audio signals to a level for driving one or more of the speakers  212 . The speaker(s)  212  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)  212  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  212  may be driven by an individual corresponding audio amplifier of the audio amplifier(s)  210 . In addition to producing analog signals for playback by the playback device  200 , the audio processing components  208  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  200  may be received from an external source, such as via an audio line-in input connection (e.g., an auto-detecting 3.5 mm audio line-in connection) or the network interface  214 . 
     The network interface  214  may be configured to facilitate a data flow between the playback device  200  and one or more other devices on a data network. As such, the playback device  200  may be configured to receive audio content over the data network from one or more other playback devices in communication with the playback device  200 , 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  200  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  214  may be configured to parse the digital packet data such that the data destined for the playback device  200  is properly received and processed by the playback device  200 . 
     As shown, the network interface  214  may include wireless interface(s)  216  and wired interface(s)  218 . The wireless interface(s)  216  may provide network interface functions for the playback device  200  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  200  is associated with) in accordance with a communication protocol (e.g., any wireless standard including IEEE 802.11a, 802.11b, 802.11g, 802.11n, 802.11ac, 802.15, 4G mobile communication standard, and so on). The wired interface(s)  218  may provide network interface functions for the playback device  200  to communicate over a wired connection with other devices in accordance with a communication protocol (e.g., IEEE 802.3). While the network interface  214  shown in  FIG.  2    includes both wireless interface(s)  216  and wired interface(s)  218 , the network interface  214  may in some embodiments include only wireless interface(s) or only wired interface(s). 
     The microphone(s)  220  may be arranged to detect sound in the environment of the playback device  200 . For instance, the microphone(s) may be mounted on an exterior wall of a housing of the playback device. The microphone(s) may be any type of microphone now known or later developed such as a condenser microphone, electret condenser microphone, or a dynamic microphone. The microphone(s) may be sensitive to a portion of the frequency range of the speaker(s)  220 . One or more of the speaker(s)  220  may operate in reverse as the microphone(s)  220 . In some aspects, the playback device  200  might not have microphone(s)  220 . 
     In one example, the playback device  200  and one other playback device may be paired to play two separate audio components of audio content. For instance, playback device  200  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  200  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  200  is a playback device designed to render low frequency range audio content (i.e. a subwoofer), the playback device  200  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  200 , may be configured to render only the mid and high frequency components of audio content, while the low frequency range playback device  200  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:1,” “PLAY:3,” “PLAY:5,” “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.  2    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. 
     b. Example Playback Zone Configurations 
     Referring back to the media playback system  100  of  FIG.  1   , the environment may have one or more playback zones, each with one or more playback devices. The media playback system  100  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.  1   . 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.  1   , 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  104 ,  106 ,  108 , and  110  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  122  and  124  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.  1    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  102  while another user may be preparing food in the kitchen zone and listening to classical music being played by the playback device  114 . 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  118  is playing the same rock music that is being playing by playback device  102  in the balcony zone. In such a case, playback devices  102  and  118  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 U.S. Pat. No. 8,234,395. 
     As suggested above, the zone configurations of the media playback system  100  may be dynamically modified, and in some embodiments, the media playback system  100  supports numerous configurations. For instance, if a user physically moves one or more playback devices to or from a zone, the media playback system  100  may be reconfigured to accommodate the change(s). For instance, if the user physically moves the playback device  102  from the balcony zone to the office zone, the office zone may now include both the playback device  118  and the playback device  102 . The playback device  102  may be paired or grouped with the office zone and/or renamed if so desired via a control device such as the control devices  126  and  128 . On the other hand, if the one or more playback devices are moved to a particular area in the home environment that is not already a playback zone, a new playback zone may be created for the particular area. 
     Further, different playback zones of the media playback system  100  may be dynamically combined into zone groups or split up into individual playback zones. For instance, the dining room zone and the kitchen zone  114  may be combined into a zone group for a dinner party such that playback devices  112  and  114  may render audio content in synchrony. On the other hand, the living room zone may be split into a television zone including playback device  104 , and a listening zone including playback devices  106 ,  108 , and  110 , if the user wishes to listen to music in the living room space while another user wishes to watch television. 
     c. Example Control Devices 
       FIG.  3    shows a functional block diagram of an example control device  300  that may be configured to be one or both of the control devices  126  and  128  of the media playback system  100 . As shown, the control device  300  may include a processor  302 , memory  304 , a network interface  306 , a user interface  308 , microphone(s)  310 , and software components  312 . In one example, the control device  300  may be a dedicated controller for the media playback system  100 . In another example, the control device  300  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  302  may be configured to perform functions relevant to facilitating user access, control, and configuration of the media playback system  100 . The memory  304  may be data storage that can be loaded with one or more of the software components executable by the processor  302  to perform those functions. The memory  304  may also be configured to store the media playback system controller application software and other data associated with the media playback system  100  and the user. 
     In one example, the network interface  306  may be based on an industry standard (e.g., infrared, radio, wired standards including IEEE 802.3, wireless standards including IEEE 802.11a, 802.11b, 802.11g, 802.11n, 802.11ac, 802.15, 4G mobile communication standard, and so on). The network interface  306  may provide a means for the control device  300  to communicate with other devices in the media playback system  100 . In one example, data and information (e.g., such as a state variable) may be communicated between control device  300  and other devices via the network interface  306 . For instance, playback zone and zone group configurations in the media playback system  100  may be received by the control device  300  from a playback device or another network device, or transmitted by the control device  300  to another playback device or network device via the network interface  306 . 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  300  to a playback device via the network interface  306 . As suggested above, changes to configurations of the media playback system  100  may also be performed by a user using the control device  300 . 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  300  may sometimes be referred to as a controller, whether the control device  300  is a dedicated controller or a network device on which media playback system controller application software is installed. 
     Control device  300  may include microphone(s)  310 . Microphone(s)  310  may be arranged to detect sound in the environment of the control device  300 . Microphone(s)  310  may be any type of microphone now known or later developed such as a condenser microphone, electret condenser microphone, or a dynamic microphone. The microphone(s) may be sensitive to a portion of a frequency range. Two or more microphones  310  may be arranged to capture location information of an audio source (e.g., voice, audible sound) and/or to assist in filtering background noise. 
     The user interface  308  of the control device  300  may be configured to facilitate user access and control of the media playback system  100 , by providing a controller interface such as the controller interface  400  shown in  FIG.  4   . The controller interface  400  includes a playback control region  410 , a playback zone region  420 , a playback status region  430 , a playback queue region  440 , and an audio content sources region  450 . The user interface  400  as shown is just one example of a user interface that may be provided on a network device such as the control device  300  of  FIG.  3    (and/or the control devices  126  and  128  of  FIG.  1   ) and accessed by users to control a media playback system such as the media playback system  100 . 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. 
     The playback control region  410  may include selectable (e.g., by way of touch or by using a cursor) icons to cause playback devices in a selected playback zone or zone group to play or pause, fast forward, rewind, skip to next, skip to previous, enter/exit shuffle mode, enter/exit repeat mode, enter/exit cross fade mode. The playback control region  410  may also include selectable icons to modify equalization settings, and playback volume, among other possibilities. 
     The playback zone region  420  may include representations of playback zones within the media playback system  100 . In some embodiments, the graphical representations of playback zones may be selectable to bring up additional selectable icons to manage or configure the playback zones in the media playback system, such as a creation of bonded zones, creation of zone groups, separation of zone groups, and renaming of zone groups, among other possibilities. 
     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  400  are also possible. The representations of playback zones in the playback zone region  420  may be dynamically updated as playback zone or zone group configurations are modified. 
     The playback status region  430  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  420  and/or the playback status region  430 . 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  400 . 
     The playback queue region  440  may include graphical representations of audio content in a playback queue associated with the selected playback zone or zone group. In some embodiments, each playback zone or zone group may be associated with a playback queue containing information corresponding to zero or more audio items for playback by the playback zone or zone group. For instance, each audio item in the playback queue may comprise a uniform resource identifier (URI), a uniform resource locator (URL) or some other identifier that may be used by a playback device in the playback zone or zone group to find and/or retrieve the audio item from a local audio content source or a networked audio content source, possibly for playback by the playback device. 
     In one example, a playlist may be added to a playback queue, in which case information corresponding to each audio item in the playlist may be added to the playback queue. In another example, audio items in a playback queue may be saved as a playlist. In a further example, a playback queue may be empty, or populated but “not in use” when the playback zone or zone group is playing continuously streaming audio content, such as Internet radio that may continue to play until otherwise stopped, rather than discrete audio items that have playback durations. In an alternative embodiment, a playback queue can include Internet radio and/or other streaming audio content items and be “in use” when the playback zone or zone group is playing those items. Other examples are also possible. 
     When playback zones or zone groups are “grouped” or “ungrouped,” playback queues associated with the affected playback zones or zone groups may be cleared or re-associated. For example, if a first playback zone including a first playback queue is grouped with a second playback zone including a second playback queue, the established zone group may have an associated playback queue that is initially empty, that contains audio items from the first playback queue (such as if the second playback zone was added to the first playback zone), that contains audio items from the second playback queue (such as if the first playback zone was added to the second playback zone), or a combination of audio items from both the first and second playback queues. Subsequently, if the established zone group is ungrouped, the resulting first playback zone may be re-associated with the previous first playback queue, or be associated with a new playback queue that is empty or contains audio items from the playback queue associated with the established zone group before the established zone group was ungrouped. Similarly, the resulting second playback zone may be re-associated with the previous second playback queue, or be associated with a new playback queue that is empty, or contains audio items from the playback queue associated with the established zone group before the established zone group was ungrouped. Other examples are also possible. 
     Referring back to the user interface  400  of  FIG.  4   , the graphical representations of audio content in the playback queue region  440  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. 
     The audio content sources region  450  may include graphical representations of selectable audio content sources from which audio content may be retrieved and played by the selected playback zone or zone group. Discussions pertaining to audio content sources may be found in the following section. 
     d. Example Audio Content Sources 
     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  100  of  FIG.  1   , 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. 
     In some embodiments, audio content sources may be regularly added or removed from a media playback system such as the media playback system  100  of  FIG.  1   . In one example, an indexing of audio items may be performed whenever one or more audio content sources are added, removed or updated. 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. Other examples for managing and maintaining audio content sources may also be possible. 
     The above discussions relating to playback devices, controller devices, playback zone configurations, and media content sources provide only some examples of operating environments within which functions and methods described below may be implemented. Other operating environments and configurations of media playback systems, playback devices, and network devices not explicitly described herein may also be applicable and suitable for implementation of the functions and methods. 
     e. Example Plurality of Networked Devices 
       FIG.  5    shows an example plurality of devices  500  that may be configured to provide an audio playback experience based on voice control. One having ordinary skill in the art will appreciate that the devices shown in  FIG.  5    are for illustrative purposes only, and variations including different and/or additional devices may be possible. As shown, the plurality of devices  500  includes computing devices  504 ,  506 , and  508 ; network microphone devices (NMDs)  512 ,  514 , and  516 ; playback devices (PBDs)  532 ,  534 ,  536 , and  538 ; and a controller device (CR)  522 . 
     Each of the plurality of devices  500  may be network-capable devices that can establish communication with one or more other devices in the plurality of devices according to one or more network protocols, such as NFC, Bluetooth, Ethernet, and IEEE 802.11, among other examples, over one or more types of networks, such as wide area networks (WAN), local area networks (LAN), and personal area networks (PAN), among other possibilities. 
     As shown, the computing devices  504 ,  506 , and  508  may be part of a cloud network  502 . The cloud network  502  may include additional computing devices. In one example, the computing devices  504 ,  506 , and  508  may be different servers. In another example, two or more of the computing devices  504 ,  506 , and  508  may be modules of a single server. Analogously, each of the computing device  504 ,  506 , and  508  may include one or more modules or servers. For ease of illustration purposes herein, each of the computing devices  504 ,  506 , and  508  may be configured to perform particular functions within the cloud network  502 . For instance, computing device  508  may be a source of audio content for a streaming music service. 
     As shown, the computing device  504  may be configured to interface with NMDs  512 ,  514 , and  516  via communication path  542 . NMDs  512 ,  514 , and  516  may be components of one or more “Smart Home” systems. In one case, NMDs  512 ,  514 , and  516  may be physically distributed throughout a household, similar to the distribution of devices shown in  FIG.  1   . In another case, two or more of the NMDs  512 ,  514 , and  516  may be physically positioned within relative close proximity of one another. Communication path  542  may comprise one or more types of networks, such as a WAN including the Internet, LAN, and/or PAN, among other possibilities. 
     In one example, one or more of the NMDs  512 ,  514 , and  516  may be devices configured primarily for audio detection. In another example, one or more of the NMDs  512 ,  514 , and  516  may be components of devices having various primary utilities. For instance, as discussed above in connection to  FIGS.  2  and  3   , one or more of NMDs  512 ,  514 , and  516  may be the microphone(s)  220  of playback device  200  or the microphone(s)  310  of network device  300 . Further, in some cases, one or more of NMDs  512 ,  514 , and  516  may be the playback device  200  or network device  300 . In an example, one or more of NMDs  512 ,  514 , and/or  516  may include multiple microphones arranged in a microphone array. 
     As shown, the computing device  506  may be configured to interface with CR  522  and PBDs  532 ,  534 ,  536 , and  538  via communication path  544 . In one example, CR  522  may be a network device such as the network device  200  of  FIG.  2   . Accordingly, CR  522  may be configured to provide the controller interface  400  of  FIG.  4   . Similarly, PBDs  532 ,  534 ,  536 , and  538  may be playback devices such as the playback device  300  of  FIG.  3   . As such, PBDs  532 ,  534 ,  536 , and  538  may be physically distributed throughout a household as shown in  FIG.  1   . For illustration purposes, PBDs  536  and  538  may be part of a bonded zone  530 , while PBDs  532  and  534  may be part of their own respective zones. As described above, the PBDs  532 ,  534 ,  536 , and  538  may be dynamically bonded, grouped, unbonded, and ungrouped. Communication path  544  may comprise one or more types of networks, such as a WAN including the Internet, LAN, and/or PAN, among other possibilities. 
     In one example, as with NMDs  512 ,  514 , and  516 , CR  522  and PBDs  532 ,  534 ,  536 , and  538  may also be components of one or more “Smart Home” systems. In one case, PBDs  532 ,  534 ,  536 , and  538  may be distributed throughout the same household as the NMDs  512 ,  514 , and  516 . Further, as suggested above, one or more of PBDs  532 ,  534 ,  536 , and  538  may be one or more of NMDs  512 ,  514 , and  516 . 
     The NMDs  512 ,  514 , and  516  may be part of a local area network, and the communication path  542  may include an access point that links the local area network of the NMDs  512 ,  514 , and  516  to the computing device  504  over a WAN (communication path not shown). Likewise, each of the NMDs  512 ,  514 , and  516  may communicate with each other via such an access point. 
     Similarly, CR  522  and PBDs  532 ,  534 ,  536 , and  538  may be part of a local area network and/or a local playback network as discussed in previous sections, and the communication path  544  may include an access point that links the local area network and/or local playback network of CR  522  and PBDs  532 ,  534 ,  536 , and  538  to the computing device  506  over a WAN. As such, each of the CR  522  and PBDs  532 ,  534 ,  536 , and  538  may also communicate with each over such an access point. 
     In one example, communication paths  542  and  544  may comprise the same access point. In an example, each of the NMDs  512 ,  514 , and  516 , CR  522 , and PBDs  532 ,  534 ,  536 , and  538  may access the cloud network  502  via the same access point for a household. 
     As shown in  FIG.  5   , each of the NMDs  512 ,  514 , and  516 , CR  522 , and PBDs  532 ,  534 ,  536 , and  538  may also directly communicate with one or more of the other devices via communication means  546 . Communication means  546  as described herein may involve one or more forms of communication between the devices, according to one or more network protocols, over one or more types of networks, and/or may involve communication via one or more other network devices. For instance, communication means  546  may include one or more of for example, Bluetooth™ (IEEE 802.15), NFC, Wireless direct, and/or Proprietary wireless, among other possibilities. 
     In one example, CR  522  may communicate with NMD  512  over Bluetooth™, and communicate with PBD  534  over another local area network. In another example, NMD  514  may communicate with CR  522  over another local area network, and communicate with PBD  536  over Bluetooth. In a further example, each of the PBDs  532 ,  534 ,  536 , and  538  may communicate with each other according to a spanning tree protocol over a local playback network, while each communicating with CR  522  over a local area network, different from the local playback network. Other examples are also possible. 
     In some cases, communication means between the NMDs  512 ,  514 , and  516 , CR  522 , and PBDs  532 ,  534 ,  536 , and  538  may change depending on types of communication between the devices, network conditions, and/or latency demands. For instance, communication means  546  may be used when NMD  516  is first introduced to the household with the PBDs  532 ,  534 ,  536 , and  538 . In one case, the NMD  516  may transmit identification information corresponding to the NMD  516  to PBD  538  via NFC, and PBD  538  may in response, transmit local area network information to NMD  516  via NFC (or some other form of communication). However, once NMD  516  has been configured within the household, communication means between NMD  516  and PBD  538  may change. For instance, NMD  516  may subsequently communicate with PBD  538  via communication path  542 , the cloud network  502 , and communication path  544 . In another example, the NMDs and PBDs may never communicate via local communications means  546 . In a further example, the NMDs and PBDs may communicate primarily via local communications means  546 . Other examples are also possible. 
     In an illustrative example, NMDs  512 ,  514 , and  516  may be configured to receive voice inputs to control PBDs  532 ,  534 ,  536 , and  538 . The available control commands may include any media playback system controls previously discussed, such as playback volume control, playback transport controls, music source selection, and grouping, among other possibilities. In one instance, NMD  512  may receive a voice input to control one or more of the PBDs  532 ,  534 ,  536 , and  538 . In response to receiving the voice input, NMD  512  may transmit via communication path  542 , the voice input to computing device  504  for processing. In one example, the computing device  504  may convert the voice input to an equivalent text command, and parse the text command to identify a command. Computing device  504  may then subsequently transmit the text command to the computing device  506 . In another example, the computing device  504  may convert the voice input to an equivalent text command, and then subsequently transmit the text command to the computing device  506 . The computing device  506  may then parse the text command to identify one or more playback commands. 
     For instance, if the text command is “Play ‘Track 1’ by ‘Artist 1’ from ‘Streaming Service 1’ in ‘Zone 1’,” The computing device  506  may identify (i) a URL for “Track 1” by “Artist 1” available from “Streaming Service 1,” and (ii) at least one playback device in “Zone 1.” In this example, the URL for “Track 1” by “Artist 1” from “Streaming Service 1” may be a URL pointing to computing device  508 , and “Zone 1” may be the bonded zone  530 . As such, upon identifying the URL and one or both of PBDs  536  and  538 , the computing device  506  may transmit via communication path  544  to one or both of PBDs  536  and  538 , the identified URL for playback. One or both of PBDs  536  and  538  may responsively retrieve audio content from the computing device  508  according to the received URL, and begin playing “Track 1” by “Artist 1” from “Streaming Service 1.” 
     One having ordinary skill in the art will appreciate that the above is just one illustrative example, and that other implementations are also possible. In one case, operations performed by one or more of the plurality of devices  500 , as described above, may be performed by one or more other devices in the plurality of device  500 . For instance, the conversion from voice input to the text command may be alternatively, partially, or wholly performed by another device or devices, such as NMD  512 , computing device  506 , PBD  536 , and/or PBD  538 . Analogously, the identification of the URL may be alternatively, partially, or wholly performed by another device or devices, such as NMD  512 , computing device  504 , PBD  536 , and/or PBD  538 . 
     f. Example Network Microphone Device 
       FIG.  6    shows a function block diagram of an example network microphone device  600  that may be configured to be one or more of NMDs  512 ,  514 , and  516  of  FIG.  5   . As shown, the network microphone device  600  includes a processor  602 , memory  604 , a microphone array  606 , a network interface  608 , a user interface  610 , software components  612 , and speaker(s)  614 . One having ordinary skill in the art will appreciate that other network microphone device configurations and arrangements are also possible. For instance, network microphone devices may alternatively exclude the speaker(s)  614  or have a single microphone instead of microphone array  606 . 
     The processor  602  may include one or more processors and/or controllers, which may take the form of a general or special-purpose processor or controller. For instance, the processing unit  602  may include microprocessors, microcontrollers, application-specific integrated circuits, digital signal processors, and the like. The memory  604  may be data storage that can be loaded with one or more of the software components executable by the processor  602  to perform those functions. Accordingly, memory  604  may comprise one or more non-transitory computer-readable storage mediums, examples of which may include volatile storage mediums such as random access memory, registers, cache, etc. and non-volatile storage mediums such as read-only memory, a hard-disk drive, a solid-state drive, flash memory, and/or an optical-storage device, among other possibilities. 
     The microphone array  606  may be a plurality of microphones arranged to detect sound in the environment of the network microphone device  600 . Microphone array  606  may include any type of microphone now known or later developed such as a condenser microphone, electret condenser microphone, or a dynamic microphone, among other possibilities. In one example, the microphone array may be arranged to detect audio from one or more directions relative to the network microphone device. The microphone array  606  may be sensitive to a portion of a frequency range. In one example, a first subset of the microphone array  606  may be sensitive to a first frequency range, while a second subset of the microphone array may be sensitive to a second frequency range. The microphone array  606  may further be arranged to capture location information of an audio source (e.g., voice, audible sound) and/or to assist in filtering background noise. Notably, in some embodiments the microphone array may consist of only a single microphone, rather than a plurality of microphones. 
     The network interface  608  may be configured to facilitate wireless and/or wired communication between various network devices, such as, in reference to  FIG.  5   , CR  522 , PBDs  532 - 538 , computing device  504 - 508  in cloud network  502 , and other network microphone devices, among other possibilities. As such, network interface  608  may take any suitable form for carrying out these functions, examples of which may include an Ethernet interface, a serial bus interface (e.g., FireWire, USB 2.0, etc.), a chipset and antenna adapted to facilitate wireless communication, and/or any other interface that provides for wired and/or wireless communication. In one example, the network interface  608  may be based on an industry standard (e.g., infrared, radio, wired standards including IEEE 802.3, wireless standards including IEEE 802.11a, 802.11b, 802.11g, 802.11n, 802.11ac, 802.15, 4G mobile communication standard, and so on). 
     The user interface  610  of the network microphone device  600  may be configured to facilitate user interactions with the network microphone device. In one example, the user interface  608  may include one or more of physical buttons, graphical interfaces provided on touch sensitive screen(s) and/or surface(s), among other possibilities, for a user to directly provide input to the network microphone device  600 . The user interface  610  may further include one or more of lights and the speaker(s)  614  to provide visual and/or audio feedback to a user. In one example, the network microphone device  600  may further be configured to playback audio content via the speaker(s)  614 . 
     III. Example Method of Playing an Audio Response 
     As discussed above, embodiments described herein may involve playing back an audio response to a voice command.  FIG.  7    shows an example flow diagram  700  of a method for playing an audio response, and  FIG.  8    shows an example flow diagram  800  presenting aspects of blocks  708  and  712  of  FIG.  7    in more detail. Methods  700  and  800  present embodiments of methods that can be implemented within an operating environment involving, for example, the media playback system  100  of  FIG.  1   , one or more of the playback device  200  of  FIG.  2   , one or more of the control device  300  of  FIG.  3   , and one or more of the plurality of devices in system  500  of  FIG.  5   . Methods  700  and  800  may include one or more operations, functions, or actions. Although the blocks in  FIGS.  7  and  8    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  700  and  800  and other processes and methods disclosed herein, the flow diagrams 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 or hard drive. The computer readable medium may include non-transitory computer readable medium, 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  700  and  800  and other processes and methods disclosed herein, each block in  FIGS.  7  and  8    may represent circuitry that is wired to perform the specific logical functions in the process. 
     As discussed above,  FIG.  7    depicts a flow diagram of a method  700  for playing an audio response. At block  702  of method  700 , a network microphone device  512 ,  514 ,  516  may be assigned (e.g., paired or bonded) to a zone comprising one or more playback devices such as playback devices  532 ,  534 ,  536 ,  538 . Network microphone devices may be assigned to a zone as described in the application identified as U.S. Provisional Application No. 62/298,410 entitled Default Playback Device(s), the contents of which is hereby incorporated by reference in its entirety. At block  704 , a user may provide a voice command to one or more devices of the plurality of devices  500  which contain a microphone (e.g., NMD  512 ,  514 ,  516 , PBD  532 ,  534 ,  536 ,  538 , CR  522 ). The one or more microphone devices may pass the voice command to other devices of the plurality or system of devices  500  (e.g., one or more computing devices  504 ,  506 ,  508  in cloud network  502 , NMD  512 ,  514 ,  516 , PBD  532 ,  534 ,  536 ,  538 ) for processing. At block  706 , the one or more processing devices may process the voice command and return a response to be played back. The response to be played back may be returned in the form of a voice response message comprising the audio clip to be played, text to be converted to speech, and/or an identifier (e.g., URL or URI) of a pre-recorded response to be played that may be stored locally on a device of system  500 ). The response may be returned via one or more communication paths  542 ,  544 ,  546 . 
     At block  708 , system  500  may select one or more devices or one or more zones to play the voice response. The determination or selection of which one or more devices or zones to play the voice response may depend on a variety of factors including context information, pairing information, and/or user settings. Block  708  will be discussed in more detail with respect to  FIG.  8   . 
     At block  710 , system  500  may receive the voice response message indicating the response to play. Block  710  may occur before, in conjunction with, or after block  708 . At block  712 , the system  500  may cause the one or more device(s) selected in block  708  to play the voice response. The default zone may be grouped for synchronous playback with another zone and playback of the audio response may be adjusted based on the grouping which will be described in more detail with respect to  FIG.  8   . 
       FIG.  8    shows an illustrative flow diagram of selecting one or more zones or devices (e.g., individual device, zone comprising one or more devices) to play the voice response to the voice command according to aspects described herein. At block  802 , a computing device (e.g., NMD, playback device, control device, computing device) can determine whether to use a predetermined response device (e.g., default PBD) or zone (e.g., default zone) or dynamically select a response device or zone to play the voice response. A predetermined response device or zone may be determined during initial system setup or configuration (e.g., assignment, pairing, bonding) when adding new devices to system  500 . For example, initial setup or configuration may be to add a new playback device to system  500  and/or to add or assign a new NMD to a zone (e.g., default zone). The predetermined response device may be selected by the user and/or automatically selected by the system  500 . A response device or zone may be dynamically selected based on various information such as context information (e.g., location information, orientation information, presence information) which may include pairing information (e.g., pairing dependent on location of a user, pairing dependent on location of microphone device), and/or capability information (e.g., available sensors, available devices, available networks, available processing power). 
     The decision of whether to use a predetermined device or to dynamically select an audio response device may be based on the capabilities of system  500  to dynamically select a response device and/or for an efficient determination of the response device. Certain devices and/or hardware may be used in order to make a dynamic selection, and if the certain devices and/or hardware are not available to participate in the dynamic selection, system  500  may default to using a predetermined response device. For example, the system  500  might not have the capability to determine location information related to the user&#39;s position and/or the position of a microphone device (e.g., NMD, PBD, CR) receiving or having responsibility of processing a voice command spoken by the user, and/or the system  500  might not have previously determined location information of devices in system  500 . In such an example, a determination to use a predetermined device may be the most expedient avenue to provide the user with an immediate acknowledgement or response to the voice command. As another example, the system  500  may lack hardware such as a sensor, camera, or other input device which can be used to determine context information (e.g., location information, presence information, etc.). In this instance, the system  500  may decide to use a predetermined response device (e.g., default zone, default playback device). As yet another example, the system  500  may have only one zone in which case the system can automatically determine to set the one zone as the default zone and/or to use the one zone for all audio responses. Similarly, the system  500  may have only a single PBD. In view of this, the system may select to use the single PBD as the default device and/or predetermined audio response device. 
     In some instances, location information may be determined or processed by transmitting information detected by devices in the system  500  to cloud network  502  for processing via communication paths  542 ,  544 , and/or  546 . Cloud network  502  may possess more processing power than the devices NMD  512 ,  514 ,  516 , CR  522 , and PBD  532 ,  534 ,  536 ,  538 . In the event the cloud network  502  is not available, the system  500  may use one of the predetermined devices and may defer to a user&#39;s preferences stored in a user profile for the specific predetermined device (e.g., default response device) to speak or play an audio response. In some aspects, the location information may be processed locally by one or more of the NMDs, CRs, PBDs. 
     If the system  500  has determined at block  802  to select one or more predetermined response devices or zones to play the audio response to the voice command, method  800  may proceed to block  804 . If the system  500  has determined at block  802  to dynamically select one or more response devices to play the audio response, method  800  may proceed to block  806 . 
     At block  804 , a processing device (e.g., any of the plurality of devices  500 ) may determine to select a predetermined zone or one or more predetermined devices. For example, a user may designate one or more devices or one or more zones to play the audio response to any voice command during initial setup or configuration (e.g., assignment, pairing or bonding), and the user designation may be saved as a default setting in a user profile associated with the user. The user profile may be stored in any device of the plurality of devices  500 . In response to receiving a voice command, the receiving device or any other device in system  500  may retrieve the user profile stored locally or in another device to determine which predetermined speaker(s) or zone(s) of playback device(s) to use as the device(s) to play the audio response to the voice command. 
     In one example, a network microphone device may include a speaker, and the speaker of the networked microphone device may be used to play the voice response. 
     In another aspect, a speaker in an audio response device (e.g., NMD(s), playback device(s), control device) may be configured during initial setup with the NMD to play audio responses. For example, a user may select a particular device in the default zone to be a default response device. In other instances, the default zone may include one playback device, and the one playback device may be identified as the default response device. In some other instances, the default zone may include more than one playback device, and a user may select one of the playback devices or two or more of the playback devices as the default response device. 
     In some aspects, the zone to playback an audio response may be a bonded zone (e.g., bonded zone  530 ) including two or more playback devices (e.g., PBDs  536 ,  538 ). In a bonded zone, the audio response may be played by one or more the playback devices in the bonded zone, and which of the playback devices of the bonded zone play the audio may depend on the type of playback devices. For example, the bonded zone may include a surround sound system where playback devices may be placed at different locations around a user and be responsible for playing one or more channels of audio. In this arrangement, the playback devices may be placed both in front of and behind the user. Based on the orientation of the user to the PBDs, the PBD(s) in front of the user may be selected to play the audio response. 
     In some aspects, the NMD may be usually stationary such that a relative location may be configured during initial setup. In one aspect, a user may identify a response device nearest to the NMD. The response device may be part of the default zone or another zone. In another aspect, the response device nearest to the NMD may be identified automatically by nearby response devices and/or the NMD. For example, proximity detection may be performed using the microphone(s) of the nearby response devices and/or NMD. For example, one or more playback devices in the default zone may emit or play a predetermined tone. The predetermined tone may be played at the same power level or volume at each playback device. The microphone(s) of the NMD may receive the test tone and determine based on highest power level which playback device is closest to the NMD. 
     In some aspects, the default response device may be determined based on orientation of the playback devices relative to the NMD. For example, playback devices which are facing towards the NMD may have higher priority to be the default response device over a playback device which is physically nearer to the NMD. Similar to using a test tone to determine a nearest playback device, a test tone picked up by the microphone(s) of the NMD may be used to determine orientation of playback devices relative to the NMD. The NMD may pick up or detect a tone played from a playback device positioned so that speakers facing towards the NMD detected more loudly or at a higher power than a speaker directed away from the NMD. Other techniques for proximity or location determination are possible including those described herein. 
     As another example, all playback devices may be selected to play the audio response to the voice command. For example, all playback devices in a default zone (e.g., zone to which the NMD is assigned) may play any or all audio responses which are responsive to an audio or voice command. 
     After determining one or more predetermined response devices, the method may proceed to block  808  and determine whether the default zone is grouped with another zone. The default zone may be grouped with another zone for synchronous playback of media items (e.g., audio content, video clips, radio). 
     Returning to block  806 , the system  500  may dynamically select one or more response devices or one or more zones to play the audio response to the audio command. The dynamically selected audio response device(s) may be selected based on pairing information (e.g., NMD dynamic pairing based on user location and/or device location) and/or context information (e.g., orientation of user, context at time of the voice command, location information). The pairing information may be dependent on the context information. The dynamically selected device(s) may be selected independent of pairing information. The zone or device selected for the response may be the same or different from the device or zone to which the NMD is assigned. 
     As discussed above, a NMD may be paired or assigned to a zone or a device. The dynamically selected audio response device may be the device to which a NMD is paired where the pairing between the NMD and another device may change dynamically based on (e.g., change in response to a change in) a user&#39;s location which can be determined at any time, in response to a particular event (e.g., user requests a particular zone) and/or a location of the NMD relative to another device (e.g., NMD, PBD, CR). For example, at the time voice command is received or at the time the audio response is to be played to the user. The user&#39;s location may be determined using one or more of the plurality of devices  500  and various techniques. For example, microphones in two or more different devices of the plurality of devices  500  may be used in determining the location of the user relative to the two or more different devices. 
     Two or more different devices may be listening for a user&#39;s voice and determine a closest speaker by comparing a magnitude (e.g., volume, power level) of the user&#39;s voice and/or determining a delay or timing difference between when each of two or more different devices receives the user&#39;s voice. As an example, a first device (e.g., PBD  532 ) and a second device (e.g., PBD  534 ) may be located in the same zone as the user, and the microphones of these playback devices may be able to pickup the user&#39;s voice command. The devices may be able to record and/or analyze the user&#39;s speech or voice when the user speaks the voice command. The recording may be done by any of the devices  500  which include a microphone (e.g., NMD, PBD CR), and the analysis may be done by any of the devices of the plurality of devices  500 . The analysis may include receiving the recorded user&#39;s speech or voice from one or more other devices and comparing based on timestamp and/or by spoken word and/or by syllable of the user&#39;s speech or other characteristic of the recording. In some aspects, the comparison may be performed after each word, syllable, and/or phrase and need not wait until the user has completed speaking the voice command. 
     The delay or timing difference between when different devices receive the sound of a user&#39;s voice may be indicative of a relative distance between the user and the receiving devices since devices closer to the user may receive the sound of the user&#39;s voice before devices further away from the user. For example, the two or more devices can each timestamp when certain sound characteristics or sound markers occur in the voice input and compare the timestamp to determine which of the two or more devices received the sound of the voice first. The two or more devices may maintain synchronized clocks and can directly compare timestamps of the sound characteristics to determine which device received the sound characteristic first. In some aspects, the two or more devices may determine a time difference between their respective clocks and compare the difference of the timestamps while subtracting the time difference between their respective clocks. 
     The recording or analysis of the user&#39;s speech may be performed by one or more devices and may be initiated by another device. For example, a NMD or other device containing a microphone (e.g., CR, PBD) may always be listening for a voice command, and when the NMD or other microphone device detects that the user has started speaking a command, the NMD may alert other microphone devices (e.g., NMD, CR, PBD) to begin receiving, recording, and/or analyzing the user&#39;s voice command by transmitting an alert (e.g., message) over a communication connection (e.g.,  542 ,  544 ,  546 ) to other microphone devices which may or might not be in the same zone as the NMD. 
     Similarly, the analysis of the user&#39;s speech may be used to determine a user&#39;s orientation relative to the speaker. For example, a user may be facing towards a first speaker and have a second speaker directed to the user&#39;s back. In some instances, the system  500  may select the first speaker to play the audio response even though the user is closer to the second speaker since it may be desirable to have a speaker in front the of user play the audio response rather than a speaker behind the user. A microphone in a device (e.g., PBD, CR, NMD) in front of the user may pick up or detect a user&#39;s voice more loudly or at a higher power than a microphone in a device (e.g., PBD, CR, NMD) to the side or behind the user. 
     In some aspects, location information can include location of the microphone device (e.g., NMD, PBD, CR) relative to a speaker. For example, one or more playback devices in the default zone may emit or play a predetermined tone. The predetermined tone may be played at the same power level or volume at each playback device and/or may be within or outside a human hearing range (e.g., approximately 20 Hz to 20 kHz). The microphone(s) of the NMD may receive the test tone and determine based on highest power level which playback device is closest to the NMD. 
     In some aspects, NMD  512  may include a microphone array  606 . Using the microphone array  606 , the NMD may be able to generally identify direction, distance, and/or orientation of the user by determining which microphone(s) of microphone array  606  detects the loudest volume or highest power of the user&#39;s voice. In some aspects, the system or NMD  500  may have previously determined relative positions of playback devices and/or been programmed with relative positions of the playback devices, and the NMD may be able to use the microphones of the playback devices in combination with its own microphone(s) to determine general direction, distance, and/or orientation of a user using the user&#39;s voice when the voice command is spoken. Each determination of the user&#39;s location may be stored in one or more of the devices  500  and may be referenced in response to later voice commands for a quicker determination of a user&#39;s location and/or orientation. 
     Another technique for determining the location of the user may be to use interference and/or strength of wireless signals in an environment (e.g., location, zone). In some aspects, the location of the user may be determined based on wireless signals in an environment where the user and the PBD(s) and/or the NMD are located. The wireless signals may include wireless communication signals according to any wireless communication protocol such as an industry standard (e.g., IEEE 802.11a, 802.11b, 802.11g, 802.11n, 802.11ac, 802.15, Bluetooth, 4G mobile communication standard, LTE mobile communication standard, Bluetooth®, Near-Field Communications (NFC), etc.). The user may have a device (e.g., computing device, mobile device, wearable, tablet, etc.) which includes a wireless interface to transmit wireless communication signals according to a wireless communication protocol. The wireless signals emitted from the device may cause interference with other wireless signals present in the environment where the user is located. Based on the strength of the interference with other wireless signals, other devices which can detect the wireless signals and interference can determine a location of the user. 
     To determine the location of the user based on the strength of wireless signals in an environment, the user&#39;s device may measure the signal strength (e.g., received signal strength indicator (RSSI)) of a signal emitted by any wireless device in the environment with the user and identify the device with the strongest signal strength as the device nearest the user. Similarly, wireless device(s) (e.g., PBD, NMD, wireless router, beacon, NFC) in the environment can measure the signal strength of a wireless signal emitted by the user&#39;s device and transmit and/or collect signal strength measurements of the user device&#39;s wireless signal by other devices. The signal strength measurements may be collected and/or compared by any device in system  500 , and the device with the strongest signal strength measurement can be identified as the device nearest to the user. 
     In some aspects, the NMD may become unpaired with a zone and re-paired with the zone. Such an unpairing may occur if the NMD leaves the environment associated with the media playback system (e.g., leaves the home environment, leaves the zone), moves outside of the range of a communication path (e.g., communication path  542 ,  544 , and/or  546 ) (e.g., moves outside of wireless signal range of the communication paths), and/or disconnects from the communication path (e.g., disconnects from a network, logs out of a system or service, disables a communication interface, enters airplane mode). The NMD may later re-pair with the zone, for example, if the NMD returns to the environment associated with the media playback system (e.g., re-enters the home environment), returns to within range of a communication path (e.g., moves into wireless signal range of the communication paths), and/or reconnects to the communication path (e.g., establishes connection to a network, enables a communication interface, exits airplane mode). 
     As an example, a user may be carrying the NMD and may remove the NMD from the premises of the user&#39;s home. Consequentially, the NMD may lose connection with a zone or device to which the NMD was paired. The NMD may store this last-known connection or pairing and automatically attempt to re-connect or re-pair with this last-known connection or pairing upon returning to the user&#39;s home. In some aspects, the NMD may dynamically pair based on location information as described herein, and the dynamic pairing may occur automatically by the NMD once the NMD determines that the NMD is able to pair with a zone or device. 
     Any voice commands spoken by the user and received by the NMD while the NMD is unpaired may be processed and/or executed immediately or queued for processing and/or execution upon re-pairing, and any audio responses to the voice commands may be played on a dynamically selected device as described herein. For example, the user may play a playlist outside of the home and speak a voice command to continue playing the same playlist after returning home. The NMD may begin the processing of the voice command (e.g., begin processing locally, transmit to another device in system  500  for processing) prior to the user entering the home, prior to re-pairing with any devices or zones in the home, after entering the home, or after re-pairing with any devices or zones in the home. The audio response to the voice command may be played by the first zone or device with which the NMD is paired which may be according to dynamic pairing aspects described herein. The same un-pairing and re-pairing features may apply to a user or NMD moving between different zones. In shifting the pairing between different zones or un-pairing and re-pairing with a particular zone or device, state information of currently playing content or last-played content may be transferred with or separately from the pairing procedure. 
     In some instances, the voice command may include a particular zone in which to execute a command (e.g., play music in the Kitchen). In response to the request in the voice command of a particular zone (e.g., Kitchen), the NMD can automatically change its pairing to the Kitchen zone. A request for a particular zone in the voice command may override dynamic pairing selections that the NMD may have otherwise made based on the detected location of the user or NMD. 
     Other techniques to determine location information related to a user or other device are described in U.S. patent application Ser. No. 13/340,126 filed Dec. 29, 2011 issued as U.S. Pat. No. 9,084,058, U.S. patent application Ser. No. 13/536,250 filed Jun. 28, 2012 issued as U.S. Pat. No. 9,225,307, U.S. patent application Ser. No. 13/568,993 filed Aug. 7, 2012 issued as U.S. Pat. No. 8,930,005, U.S. patent application Ser. No. 13/777,780 filed Feb. 26, 2013 issued as U.S. Pat. No. 9,195,432, U.S. application Ser. No. 14/475,191 filed Sep. 2, 2014, and U.S. patent application Ser. No. 14/681,735 filed Apr. 8, 2015, the contents of which are all incorporated by reference in their entireties. 
     The method may proceed to block  808  to determine whether the selected zone (e.g., default zone or device(s) or dynamically selected zone or device(s)) is grouped with an additional zone as discussed above. If the selected zone is not grouped with another zone, the system  500  can cause the selected zone which can include one or more response devices to play the audio response at block  810 . The audio response may be generated or stored in the device playing the audio response and/or the audio response may be transmitted from any other device in system  500  over any of communication paths  542 ,  544 ,  546  to the device playing the audio response. The audio response may be received in a message from other devices and/or the selected response device(s) may receive a message from a device processing the voice command (e.g., any device in system  500 ) containing an identifier that corresponds to the particular audio response to play. 
     In some aspects, the system may determine that the selected zone (e.g., predetermined zone, default zone, dynamically selected zone) or the selected device(s) (e.g., predetermined device, default device, dynamically selected device) are in a zone that is grouped with another zone and proceed to block  812 . For example, the selected zone and the additional zone grouped with the selected zone may be playing audio content synchronously (e.g., playing the same audio content simultaneously in sync). While receiving the voice command processing the voice command, and/or playing the audio response to the voice command, playback of currently playing media items or audio content (e.g., songs, playlist, radio station, video) may continue uninterrupted while the audio response is played from device(s) of the selected zone. Meanwhile, any media item or audio content which is to be played as a result of an audio or voice command may be played in the selected zone in addition to any other zones grouped with the selected zone. For example, the voice command may be a request to play a particular song, and while the voice command is processed and the song is requested, audio playback of any currently playing audio content may continue while audio responses are played by the dynamically selected or predetermined response device(s). Once the voice command is processed and the requested song is identified and retrieved, playback by all playback devices of the selected zone and any zones grouped with the default zone may change to the requested song. 
     In some aspects, all playback devices in the same zone as the response device and zones grouped with the response device may play the audio response. The determination of whether the audio response is to be played in these zones may be based on context information (e.g., user presence). For example, if the selected response device(s) are in a first zone that is grouped for synchronous audio playback with a second zone, the system may determine that user(s) are present in the second zone and play the audio response to notify other user(s) that a received voice command is causing a change in the playback state. 
     In some aspects, more than one audio response may be provided for a single voice command. For example, a first audio response may be played in response to a device of the plurality of devices  500  receiving a voice command to provide acknowledgment or notification to the user that the voice command has been received, and a second audio response may be played in response to processing and/or completion of processing of the voice command. The first audio response and second audio response may be played on any combination of one or more predetermined devices or dynamically selected devices. For example, a user may speak a voice command of playing to play a “Top 40 Playlist,” and a default audio response device may play a first audio response (e.g., tone, ringtone, notification sound, sound clip) indicating that the voice command has been received by a NMD (e.g., NMD associated with the default zone). In response to receiving an indication that the voice command is being processed or processing is complete, a second audio response, such as “The Top 40 Playlist is now being played,” may be generated and/or received. The second audio response may be played on a dynamically selected device. The various blocks of  FIGS.  7  and  8    may be repeated, as needed, for additional audio commands and/or audio responses. 
     In some aspects, the selected one or more response devices may adjust the playback volume of the audio response based on various factors. Some of the response device(s) may already be set at a particular volume level before receiving the voice command and/or before playing the audio response, and the response device(s) may play the audio response at the particular volume level. The response device(s) may be set at the particular volume level even though the response device(s) might not be currently playing any media content. The audio response to the voice command may be played at a volume greater than, less than, or equal to the particular volume level. 
     In some instances, the system may determine that the selected one or more zones are still some distance from the user, and the system may play the audio response at a louder volume so that the user can hear the audio response. For example, the system may have selected a playback device in the kitchen zone because the kitchen playback device(s) is closest to the user, but the user may be located outside in the backyard where there is no playback device. In order for the user to hear the audio response from the playback device, the audio response may need to be played at a greater volume. The volume of the audio response may be independent of the volume or loudness at which media content may be played. In this instance, the NMD may also be in the kitchen zone, and the system may determine to use an inverse relationship between the loudness of the user&#39;s voice as received by the NMD and volume of the audio response playback. 
     The determination of whether to adjust the playback volume may depend on context information such as user location and/or user presence information. For example, the system may have determined that the user is greater than a threshold distance from the selected playback device or is the user is in a particular zone which may be predetermined to be at a distance where volume of audio response playback is to be adjusted. In some aspects, the system might not increase the volume of the audio response playback above a threshold volume level if the system determines that another person or use is in the selected zone. 
     In some aspects, the system may use other context information such as the time of day, day of the week, and/or volume of currently played media content when determining the volume at which to play the audio response. The other context information may be used to distinguish from whether the user is at a distance from the NMD or whether the user is providing a voice command at a low volume (e.g., whisper). For example, the time of day may be the evening or late at night when other users in same location may be sleeping. The user may not wish to disturb other users who are sleeping and may therefore provide a voice command at a low volume. Based on the time of day being after a certain time (e.g., 9 pm), the system may determine to switch to a special mode such as a night mode and play the audio response at the same or around the same volume at which the NMD received the voice command. In some aspects, a user may be provided an option to use the night mode via a control device. In yet another example, sleeping times may be more flexible on weekends, and therefore the system may determine that even though the time of day is after a certain time, the system might not use a night mode because the day is a weekend. 
     Another example may be to determine the volume of the audio response based in part on the volume at which the currently playing music may be played. For example, the system may decide to automatically use a night mode audio response volume when the volume of music is set below or equal to a threshold volume level. The user may be playing music at a lower volume so as to not disturb other people who may be within hearing range at a higher volume. In this example, there may be a direct correlation between the volume of the music playback and/or the loudness of the user&#39;s voice and the volume of the audio response. 
     The system may receive context information from other devices in the environment such as presence information and/or location information of people in the environment using various techniques described herein. The system may determine that the volume at which an audio response is to be played may be changed from current volume settings based on the context information and/or location information. 
     The audio response playback volume may be adjusted independent of or in combination with an adjustment of the playback volume of media content during the audio response playback period, or the playback volume of media content may be adjusted during the audio response playback period as described in U.S. application Ser. No. 15/098,760 filed Apr. 14, 2016 and entitled “Content Mixing,” the contents of which are incorporated by reference. 
     In causing the selected one or more playback devices to play an audio response with an adjusted volume, a playback device of the one or more playback devices and/or one or more computing devices in cloud network  502  may determine the adjusted volume. For example, one or more of the computing devices in cloud network  502  may determine the adjusted volume (e.g., volume level, gain level, gain adjustment amount) and transmit the adjust volume information to the selected one or more playback devices. In another example, the selected one or more devices may determine the adjusted volume. 
     While the features described herein address selecting one or more devices to play an audio response to a voice command, the selected one or more devices may provide a visual indication as a response to the voice command instead of or in addition to playing the audio response. 
     IV. Conclusion 
     The description above discloses, among other things, various example systems, methods, apparatus, and articles of manufacture including, among other components, firmware and/or software executed on hardware. It is understood that such examples are merely illustrative and should not be considered as limiting. For example, it is contemplated that any or all of the firmware, hardware, and/or software aspects or components can be embodied exclusively in hardware, exclusively in software, exclusively in firmware, or in any combination of hardware, software, and/or firmware. Accordingly, the examples provided are not the only way(s) to implement such systems, methods, apparatus, and/or articles of manufacture. 
     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. 
     When any of the appended claims are read to cover a purely software and/or firmware implementation, at least one of the elements in at least one example is hereby expressly defined to include a tangible, non-transitory medium such as a memory, DVD, CD, Blu-ray, and so on, storing the software and/or firmware.