Patent Publication Number: US-2023145511-A1

Title: Dynamic Computation of System Response Volume

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. application Ser. No. 17/391,404, filed Aug. 2, 2021, titled “Dynamic Computation of System Response Volume.” U.S. application Ser. No. 17/391,404 is a continuation of U.S. application Ser. No. 16/600,949, filed Oct. 14, 2019, titled “Dynamic Computation of System Response Volume.” U.S. application Ser. No. 16/600,949 is a continuation of U.S. application Ser. No. 16/102,153, filed Aug. 13, 2018, titled “Dynamic Computation of System Response Volume.” U.S. application Ser. No. 16/102,153 is a continuation of U.S. application Ser. No. 15/699,982, filed Sep. 8, 2017, titled “Dynamic Computation of System Response Volume.” The entire contents of the Ser. Nos. 15/699,982, 16/102,153, 16/600,949, and 17/391,404 applications are incorporated by reference herein. 
     This application relates to: (i) App. No. 62/298,410, titled “Default Playback Device(s),” filed Feb. 22, 2016; (ii) App. No. 62/298,418, titled “Audio Response Playback,” filed Feb. 22, 2016; (iii) App. No. 62/298,433, titled “Room-corrected Voice Detection,” filed Feb. 22, 2016; (iv) App. No. 62/298,439, titled “Content Mixing,” filed Feb. 22, 2016; (v) App. No. 62/298,425, titled “Music Service Section,” filed Feb. 22, 2016; (vi) App. No. 62/298,350, titled “Metadata exchange involving a networked playback system and a networked microphone system,” filed Feb. 22, 2016; (vii) App. No. 62/298,388, titled “Handling of loss of pairing between networked devices,” filed Feb. 22, 2016; (viii) App. No. 62/298,393, titled “Action based on User ID,” filed Feb. 22, 2016; (ix) App. No. 62/132,350, titled “Voice Control of a Media Playback System,” filed Mar. 12, 2015. The entire contents of the 62/298,410; 62/298,418; 62/298,433; 62/298,439; 62/298,425; 62/298,350; 62/298,388; 62/298,393; and 62/132,350 applications are incorporated herein by reference for all purposes. 
    
    
     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 and aspects 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. 
     SUMMARY 
     The present disclosure describes systems and methods for, among other things, determining and setting a system response volume for networked devices that generate and output system responses (e.g., a voice response or other system response) in response to voice commands. An example of a voice command is “What song is playing?” The system response may be, “Let it Be by the Beatles.” In another example, the voice command may be “What movie is playing on my television?” And the system response might be, “Mothra versus Godzilla.” In operation, the playback volume of audio content played by the system (i.e., the volume of music or audio associated with video programming) may be different than the system response volume (i.e., the volume for voice responses). 
     The present disclosure describes many examples for determining a system response volume for one or more networked devices under many different configuration scenarios. The disclosed examples describe functions performed by networked devices, voice enabled devices (VEDs), networked microphone devices (NMDs), audio playback devices (PBDs), and video playback devices (VPDs). As used herein, the term networked device is a class of devices that includes, but is not limited to VEDs, NMDs, PBDs, and VPDs. 
     VEDs are a similarly class of devices that includes but is not limited to NMDs, PBDs, and VPDs. For example, one type of VED is an NMD, which is a networked device comprising one or more processors, a network interface, and one or more microphones. Some NMDs may additionally include one or more speakers and perform media playback functions. Another type of VED is a PBD, which is a networked device comprising one or more processors, a network interface, and one or more speakers. Some PBDs may optionally include one or more microphones and perform the functions of an NMD. Yet another type of VED is a VPD, which is a networked device comprising one or more processors, a network interface, one or more speakers, and at least one video display. Some VPDs may optionally include one or more microphones and perform the functions of an NMD. PBDs and VPDs may be generally referred to as media playback devices. 
     Some examples include determining that a requirement exists to output a system response; and in response to determining that a requirement exists to output a system response, (i) setting a system response volume for a first speaker associated with the first networked device and (ii) outputting a system response at the set system response volume via the first speaker associated with the first networked device. 
     In some examples, these steps occur at the time (or substantially the same time) the system outputs a system response or in response to particular trigger events. This may be advantageous as it allows the system to assess the surrounding environment at the time the system outputs the system response or at the time of the particular trigger event. Specifically, this may reduce the likelihood of hearing a system response at an undesirably high or undesirably low system response volume attributed to a change in the surrounding environment between determining that a requirement exists to output a system response and the outputting of the system response. 
     Performing these steps at the time of the system output also allows the system to dynamically set the system response volume and output the system response because the system assesses the environment at the time of outputting the system response (or substantially right before outputting the system response), which accounts for rapid environmental change. For example, a user may be playing audio content through a PBD at a loud volume. Shortly after, the user may mute the audio content. Setting the system response volume at the time of outputting the system response ensures the system recognizes that user muted the audio content, which allows the system to set an appropriate system response volume. 
     In some examples, determining that a requirement exists to output a system response comprises receiving a voice input via a first microphone associated with the first networked device. In some examples, determining that a requirement exists to output a system response comprises activating a system alert or notification. 
     In some examples, the first networked device comprises the first speaker and the first microphone. In some examples, the first networked device comprises the first microphone and a second networked device comprises the first speaker. In some examples, the first networked device comprises the first speaker and a second networked device comprises the first microphone. 
     In some examples, the first networked device comprises the first speaker and a second networked device comprises a second speaker, and outputting the system response at the set system response volume via the first speaker associated with the first networked device comprises outputting the system response at the set system response volume via the first speaker associated with the first networked device in synchrony with the second networked device outputting the system response at the set system response volume via the second speaker. 
     In some examples, setting the system response volume for the first speaker associated with the first networked device comprises: (i) obtaining a sound pressure level (SPL) measurement via one or more microphones associated with the first networked device; and (ii) setting the system response volume based on the SPL measurement. 
     In some circumstances, the system may set the system response volume to a predetermined amount higher than the obtained SPL measurement. This may be beneficial in situations where there is ambient noise (e.g., conversations between people in the listening area and/or media content playing) because it may allow the user to hear the system response over the ambient noise. 
     In some examples, setting the system response volume based on the obtained sound pressure level measurement comprises setting the system response volume to between about 1 dB to about 6 dB higher than instantaneous and/or prior sound measurements (e.g., an SPL measurement and/or a measurement derived from an SPL measurement). 
     In some examples, setting the system response volume for the first speaker associated with the first networked device comprises: (i) accessing a previously-determined system response volume; and (ii) setting the system response volume to the previously-determined system response volume. 
     In some examples, the previously-determined system response volume was determined via steps comprising: (i) detecting a trigger event; and (ii) in response to detecting the trigger event, determining the system response volume. In some examples, the trigger event comprises, during media playback via the first speaker, changing a volume of the media playback, and determining the system response volume for the first speaker associated with the first networked device comprises: (i) obtaining an SPL measurement via one or more microphones associated with the first networked device; and (ii) setting the system response volume based on the SPL measurement. In some examples, changing a volume of the media playback comprises at least one of (i) increasing the volume of the media playback, (ii) decreasing the volume of the media playback, (iii) muting the media playback, and (iv) unmuting the media playback. 
     In some examples, the trigger event comprises a reconfiguration of the first networked device. In some examples, the reconfiguration comprises one of (i) configuring the first networked device from playing back media content as a standalone playback device to playing back media in synchrony with at least a second networked device and (ii) configuring the first networked device from playing back media in synchrony with at least a second networked device to playing back media as a standalone playback device. 
     In some examples, the trigger event comprises expiration of a timeframe, and wherein determining the system response volume for the first speaker associated with the first networked device comprises: (i) obtaining an SPL measurement via one or more microphones associated with the first networked device; and (ii) setting the system response volume based on the SPL measurement. 
     In some examples, the trigger event comprises at least one of (i) detection of motion in an area of the first networked device by a motion detector associated with the first networked device and (ii) detecting a change in light in an area of the first networked device by a light detector associated with the first networked device. 
    
    
     
       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; 
         FIG.  3    shows a functional block diagram of an example control device; 
         FIG.  4    shows an example controller interface; 
         FIG.  5    shows an example plurality of network devices; 
         FIG.  6    shows a function block diagram of an example network microphone device; 
         FIG.  7    shows an example media playback system configuration in which certain embodiments may be practiced. 
         FIG.  8    shows an example method according to some embodiments. 
     
    
    
     The drawings are for the purpose of illustrating example embodiments, but it is understood that the inventions are not limited to the arrangements and instrumentalities shown in the drawings. 
     DETAILED DESCRIPTION 
     I. OVERVIEW 
     As mentioned above, this disclosure is related to functions performed by a class of networked device generally referred to herein as voice enabled devices (“VED”). One type of VED is a networked microphone device (“NMD”), which is a networked device comprising one or more processors, a network interface, and one or more microphones. Some NMDs may additionally include one or more speakers. Another type of VED is an audio playback device (“PBD”), which is a networked device comprising one or more processors, a network interface, one or more microphones, and one or more speakers. Yet another type of VED is a video playback device (“VPD”), which is a networked device comprising one or more processors, a network interface, one or more microphones, one or more speakers, and at least one video display. PBDs and VPDs may be generally referred to as media playback devices. As used herein, the term networked device includes but is not necessarily limited to VEDs, PBDs, NMDs, and PVDs, and the term VED includes but is not necessarily limited to PBDs, NMDs, and PVDs. 
     Each of the above-described VEDs implements at least some voice control functionality, which allows the VED (individually or perhaps in combination with one or more other computing devices) to act upon voice commands received via the microphone, thereby allowing a user to control the VED and perhaps other devices, too. 
     One aspect of the voice control functionality includes playing back a system response via one or more speakers. A system response as used herein includes a voice response or any other type of audible response (e.g., an alarm, a beep, a click, or other notification, response, or confirmatory sound) that a VED plays via one or more speakers associated with the VED in response to a voice command received via one or more microphones associated with the VED. 
     In some embodiments, a VED equipped with a microphone(s) and a speaker(s) may play a voice response (or other system response) via its speaker(s) in response to a voice command received via its microphone(s). 
     In other embodiments, a first VED equipped with a microphone(s) may command or otherwise cause a second VED equipped with at least a speaker(s) to play a voice response (or other system response) via the second VED&#39;s speaker(s) in response to a voice command received via the first VED&#39;s microphone(s). 
     In further embodiments, a first VED equipped with a microphone and a speaker(s) may command or otherwise cause a second VED equipped with at least a speaker(s) to play a voice response (or other system response) in synchrony with the first VED in response to a voice command received via the first VED&#39;s microphone(s). 
     As described above, some VEDs include one or more speakers, e.g., NMDs equipped with one or more speakers, PBDs equipped with one or more speakers, and VPDs equipped with one or more speakers. In operation, any of these VEDs equipped with one or more speakers can play both audio content (e.g., music, audio tracks associated with video, spoken word content, or other audio content) and a voice response (or other system response) via its one or more speakers. Any of these speaker-equipped VEDs may additionally play other general system responses (e.g., wake up alarms, timer notifications, and/or system notifications such as dings, beeps, clicks, or other notifications) via its one or more speakers, too. 
     In some cases, a VED plays back audio content and system responses at the same volume. For example, if a user is having a party and raises the volume of a PBD to better fill the room with music, the system response volume for the PBD is also raised. This can be undesirable because a system response may interrupt conversations or make the audio content less enjoyable. Further, if the audio content stops playing, the system response volume may still be set to a higher volume, which may be alarming to users in the room when the PBD (or other VED) outputs a system response in the future. 
     In some cases, a VED plays back a system response at a static volume that does not change, regardless of the volume of any audio content. In these cases, the volume of the system response may not be appropriate depending on the volume of the audio content. For example, if the user sets the audio playback at a high volume, the user may not hear a system response when it occurs. On the contrary, when there is no audio playback, the system response volume may be too loud or quiet depending on the location of the VED. 
     In some cases, a VED plays a system response in the form of an alarm that is emitted at a volume level different from a volume level of audio content. This may be useful when a user is using the alarm to wake up, and wants the alarm set at a specific volume. However, the user may need to repeatedly set (or reset) the system response volume throughout the day when using media playback system  700  for different daily events (e.g., setting additional alarms, issuing commands, etc.). If the user forgets to reset the system response volume to an appropriate volume for an alarm, the alarm may jar the user if the volume of the alarm is too loud, or fail to alert the user if the volume of the alarm is too quiet. 
     It may be desirable in some cases for a VED to dynamically set the volume of the system response based on surrounding circumstances, such as volume of audio playback and/or a sound pressure level (“SPL”) measured in an area where the VED is located. For example, in some embodiments, a VED calculates a system response volume in response to determining (or detecting) a requirement to output a system response. In operation, upon determining (or detecting) a requirement to output a system response, the VED measures SPL via one or more microphones associated with the VED, and then sets the system response volume based at least in part on the measured SPL. 
     In some embodiments, a VED additionally or alternatively sets (or resets) a system response volume in response to conditions other than determining (or detecting) a requirement to output a system response. For example, in some embodiments, a VED may take a new SPL measurement and set (or reset) a system response volume based at least in part on the SPL measurement in response to receiving a new configuration and/or a command or instruction to reconfigure VED device settings, e.g., (i) receiving a new audio volume setting, (ii) receiving a command to group/un-ungroup the VED with one or more other VEDs in a synchrony group, stereo pair, bonded group of VEDs, or consolidated VED (described herein), and/or (iii) receiving other VED configuration settings. 
     In some embodiments, a VED may calculate an SPL and reset a system response volume at a number of times and in a number of different ways. The new SPL calculation may occur prior to a system response, on a pre-defined periodic basis, or a combination of both. The new SPL calculation may be performed by one or more of a plurality of VEDs in an audio playback configuration. The SPL measurement and/or calculation may be performed by (i) the VED outputting the system response, (ii) another VED or other networked device in the configuration that is not tasked with outputting the system response, and/or (iii) a group of two or more VEDs and/or networked devices. 
     In operation, calculating the system response volume may also be accomplished in a number of different ways. The system response volume may be determined and set by one or more networked devices in a set of networked devices configured to operate as an media playback system. For example, in a media playback system comprising one NMD and two PBDs, the NMD may take an SPL measurement and set the system response volume, and one or more of the PBDs may play the actual system response at the system response volume set by the NMD. In such media playback systems, any one of the one or more networked devices of the media playback system (individually or in combination with any one or more of the other networked devices of the media playback system) may perform any one or more of (i) measuring the SPL, (ii) setting the system response volume, and/or (iii) playing back the actual system response at the system response volume. 
     Further embodiments include tangible, non-transitory computer-readable media having stored thereon program instructions that, upon execution by a computing device, cause the computing device to perform the features and functions disclosed and described herein. 
     Some embodiments include a computing device comprising at least one processor, as well as data storage and program instructions. In operation, the program instructions are stored in the data storage, and upon execution by the at least one processor, cause the computing device (individually or in combination with other components or systems) to perform the features and functions disclosed and described herein. 
     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 . In operation, any of the playback devices (PBDs)  102 - 124  may be voice-enabled devices (VEDs) as described earlier. 
     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   . As described above, a playback device (PBD)  200  is one type of voice-enabled device (VED). 
     The playback device  200  includes one or more processors  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 some examples, the one or more processors  202  include one or more clock-driven computing components configured to process input data according to instructions stored in the memory  206 . The memory  206  may be a tangible, non-transitory computer-readable medium configured to store instructions executable by the one or more processors  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 one or more processors  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 one or more processors  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, including but not limited to data to/from other VEDs (e.g., commands to perform an SPL measurement, SPL measurement data, commands to set a system response volume, and other data and/or commands to facilitate performance of the features and functions disclosed and described herein). 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. The playback device  200  may transmit metadata to and/or receive metadata from other devices on the network, including but not limited to components of the networked microphone system disclosed and described herein. In one example, the audio content and other signals (e.g., metadata 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”, “bonded group”, or “stereo pair”) 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 and/or other VEDs. 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 may be combined into a zone group for a dinner party such that playback devices  112  and  114  may render (e.g., play back) 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 one or more processors  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 one or more processors  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 one or more processors  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, 3G, 4G, or 5G mobile communication standards, 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 example 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 networked devices  500  that can be configured to provide an audio playback experience with 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 (or fewer) devices may be possible. As shown, the plurality of networked 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 . As described previously, any one or more (or all) of the NMDs  512 - 16 , PBDs  532 - 38 , and/or CR  522  may be voice-enabled devices (VEDs). 
     Each of the plurality of networked devices  500  are 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  are part of a cloud network  502 . The cloud network  502  may include additional computing devices (not shown). 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  are 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 (or at least may include or be a component of) 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 (or at least may include or be a component of) 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. In some embodiments, one or more of NMDs  512 ,  514 , and/or  516  may be a microphone on a mobile computing device (e.g., a smartphone, tablet, or other computing device). 
     As shown, the computing device  506  is 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  are shown as members of a bonded zone  530 , while PBDs  532  and  534  are members 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 . For example, any one or more (or perhaps all) of NMDs  512 - 16 , PBDs  532 - 38 , and/or CR  522  may be voice-enabled devices (VEDs). 
     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 and/or include 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 be different (or perhaps change) depending on types of communication requirements 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 , and computing device  506  in turn may then control one or more of PBDs  532 - 538  to execute the command. 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, and then computing device  506  may additionally control one or more of PBDs  532 - 538  to execute the command. 
     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 network devices  500 , as described above, may be performed by one or more other devices in the plurality of network devices  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 CR  522 , 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   , and/or any of the VEDs disclosed and described herein. As shown, the network microphone device  600  includes one or more processors  602 , tangible, non-transitory computer-readable memory  604 , a microphone array  606  (e.g., one or more microphones), 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 one or more processors  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 one or more processors  602  may include microprocessors, microcontrollers, application-specific integrated circuits, digital signal processors, and the like. The tangible, non-transitory computer-readable memory  604  may be data storage that can be loaded with one or more of the software components executable by the one or more processors  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 devices  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  610  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 SYSTEMS AND METHODS 
     It may be desirable in some instances for a voice-enabled device (VED) to dynamically calculate and set a system response volume. In some circumstances, audio playback systems might set a system response volume based on the environment generally (e.g., on initialization). This method might not account for a subsequent change in sound of the room, resulting in a system response that is too loud or too quiet for the environment at the point in time when the system issues a system response. To address this potential problem, in some examples, the VED may dynamically calculate and set the system response volume at the time of playing the system response (or just prior to playing the system response). This may be beneficial in circumstances where the sound environment of a room is volatile. For instance, a user may play audio content through a VED at a loud volume while muting the audio content sporadically to receive phone calls. The VED may assess the environment to calculate and set a system response volume while outputting the system response (or right before outputting the system response). This allows the system to output a system response at an appropriate system response volume for the environment. 
     It may be further desirable for one or more voice-enabled devices (VEDs) in a system of multiple networked devices to calculate and set a system response volume for the system of multiple networked devices. The one or more VEDs in the system of multiple networked devices may calculate and set a system response volume for the system of multiple networked devices (i) locally, via a local-area-network (LAN), and/or (ii) remotely, via a cloud server. For example, one of the one or more VEDs in a system may calculate and set the system response volume, then send the system response volume to the other VEDs in the system via a LAN. In another example, one of the one or more VEDs in the system may calculate and set the system response volume, then send the system response to a cloud server. In this example, the other VEDs in the system may retrieve the system response volume from the cloud server and set the system response volume accordingly. In another example embodiment, one or more VEDs may send a sample of the ambient sound (measured in the room where the system of multiple networked devices is located) to a cloud computing system, and in turn, the cloud computing system may set a system response volume for the system of multiple networked devices. In such example embodiments, the cloud computing system may set the system response volume for each VED in the system of multiple networked devices to the same volume level, or the cloud computing system may set the system response volume for individual VEDs in the system of multiple networked devices to two or more different volume levels. 
     As described previously, a voice enabled device (VED) may be a playback device (PBD), a networked microphone device (NMD), a video playback device (VPD), or any other networked device equipped with one or more microphones and/or speakers. In operation, VEDs equipped with one or more speakers can play both audio content (e.g., music, audio tracks associated with video, spoken word content, or other audio content) and a voice response (or other system response) via the one or more speakers. A VED may additionally play other general system responses (e.g., wake up alarms, timer notifications, and/or system notifications such as dings, beeps, clicks, or other notifications) via the one or more speakers, too. 
     As described earlier, some conventional networked devices set their system response volume (i) to be the same as audio content volume, (ii) at a static volume, and/or (iii) based on a manual input setting from the user. 
     In many circumstances, however, a VED&#39;s or other networked device&#39;s system response volume is not an appropriate volume for the room, situation, or user. For example, if the VED or other networked device is located in a large room, the system response volume may not be loud enough to alert a user standing across the room from the networked device. In another example, if the user is hard of hearing, the system response volume may not be loud enough to alert the user. In yet another example, if audio content is not playing in the room, the system response volume may be too loud and alarm the user. 
     Therefore, it may be desirable for a VED or other networked device to set a system response volume based on factors including, but not limited to, (i) the size of the room, (ii) various sound pressure level (“SPL”) measurements, (iii) the audio playback volume, (iv) the loudness of the audio playback content, (v) the number of networked devices in a system, and (vi) the configuration of networked devices in a system. 
       FIG.  7    shows a media playback system  700 , according to example embodiments. Media playback system  700  includes VEDs  704 ,  706 , and  708 . VED  704  comprises microphone  710  and speaker  712 . VED  706  comprises microphone  714  and speaker  716 . And VED  708  comprises microphone  718  and speaker  720 . In operation, VEDs  704 ,  706 , and  708  are configured to play audio content and output system responses in listening area  702 . 
     Each of VEDs  704 ,  706 , and  708  may be any of a networked microphone device (NMD), audio playback device (PBD), video playback device (VPD), or any other networked device comprising one or more microphones and one or more speakers. VEDs  704 ,  706 , and  708  may operate independently of one another, be grouped to operate in a stereo pair, and/or be grouped to play music or other audio content in synchrony with one another. 
     In operation, VEDs  704 ,  706 , and  708  are configured to receive voice commands from a user via their microphones, and output audio content and system responses via their speakers. In some alternative embodiments (not shown), one or more of the VEDs  704 ,  706 , and  708  may include both a microphone(s) and a speaker(s), one or more of the one or more VEDs  704 ,  706 , and  708  may include a microphone(s) but not a speaker(s), and one or more of the VEDs  704 ,  706 , and  708  may include a speaker(s) but not a microphone(s). 
     In some embodiments, VEDs  704 ,  706 , and  708  may be configured to operate and interact with one another in a similar manner as NMDs  512 ,  514 , and  516  and/or PBDs  532 ,  534 ,  536 , and  538  operate and interact with one another, as described with respect to  FIG.  5   . 
     a. Example System Response Volume Calculation 
     In some embodiments, each or all of VEDs  704 ,  706 , and  708  may calculate and set a system response volume (SRV) in response to a determination that a requirement exists to output a system response. Specifically, VEDs  704 ,  706 , and/or  708  may (i) calculate and set its own SRV independently of one another, and/or (ii) calculate and set an SRV for all of VEDs  704 ,  706 , and  708 . Alternatively, one of the VEDs  704 ,  706 , or  708  may be designated to provide system responses, and the designated VED (or perhaps a different VED or another computing system) may calculate and set the SRV for the designated VED. 
     In one example, VED  704  may determine that a requirement exists to output a system response and then calculate and/or set the system response volume for media playback system  700 . VED  704  may calculate a desired system response volume (i) prior to an output of a system response, (ii) responsive to a new SPL computation, (iii) responsive to a new system configuration, (iv) responsive to a new audio volume setting, and/or (v) responsive to a manual configuration of the SRV. 
     In the embodiments described herein, VED  704  is used as the networked device determining whether a requirement exists to output a system response and calculating a new system response volume. In operation, any of VEDs  704 ,  706 , and  708  (individually or in combination with one or more other connected networked devices) may (i) determine that a requirement exists to output a system response and (ii) calculate and/or set a system response volume for an individual VED and/or for the entire audio playback system  700 . VED  704  is simply used as an example device for describing the functions of determining whether the requirement exists and calculating a new system response volume in response to the determination. Moreover, in scenarios when two or more of the VEDs  704 ,  706 , and  708  cooperate, interoperate, or otherwise work together to determine whether a requirement exists to output a system response and calculate and/or set a new system response volume, VEDs  704 ,  706 , and  708  can be configured to communicate with one another, via wireless and/or wired networking functionality, any one or more of (i) a determination that a requirement exists to output a system response, (ii) data to make a determination as to whether a requirement exists to output a system response, (iii) a calculated system response volume setting, (iv) data to calculate a system response volume, and/or (v) commands to set a system response volume . 
     In some embodiments, VED  704  determines that a requirement exists to output a system response and then calculates a system response volume prior to outputting the system response. In some embodiments, after determining that a requirement exists to output a system response, VED  704  uses microphone  710  to record sound in the area around VED  704 . VED  704  then processes the recorded sound to determine an SPL of the sound in the area around VED  704 . 
     The requirement to output a system response may include a requirement for one or more of VEDs  704 ,  706 , and/or  708  to (i) activate an alarm, (ii) issue a notification, and/or (iii) respond to a voice command received from a user. 
     For example, in some embodiments, if a user speaks a voice command in the area of VED  704 , VED  704  (i) determines that a requirement exists to output a system response (i.e., a response to the voice command), and then (ii) calculates an appropriate system response volume before outputting its response. In this example, if the user speaks a command in a quiet room that the requires a voice response (or other system response) from media playback system  700 , VED  704  determines that a requirement exists to output a system response, calculates the SPL in the room, and then sets the system response volume based on the SPL calculation. Because the room is quiet, setting the system response volume based on the SPL calculation may include reducing the system response volume from its previous volume level. 
     In operation, the SPL calculation may be based on sound measurements obtained from any one or more of microphones  710 ,  714 , and/or  718 , of VEDs  704 ,  706 , and  708 , respectively. VEDs  704 ,  706 , and  708  are configured to (i) receive various sound measurements and/or calculations or SPL calculations from the other VEDs in the configuration, and (ii) send system response volume setting to the other VEDs in the configuration. For example, VED  704  may receive various sound measurements from microphone  714  of VED  706  and microphone  718  of VED  708 . VED  704  may use these measurements to calculate the SPL of listening area  702  and set an appropriate system response volume based on the calculated SPL. VED  704  may then send the appropriate system response volume to VEDs  706  and  708  via a network interface (e.g., over the LAN and/or via a cloud server) for implementation by VEDs  706  and  708 . In another example, VEDs  704 ,  706 , and/or  708  may all calculate a SPL independently of one another. In this example, VED  704  may receive the SPL calculations from VEDs  706  and  708  and use the SPL calculations to set a system response volume. VED  704  may then send the system response volume to VEDs  706  and  708  via a network interface for implementation by VEDs  706  and  708 . 
     In another example, if the user speaks a command in a noisy room that requires a voice response (or other system response) from media playback system  700 , VED  704  determines that a requirement exists to output a system response, calculates the SPL in the room, and then sets the system response volume based on the SPL calculation. As described above, the SPL calculation may be based on sound measurements obtained from any one or more of microphones  710 ,  714 , and/or  718 , of VEDs  704 ,  706 , and  708 , respectively. Because the room is loud, setting the system response volume based on the SPL calculation may include increasing the system response volume from its previous volume level. 
     In some embodiments, the amount VED  704  raises or lowers the system response volume in response to determining that a requirement exists to output a system response may depend on hearing characteristics of the user. The hearing characteristics may be based on (i) one or more user account settings for or (ii) a manual input from the user. The user account settings may contain settings related to a user&#39;s hearing ability (i.e., normal hearing or hearing impaired (and perhaps a degree of hearing impairment)). Thus, for hearing impaired users, VED  704  in some embodiments may increase a system volume more in a loud environment and/or decrease a system volume less in a quiet environment, as compared to the amount of increase and/or decrease for a non-hearing-impaired user. For example, for a hearing impaired user, the VED  704  may set the system response volume to a level that is +3 decibels (“dBs”) higher than a volume level the VED  704  would have set the system response volume to for a non-hearing-impaired user. 
     In some embodiments, setting the system response volume based on the SPL calculation, and then outputting the system response at the set system response volume includes “un-muting” one or more VEDs. For example, if all VEDs  704 ,  706 , and  708  are muted when VED  704  determines that a requirement exists to output a voice response (or other system response), then setting the system response volume includes (i) un-muting one or more of VED  704 ,  706 , and  708 , and setting the system response volume, and (ii) outputting the voice response (or other system response) at the set system response volume. Some embodiments may additionally include re-muting the previously un-muted VED. Still further embodiments, may distinguish between muting playback of audio content from playing back a voice response, so that the VED can playback a voice response from one or more speakers even though audio playback is muted. 
     In some circumstances, the system response volume is set based on the audio playback volume of VED  704  when VED  704  is playing media content. This may cause a problem if, after the user mutes the audio playback volume of VED  704 , VED  704  outputs a system response, because the system response volume is still based on the audio playback volume of VED  704  when VED  704  was playing media content. To overcome this problem, some embodiments involve VED  704 , when VED  704  is in a muted state, limiting the system response volume to a predetermined threshold value. The threshold value may be a value ranging from  1 - 10  (other ranges could be used, too), depending on the placement and configuration of media playback system  700 . For example, a user may be listening to media content via VED  704  at an audio playback volume of 8. If the user mutes the audio playback volume of VED  704 , VED may limit the system response volume to an appropriate threshold value (i.e., some value less than 8). Then, if VED  704  outputs a system response, the system response volume will be appropriate and less likely to startle the user. 
     In some embodiments, the system response volume is set based on the loudness of the audio playback content when VED  704  is playing media content. This may be beneficial because it allows VED  704  to set the system response volume relative to the volume of the audio content played back by VED  704 . For example, a user may be playing media content through VED  704  that features sporadic bursts of sound, followed by longer lulls. VED  704  may monitor the loudness of the audio playback content via microphone  710  to obtain an up-to-date loudness measurement at the time VED  704  outputs a system response. VED  704  then sets an appropriate system response volume based on the loudness of the audio playback content. For additional discussion related to setting an output volume based on the volume of audio content, see Pat. App. No. 62/298,439 paragraphs 100-103, the contents of which are incorporated by reference herein. 
     In some embodiments, VED  704  may set the system response volume based on the loudness of the audio playback content in addition to an instantaneous SPL measurement prior to outputting a system response. For example, VED  704  may monitor the loudness of the audio playback content via microphone  710  and, after determining a requirement exists to output a system response, VED  704  may obtain an instantaneous SPL measurement. VED  704  may then set the system response volume at an appropriate value based on the loudness of the audio playback content and the instantaneous SPL measurement. This may be beneficial because it allows VED  704  to account for the loudness of the audio played back by VED  704  in addition to other sources of sound and/or noise in listening area  702 . 
     Alternatively, in some embodiments, rather than calculating an SPL just before outputting a system response, or one or more VEDs in media playback system  700  may instead be configured to periodically (or perhaps semi-periodically or some other scheduled basis) calculate an SPL in the listening area  702 , and in response to calculating the new SPL in the listening area  702 , setting a system response volume based at least in part on the calculated SPL. In some embodiments, one or more of the VEDs may be configured to both (i) calculate an SPL periodically, semi-periodically, or on some other scheduled basis, and then set the system response volume based at least in part on the calculated SPL and (ii) calculate an SPL in response to determining that a VED needs to output a voice response (or some other system response), and then set the system response volume based at least in part on the calculated SPL. 
     In some scenarios where VEDs  704 ,  706 , and/or  708  are playing loud and/or sporadic audio content via their respective speakers, an instantaneous SPL measurement obtained by the one or more of VEDs  704 ,  706 , and/or  708  to assess the SPL may not accurately reflect the average SPL of listening area  702 . For example, if VED  704  takes an SPL measurement during a period of a song that is uncharacteristically loud, the SPL measurement obtained during that loud moment may cause VED  704  to set a system response volume that is too loud for listening area  702 . In some embodiments, VEDs  704 ,  706 , and/or  708  may counteract this problem by (i) lowering the audio playback volume of the VED or VEDs playing the audio content while taking the SPL measurement, and/or (ii) taking an SPL measurement during a lull in the audio playback or during a song transition. This may allow VEDs  704 ,  706 , and/or  708  to better assess other sound sources in listening area  702  that might otherwise be drowned out by the audio playback volume. 
     However, in some embodiments, VEDs  704 ,  706 , and/or  708  may use the unaltered (e.g., not lowered) audio playback volume when setting a system response volume to provide a system response volume in accordance to the audio playback volume. 
     In other scenarios, all of VEDs  704 ,  706 , and  708  may be playing audio content, again complicating the setting of the system response volume based on an SPL measurement. One or more of VEDs  704 ,  706 , and/or  708  may counteract this problem by lowering the audio playback volume of one or more of VEDs  704 ,  706 , and/or  708  to a suitable volume for taking an SPL measurement. The specific VEDs chosen to have their volume lowered may depend on the configuration of the VEDs  704 ,  706 , and/or  708  in media playback system  700 . 
     For example, VEDs  704 ,  706 , and  708  may be playing audio content in synchrony with each another within listening area  702  as depicted in  FIG.  7   . In this example, if VED  704  needs to perform an SPL measurement, VED  704  may lower the audio playback volume of VED  706  due to the proximity of VED  704  to VED  706 . It might not be necessary for VED  704  to lower the audio playback volume of VED  708  since it is not located as close to VED  704  as VED  706 , and thus the audio playback volume of VED  708  might not affect an SPL measurement performed by VED  704  to the same extent as the audio playback volume of VED  706 . 
     However, in some scenarios, it may be advantageous for VEDs  704 ,  706 , and/or  708  to take an SPL measurement while one or more of VEDs  704 ,  706 , and  708  are playing audio content. For example, if the audio playback volume of VED  704  would not impede an SPL measurement, a VED may take an SPL measurement without altering the audio playback volume of itself and/or other VEDs. In another example, if VED  704  is playing audio content that does not include many alternating loud and soft passages, VED  704  may be able to assess the SPL in area  702  more easily by not lowering the volume before taking the SPL measurement than if it lowered the audio playback volume prior to taking the SPL measurement because the SPL measurement would include the audio content playing at full volume. 
     In some embodiments, VED  704  calculates a new system response volume based on the signal-to-noise ratio of the volume of a user&#39;s voice command and a measurement of ambient sound in listening area  702 . In these embodiments, VED  704  measures the ambient sound in listening area  702  prior to outputting a system response. VED  704  then measures the volume of a user&#39;s voice command (e.g., a command requesting VED  704  to perform an action). In response to taking these measurements, VED  704  calculates the signal-to-noise ratio of the volume of the user&#39;s voice to the measurement of ambient sound and uses the ratio to set an appropriate system response volume. In one example, if the volume of the user&#39;s voice is high compared to the ambient noise in listening area  702 , VED  704  may set the system response volume to a lower value because the ambient noise will have little effect on the system response. In another example, if the volume of the user&#39;s voice is low compared to the ambient noise, VED  704  may set the system response volume to a higher value to compensate for the high level of ambient noise. In yet another example, if the volume of the user&#39;s voice is substantially the same volume as the ambient noise, VED may set the system response volume to a value higher than the ambient noise to ensure the user can discern the response from the ambient noise. 
     Additionally, VED  704  may calculate a new system response volume based on the signal-to-noise ratio of the user&#39;s voice command to the ambient sound in listening area  702  in addition to the distance from which the user issues the voice command. The location of the user may cause VED  704  to raise or lower the system response volume. In one example, if the user issues a voice command a short distance from VED  704  and the volume of the user&#39;s voice is low compared to the ambient noise, VED  704  may set a system response volume that is higher than the ambient noise, but not as high as it would if the user were located at a distance further from VED  704 . In another example, if the user issues a voice command at a distance far from VED  704  and the volume of the user&#39;s voice is high compared to the ambient noise, VED  704  may set a system response volume that is lower than the user&#39;s voice, but not as low as it would if the user issued the voice command at a distance closer to VED  704 . 
     In some circumstances, the ambient noise level may change after the user issues a voice command but before VED  704  outputs a system response. To overcome this potential problem, in some embodiments, VED  704  may modify the system response calculated using the signal-to-noise ratio of the user&#39;s voice command to the ambient sound in listening area  702  with an instantaneous SPL measurement. For example, VED  704  may calculate a new system response based on the previously described signal-to-noise ratio of the user&#39;s voice command to the ambient sound in listening area  702 . Then, just prior to outputting a system response, VED  704  may obtain an instantaneous SPL measurement. If the instantaneous SPL measurement indicates the ambient noise has changed since calculating the system response volume, VED  704  may adjust the system response volume based on the instantaneous SPL measurement. 
     In some embodiments, VED  704  calculates a new system response volume in response to a new system configuration. A new system configuration may occur when a user (i) adds and/or removes a VED or other networked device to/from media playback system  700 , and/or (ii) runs a diagnostic or calibration in response to repositioning one or more VEDs or other networked devices within listening area  702 . 
     For example, if media playback system  700  only contained VED  704  and  706 , and a user added VED  708  to the media playback system  700  configuration, then in some embodiments, VED  704  calculates a new system response volume in response to the change in configuration (i.e., adding VED  708  to the media playback system  700 ). 
     In another example, the user may perform a diagnostic and/or calibration procedure for audio playback system  700 , such as tuning one or more of VEDs  704 ,  706 , and/or  708  according to the Sonos Trueplay™ calibration procedure or other automated calibration procedure. In some embodiments, one or more of VED  704 ,  706 , and/or  708  performs a new SPL calculation and/or sets a new system response volume in response to completing the diagnostic and/or calibration procedure, or at least after completing the diagnostic and/or calibration procedure. 
     In some embodiments, VED  704  calculates a new system response in response to a new system configuration and just before outputting a system response. This may be advantageous as it allows VED  704  to calculate an up-to-date system response volume. For example, if media playback system  700  only contained VED  704  and  706 , and a user added VED  708  to the media playback system  700  configuration, VED  704  calculates a new system response volume in response to the change in configuration (i.e., adding VED  708  to the media playback system  700 ). VED  704  may subsequently determine that a requirement exists to output a system response, and in response to the determination, calculate a new system response volume. 
     In some embodiments, VED  704  calculates a new system response volume in response to receiving new audio playback volume setting. A new audio volume setting may include when a user (i) raises, (ii) lowers, or (iii) mutes the volume. For example, when a user raises the audio volume, VED  704  calculates and sets a higher system response volume based on the amount the user raised the volume. Similarly, when a user lowers the audio playback volume, VED  704  calculates and sets a lower system response volume based on the amount the user lowered the audio playback volume. In some embodiments, VED  704  may raise and/or lower the system response volume based on the amount that the audio playback volume was raised and/or lowered, without conducting a new SPL measurement. In other embodiments, raising and/or lowering the audio playback volume may trigger or otherwise cause VED  704  to perform a new SPL measurement, and then set the system response volume based at least in part on the new SPL measurement. Additionally, when a user mutes the audio playback volume, VED  704  calculates and sets a system response volume based on a default system response volume. In some embodiments, the default system response volume may be based on a new or previous SPL calculation. 
     In some embodiments, VED  704  calculates a new system response volume in response a user specifically adjusting the system response volume for VED  704 . In operation, a user may adjust the system response volume via (i) a physical mechanism located on VED  704  (e.g., a knob, button, slider, or other control) and/or (ii) a wirelessly connected controller (e.g., via RF, IR, or other wireless method) configured to send a control/instruction signal to VED  704  that causes VED  704  set the system response volume in response to a system response volume control setting command received from the user. 
     For example, a user may desire a higher system response volume because the user is interested in hearing a specific notification from VED  704 . One scenario may include a user raising the system response volume in order to hear an alarm indicating that the user should complete an important action (i.e., taking medication, turning off the stove, etc.). 
     In another example, a user may desire a lower system response volume due to a guest having sensitive hearing or in response to a medical condition. One scenario may include a user suffering from a migraine headache. In this scenario, it is advantageous to lower the system response volume to avoid aggravating the user&#39;s migraine symptoms. 
     In some embodiments, VED  704  sets a new system response volume based at least in part on a previously-determined system response volume in response to a triggering event. The trigger event may include a user (i) changing the audio playback volume of one or more of VEDs  704 ,  706 , and/or  708 , (ii) configuring one or more of VEDs  704 ,  706 , and/or  708  to operate as a standalone audio playback device or to operate in a group with one or more of the other VEDs, (iii) detecting motion within listening area  702  (or perhaps some other area), (iv) detecting a change in light within listening area  702  (or perhaps some other area), and/or (v) a time of day or a configured timeframe. 
     For example, if VED  704  has previously determined a system response volume that is suitable for nighttime or early morning, VED  704  may set a system response volume according to that previously-determined system response volume upon determining that it is nighttime or early morning (based on a system clock). 
     In another example, if VED  704  has previously determined a system response volume that is suitable for when the user has turned out his or her bedroom lights for the evening, then VED  704  may set a system response volume according to that previously-determined system response volume upon determining both (i) it is nighttime (based on a system clock) and (ii) the lights are off in listening area  702  (based on a light sensor, a message from a light sensor, and/or a message from a lighting control system). 
     In yet another example, if VED  704  has previously determined a system response volume that is suitable for a certain configuration of VEDs (e.g., a stereo pair of VED  704  and  706 ), then VED  704  may set a system response volume according to that previously-determined system response volume upon determining that VED  704  and VED  706  have been configured in a stereo pair, or perhaps as a step of configuring VED  704  and VED  706  to operate as a stereo pair. 
     In yet another example, if VED  704  has previously-determined a system response volume that is suitable in the afternoon when children are home from school, then VED  704  may set a system response volume according to that previously-determined system response volume upon determining (i) it is between 3:00 pm and 6:00 pm and (ii) there is motion in the listening area  702 , which suggests the presence of children (based on a motion sensor or a message from a motion sensor). 
     In some embodiments, two or more of VEDs  704 ,  706 , and  708  are configured to output a system response at a system response volume. In these embodiments, the system response volume may be based at least in part on the number of networked devices that will output a system response. In operation, the system response volume for each VED configured to output the system response can be set at a level so that the aggregate volume of the system response played by the multiple VEDs is at a desired system response volume. For example, assuming a desired system response volume is X dB, then then (i) for a system configured to output a system response via a single VED, that single VED&#39;s system response volume is set to X dB, and (ii) for a system configured to output a system response via two VEDs, each VED&#39;s system response volume might be set to X-3 dB, or perhaps some other offset factor to account for the fact that multiple VEDs will output a system response. 
     Alternatively or additionally, in some embodiments, the system response volume may also be based on at least in part on the configuration of media playback system  700 . In these embodiments, VEDs  704 ,  706 , and/or  708  may be operating as different types of playback devices (e.g., speaker or subwoofer) or in synchrony with one another (e.g., a bonded stereo pair). For example, VED  704  and  706  may be operating as a bonded stereo pair, while VED  708  is operating as a subwoofer. In this configuration, VEDs  704  and  706  may set their system response volumes lower than VED  708  to account for the bonded stereo pair having multiple speakers  710  and  714  outputting a system response. The amount the VEDs  704  and  706  lower their system response volumes may correspond to a reference table containing equal-loudness system response volume modifications for different configurations of media playback system  700  (e.g., lower the system response volume −2 dB for a stereo pair configuration or −4 dB for a 5.1 home theater configuration). 
     In some embodiments, each (or any) of VEDs  704 ,  706 , and  708  determines whether a requirement exists to output a system response and, in response to determining that a requirement exists to output a system response, determines a new system response volume based on one or more factors including but not limited to (i) the number of networked devices connected to media playback system  700 , (ii) an SPL measurement from one or more (or all) of the VEDs of the media playback system  700 , and/or (iii) the types of VEDs of the media playback system  700 . 
     In some embodiments, each of VEDs  704 ,  706 , and  708  determines whether a requirement exists to output a system response and, in response to that determination, determines and/or sets a new system response volume for one or more of the VEDs  704 ,  706 , and/or  708  (individually or as a group) based at least in part on the number of VEDs in the media playback system  700 . In these embodiments, each of VEDs  704 ,  706  and  708  calculates a separate system response volume and then, in response to determining that more than one networked device is connected, each VED modifies its calculated system response volume to account for the other VEDs in the media playback system  700 . Because each VED modifies (e.g., reduces) its own system response volume to account for the other VEDs in the media playback system  700 , the set of VEDs in the media playback system  700  avoids playing back a system response at a volume that is higher than desired. For example, if VED  704  (individually or in combination with VEDs  706 , VED  708 , and/or perhaps other computing devices (not shown)) determines that the system response volume for the set of VEDs  704 ,  706 , and  708  of media playback system should be 5 (e.g., on a scale of 1-10), if every VED set its system response volume to 5, then the effective volume for a system response played by all of the VEDs  704 ,  706 , and  708  would be greater than 5. But if each VED reduces its system response volume from 5 to 3.5, for example, based on the media playback system  700  having two other VEDs playing a system response, then the effective volume for a system response played by all of the VEDs  704 ,  706 , and  705  would be about 5, assuming each VED has set its system response volume to 3.5, for example. 
     Additionally or alternatively, in some embodiments, each of VEDs  704 ,  706 , and  708  determines whether a requirement exists to output a system response and, in response to that determination, determines and/or sets a new system response volume for one or more of the VEDs  704 ,  706 , and/or  708  (individually or as a group) based at least in part on one or more SPL measurements from one or more of VEDs  704 ,  706 , and/or  708 , or perhaps a collective SPL measurement from the set of VEDs  704 ,  706 , and  708 . For example, each of VEDs  704 ,  706  and  708  may make a separate SPL measurement. A group coordinator (i.e., one of VEDs  704 ,  706 , and  708 ) analyzes the individual SPL measurements and determines a collective SPL measurement for the listening area  702 . The group coordinator (e.g., VED  704 ) then determines a new system response volume based on the collective SPL measurement, configures itself with the determined system response volume based on the collective SPL measurement, and either (i) configures the other VEDs (e.g., VEDs  706  and  708 ) for the determined system response volume based on the collective SPL measurement or (ii) transmits the determined system response volume to the other VEDs (e.g., VEDs  706  and  708 ) so that the other VEDs can configure themselves for the determined system response volume. 
     Additionally or alternatively, in some embodiments, each of VEDs  704 ,  706 , and  708  determines whether a requirement exists to output a system response and, in response to that determination, determines and/or sets a new system response volume based at least in part on the type(s) of VEDs of the media playback system  700 . In operation, some VEDs may have more or fewer speakers than other VEDs and/or differently-configured speakers. For example, VEDs  704  and  706  may have 2-4 small-to-mid-sized speakers (e.g., about 2-8 inches in diameter) configured to output a full range of sound, whereas VED  708  may have 1 or 2 large speakers (e.g., 8-12 inches in diameter) configured to output lower frequency sounds. In this example configuration, if the system response volume setting for VEDs  704  and  706  may be different than the system response volume setting for VED  708  to account for the difference in speaker types and configurations between the different VEDs. 
     Additionally or alternatively, in some embodiments, VEDs  704 ,  706 , and/or  708  may calculate different system response volumes. This might occur if each VED is located in a separate room or in different areas of the same room that have different SPL measurements. One example might be when the user is having a conversation in close proximity to one or more of VEDs  704 ,  706 , and  708 . In these embodiments, a group coordinator (i.e., one of VEDs  704 ,  706 , or  708  that is tasked with compiling system response volume calculations) may communicate with the other VEDs in media playback system  700 , receive their respective system volume determinations, calculate an average or weighted master system response volume, and instructs the other networked devices to set their system response volumes to the master system response volume, or perhaps to individual system response volume settings so that, when the set of VEDs plays a system response, the effective system response volume for the set of VEDs will be at the determined master system response volume. For example, if the group coordinator (e.g., VED  704 ) determines that the master system response volume should be 5 (e.g., on a scale of 1-10), then the group coordinator may set the system response volume of itself to 4, set the system response volume of VED  706  to 4, and set the system response volume of VED  708  to 2, so that when the set of VEDs  704 ,  706 , and  708  plays a system response, the set of VEDs will play that system response at an effective master system response volume of 5, for example. 
     In some circumstances, when one of VEDs  704 ,  706 , and  708  output the system response while all of VEDs  702 ,  704 , and  706  are playing media content, the system response volume may be too quiet in listening area  702 . For example, in the context of decibel output, 10 speakers each playing media content at 50 dB is equivalent to one speaker playing media content at 60 dB. This additive effect may be even more pronounced if VEDs  704 ,  706 , and  708  are in close proximity to one another. For instance, if the group coordinator (e.g., VED  704 ) sets the audio playback volume to 5 for each VED, the effective audio playback volume (the effective volume when all of VEDs  704 ,  706 , and  708  are playing media content) may be 7 or 8 depending on the configuration of media playback system  700 . To overcome this problem, the group coordinator, after determining a system response volume, modifies the system response volume to take into account the number of VEDs in the configuration of media playback system  700 . For example, media playback system  700  may have a configuration including VEDs  704 ,  706 , and  708  arranged as shown in  FIG.  7   , with VED  704  assigned as the group coordinator. In this example, VED  704  may determine that there are three VEDs in the configuration (VEDs  704 ,  706 , and  708 ), and modify the system response volume to an appropriate value for a configuration with three VEDs. 
     In operation, VED  704  may modify the system response volume using a formula such as: L m =L u 10 log 10  N 
     In the above formula, L m  represents a modified system response volume, L u  represents an unmodified system response volume (i.e., the system response volume determined by the group coordinator), and N represents the number of VEDs present in the configuration. After the group coordinator (VED  704  in this example) calculates the modified system response volume, the group coordinator sets the system response volume according to the modified system response volume. 
     In some circumstances, when the group coordinator determines and sets a system response volume for VEDs  704 ,  706 , and  708  in listening area  702 , the system response volume may be too loud or too quiet for the user in listening area  702 . To overcome this potential problem, some embodiments may include the group coordinator limiting the system response volume of VEDs  704 ,  706 , and  708  based on predefined thresholds. These thresholds may represent the highest and/or lowest system response volumes acceptable to a user. For example, based on the characteristics of listening area  702 , the predefined thresholds may be system response volumes of  2  and  8  for the low threshold and high threshold, respectively. The user may set the predefined thresholds, or one or more of VEDs  704 ,  706 , and  708  may automatically set the predefined thresholds based on listening area  702 . In this example, if the group coordinator (individually or in combination with one or more other devices) determines the system response volume should be 9, the group coordinator may set the system response volume to 8 to avoid the system response being too loud. Likewise, if the group coordinator determines the system response volume should be 1, group coordinator may set the system response volume to 2 to avoid the system response being too quiet. 
     Additionally or alternatively, in some embodiments, the group coordinator limits the system response volume based on the audio playback volume of media playback system  700 . This may be advantageous because it avoids the system response from being too quiet or too loud when media playback system  700  is playing audio content. For example, if the group coordinator determines a system response volume of 3, but the audio playback volume of media playback system  700  is 6, the group coordinator may set the system response volume to 6 (e.g., the audio playback volume) to avoid the system response being too quiet and/or drowned out by the audio content. This feature is useful in scenarios where the media playback system is configured to “duck” (or temporarily reduce) the audio playback volume when one or more VEDs play back a system response. In another example, if the group coordinator determines a system response volume of 7, but the audio playback volume of media playback system  700  is 3, the group coordinator may set the system response volume to a predetermined maximum of  5  to avoid the system response being too loud compared to the audio playback. 
     In any of the above-described examples, one or more VEDs can send information to any other one or more VEDs, including but not limited to information for the purpose of determining and/or setting a system response volume. For example, a first VED can send to a second VED (and perhaps additional VEDs) any one or more of (i) its current audio playback volume level, (ii) its current system volume level, (iii) an SPL measurement, (iv) measurement data on which to base an SPL measurement, (v) configuration state information (e.g., standalone, stereo pair, synchrony group, bonded player, home theater, and so on), and/or (vi) any other information that might be used in connection with determining a system response volume. And in response to receiving any of that information from the first VED, the second VED can use that information to (i) determine and set its own system response volume and/or (ii) determine and/or set a system response volume for one or more additional VEDs. 
     In some of the above-described examples, one or more VEDs can additionally or alternatively send information to a cloud computing system to determine and/or set a system response volume for one or more (or all) VEDs in a particularly system. For example, a first VED can send to the cloud computing system any one or more of (i) its current audio playback volume level, (ii) its current system volume level, (iii) an SPL measurement, (iv) measurement data on which to base an SPL measurement, (v) configuration state information (e.g., standalone, stereo pair, synchrony group, bonded player, home theater, and so on), and/or (vi) any other information that might be used in connection with determining a system response volume. And in response to receiving any of that information from the first VED, the cloud computing system can use that information to determine and/or set a system response volume for the first VED and/or additional VEDs in a particular media playback system. 
     b. Example Audio Playback Volume Calculation 
     In some embodiments, when content is playing from media playback system  700  prior to a system response, VEDs  704 ,  706 , and/or  708  lower the audio playback volume a predetermined amount (e.g., 35% or −3 dB at each VED) just before playing a system response so that a user can better hear the system response over the audio content. For example, if VEDs  704 ,  706 , and/or  708  determine a requirement exists to output a system response while playing content, VEDs  704 ,  706 , and/or  708  may lower their respective audio playback volume by 35% to allow a user to better hear the system response. 
     One challenge for media playback systems with multiple VEDs is that if media content is playing from all of the VEDs, lowering the audio playback volume of each VED by only 35% or −3 dB may not cause the effective audio playback volume to fall below the calculated system response volume. The effective audio playback volume is the aggregated audio playback volume of all VEDs in media playback system  700 . As explained above, in the context of decibel output, 10 speakers each playing a system response at 50 dB is equivalent to one speaker playing a system response at 60 dB. For example, in the context of a volume setting on a 1-10 scale (other scales are possible, too), if VEDs  704 ,  706 , and  708  are playing media content at an audio playback volume of 4, the effective audio playback volume of media playback system  700  may be 5 or 6. 
     To overcome this problem, in some embodiments, VEDs  704 ,  706 , and/or  708  modify (e.g., lower) the audio playback volume (sometimes referred to as “ducking”) when outputting a system response. The amount VEDs  704 ,  706  and/or  708  modify the audio playback volume is based on the number of VEDs present in media playback system  700 . For example, media playback system  700  may have a configuration including VEDs  704 ,  706 , and  708  arranged as shown in  FIG.  7   , with VED  704  assigned as the group coordinator. In this example, VED  704  may determine (or otherwise know) that there are three VEDs in the configuration (VEDs  704 ,  706 , and  708 ), and modify the audio playback volume of each VED to an appropriate value for a configuration with three VEDs. 
     In operation, VED  704  may modify the audio playback volume using a formula such as: 
         L   m   =L   u −10 log 10    N  
 
     In the above formula, L m  represents a modified audio playback volume, L u  represents an unmodified audio playback volume (i.e., the audio playback volume of each of VEDs  704 ,  706 , and  708 ), and N represents the number of VEDs present in the configuration. After the group coordinator (VED  704  in this example) calculates the modified audio playback volume, the group coordinator sets the audio playback volume according to the modified audio playback volume. 
     Additionally or alternatively, in some embodiments, VEDs  704 ,  706 , and/or  708  modify the audio playback volume based on the configuration of media playback system  700 . In these embodiments, VEDs  704 ,  706 , and/or  708  have access to a reference table containing equal-loudness audio playback volume modifications for different configurations of media playback system  700  (i.e., modification of −3 dB for a stereo pair configuration). The reference table may be added to or updated via a network interface on a periodic or semi-periodic basis. VEDs  704 ,  706 , and/or  708  may have the reference table in its memory, or may access the reference table through a network interface (e.g., cloud-based server, LAN, etc.). For example, media playback system  700  may have VEDs  704  and  706  operating as a stereo pair. In this configuration, before outputting a system response, VEDs  704  and/or  706  may access the reference table and modify the audio playback volume by −2 to −4 dB (or some other table defined in the table). In another example, media playback system  700  may have VEDs  704  and  706  operating as a stereo pair, and have VED  708  operating as a subwoofer. In this configuration, before outputting a system response, VEDs  704 ,  706 , and/or  708  may access the reference table and modify the audio playback volume by −3 to −5 dB (or some other value defined in the table). 
     Additionally or alternatively, in some embodiments, VEDs  704 ,  706 , and/or  708  modify the audio playback volume based on a playback mode of media playback system  700  (e.g., ambient audio mode, full audio mode, and/or home theater mode). In these embodiments, VEDs  704 ,  706 , and/or  708  have access to a reference table containing additional equal-loudness audio playback volume modifications for different playback modes of media playback system  700 . For example, media playback system  700  may have VEDs  704 ,  706 ,  708 , and two additional VEDs (not shown) in a five speaker configuration, operating in home theater mode. In this configuration and playback mode, before outputting a system response, one or more of the VEDs may access the reference table and modify the audio playback volume for one or more VEDs by −6 to −8 dB based on volume adjustment values in the table. In another example, media playback system  700  may have VEDs  704 ,  706 ,  708 , and three additional VEDs (not shown) in a five speaker and one subwoofer configuration, operating in full audio mode. In this configuration, before outputting a system response, one or more of the VEDs may access the reference table and modify the audio playback volume of one or more VEDs by −7 to −9 dB, based on the adjustment values in the table. 
     In some embodiments, VEDs  704 ,  706 , and/or  708  modify the audio playback volume based on the loudness of the audio playback content when VED  704  is playing media content. This may be beneficial as it allows VED  704  to lower the audio playback volume during a system response to an appropriate volume relative to the volume of the audio content played back by VED  704 . For example, a user may be playing media content through VED  704  that features sporadic bursts of sound, followed by longer lulls. VED  704  may monitor the loudness of the audio playback content via microphone  710  to obtain an up-to-date loudness measurement at the time VED  704  outputs a system response. VED  704  then, while outputting a system response, lowers the audio playback volume an appropriate amount based on the loudness of the audio playback content. 
     c. Example Method 
     Method  800  in  FIG.  8    shows an embodiment of a method that can be implemented within an operating environment including or involving, for example, the media playback system  100  of  FIG.  1   , one or more playback devices  200  of  FIG.  2   , one or more control devices  300  of  FIG.  3   , the user interface of  FIG.  4   , the configuration shown in  FIG.  5   , the NMD shown in  FIG.  6   , and/or the media playback system  700  in  FIG.  7   . Method  800  may include one or more operations, functions, or actions as illustrated by one or more of blocks  802  and  804 . Although the blocks are illustrated in sequential order, these blocks may also be performed in parallel, and/or in a different order than those described herein. Also, the various blocks may be combined into fewer blocks, divided into additional blocks, and/or removed based upon the desired implementation. 
     In addition, for the method  800  and other processes and methods disclosed herein, the flowchart shows functionality and operation of one possible implementation of some 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 one or more processors 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 tangible, non-transitory 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 method  800  and other processes and methods disclosed herein, each block in  FIG.  8    may represent circuitry that is wired to perform the specific logical functions in the process. 
     Method  800  begins at block  802 , which includes a first networked device (or alternatively a computing device configured to control the first networked device), determining that a requirement exists to output a system response. In some embodiments, determining that a requirement exists to output a system response includes receiving a voice input via a first microphone associated with the first networked device. In some embodiments, determining that a requirement exists to output a system response comprises activating a system alert or notification. 
     Next, method  800  advances to block  802 , which includes, in response to determining that a requirement exists to output a system response, (i) setting a system response volume for a first speaker associated with the first networked device and (ii) outputting a system response at the set system response volume via the first speaker associated with the first networked device. 
     In some embodiments, the first networked device includes the first speaker and the first microphone. In some embodiments, the first networked device includes the first microphone and a second networked device comprises the first speaker. 
     In some embodiments, the first networked device includes the first speaker and a second networked device includes a second speaker. And in some embodiments, outputting the system response at the set system response volume via the first speaker associated with the first networked device includes outputting the system response at the set system response volume via the first speaker associated with the first networked device in synchrony with the second networked device outputting the system response at the set system response volume via the second speaker. 
     In some embodiments, setting the system response volume for the first speaker associated with the first networked device includes (i) obtaining a sound pressure level (SPL) measurement via one or more microphones associated with the first networked device (e.g., the first microphone) and (ii) setting the system response volume based at least in part on the SPL measurement. 
     In some embodiments, the SPL measurement is based on one or more of (i) an SPL measurement at an output of the first speaker, (ii) an SPL measurement at an output of a second speaker, (iii) an SPL measurement at a designated listening location in a room, (iv) an SPL measurement based on multiple SPL measurements from multiple microphones, (v) an SPL measurement of sound within a predefined frequency band. In some embodiments, the SPL measurement is a first type of SPL measurement when the first speaker is playing a first type of media content (e.g., playing music), and wherein the SPL measurement is a second type of SPL measurement when the first speaker is playing a second type of media content (e.g., playing audio associated with a television program or movie). 
     In some embodiments, setting the system response volume based on the obtained sound pressure level measurement includes setting the system response volume to between about 1 dB to about  6 dB higher than instantaneous and/or prior sound measurements (e.g., an SPL measurement and/or a measurement derived from an SPL measurement). 
     In some embodiments, setting the system response volume for the first speaker associated with the first networked device includes (i) accessing a previously-determined system response volume, and (ii) setting the system response volume to the previously-determined system response volume. 
     In some embodiments, the previously-determined system response volume was determined via steps including (i) detecting a trigger event, and (ii) in response to detecting the trigger event, determining the system response volume. In some embodiments, the trigger event includes, during media playback via the first speaker, changing a volume of the media playback. And in some embodiments, determining the system response volume for the first speaker associated with the first networked device includes (i) obtaining an SPL measurement via one or more microphones associated with the first networked device, and (ii) setting the system response volume based on the SPL measurement. 
     In some embodiments, changing a volume of the media playback includes at least one of (i) increasing the volume of the media playback, (ii) decreasing the volume of the media playback, (iii) muting the media playback, and (iv) unmuting the media playback. 
     In some embodiments, the trigger event comprises a reconfiguration of the first networked device. In some embodiments, the reconfiguration includes one of (i) configuring the first networked device from playing back media content as a standalone playback device to playing back media in synchrony with at least a second networked device and (ii) configuring the first networked device from playing back media in synchrony with at least a second networked device to playing back media as a standalone playback device. 
     In some embodiments, the trigger event includes expiration of a timeframe, and determining the system response volume for the first speaker associated with the first networked device comprises: (i) obtaining an SPL measurement via one or more microphones associated with the first networked device; and (ii) setting the system response volume based on the SPL measurement. 
     In some embodiments, the trigger event includes at least one of (i) detection of motion in an area of the first networked device by a motion detector associated with the first networked device and (ii) detecting a change in light in an area of the first networked device by a light detector associated with the first networked device. 
     In some embodiments, the system response volume is different than a volume of media playback by the first speaker associated with the first networked device. 
     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.