Patent Publication Number: US-2023141824-A1

Title: Compact home assistant having a controlled sound path

Description:
RELATED APPLICATIONS 
     This application claims priority to U.S. Provisional Patent Application No. 62/878,269, filed Jul. 24, 2019, titled “Compact Home Assistant Having Touch Sensitive Housing and Controlled Sound Path,” which is incorporated by reference herein in its entirety. 
     This application is related to U.S. patent application Ser. No. ______ (Attorney Docket No. 060963-7401-US), filed ______, titled_“Compact Home Assistant Having Touch Sensitive Housing,” which is incorporated by reference herein in its entirety. 
     This application is related to U.S. patent application Ser. No. 16/285,061, filed Feb. 25, 2019, entitled “Compact Speaker Device” and U.S. patent application Ser. No. 15/840,844, filed Dec. 13, 2017, entitled “Design for Compact Home Assistant with Combined Acoustic Waveguide and Heat Sink,” which claims priority to U.S. Provisional Patent Application No. 62/441,144, titled “Design for Compact Home Assistant with Combined Acoustic Waveguide and Heat Sink,” filed on Dec. 30, 2016. Each of the aforementioned applications is incorporated by reference herein in its entirety. 
    
    
     TECHNICAL FIELD 
     This application relates generally to computer technology, including but not limited to methods and systems for providing a voice activated electronic device that is used as a user interface in a smart home or media environment and has a touch sensitive housing and/or a controlled sound path accessible to a microphone. 
     BACKGROUND 
     Electronic devices integrated with microphones have been widely used to collect voice inputs from users and implement different voice-activated functions according to the voice inputs. In many operating environments it is more desirable and convenient (or even necessary) for a user to receive audible responses to their voice inputs instead of visual information shown on a display. This can be the case when an electronic device that is providing user assistance does not have a display screen (as is the case with the Google Home voice-activated speaker, which is powered by the Google Assistant) or when a user is not able to interact with a display screen (as is the case in many home environments, where a user is interacting with a voice-activated assistant device that is not nearby or where a user is focused on a particular task). For such operating environments, the electronic device is oftentimes provided with a speaker system that generates sound of sufficient clarity and volume to provide effective audible responses to user requests for assistance. Depending on the home/operating environment in which such electronic assistant devices are deployed, the assistant devices can also be designed with different appearances and/or form factors. 
     Particularly, it is helpful to calibrate available user interfaces of an electronic device to allow them to perform reliably and to provide supplemental user interface functions in addition to the microphones, the speaker system or simple light emitting diode (LED) indicators. These challenges are heightened when it is desired that the electronic device possess a relatively simple and compact form factor and can be made at a low cost. Thus, there is a need for compact designs for electronic voice-assistant devices that has multiple user interface options calibrated for reliable performance. 
     SUMMARY 
     Voice-activated electronic devices provide in a small form factor voice assistant capabilities that enable users to perform a range of activities through natural language voice commands, including one or more of: controlling local and remote electronic devices, issuing requests for services and information to remote servers, and/or sending media information to other electronic devices for consumption by the user or other users. In some implementations, voice-activated electronic devices include visual indicators, such as one or more full-color LEDs that are used to indicate the status of voice processing associated with a spoken user request. In some implementations, voice-activated electronic devices include one or more speakers that can be used to relay audible information to a user to provide an answer to a user request (such a search query or a request for a basketball score), provide a spoken status of a voice processing operation, play a musical selection, and/or read digest of current news or the current weather forecast. Given that voice inputs are convenient for users, some implementations allow a user to use voice inputs to control other electronic devices accessible to the user in addition to requesting Internet-based services and functions from remote servers and mobile devices. 
     Implementations of electronic devices are described herein that provide an eyes-free and hands-free voice interface to enable users to activate voice-activated functions on associated media player devices, issue information requests to remote servers, consume audible information or media, and/or control smart home or smart media devices coupled within the voice-activated electronic devices in a smart media or smart home environment. In various implementations described herein, a smart media environment includes one or more voice-activated electronic devices and multiple media display devices each disposed at a distinct location. In some implementations, these devices are coupled to a cast device (e.g., a set top box, a Google Chromecast™ device or a smart TV). These devices can be directed via voice requests issued to a voice-activated electronic device to play media items identified verbally by a user. These network-connected and voice-activated electronic devices are normally placed on surfaces at different locations of the smart home environment. As such, in some implementations, electronic voice assistant devices are configured to have a form factor and appearance that matches the overall smart home environment and/or can be integrated with multiple compatible surfaces and devices throughout the environment. 
     It is desirable to provide supplemental user interface functions to a voice-activated electronic device in addition to the microphones, the speaker system or simple LED indicators. Accordingly, in one aspect of the application, an electronic device is provided with one or more touch sensors. Specifically, the electronic device includes a housing, a printed circuit board (PCB) and the one or more touch sensors coupled between the housing and the PCB. The housing has an interior surface, an exterior surface opposing the interior surface, and one or more boss structures coupled on the interior surface. The PCB has a first surface and one or more receiving holes. The first surface faces the interior surface of the housing and includes a conductive area surrounding each receiving hole. Each touch sensor includes a sensing portion and a contact portion extending from the sensing portion. In each touch sensor, the sensing portion is placed in proximity to the interior surface of the housing, and is configured to detect a touch on a corresponding area of the exterior surface of the housing. The contact portion includes an opening aligned with a receiving hole of the PCB and a boss structure of the housing. The contact portion further includes a contact ring in which the opening is defined and a spring finger physically separated from the contact ring. Both the contact ring and the spring finger are configured to electrically contact the conductive area on the PCB. In some implementations, each touch sensor includes a capacitive sensing component. 
     In some implementations, the sensing portion of each touch sensor is placed in proximity to the interior surface of the housing, when a distance between a surface of the sensing portion and the interior surface of the housing is not greater than a predetermined distance threshold. 
     In some implementations, for a first touch sensor, the spring finger extends beyond a plane of the contact ring and towards the PCB, and a tip area of the spring finger is configured to be controlled by a stiffness of the spring finger to contact the conductive area of the PCB when the contact ring is electrically coupled to the conductive area of the PCB by a fastener coupled to the boss structure of the housing. Further, in some implementations, the tip area of the spring finger is configured to be controlled by the stiffness of the spring finger to contact the conductive area of the PCB when the fastener is loosened from the boss structure of the housing to cause the contact ring to be electrically decoupled from the conductive area of the PCB. 
     In some implementations, the sensing portion and contact portion of each touch sensor are made from a single sheet of conductive material and connected to each other at an intersection area. Further, in some implementations, the contact portion further includes an arm that connects the intersection area to the contact ring. The arm merges with the spring finger at the intersection area, and has a first stiffness and a first bending curvature with respect to the sensing portion. The first stiffness is distinct from a second stiffness of the spring finger, and the first bending curvature is distinct from a second bending curvature of the spring finger. Further, in some implementations, the second stiffness and second bending curvature of the spring finger are configured to create a force in a target force range when the contact portion is electrically coupled to the corresponding conductive area on the PCB via the contact ring and a tip area of the spring finger. In some situations, the spring finger is physically modified to result in the second stiffness of the spring finger. 
     In some implementations, the one or more touch sensors includes a first touch sensor configured to bridge the housing and the PCB, and the contact portion of the first touch sensor is mechanically bent from the sensing portion of the first touch sensor that is placed in proximity to the interior surface of the housing to reach the corresponding conductive area of the PCB. 
     In some implementations, for each touch sensor, a shank of the corresponding boss structure of the housing is configured to fit in both the opening of the touch sensor and the receiving hole of the PCB and mate to a fastener to couple the touch sensor between the housing and the PCB. Further, in some implementations, the receiving hole of the PCB is configured to have a diameter less than a diameter of a head of the fastener and greater than an outer diameter of the shank of the boss structure of the housing. 
     In some implementations, one of the receiving holes of the PCB has a first diameter for a first portion of a thickness of the PCB and a second diameter for a second portion of the thickness of the PCB. The first diameter is less than a diameter of a head of a fastener. A diameter of the boss structure of the housing is greater than the first diameter and less than the second diameter of the one of the receiving holes. When the fastener is fastened to the boss structure, the boss structure sits in the one of the receiving holes of the PCB and does not rise out of the one of the receiving holes. 
     In some implementations, the one or more touch sensors include three touch sensors that are disposed in proximity to a top area and two opposing peripheral (e.g., off-center) area of the housing, respectively. 
     In some implementations, the one or more touch sensors include a capacitive electrode that forms a capacitive touch sensor with a ground of the electronic device. The PCB includes a capacitive sense circuit that is electrically coupled to the capacitive electrode via the corresponding conductive area of the PCB. The capacitive sense circuit is configured to measure a capacitive sense signal of the capacitive touch sensor and determine a touch on the corresponding area of the exterior surface of the housing based on the measured capacitive sense signal. 
     In some implementations, the one or more touch sensors include a touch sensing electrode, and the sensing portion of the touch sensing electrode includes a cutout opening aligned with a light emitting diode (LED) mounted on the PCB. A light guide is disposed in the cutout opening, and is configured to receive light emitted by the LED and provide illumination via an LED opening on the housing to indicate a corresponding location on the exterior surface of the housing where the touch sensing electrode is located. Alternatively, in some implementations, the one or more touch sensors includes a touch sensing electrode. A light guide is disposed in proximity to the touch sensing electrode, and is configured to receive light emitted by a LED mounted on the PCB and provide illumination via an LED opening on the housing to indicate a corresponding location on the exterior surface of the housing to which the touch sensing electrode is adjacent. 
     In some implementations, the one or more touch sensors includes a touch sensing electrode, and the sensing portion of the touch sensing electrode includes a cutout opening aligned with one or more LEDs mounted on the PCB. One or more light guides are disposed in the cutout opening, and are configured to receive light emitted by the LEDs and provide illumination via LED openings on the housing to indicate a status of the electronic device according to a visual specification. 
     In some implementations, for each touch sensor, one or more of the conductive area on the PCB, the contact ring and a tip area of the spring finger are coated with a conductive material having a resistivity lower than a resistivity threshold to improve contact of the conductive area on the PCB with the contact ring or the tip area of the spring finger. 
     Further, it is helpful to calibrate available user interfaces of a voice-activated electronic device to allow them to perform reliably. In another aspect of the application, an electronic device is provided with a controlled sound path to a microphone that is concealed within an acoustically porous cover. The electronic device includes a housing having an exterior surface and an aperture, a microphone enclosed in the housing and having a diaphragm, and an acoustically porous cover at least partially covering the exterior surface of the housing. The diaphragm of the microphone faces the aperture and is configured to receive sound via the aperture. The acoustically porous cover conceals the aperture of the housing. The exterior surface of the housing includes a sealing area surrounding but not including the aperture, and the acoustically porous cover is affixed to the sealing area of the exterior surface via an adhesive. The adhesive covers the sealing area of the exterior and permeates a thickness of the acoustically porous cover above the sealing area, thereby enabling formation of the controlled sound path to the microphone by coupling of a microphone testing fixture to a region of the acoustically porous cover corresponding to the sealing area. In some implementations, the sealing area includes a circular ring area. 
     In some implementations, the aperture of the housing includes a first aperture. The electronic device further includes a PCB that is enclosed in the housing and has a first surface facing an interior surface of the housing, a second surface opposing the first surface, and a second aperture aligned with the first aperture of the housing. The microphone is coupled to the second surface of the PCB, and the diaphragm of the microphone faces the second aperture of the PCB directly and is configured to receive sound via the second aperture of the PCB. A sound control structure is coupled to the interior surface of the housing and the first surface of the PCB, and forms a sound channel connecting the first aperture of the housing and the second aperture of the PCB and extending to the controlled sound path that passes across the acoustically porous cover. Further, in some implementations, the sound control structure includes a hollow cylinder that is concentric with the sealing area on the exterior surface of the housing and the controlled sound path that passes across the acoustically porous cover. 
     Alternatively, in some implementations, the aperture of the housing includes a first aperture. The electronic device further includes a sound control structure coupled to the interior surface of the housing and the microphone. The sound control structure forms a sound channel connecting the first aperture of the housing and the microphone and extending to the controlled sound path that passes across the acoustically porous cover. Further, in some implementations, a PCB is enclosed in the housing and has a first surface facing an interior surface of the housing. The microphone is mounted on the first surface of the PCB, and the diaphragm of the microphone faces the first aperture of the housing directly. 
     In some implementations, the acoustically porous cover is flexible and substantially transparent to audible sound. 
     In some implementations, the controlled sound path in the acoustically porous cover is configured to match a dimension of the microphone testing fixture and guide sound generated by the microphone towards the microphone testing fixture. When the microphone testing fixture is coupled to the controlled sound path, a portion of sound generated by the microphone testing fixture is collected by the microphone. The portion of sound is greater than a predetermined portion of the sound generated by the microphone testing fixture. 
     In some implementations, the adhesive is not visible from an exterior surface of the acoustically porous cover, so that the electronic device keeps a clean look. 
     In some implementations, the adhesive is configured to be applied on the sealing area of the housing and covered by the acoustically porous cover, and the adhesive permeates the thickness of the acoustically porous cover and is hardened in response to heat treatment under a predetermined condition. 
     In some implementations, the adhesive permeates at least a predetermined portion of an entire thickness of the acoustically porous cover, and the microphone testing fixture is configured to be pressed onto the region of the acoustically porous cover to compress microcavities in part of the entire thickness of the acoustically porous cover that is not permeated with the adhesive, thereby enabling formation of the controlled sound path of the microphone. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a better understanding of the various described implementations, reference should be made to the Description of Implementations below, in conjunction with the following drawings in which like reference numerals refer to corresponding parts throughout the figures. 
         FIG.  1    illustrates an example operating environment of one or more voice-activated electronic devices in accordance with some implementations. 
         FIG.  2    is a block diagram illustrating an example voice-activated electronic device that is applied as a voice interface to collect user voice commands in an operating environment in accordance with some implementations. 
         FIGS.  3 A and  3 B  are a front view and a rear view of an example voice-activated electronic device in accordance with some implementations, respectively. 
         FIG.  4    is a cross sectional view of an example voice-activated electronic device showing a dual purpose waveguide/heatsink and a speaker assembly in accordance with some implementations. 
         FIG.  5    is an exploded view of an example voice-activated electronic device in accordance with some implementations. 
         FIG.  6    illustrates an upper interior surface of an example voice-activated electronic device in accordance with some implementations. 
         FIGS.  7 A and  7 B  illustrate an example touch sensor disposed in proximity to an upper interior surface of a voice-activated electronic device in accordance with some implementations.  FIG.  7 C  is an enlarged view of a contact portion of an example touch sensor in accordance with some implementations. 
         FIGS.  7 D- 1  and  7 D- 2    are example cross sections of a voice-activated electronic device including a touch sensor in accordance with some implementations. 
         FIG.  7 E  is another example cross sections of a voice-activated electronic device including a touch sensor in accordance with some implementations. 
         FIG.  7 F  illustrates an example PCB having a receiving hole and a conductive area in accordance with some implementations. 
         FIG.  7 G  is an example stress distribution diagram of an example touch sensor that is assembled in a voice-activated electronic device shown in  FIGS.  7 D- 1  and  7 E  in accordance with some implementations. 
         FIG.  8 A  illustrates another example touch sensor disposed in proximity to an upper interior surface of a voice-activated electronic device in accordance with some implementations.  FIG.  8 B  is a cross sectional view of a voice-activated electronic device including a touch sensor shown in  FIG.  8 A  in accordance with some implementations.  FIG.  8 C  is an example stress distribution diagram of an example touch sensor that is assembled in a voice-activated electronic device shown in  FIG.  8 B  in accordance with some implementations. 
         FIGS.  9 A and  9 B  are a cross sectional view and a top view of a region of a voice-activated electronic device in which a microphone is disposed in accordance with some implementations, respectively. 
         FIGS.  10 A- 10 C  are enlarged cross sectional views of example microphone aperture areas of a voice-activated electronic device in accordance with some implementations. 
     
    
    
     Like reference numerals refer to corresponding parts throughout the several views of the drawings. 
     DESCRIPTION OF IMPLEMENTATIONS 
     Electronic devices are conveniently used as voice interfaces to receive voice inputs from users and initiate voice-activated functions, and thereby offer eyes-free and hands-free solutions for enabling simple and productive user interaction with both existing and emerging technology. Specifically, the voice inputs received at an electronic device with voice activated features can carry instructions and information even if a user&#39;s line of sight is obscured and his or her hands are full. To enable a hands-free and eyes-free experience, a voice-activated electronic device in accordance with the present invention “listens” to the ambient (i.e., constantly processes audio signals collected from the ambient) constantly or only when triggered to do so (e.g., via user utterance of a “hot word” to trigger operation of the electronic device”). On the other hand, user identities are linked with a user&#39;s voice and a language used by the user. To protect the user identities, these voice-activated electronic devices are normally used in non-public places that are protected, controlled and intimate spaces (e.g., home and car). 
     In accordance with various implementations of this application, a network-connected and voice-activated electronic device is a compact device that includes one or more microphones, one or more speakers and a plurality of electronic components, including one or more of: microprocessors, memory, support chips, wireless receivers and transmitters, antennas, power supply circuitry, one or more cameras, power and/or data connectors, etc., some of which are mounted on one or more printed circuit boards. In some implementations, the microphones and corresponding apertures are enclosed in a housing of the electronic device and concealed under an acoustically porous cover of the electronic device. The microphones must be calibrated with a microphone testing fixture to verify audio performances of the microphones (e.g., a sound leakage level at a microphone, an attenuation between an open state and a sealed state of a microphone), thereby guaranteeing that the microphones can reliably detect hot words in a smart home environment. An exterior surface of the housing includes a sealing area surrounding but not including each microphone aperture, and the acoustically porous cover is affixed to the sealing area of the exterior surface via an adhesive. The adhesive covers the sealing area on the exterior surface of the housing and permeates a thickness of the acoustically porous cover above the sealing area, thereby enabling formation of a controlled sound path to the microphone by coupling of the microphone testing fixture to a region of the acoustically porous cover corresponding to the sealing area. 
     In some implementations, a network-connected and voice-activated electronic device is capable of detecting touch events occurring on its exterior surface (particularly, on one or more selected areas on the exterior surface). The electronic device includes one or more touch sensors disposed inside the housing and in proximity to an interior surface of the housing corresponding to the selected areas of the exterior surface where the touch events are detected. Each touch sensor includes a sensing portion placed in proximity to the interior surface of the housing, and a contact portion extending from the sensing portion to a PCB where a plurality of electronic components (including a touch sensing circuit) are mounted. To enhance its electrical contact with the PCB, the contact portion relies on both a contact ring and a spring finger that are physically separate from each other to form electrical contacts with the PCB. Specifically, the contact portion includes an opening that is defined by the contact ring and is aligned with a receiving hole of the PCB and a boss structure of the housing. While the contact ring is electrically coupled to a conductive area of the PCB surrounding the receiving hole, the spring finger also comes into contact with the conductive area of the PCB under the influence of a mechanical stiffness provided by its own mechanical structure. Under some circumstances, the contact ring of the contact portion is slightly detached from the conductive area, thereby compromising the quality of its electrical contact with the conductive area of the PCB. The mechanical stiffness provided by the mechanical structure of the spring finger can continue to hold the spring finger down onto the contact area of the PCB and provide a low resistance electrical path to access the PCB. 
     Reference will now be made in detail to implementations, examples of which are illustrated in the accompanying drawings. In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the various described implementations. However, it will be apparent to one of ordinary skill in the art that the various described implementations may be practiced without these specific details. In other instances, well-known methods, procedures, components, circuits, and networks have not been described in detail so as not to unnecessarily obscure aspects of the implementations. 
     Voice Assistant Operating Environment 
       FIG.  1    is an example operating environment  100  in accordance with some implementations. Operating environment  100  includes one or more voice-activated electronic devices  104  (e.g., voice-activated electronic devices  104 - 1  thru  104 -N, hereinafter “voice-activated device(s)”). The one or more voice-activated devices  104  may be located in one or more locations (e.g., all in a room or space of a structure, spread out throughout multiple spaces within a structure or throughout multiple structures (e.g., one in a house and one in the user&#39;s car)). 
     The environment  100  also includes one or more controllable electronic devices  106  (e.g., electronic device  106 - 1  thru  106 -N, hereinafter “controllable device(s)”). Examples of controllable devices  106  include media devices (smart televisions, speaker systems, wireless speakers, set-top boxes, media streaming devices, cast devices), and smart home devices (e.g., smart camera, smart thermostat, smart light, smart hazard detector, smart door lock). 
     The voice-activated devices  104  and the controllable devices  106  are communicatively coupled, through communication networks  110 , to a voice assistant service  140  (e.g., to a voice assistance server system  112  of the voice assistant service  140 ). In some implementations, one or more of the voice-activated devices  104  and the controllable devices  106  are communicatively coupled to a local network  108 , which is communicatively coupled to the communication networks  110 ; the voice-activated device(s)  104  and/or the controllable device(s)  106  are communicatively coupled to communication network(s)  110  (and, through the communication networks  110 , to the voice assistance server system  112 ) via the local network  108 . In some implementations, the local network  108  is a local area network implemented at a network interface (e.g., a router). The voice-activated devices  104  and the controllable devices  106  that are communicatively coupled to the local network  108  may also communicate with each other through the local network  108 . 
     Optionally, one or more of the voice-activated devices  104  are communicatively coupled to the communication networks  110  and are not on the local network  108 . For example, these voice-activated devices are not on the Wi-Fi network corresponding to the local network  108  but are connected to the communication networks  110  through a cellular connection. In some implementations, communication between voice-activated devices  104  that are on the local network  108  and voice-activated devices  104  that are not on the local network  108  are done through the voice assistance server system  112 . The voice-activated devices  104  (whether on the local network  108  or on the network  110 ) are registered in a device registry  118  of the voice assistant service  140  and thus known to the voice assistance server system  112 . Similarly, the voice-activated devices  104  that are not on the local network  108  may communicate with controllable devices  106  through the voice assistant server system  112 . The controllable devices  106  (whether on the local network  108  or on the network  110 ) are also registered in the device registry  118 . In some implementations, communications between the voice-activated devices  104  and the controllable devices  106  go through the voice assistance server system  112 . 
     In some implementations, the environment  100  also includes one or more content hosts  114 . A content host  114  may be a remote content source from which content is streamed or otherwise obtained in accordance with a request included in a user voice input or command. A content host  114  may be an information source from which the voice assistance server system  112  retrieves information in accordance with a user voice request. 
     In some implementations, controllable devices  106  are capable of receiving commands or requests to perform specified operations or to transition to specified states (e.g., from a voice-activated device  104  and/or the voice assistance server system  112 ) and to perform the operations or transition states in accordance with the received commands or requests. 
     In some implementations, one or more of the controllable devices  106  are media devices that are disposed in the operating environment  100  to provide to one or more users media content, news and/or other information. In some implementations, the content provided by the media devices is stored at a local content source, streamed from a remote content source (e.g., content host(s)  114 ), or generated locally (e.g., through a local text to voice processor that reads a customized news briefing, emails, texts, a local weather report, etc. to one or more occupants of the operating environment  100 ). In some implementations, the media devices include media output devices that directly output the media content to an audience (e.g., one or more users), and cast devices that are networked to stream media content to the media output devices. Examples of the media output devices include, but are not limited to television (TV) display devices and music players. Examples of the cast devices include, but are not limited to, set-top boxes (STBs), DVD players, TV boxes, and media streaming devices, such as Google&#39;s Chromecast™ media streaming device. 
     In some implementations, a controllable device  106  is also a voice-activated device  104 . In some implementations, a voice-activated device  104  is also a controllable device  106 . For example, a controllable device  106  may include a voice interface to the voice assistance service  140  (e.g., a media device that can also receive, process, and respond to user voice inputs). As another example, a voice-activated device  104  may also perform particular operations and transition to particular states in accordance with requests or commands in voice inputs (e.g., a voice interface device that can also play streaming music). 
     In some implementations, the voice-activated devices  104  and the controllable deices  106  are associated with a user having a respective account, or with multiple users (e.g., a group of related users, such as users in a family or in an organization; more generally, a primary user and one or more authorized additional users) having respective user accounts, in a user domain. A user may make voice inputs or voice commands to the voice-activated device  104 . The voice-activated device  104  receives these voice inputs from the user (e.g., user  102 ), and the voice-activated device  104  and/or the voice assistance server system  112  proceeds to determine a request in the voice input and generate a response to the request. 
     In some implementations, the request included in a voice input is a command or request to a controllable device  106  to perform an operation (e.g., play media, pause media, fast forward or rewind media, change volume, change screen brightness, change light brightness) or transition to another state (e.g., change the mode of operation, turn on or off, go into sleep mode or wake from sleep mode). 
     In some implementations, a voice-activated electronic device  104  responds to voice inputs by: generating and providing a spoken response to a voice command (e.g., speaking the current time in response to the question, “what time is it?”); streaming media content requested by a user (e.g., “play a Beach Boys song”); reading a news story or a daily news briefing prepared for the user; playing a media item stored on the personal assistant device or on the local network; changing a state or operating one or more other connected devices within the operating environment  100  (e.g., turning lights, appliances or media devices on/off, locking/unlocking a lock, opening windows, etc.); or issuing a corresponding request to a server via a network  110 . 
     In some implementations, the one or more voice-activated devices  104  are disposed in the operating environment  100  to collect audio inputs for initiating various functions (e.g., media play functions of the media devices). In some implementations, these voice-activated devices  104  (e.g., devices  104 - 1  thru  104 -N) are disposed in proximity to a controllable device  104  (e.g., a media device), for example, in the same room with the cast devices and the media output devices. Alternatively, in some implementations, a voice-activated device  104  is disposed in a structure having one or more smart home devices but not any media device. Alternatively, in some implementations, a voice-activated device  104  is disposed in a structure having one or more smart home devices and one or more media devices. Alternatively, in some implementations, a voice-activated device  104  is disposed in a location having no networked electronic device. Further, in some implementations, a room or space in the structure may have multiple voice-activated devices  104 . 
     In some implementations, the voice-activated device  104  includes at least one or more microphones, a speaker, a processor and memory storing at least one program for execution by the processor. The speaker is configured to allow the voice-activated device  104  to deliver voice messages and other audio (e.g., audible tones) to a location where the voice-activated device  104  is located in the operating environment  100 , thereby broadcasting music, reporting a state of audio input processing, having a conversation with or giving instructions to a user of the voice-activated device  104 . As an alternative to the voice messages, visual signals could also be used to provide feedback to the user of the voice-activated device  104  concerning the state of audio input processing. When the voice-activated device  104  is a mobile device (e.g., a mobile phone or a tablet computer), its display screen is configured to display a notification concerning the state of audio input processing. 
     In some implementations, the voice-activated device  104  is a voice interface device that is network-connected to provide voice recognition functions with the aid of a voice assistance server system  112 . For example, the voice-activated device  104  includes a smart speaker that provides music to a user and allows eyes-free and hands-free access to a voice assistant service (e.g., Google Assistant). Optionally, the voice-activated device  104  is one of a desktop or laptop computer, a tablet, a mobile phone that includes a microphone, a cast device that includes a microphone and optionally a speaker, an audio system (e.g., a stereo system, a speaker system, a portable speaker) that includes a microphone and a speaker, a television that includes a microphone and a speaker, and a user interface system in an automobile that includes a microphone and a speaker and optionally a display. Optionally, the voice-activated device  104  is a simple and low cost voice interface device. Generally, the voice-activated device  104  may be any device that is capable of network connection and that includes a microphone, a speaker, and programs, modules, and data for interacting with voice assistant service. Given simplicity and low cost of the voice-activated device  104 , the voice-activated device  104  includes an array of light emitting diodes (LEDs) rather than a full display screen, and displays a visual pattern on the LEDs to indicate the state of audio input processing. In some implementations, the LEDs are full color LEDs, and the colors of the LEDs may be employed as a part of the visual pattern to be displayed on the LEDs. Multiple examples of using LEDs to display visual patterns in order to convey information or device status are described in U.S. Provisional Patent Application No. 62/336,566, entitled “LED Design Language for Visual Affordance of Voice User Interfaces,” filed May 13, 2016, which is incorporated by reference in its entirety. In some implementations, visual patterns indicating the state of voice processing operations are displayed using characteristic images shown on conventional displays associated with voice-activated devices that are performing the voice processing operations. 
     In some implementations, LEDs or other visual displays are used to convey a collective voice processing state of multiple participating electronic devices. For example, in an operating environment where there are multiple voice processing or voice interface devices (e.g., multiple electronic devices  400  as shown in  FIG.  4 A  of the &#39;566 application; multiple voice-activated devices  104 ), groups of color LEDs (e.g., LEDs  404  as shown in  FIG.  4 A  of the &#39;566 application) associated with respective electronic devices can be used to convey which of the electronic devices is listening to a user, and which of the listening devices is the leader (where the “leader” device generally takes the lead in responding to a spoken request issued by the user). 
     More generally, the &#39;566 application describes (e.g., see paras. [0087]-[0100]) a “LED Design Language” for indicating visually using a collection of LEDs a variety of voice processing states of an electronic device, such as a “Hot word detection state and listening state,” a “Thinking mode or working mode,” and a “Responding mode or speaking mode.” In some implementations, unique states of voice processing operations described herein are represented using a group of LEDs in accordance with one or more aspects of the “LED Design Language” of the &#39;566 application. These visual indicators can also be combined with one or more audible indicators generated by electronic devices that are performing voice processing operations. The resulting audio and/or visual indicators will enable users in a voice-interactive environment to understand the state of various voice processing electronic devices in the environment and to effectively interact with those devices in a natural, intuitive manner. 
     In some implementations, when voice inputs to the voice-activated device  104  are used to control the media output devices via the cast devices, the voice-activated device  104  effectively enables a new level of control of cast-enabled media devices. In a specific example, the voice-activated device  104  includes a casual enjoyment speaker with far-field voice access and functions as a voice interface device for the voice assistant service. The voice-activated device  104  could be disposed in any area in the operating environment  100 . When multiple voice-activated devices  104  are distributed in multiple rooms, they become cast audio receivers that are synchronized to provide voice inputs from these rooms. 
     Specifically, in some implementations, the voice-activated device  104  includes a Wi-Fi speaker with a microphone that is connected to a voice-activated voice assistant service (e.g., Google Assistant). A user can issue a media play request via the microphone of voice-activated device  104 , and ask the voice assistant service to play media content on the voice-activated device  104  itself or on another connected media output device. For example, the user can issue a media play request by saying to the Wi-Fi speaker “OK Google, play cat videos on my Living room TV.” The voice assistant service then fulfils the media play request by playing the requested media content on the requested device using a default or designated media application. 
     In some implementations, a user can issue a voice request, via the microphone of the voice-activated device  104 , concerning media content that has already been played or is being played on a display device (e.g., the user can ask for information about the media content, buy the media content through an online store, or compose and issue a social post about the media content). 
     In some implementations, a user may want to take a current media session with them as they move through the house and can request such a service from one or more of the voice-activated devices  104 . This requires the voice assistant service  140  to transfer the current media session from a first cast device to a second cast device that is not directly connected to the first cast device or has no knowledge of the existence of the first cast device. Subsequent to the media content transfer, a second output device coupled to the second cast device continues to play the media content previously a first output device coupled to the first cast device from the exact point within a music track or a video clip where play of the media content was forgone on the first output device. In some implementations, the voice-activated device  104  that receives the request to transfer the media session can satisfy the request. In some implementations, the voice-activated device  104  that receives the request to transfer the media session relays the request to another device or system (e.g., voice assistance server system  112 ) for handling. 
     Further, in some implementations, a user may issue, via the microphone of voice-activated device  104 , a request for information or for performance of an action or operation. The information requested may be personal (e.g., the user&#39;s emails, the user&#39;s calendar events, the user&#39;s flight information, etc.), non-personal (e.g., sports scores, news stories, etc.) or somewhere in between (e.g., scores for teams or sports preferred by the user, news stories from the user&#39;s preferred sources, etc.). The requested information or action/operation may involve access to personal information (e.g., purchasing a digital media item with payment information provided by the user, purchasing a physical good). The voice-activated device  104  responds to the request with voice message responses to the user, where the response may include, for example, requests for additional information to fulfill the request, confirmation that the request has been fulfilled, notice that the request cannot be fulfilled, and so forth. 
     In some implementations, in addition to the voice-activated devices  104  and the media devices amongst the controllable devices  106 , the operating environment  100  may also include one or more smart home devices amongst the controllable devices  106 . The integrated smart home devices include intelligent, multi-sensing, network-connected devices that integrate seamlessly with each other in a smart home network and/or with a central server or a cloud-computing system to provide a variety of useful smart home functions. In some implementations, a smart home device is disposed at the same location of the operating environment  100  as a cast device and/or an output device, and therefore, is located in proximity to or with a known distance with respect to the cast device and the output device. 
     The smart home devices in the operating environment  100  may include, but are not limited to, one or more intelligent, multi-sensing, network-connected thermostats, one or more intelligent, network-connected, multi-sensing hazard detectors, one or more intelligent, multi-sensing, network-connected entryway interface devices and (hereinafter referred to as “smart doorbells” and “smart door locks”), one or more intelligent, multi-sensing, network-connected alarm systems, one or more intelligent, multi-sensing, network-connected camera systems, one or more intelligent, multi-sensing, network-connected wall switches, one or more intelligent, multi-sensing, network-connected power sockets, and one or more intelligent, multi-sensing, network-connected lights. In some implementations, the smart home devices in the operating environment  100  of  FIG.  1    includes a plurality of intelligent, multi-sensing, network-connected appliances (hereinafter referred to as “smart appliances”), such as refrigerators, stoves, ovens, televisions, washers, dryers, lights, stereos, intercom systems, garage-door openers, floor fans, ceiling fans, wall air conditioners, pool heaters, irrigation systems, security systems, space heaters, window AC units, motorized duct vents, and so forth. In some implementations, any one of these smart home device types can be outfitted with microphones and one or more voice processing capabilities as described herein so as to in whole or in part respond to voice requests from an occupant or user. 
     In some implementations, each of the controllable devices  104  and the voice-activated devices  104  is capable of data communications and information sharing with other controllable devices  106 , voice-activated electronic devices  104 , a central server or cloud-computing system, and/or other devices (e.g., a client device) that are network-connected. Data communications may be carried out using any of a variety of custom or standard wireless protocols (e.g., IEEE 802.15.4, Wi-Fi, ZigBee, 6LoWPAN, Thread, Z-Wave, Bluetooth Smart, ISA100.11a, WirelessHART, MiWi, etc.) and/or any of a variety of custom or standard wired protocols (e.g., Ethernet, HomePlug, etc.), or any other suitable communication protocol, including communication protocols not yet developed as of the filing date of this document. 
     Through the communication networks  110  (e.g., the Internet), the controllable devices  106  and the voice-activated devices  104  may communicate with a server system (also called a central server system and/or a cloud-computing system herein). Optionally, the server system may be associated with a manufacturer, support entity, or service provider associated with the controllable devices and the media content displayed to the user. Accordingly, the server system includes the voice assistance server  112  that processes audio inputs collected by voice-activated devices  104 , one or more content hosts  114  that provide the displayed media content, optionally a cloud cast service server creating a virtual user domain based on distributed device terminals, and the device registry  118  that keeps a record of the distributed device terminals in the virtual user environment. Examples of the distributed device terminals include, but are not limited to the controllable devices  106 , the voice-activated devices  104 , and the media output devices. In some implementations, these distributed device terminals are linked to a user account (e.g., a Google user account) in the virtual user domain. It should be appreciated that processing of audio inputs collected by voice-activated devices  104  can be performed locally at a voice-activated device  104 , at a voice assistance server  112 , at another smart home device (e.g., a hub device) or at some combination of all or subset of the above. 
     It will be appreciated that in some implementations the voice-activated device(s)  104  also function in an environment without smart home devices. For example, a voice-activated device  104  can, even in the absence of smart home devices, respond to user requests for information or performance of an action, and/or to initiate or control various media play functions. A voice-activated device  104  can also function in a wide range of environments, including, without limitation, a vehicle, a ship, a business, or a manufacturing environment. 
     In some implementations, a voice-activated device  104  is “awakened” (e.g., to activate an interface for the voice assistant service on the voice-activated device  104 , to put the voice-activated device  104  into a state where the voice-activated device  104  is ready to receive voice requests to the voice assistant service) by a voice input that includes a hot word (also called a “wake word”). In some implementations, the voice-activated device  104  requires awakening if the voice-activated device  104  has been idle with respect to receipt of voice inputs for at least a predefined amount of time (e.g., 5 minutes); the predefined amount of time corresponds to an amount of idle time allowed before a voice interface session or conversation times out. The hot word may be a word or phrase, and may be a predefined default and/or may be customized by a user (e.g., a user may set a nickname for a particular voice-activated device  104  as the device&#39;s hot word). In some implementations, there may be multiple hot words that can awaken a voice-activated device  104 . A user may speak the hot word, wait for an acknowledgement response from the voice-activated device  104  (e.g., the voice-activated device  104  outputs a greeting), and them make a first voice request. Alternatively, the user may combine the hot word and the first voice request in one voice input (e.g., the voice input includes the hot word followed by the voice request). 
     In some implementations, a voice-activated device  104  interacts with a controllable device  106  (e.g., a media device, a smart home device), a client device or a server system of an operating environment  100  in accordance with some implementations. The voice-activated device  104  is configured to receive audio inputs from an environment in proximity to the voice-activated device  104 . Optionally, the voice-activated device  104  stores the audio inputs and at least partially processes the audio inputs locally. Optionally, the voice-activated device  104  transmits the received audio inputs or the partially processed audio inputs to a voice assistance server system  112  via the communication networks  110  for further processing. The voice-activated device  104  or the voice assistance server system  112  determines if there is a request in the audio input and what the request is, determines and generates a response to the request, and transmits the request to one or more controllable device(s)  106 . The controllable device(s)  106  receiving the response is configured to perform operations or change states in accordance with the response. For example, a media device is configured to obtain media content or Internet content from one or more content hosts  114  for display on an output device coupled to the media device, in accordance with a response to a request in the audio input. 
     In some implementations, the controllable device(s)  106  and the voice-activated device(s)  104  are linked to each other in a user domain, and more specifically, associated with each other via a user account in the user domain. Information on the controllable device  106  (whether on the local network  108  or on the network  110 ) and the voice-activated device  104  (whether on the local network  108  or on the network  110 ) are stored in the device registry  118  in association with the user account. In some implementations, there is a device registry for controllable devices  106  and a device registry for voice-activated devices  104 . The controllable devices registry may reference devices in the voice-activated devices registry that are associated in the user domain, and vice versa. 
     In some implementations, one or more of the voice-activated devices  104  (and one or more cast devices) and one or more of the controllable devices  106  are commissioned to the voice assistant service  140  via a client device  103 . In some implementations, the voice-activated device  104  does not include any display screen, and relies on the client device  103  to provide a user interface during a commissioning process, and similarly for a controllable device  106  as well. Specifically, the client device  103  is installed with an application that enables a user interface to facilitate commissioning of a new voice-activated device  104  and/or a controllable device  106  disposed in proximity to the client device. A user may send a request on the user interface of the client device  103  to initiate a commissioning process for the new electronic device  104 / 106  that needs to be commissioned. After receiving the commissioning request, the client device  103  establishes a short range communication link with the new electronic device  104 / 103  that needs to be commissioned. Optionally, the short range communication link is established based near field communication (NFC), Bluetooth, Bluetooth Low Energy (BLE) and the like. The client device  103  then conveys wireless configuration data associated with a wireless local area network (WLAN) (e.g., local network  108 ) to the new or electronic device  104 / 106 . The wireless configuration data includes at least a WLAN security code (i.e., service set identifier (SSID) password), and optionally includes a SSID, an Internet protocol (IP) address, proxy configuration and gateway configuration. After receiving the wireless configuration data via the short range communication link, the new electronic device  104 / 106  decodes and recovers the wireless configuration data, and joins the WLAN based on the wireless configuration data. 
     In some implementations, additional user domain information is entered on the user interface displayed on the client device  103 , and used to link the new electronic device  104 / 106  to an account in a user domain. Optionally, the additional user domain information is conveyed to the new electronic device  104 / 106  in conjunction with the wireless communication data via the short range communication link. Optionally, the additional user domain information is conveyed to the new electronic device  104 / 106  via the WLAN after the new device has joined the WLAN. 
     Once the electronic device  104 / 106  has been commissioned into the user domain, other devices and their associated activities may be controlled via multiple control paths. In accordance with one control path, an application installed on the client device  103  is used to control the other device and its associated activities (e.g., media play activities). Alternatively, in accordance with another control path, the electronic device  104 / 106  is used to enable eyes-free and hands-free control of the other device and its associated activities. 
     In some implementations, voice-activated devices  104  and controllable devices  106  may be assigned nicknames by a user (e.g., by the primary user with whom the devices are associated in the user domain). For example, a speaker device in the living room may be assigned a nickname “living room speaker.” In this way, the user may more easily refer to a device in a voice input by speaking the device&#39;s nickname. In some implementations, the device nicknames and mappings to corresponding devices are stored at a voice-activated device  104  (which would store the nicknames of just the devices associated with the same user as the voice-activated device) and/or the voice assistance server system  112  (which would store deice nicknames of devices associated with different users). For example, the voice assistance server system  112  stores many device nicknames and mappings across different devices and users, and voice-activated devices  104  associated with a particular user download nicknames and mappings for devices associated with the particular user for local storage. 
     In some implementations, a user may group one or more of the voice-activated devices  104  and/or controllable devices  106  into a group of devices created by the user. The group may be given a name, and the group of devices may be referred by the group name, similarly to referring to individual devices by nickname. Similarly to device nicknames, device groups and group names may be stored at a voice-activated device  104  and/or the voice assistance server system  112 . 
     A voice input from the user may explicitly specify a target controllable device  106  or a target group of devices for the request in the voice input. For example, a user may utter a voice input “play classical music on the living room speaker.” The target device in the voice input is “living room speaker”; the request in the voice input is a request to have the “living room speaker” play classical music. As another example, a user may utter a voice input “play classical music on the house speakers,” where “house speakers” is a name of a group of devices. The target device group in the voice input is “house speakers”; the request in the voice input is a request to have the devices in the group “house speakers” play classical music. 
     A voice input from the user may not have an explicit specification of a target device or device group; a reference to a target device or device group by name is absent in the voice input. For example, following on the example voice input “play classical music on the living room speaker” above, the user may utter a subsequent voice input “pause.” The voice input does not include a target device specification for the request for a pause operation. In some implementations, the target device specification in the voice input may be ambiguous. For example, the user may have uttered the device name incompletely. In some implementations, a target device or device group may be assigned to the voice input where an explicit target device specification is absent or the target device specification is ambiguous, as described below. 
     In some implementations, when a voice-activated device  104  receives a voice input with an explicit specification of a target device or device group, the voice-activated device  104  establishes a focus session with respect to the specified target device or device group. In some implementations, the voice-activated device  104  stores, for the focus session, a session start time (e.g., the timestamp of the voice input based on which the focus session was started) and, as the in-focus device for the focus session, the specified target device or device group. In some implementations, the voice-activated device  104  also logs subsequent voice inputs in the focus session. The voice-activated device  104  logs at least the most recent voice input in the focus session and optionally logs and retains preceding voice inputs within the focus session as well. In some implementations, the voice assistance server system  112  establishes the focus session. In some implementations, the focus session may be ended by a voice input explicitly specifying a different target device or device group. 
     While a focus session with respect to a device is active and the voice-activated device receives a voice input, the voice-activated device  104  makes one or more determinations with respect to the voice input. In some implementations, the determinations include: whether the voice inputs includes an explicit target device specification, whether the request in the voice input is one that can be fulfilled by the in-focus device, and a time of the voice input compared to the time of the last voice input in the focus session and/or the session start time. If the voice input does not include an explicit target device specification, includes a request that can be fulfilled by the in-focus device, and satisfies predefined time criteria with respect to the time of the last voice input in the focus session and/or the session start time, then the in-focus device is assigned as the target device for the voice input. Further details regarding focus sessions are described below. 
     Devices in the Operating Environment 
       FIG.  2    is a block diagram illustrating an example voice-activated electronic device  104  that is applied as a voice interface to collect user voice commands in an operating environment (e.g., operating environment  100 ) in accordance with some implementations. The voice-activated device  104 , typically, includes one or more processing units (CPUs)  202 , one or more network interfaces  204 , memory  206 , and one or more communication buses  208  for interconnecting these components (sometimes called a chipset). The voice-activated device  104  includes one or more input devices  210  that facilitate user input, such as a button  212 , one or more touch sensors  214 , and one or more microphones  216 . The voice-activated device  104  also includes one or more output devices  218 , including one or more speakers  220 , optionally an array of LEDs  222 , and optionally a display  224 . In some implementations, the array of LEDs  222  is an array of full color LEDs. In some implementations, a voice-activated device  104 , depending on the type of device, has either the array of LEDs  222 , or the display  224 , or both. In some implementations, the voice-activated device  104  also includes a location detection device  226  (e.g., a GPS module) and one or more sensors  228  (e.g., accelerometer, gyroscope, light sensor, etc.). 
     In some implementations, the one or more touch sensors  214  includes a plurality of sensor electrodes that are disposed in proximity to different areas of an interior surface of a housing of the voice-activated electronic device  104 . Each of the different areas of the interior surface corresponds to a respective area of an exterior surface of the housing of the housing of the voice-activated electronic device  104 . Each sensor electrode corresponding to a respective area of the interior surface is configured to provide an electrical signal that varies in response to a touch event occurring to the respective area of the exterior surface of the housing. In an example, a first sensor electrode is disposed under a top area of the interior surface of the housing, and two additional sensor electrodes are disposed under two off-center areas that are located on two opposite sides of the top area of the interior surface of the housing. Each sensor electrode forms a capacitive sensor with reference to a ground of the electronic device  104 , and enables a capacitive sensing signal that varies in response to the touch event on the respective area of the exterior surface of the housing. 
     Memory  206  includes high-speed random access memory, such as DRAM, SRAM, DDR RAM, or other random access solid state memory devices; and, optionally, includes non-volatile memory, such as one or more magnetic disk storage devices, one or more optical disk storage devices, one or more flash memory devices, or one or more other non-volatile solid state storage devices. Memory  206 , optionally, includes one or more storage devices remotely located from one or more processing units  202 . Memory  206 , or alternatively the non-volatile memory within memory  206 , includes a non-transitory computer readable storage medium. In some implementations, memory  206 , or the non-transitory computer readable storage medium of memory  206 , stores the following programs, modules, and data structures, or a subset or superset thereof:
         Operating system  232  including procedures for handling various basic system services and for performing hardware dependent tasks;   Network communication module  234  for connecting the voice-activated device  104  to other devices (e.g., the voice assistance service  140 , one or more controllable devices  106 , one or more client devices  103 , and other voice-activated device(s)  104 ) via one or more network interfaces  204  (wired or wireless) and one or more networks  110 , such as the Internet, other wide area networks, local area networks (e.g., local network  108 ), metropolitan area networks, and so on;   Input/output control module  236  for receiving inputs via one or more input devices and enabling presentation of information at the voice-activated device  104  via one or more output devices  218 , including:
           Voice processing module  238  for processing audio inputs or voice messages collected in an environment surrounding the voice-activated device  104 , or preparing the collected audio inputs or voice messages for processing at a voice assistance server system  112 ;   LED control module  240  for generating visual patterns on the LEDs  222  according to device states of the voice-activated device  104 ; and   Touch sense module  242  for sensing touch events on a top surface (e.g., via the one or more touch sensors  214 ) of the voice-activated device  104 ;   
           Voice activated device data  244  for storing at least data associated with the voice-activated device  104 , including:
           Voice device settings  246  for storing information associated with the voice-activated device  104  itself, including common device settings (e.g., service tier, device model, storage capacity, processing capabilities, communication capabilities, etc.), information of one or more user accounts in a user domain, device nicknames and device groups, settings regarding restrictions when dealing with a non-registered user, and display specifications associated with one or more visual patterns displayed by the LEDs  222 ; and   Voice control data  248  for storing audio signals, voice messages, response messages and other data related to voice interface functions of the voice-activated device  104 ;   
           Response module  250  for performing instructions included in voice request responses generated by the voice assistance server system  112 , and in some implementations, generating responses to certain voice inputs; and   Focus session module  252  for establishing, managing, and ending focus sessions with respect to devices.       

     In some implementations, the voice processing module  238  includes the following modules (not shown):
         User identification module for identifying and disambiguating users who provide voice inputs to the voice-activated device  104 ;   Hot word recognition module for determining whether voice inputs include a hot word for waking up the voice-activated device  104  and recognizing such in the voice inputs; and   Request recognition module for determining a user request included in a voice input.       

     In some implementations, memory  206  also stores focus session data  254  for an outstanding focus session, including the following:
         Session in-focus device(s)  256  for storing an identifier of the device or device group in focus in an outstanding focus session (e.g., the device nickname, the device group name, MAC address(es) of the device(s));   Session start time  258  for storing a timestamp for the start of the outstanding focus session; and   Session command history  260  for storing a log of prior requests or commands in the focus session, including at least the most recent request/command. The log includes at least the timestamp(s) of the logged prior request(s)/command(s).       

     Each of the above identified elements may be stored in one or more of the previously mentioned memory devices, and corresponds to a set of instructions for performing a function described above. The above identified modules or programs (i.e., sets of instructions) need not be implemented as separate software programs, procedures, modules or data structures, and thus various subsets of these modules may be combined or otherwise re-arranged in various implementations. In some implementations, memory  206 , optionally, stores a subset of the modules and data structures identified above. Furthermore, memory  206 , optionally, stores additional modules and data structures not described above. In some implementations, a subset of the programs, modules, and/or data stored in the memory  206  can be stored on and/or executed by the voice assistance server system  112 . 
     In some implementations, one or more of the modules in memory  206  described above are part of a voice processing library of modules. The voice processing library may be implemented and embedded on a wide variety of devices. An example of a voice processing library is described in U.S. Provisional Patent Application No. 62/334,434, entitled “Implementations for Voice Assistant on Devices,” filed May 10, 2016, which is incorporated by reference herein in its entirety. 
     It is noted that in some implementations, the one or more touch sensors  214  are electrically coupled to a touch sensing circuit that are physically disposed on and supported by a PCB on which the CPUs  202  are mounted. Each of the one or more touch sensors  214  includes a sensing portion and a contact portion extending from the sensing portion. While the sensing portion is placed in proximity to the interior surface of the housing to facilitate detection of a touch on a corresponding area of the exterior surface of the housing, the contact portion of each touch sensor is bent to bridge the sensing portion to a conductive area on the PCB, thereby providing an electrical path to electrically couple the sensing portion to the touch sensing circuit disposed on the PCB. 
     Physical Design for a Compact Home Assistant 
       FIGS.  3 A and  3 B  are a front view and a rear view of an example voice-activated electronic device  104  in accordance with some implementations, respectively. The electronic device  104  includes an overall exterior (also called a housing) including an upper portion  306  and a base portion  308  coupled to the upper portion  306 . Optionally, the overall exterior of the electronic device  104  is radially symmetric about an axis that passes through centers of the upper and base portions  306  and  308 . In some implementations, at least a portion of the base portion  308  (e.g., a bottom surface  309 ) is flattened to enable the electronic device  104  to sit securely on a flat surface. The electronic device  104  is compact and fits naturally in many areas of a home. 
     The electronic device  104  further includes electronic components and one or more speakers contained within the overall exterior. For example, the electronic device  104  includes one or more microphones  216  and optionally includes an array of full color LEDs (not shown). The full color LEDs (e.g., LEDs  222  in  FIG.  2   ) could be hidden under a top surface of the electronic device  104  and invisible to the user when they are not lit. The rear side of the electronic device  104  optionally includes a power supply connector  310  configured to couple to a power supply, and the front side optionally includes a power switch  312 . That said, the base portion  308  has an opening that enables access to the power supply connector  310 , and the opening is optionally positioned adjacent to intersection between the upper portion  306  and the base portion  308 . 
     In some implementations, the electronic device  104  presents a clean look having no visible button or a limited number of visible buttons, and the interaction with the electronic device  104  is based on voice and touch gestures. In some implementations, when the electronic device  104  includes a limited number of physical buttons, the interaction with the electronic device  104  is further based on a press on the button in addition to the voice and touch gestures. Optionally, one of the physical buttons includes a power button that is disposed close to intersection between the first and second elements and configured to switch on or off the electronic device  104 . 
     In some implementations, a transition between the upper portion  306  and the base portion  308  is substantially continuous, such that the overall exterior has a continuously rounded shape. The upper portion  306  of the electronic device  104  has a circular cross section  314  defined by a first radius. The upper portion  306  includes and extends past the circular cross section  314 , and the base portion  308  has a second maximum radius that is smaller than the first radius. Optionally, a diameter of the circular cross section of the electronic device  104  is greater than a thickness of the electronic device  104 . In some implementations, the circular cross section  314  is approximately a middle cross section of the electronic device  104  that divides the overall exterior of the electronic device  104  into two halves having substantially equal thicknesses. The first radius corresponding to the middle cross section is optionally greater than a radius of any cross section of the electronic device  104 . 
     One or more speakers (not shown) are disposed and concealed in the electronic device  104  and project sound through a porous wall of the overall exterior to allow sound waves generated from the speaker to penetrate to the outside of the electronic device  104 . In some implementations, the upper portion  306  has a first exterior surface covering (e.g., the acoustically porous cover in  FIG.  4   ), and the base portion  308  has a second exterior surface covering different from the first exterior surface covering. The first exterior surface covering is substantially acoustically transparent to allow sound generated by the speakers to exit the electronic device  104 . In an example, at least a portion of the upper portion  306  includes perforations (e.g.,  410  in  FIGS.  4  and  5   ) configured to enable transmission of sound out of the electronic device  104 . The perforations of the upper portion  306  is covered by the first exterior surface covering, and the base portion  308  does not include any perforations to allow sound to transmit out of the electronic device  104 . 
       FIG.  4    is a cross sectional view of an example voice-activated electronic device  104  showing a dual purpose waveguide/heatsink  404  (also called a waveguide  404 ) and a speaker assembly  406  in accordance with some implementations. In some implementations, the electronic device  104  is a compact device that includes one or more speakers  406  and a plurality of electronic components, including one or more of: microprocessors, memory, support chips, wireless receivers and transmitters, antennas, power supply circuitry, one or more cameras, power and/or data connectors, touch sensing circuit, etc., some of which are mounted on one or more printed circuit boards  402 . The speakers (“speaker assembly”)  406  can be employed for any audio output purpose, including output of audible responses to user verbal inputs, playback of audio tracks of media content, and generation of audible alerts (including beeps, alarms, sirens, etc.). In some implementations, the one or more speakers  406  are mounted within the electronic device  104  such that there is no direct path for transmission to the outside of the device of sound generated by the one or more speakers  406 . In such implementations, in order to promote effective speaker operation (including effective transmission of sound output by the speaker  406  to the outside of the device), an acoustic waveguide  404  is provided within the electronic device  104  to redirect sound output by the one or more speakers  406  from the inside to the outside of the device. 
     In some implementations, the electronic device includes an upper portion  306  that serves as a speaker grill that allows transmission of sound outside the device from one or more speakers  406  contained within the electronic device  104 . In some implementations, the upper portion/speaker grill  306  can be configured with different surface finishes and/or can be securely but separably fastened to the base portion  308  as described in provisional patent application 62/403,681, entitled “Voice-Activated Electronic Device Assembly with Separable Base,” the contents of which are incorporated herein by reference in their entirety. In some implementations, the acoustic waveguide  404  is configured to redirect the sound to a speaker grill provided at an outer surface of the overall exterior of the electronic device  104 . 
     In some implementations, the acoustic waveguide  404  is also configured to serve as a heatsink to dissipate to the outside of the electronic device heat generated by operation of the electronic components and is mounted in proximity to at least some of the electronic components (e.g., components mounted on the PCB  402 , or the PCB  402 ). 
     In some implementations, the one more speakers  406  are mounted in a base portion  308  (e.g., “bottom housing”) of the electronic device  104  and have a primary sound projection direction that faces upwards within the electronic device  104 , towards a curved portion of the dual purpose waveguide/heatsink  404 . The curved portion is designed to redirect sound from the one or more speakers  406  to the outside of the electronic device  104  (e.g., via perforations  410  on the upper portion  306 ). Heat generating electronic components and/or one or more printed circuit boards  402  carrying electronic components are attached directly to a second portion of the dual purpose waveguide/heatsink  404  (or are coupled indirectly thereto using a thermal conduction path) so as to transmit to the heatsink heat generated by operation of the electronic components. The dual purpose waveguide/heatsink  404  is configured to move to the outside of the electronic device heat transmitted thereto from the attached electronic components. In some implementations, the dual purpose waveguide/heatsink  404  is made from materials that have highly effective thermal conduction properties to promote movement of heat from within the device to the outside of the device. In some implementations, the curved portion is a bottom surface of the dual purpose waveguide/heatsink  404  (e.g., a surface facing downwards towards the one or more speakers  406 ) and the second portion is an upper surface of the dual purpose waveguide/heatsink  404  that is opposite the bottom surface of the dual purpose waveguide/heatsink  404  (e.g., a surface facing upwards to which the electronic components are attached). Other shapes and forms of the upper and lower portions of the waveguide/heatsink  404  can be employed as would be apparent to one skilled in the art. 
     In some implementations, positions of the electronic components and the one more speakers  406  are interchanged such that the one more speakers  406  are located in an upper portion  306  of the electronic device  104  and project downwards towards an upper (curved) surface of the dual purpose waveguide/heatsink  404  and the electronic components are mounted in a base portion  308  of the electronic device  104  and waveguide/heatsink  404  is mounted in the base portion  308  (e.g., “bottom housing”). 
     In some implementations, the acoustic waveguide design channels sound from speaker  406  to desired output ports and thermally attached to the PCB  402  allowing the waveguide  404  to also function as heatsink/spreader. Wrapping the waveguide/heatsink  404  on the interior of the housing allows for larger thermal mass and greater surface for thermal radiation. In some implementations, a cutout pattern on a wrapped portion of the waveguide enhances thermal efficiency and allows sound to transmit out. In some implementations, during speaker function, sound waves also drives air over waveguide/heat sink  404  thus further enhancing thermal performance at time of greatest thermal generation. 
     In some implementations, the cone of the waveguide/heat sink redirects the sound from the up pointing speaker  406  to the side. Since the PCB  402  is directly on top of the dual purpose waveguide/heatsink  404 , it is also used as a heat sink. The dual purpose waveguide/heatsink  404  should be a highly thermally conductive material. In some implementations, a waveguide material of the dual purpose waveguide/heatsink  404  is a metal, (e.g., aluminum or copper), but the waveguide/heat sink  404  can also be fashioned from materials other than metal. 
     The PCB  402  is arranged and concealed within the electronic device  104 , and at least electrically coupled to the speaker assembly  406 . That said, the PCB  402  includes one or more electronic components configured to drive the speaker assembly  406 , a power supply circuitry, and a wireless transceiver configured to receive and transmit signals. Referring to  FIGS.  3 A and  3 B , in some implementations, the base portion  308  includes a power supply connector  310  configured to couple to an external power supply and the front side optionally includes a power switch  312 , and the PCB is configured to receive power from the external power supply via the power supply connect  310 . 
       FIG.  5    is an exploded view of an example voice-activated electronic device  104  in accordance with some implementations. This shows a perforated upper portion  306 , the dual purpose waveguide/heatsink  404 , an assembly  502  combining a bottom portion of the waveguide  404  and the speaker assembly  406 , and the base portion  308 . The upper portion  306  includes perforations  410  on a peripheral wall to allow transmission of sound waves generated by the speaker assembly  406  to exit the electronic device  104 . Specifically, the dual purpose waveguide/heatsink  404  is provided within the electronic device  104  to redirect sound output by the one or more speakers  406  towards the perforations  410  located on the peripheral wall of the upper portion  306 . 
     The dual purpose waveguide/heatsink  404  has a top surface  504 , and a PCB  402  is disposed on the top surface  504  of the waveguide  404 . Referring to  FIG.  4   , the waveguide  404  has a waveguide periphery physically configured to fit into the rounded shape of the upper portion  306 . When the waveguide  404  physically fits into the upper portion  306 , a space  412  is formed between an upper interior surface of the upper portion  306  and a top surface of the PCB  402 . The space  412  is configured to accommodate electronic components mounted onto the PCB  402 . In some implementation, one or more touch sensors  414  are coupled in proximity to the upper interior surface of the upper portion  306  to detect touch events occurring to an upper exterior surface opposite the upper interior surface. Each of the touch sensors  414  is configured to extend across the space  412  to reach a respective conductive area of the PCB  402  that is electrically coupled to a touch sensing circuit mounted onto the PCB  402 . In some implementations, the electronic device  104  includes a first sensor electrode and two additional sensor electrodes. The first sensor electrode  414 A is disposed under a top area of the interior surface of the upper portion  306 , and the two additional sensor electrodes  414 B and  414 C are disposed under two peripheral areas that are located on two opposite sides of the top area of the interior surface of the upper portion  306 . Each of the sensor electrodes  414 A- 414 C forms a respective capacitive sensor with reference to a ground of the electronic device  104 , and enables the touch sensing circuit (specifically, a capacitive sense circuit) coupled onto the PCB  402  to monitor a capacitive sensing signal that varies in response to the touch events on a respective area of the exterior surface of the upper portion  306 . More details on the touch sensors  414  are explained below with reference to  FIGS.  6 ,  7 A- 7 G and  8 A- 8 C . 
     Referring to  FIG.  4   , in some implementations, the electronic device  104  further includes one or more microphones  416 , and is configured to provide a controlled sound path  420  to access each of the one or more microphones  416  via a respective microphone aperture  418  opened on the upper portion  306 . Optionally, a microphone  416  is disposed on top of the PCB  402  (i.e., within the space  412 ), and coupled to the microphone aperture  418  by a sound control structure. Optionally, a microphone  416  is disposed beneath the PCB  402 , and faces a second microphone aperture  418 ′ formed on the PCB  402 . The second microphone aperture  418 ′ is further coupled to the microphone aperture  418  by a sound control structure. By these means, the controlled sound path  420  can be formed to connect each microphone  416  to the corresponding microphone aperture  418 . In some implementations, an acoustically porous cover  422  is further used to wrap the upper portion  306  and conceal the microphone aperture  418  thereon, and an adhesive is applied with the acoustically porous cover  422  to extend the controlled sound path  420  further across the acoustically porous cover  422 . More details on the controlled sound path  420  are explained below with reference to  FIGS.  9 A- 9 B and  10 A- 10 C . 
     Dual Conductive Paths Coupling a Touch Sensor to a Circuit Board 
       FIG.  6    illustrates an upper interior surface  600  of an upper portion  306  of an example voice-activated electronic device  104  in accordance with some implementations. The upper interior surface  600  includes one or more sensor areas where one or more touch sensors  414  are coupled. In some implementations, the one or more sensor areas include a top sensor area  602 A where a first touch sensor  414 A is coupled. In an example, the top sensor area  602 A has a circular shape and is concentric with a cross section of the upper portion  306 . In some implementations, the one or more sensor areas further includes one or more peripheral sensor areas (e.g.,  602 B and  602 C) where one or more additional touch sensors  414 B and/or  414 C are coupled. In this example, two additional sensor electrodes  414 B and  414 C are disposed under two peripheral sensor areas  602 B and  602 C that are located on two opposite sides of the top sensor area  602 A of the upper interior surface  600  of the upper portion  306 . The top sensor  414 A and the two additional sensors  414 B and  414 C are optionally aligned with each other. 
     The first touch sensor  414 A coupled to the first sensor area  602 A includes a sensing portion  604 A and a contact portion  606 A extending from the sensing portion  604 A. The sensing portion  604 A is substantially planar. In some situations, when it is disposed in proximity to the top sensor area  602 , the sensing portion  604 A comes into contact with the top sensor area  602 . Alternatively, in some situations, when it is disposed in proximity to the top sensor area  602 , the sensing portion  604 A does not contact the top sensor area  602  directly, and a gap between the sensing portion  605  and the top sensor area  602  is less than a predetermined distance threshold (e.g., 1 mm). In some implementations, the sensing portion  604  and contact portion  606 A of the first touch sensor  414 A are made from a single sheet of conductive material (e.g., stainless steel) and connected to each other at an intersection area  608 . The contact portion  606 A is not planar and is bent with a first average curvature. The first average curvature of the contact portion  606 A is greater than a second average curvature of the upper portion  306  near the top sensor area  602 , thereby allowing the contact portion  606 A to deflect away from the upper portion  306 . In some implementations, both the sensing and contact portions are planar, but are folded to form an angle at the intersection  608 . 
     In some implementations, the top sensor area  602 A is physically coupled to an array of light guides  610  configured to guide light generated by LED indicators towards the upper interior surface  600  of the upper portion  306 . Optionally, the upper interior surface  600  includes one or more openings to allow the light guided to the upper interior surface  600  to be visible to the outside. Optionally, at least part of the upper interior surface  600  is partially transparent to the light guided to the upper interior surface  600 . The light guides  610  rise above the top sensor area  602  by a height when they are affixed onto the top sensor area  602 . The sensing portion  604 A of the first touch sensor  414 A has one or more cutout openings. When the first touch sensor  414 A is disposed in proximity to the first sensor area  602 A, the one or more cutout openings of the sensing portion  604 A is aligned with and surround the light guides  610 , thereby allowing the first touch sensor  414  to be automatically aligned with the first sensor area  602 A. 
     Additionally, the upper interior surface  600  further includes a first boss structure  612 A disposed outside the first sensor area  602 A. When the first touch sensor  414 A is automatically aligned with the first sensor area  602 A by the light guides  610 , the contact portion  606 A extends towards the first boss structure  612 A, i.e., the contact portion  606 A is automatically aligned with the first boss structure  612 A. Specifically, the contact portion  606 A includes an opening near its tip area, and the opening of the contact portion  606 A is automatically aligned with and is configured to receive the first boss structure  612 A when the sensing portion  604  is disposed in proximity to the first sensor area  602 A. The contact portion  606 A further includes a contact ring defining its opening and a spring finger physically separated from the contact ring. Both the contact ring and the spring finger extends to the first boss structure  612 A or an area substantially close to the first boss structure  612 A (e.g., less than 5 mm from the first boss structure  612 A). 
     Each additional touch sensor  414 B coupled to a peripheral sensor area  602 B includes a sensing portion  604 B and a contact portion  606 B extending from the sensing portion  604 . The sensing portion  604 B has a shape conformal to a shape of the upper interior surface  600  locally at the peripheral sensor area  602 B. When it is disposed in proximity to the peripheral sensor area  602 B, the sensing portion  604 B optionally comes into contact with or has a substantially small gap with the top sensor area  602 B. The gap between the sensing portion  605  and the top sensor area  602  is substantially small, i.e., less than the predetermined distance threshold (e.g., 1 mm). In some implementations, the sensing portion  604 B and contact portion  606 B of the second touch sensor  414 A are made from a single sheet of conductive material. The contact portion  606 B is further bent with an average curvature greater than an average curvature of the upper portion  306  near the peripheral sensor area  602 B, thereby allowing the contact portion  606 B to deflect away from the interior surface of the upper portion  306 . 
     In some implementations, the peripheral sensor area  602 B is physically coupled to a second light guide  614  configured to guide light generated by an LED indicator towards the upper interior surface  600  of the upper portion  306 . Optionally, the upper interior surface  600  includes one or more openings or is partially transparent to allow the light guided to the upper interior surface  600  to be visible to the outside. The second light guide  614  is affixed onto and rises from the peripheral sensor area  602 B. The sensing portion  604 B of the additional touch sensor  414 B has a cutout opening configured to align with and surround the second light guide  614 , thereby allowing the additional touch sensor  414 B to be automatically aligned with the peripheral sensor area  602 B. In some implementations, a first visual pattern enabled by the one or more light guides  610  indicates a voice processing status of the electronic device  104 . A second visual pattern enabled by the second light guide  614  indicates a location of the corresponding touch sensor  414 B, and is configured to guide a user of the electronic device  104  to touch on a correct location for the purposes of activating one or more predetermined functions (e.g., increasing a volume, decrease a volume). A third visual pattern enabled by a third light guide  616  indicates a location of the corresponding touch sensor  414 C, and has a similar function as that of the second visual pattern. Optionally, the second and third visual patterns correspond to two predetermined functions (e.g., increasing and decreasing a volume) that are opposite to each other. 
     Additionally, the upper interior surface  600  further includes a second boss structure  612 B disposed outside the peripheral sensor area  602 B. When the additional touch sensor  414 B is automatically aligned with the peripheral sensor area  602 B by the second light guide  614 , the contact portion  606 B extends towards the second boss structure  612 B, i.e., the contact portion  606 B is automatically aligned with the second boss structure  612 B. 
     In some implementations, the upper interior surface  600  of the upper portion  306  further includes a plurality of microphone apertures  418  configured to let sound enter the housing of the electronic device  104  and guide sound towards one or more microphones  416  disposed inside the housing. Further, in some implementations, the upper interior surface  600  includes one or more speaker grills (i.e., perforations  410 ) formed on a peripheral wall to allow transmission of sound waves generated by a speaker assembly of the electronic device  104  to exit the housing of the electronic device  104 . In the example shown in  FIG.  6   , the electronic device  104  has two speaker grills separated by the two additional touch sensors  414 B and  414 C. 
       FIGS.  7 A and  7 B  illustrate an example touch sensor  414  configured to be disposed in proximity to an upper interior surface  600  of a voice-activated electronic device  104  in accordance with some implementations.  FIG.  7 C  is an enlarged view of a contact portion  606  of an example touch sensor  414  in accordance with some implementations. The touch sensor  414  includes a sensing portion  604  and a contact portion  606  extending from the sensing portion  604 . In this example, the sensing portion  604  is substantially planar, and is configured to be disposed in proximity to a substantially flat sensor area  602  (e.g., the top sensor area  602 A) of an upper interior surface  600  of a housing. When it is disposed in proximity to the substantially flat sensor area  602 , the sensing portion  604  comes into contact with the substantially flat sensor area  602  or is separated by a substantially small gap from the substantially flat sensor area  602 . By these means, the sensing portion is configured to detect a touch on a corresponding area of an upper exterior surface  600  of the housing corresponding to the substantially flat sensor area  602  of the housing. 
     The sensing portion  604  of the first touch sensor  414  has one or more cutout openings  702 . In some implementations, a first one  702 A of the one or more cutout openings  702  receives an array of light guides  610  that rises above the upper interior surface  600 , when the touch sensor  414  is disposed in proximity to the upper interior surface  600 . A size of the first one of the one or more cutout openings  702  matches a size of the light guide array  610 , such that when the array  610  fits in the opening  702 A, the sensing portion  604  can be automatically aligned with a boss structure  612  fixed on the upper interior surface  600 . The first one of the one or more cutout openings  702  optionally has a shape that is consistent with or distinct from a shape of the light guide array  610 . In some implementations, the one or more cutout openings  702  includes a second opening  702 B configured to align with an alignment pin  704  fixed on a corresponding sensor area  602  of the upper interior surface  600 . When the touch sensor  414  is assembled onto the electronic device  104 , the alignment pin  704  is aligned with and rises out of the second opening  702 B. In some implementations, the one or more cutout openings  702  includes one or more third openings  702 C configured to facilitate coupling the touch sensor  414  onto the upper interior surface  600  of the upper portion  306  (e.g., affixing the touch sensor  414  onto the upper interior surface  600 ). For example, a heat stake  728  is applied onto each third opening  702 C to hold the touch sensor  414  onto the upper interior surface  600 . 
     The contact portion  606  extends from an edge of the sensing portion  604 , and has an opening  706  located near its tip area and a contact ring  708  in which the opening  706  is defined. When the touch sensor  414  is so disposed to allow the light guide array  610  or the alignment pipe  704  to rise out of a corresponding opening  702 , the opening  706  of the contact portion  606  is automatically aligned with the boss structure  612  fixed on the upper interior surface  600 , and the boss structure  612  at least partially rises out of the opening  706  of the contact portion  606 . In an example, the boss structure  612  has a central shank  710  that is partially recessed around its periphery to form a flat recessed periphery  712 . The central shank  710  further includes a screw hole  714 . When the touch sensor  414  is coupled onto the upper interior surface  600 , the central shank  710  of the boss structure  612  rises out of the opening  706  of the contact portion  606 , and the contact ring  708  of the contact portion  606  sits on the flat recessed periphery  712  of the boss structure  612 . 
     In addition to the contact ring  708  and the opening  706 , the contact portion  606  further includes a spring finger  716  physically separated from the contact ring  708 , while both the contact ring  708  and the spring finger  716  are configured to reach the flat recessed periphery  712  of the boss structure  612  or nearby. In some implementations, the contact portion  606  connects to the sensing portion  604  at an intersection area  608 . The contact portion  606  further includes an arm  718  that connects the intersection area  608  to the contact ring  708 . The arm  718  merges with the spring finger  716  at the intersection area  608  or on the contact portion  606  (e.g., away from the intersection area  608 ). The arm  718  has a first stiffness and a first bending curvature with respect to the sensing portion  604 . The first stiffness is distinct from a second stiffness of the spring finger  716 , and the first bending curvature is distinct from a second bending curvature of the spring finger  716 . That said, if the first bending curvature of the arm  718  represents the first average curvature of the contact portion  606 , the spring finger  716  is bent out of a curved plane of the contact portion  606  (e.g., resulting in a deviation of d at its tip area in  FIG.  7 B ) and deviated further away from a plane of the sensing portion  604  compared with the arm  718 . In some implementations, the spring finger  716  is physically modified to result in the second stiffness or the second bending curvature of the spring finger  716 . For example, the spring finger  716  may be bent with an angle at its intersection  732  with the arm  718 . Alternatively, a thickness of the spring finger  716  may be adjusted at its intersection  732  with the arm  718 , e.g., by placing one or more beads on a rear end of the spring finger  716  near its intersection  732  with the arm  718 . It is noted that the intersection  732  optionally overlaps or is located away from the intersection area  608 . 
     It is noted that in some implementations, the contact ring  708  and a tip area of the spring finger  716  are bent or flattened with respect to bodies of the arm  718  and the spring finger  716  according to a shape of the flat recessed periphery  712  of the boss structure  612 , thereby configuring the contact ring  708  and the tip area of the spring finger  716  to come into close contact with the flat recessed periphery  712 . In a natural state shown in  FIG.  7 B , the contact ring  708  comes into contact with the flat recessed periphery  712  of the boss structure  612 , and the spring finger  716  deflects from the arm  718  of the contact portion  606  and does not contact the flat recessed periphery  712 . Further, in some implementations, the shank  710  of the boss structure  612  has a rounded shape, and the opening  706  of the contact portion is optionally circular or square, or has another shape in which the shank  710  of the boss structure  612  can fit. 
       FIGS.  7 D- 1  and  7 D- 2    are example cross sections  730  and  730 ′ of a voice-activated electronic device  104  including a touch sensor shown in accordance with some implementations, and  FIG.  7 F  illustrates an example PCB  402  having a receiving hole  722  and a conductive area  724  in accordance with some implementations. After the touch sensor  414  is coupled to an upper interior surface  600  of an upper portion  306 , the upper portion  306  is further coupled to a PCB  402  via a fastener  720 . The fastener  720  configured to be mechanically coupled to the boss structure  612  of the upper portion  306 . Specifically, the PCB  402  has a first surface  402 A and one or more receiving holes  722 . The first surface  402 A faces the upper interior surface  600  of the housing and includes a conductive area  724  surrounding each receiving hole  722 . An opening  706  of the contact portion  606  of the touch sensor  414  and a the boss structure  612  are configured to be aligned with the receiving hole  722  of the PCB  402 . A central shank  710  of the boss structure  612  is configured to be received by both the opening  706  of the touch sensor and the receiving hole  722  of the PCB  402 . When the fastener  720  is coupled to the screw hole  714 , both the PCB  402  and the contact ring  708  of the touch sensor  414  are held between a flat recessed periphery  712  of the buss structure  612  and a head of the fastener  720 . Specifically, the PCB  402  is pushed by the fastener  720  to press onto the contact ring  708  sitting on the flat recessed periphery  712 . As a result, the conductive area  724  surrounding the receiving hole  722  of the PCB  402  comes into contact with the contact ring  708 , forming an electrically conductive path between the touch sensor  414  and the PCB  402 . 
     A spring finger  716  of the contact portion  606  is separated from an arm  718  coupled to the contact ring  708  and has a bending curvature greater than that of the arm  718 . In the natural state ( FIG.  7 B ), the spring finger  716  deflects from the arm  718  of the contact portion  606  and does not contact the flat recessed periphery  712 . When the fastener  720  is applied to couple the PCB  402  to the boss structure  612 , a tip area of the spring finger  716  touches the first surface  402 A of the PCB  402  and comes into contact with the conductive area  724  of the PCB  402 . By these means, the conductive area  724  surrounding the receiving hole  722  of the PCB  402  comes into contact with both the tip area of the spring finger  716  and the contact ring  708  that are separable from each other, forming two separate conductive paths between the touch sensor  414  and the PCB  402 . Under some circumstances, the fastener  720  is loosened from the boss structure of the housing to cause the contact ring  708  to be electrically decoupled from the conductive area  724  of the PCB  402 , particularly because touches constantly occur on an exterior surface of the upper portion  306  corresponding to the touch sensor  414  for an extended duration of time. When the fastener  720  becomes loose, the contact between the contact ring  708  and the conductive area  724  may be compromised (e.g., not consistent any more). The tip area of the spring finger  716  is configured to be controlled by a stiffness of the spring finger to contact the conductive area  724  of the PCB  402  and maintain its corresponding conductive path between the touch sensor  414  and the PCB  402  when the fastener  720  becomes loose. 
     Referring to  FIG.  7 D- 1   , the central shank  710  of the boss structure  612  is configured to fit in both the opening  706  of the touch sensor  414  and the receiving hole  722  of the PCB  402 , and to mate to the fastener  720  to couple the touch sensor  414  between the upper interior surface  600  and the PCB  402 . The receiving hole  722  of the PCB  402  is configured to have a diameter less than a diameter of a head  720 A of the fastener  720  and greater than an outer diameter of the central shank  710  of the boss structure  612  of the housing. Also, the opening  706  of the contact portion  606  of the touch sensor  414  is configured to have a diameter greater than an outer diameter of the central shank  710  of the boss structure  612  of the housing and less than an outer diameter of the conductive area  724  of the PCB  402  and an outer diameter of the flat recessed periphery  712 . 
     Referring to  FIG.  7 D- 1   , in some implementations, the central shank  710  of the boss structure  612  has a length that is shorter than a thickness of the PCB  402 . When the fastener  720  is fastened to the boss structure  612 , the boss structure  612  sits in the receiving hole  722  of the PCB and does not rise out of the receiving hole  722 . Optionally, the receiving hole  722  of the PCB  402  has a single diameter through its entire thickness. Optionally, the receiving hole  722  of the PCB  402  has a first diameter for a first portion of a thickness of the PCB and a second diameter for a second portion of the thickness of the PCB. The first diameter is less than a diameter of the head  720 A of the fastener  720  to block the head  720 A of the fastener  720 . Optionally, a diameter of the boss structure  612  is greater than the first diameter and less than the second diameter of the one of the receiving holes. 
     In some implementations, one or more of the conductive area  724  on the PCB  402 , the contact ring  708  and the tip area of the spring finger  716  is coated with a conductive material (e.g., gold, copper) having a resistivity lower than a resistivity threshold to improve contact of the conductive area  724  on the PCB  402  with the contact ring  708  or the tip area of the spring finger  716 . 
     In some implementations, when the fastener  720  is coupled tightly into the screw hole of the boss structure  612  ( FIG.  7 D- 1   ), each of the contact ring  708  and the tip of the spring finger  716  is coupled between the conductive area  724  of the PCB  402  and the fat recessed periphery  712  of the boss structure  612 , and remains in contact with both of them. When the fastener  720  is loosened from the boss structure  612  ( FIG.  7 D- 2   ), the contact ring  708  is physically and electrically decoupled from the conductive area  724  of the PCB  402 . The tip area of the spring finger  716  is configured to be controlled by a stiffness of the spring finger  716  to contact the conductive area  724  of the PCB  402  and maintain a corresponding conductive path between the touch sensor  414  and the PCB  402 . However, a shift of the PCB  402  caused by the loose fastener  720  is less than the deviation of d at the tip area of the spring finger  716  in  FIG.  7 B . 
       FIG.  7 E  is another example cross section  740  of a voice-activated electronic device  104  including a touch sensor shown in  FIGS.  7 A and  7 B  in accordance with some implementations. In some implementations, after the touch sensor  414  is coupled to the upper interior surface  600 , the upper portion  306  is further coupled to both the PCB  402  and the waveguide  404  by the fastener  720 . The fastener  720  is configured to be mechanically coupled to the boss structure  612 . That said, the waveguide  406  has a receiving hole aligned with the receiving hole  722  of the PCB  402 , the contact ring  708  and opening  706  of the touch sensor  414 , and the boss structure  612 . When the fastener  720  is coupled to the screw hole  714  of the boss structure  612 , the waveguide  404  is tightly held between the flat recessed periphery  712  and the head  720 A of the fastener  720  with the contact ring  708  of the touch sensor  414  an the PCB  402 . In some implementations, the central shank  710  of the boss structure  612  has a length that is longer than the thickness of the PCB  402 . When the fastener  720  is fastened to the boss structure  612 , the boss structure  612  passes through the receiving hole  722  of the PCB and enters a receiving hole of the waveguide  404 , but does not rise out of the receiving hole of the waveguide  404 . 
       FIG.  7 G  is an example stress distribution diagram  750  of an example touch sensor  414  that is assembled in a voice-activated electronic device  104  (i.e., in a stressed state) shown in  FIGS.  7 D and  7 E  in accordance with some implementations. In a natural state ( FIG.  7 B ), before the PCB  402  is assembled, the contact ring  708  comes into contact with the flat recessed periphery  712  of the boss structure  612 , and the spring finger  716  deflects from the arm  718  of the contact portion  606  and does not contact the flat recessed periphery  712 . In a stressed state, after the PCB  402  is assembled, the contact ring  708  is held between the flat recessed periphery  712  of the boss structure  612  and the first surface  402 A of the PCB  402 , forming electrically conductive path between the touch sensor  414  and the PCB  402 , and the spring finger  716  also comes into contact with the conductive area  724  of the PCB  402  and is pushed thereby to the arm  718  of the contact portion  606 . As such, a stiffness and bending curvature of the spring finger in the natural state are configured to create a force in a target force range when the contact portion  606  is electrically coupled to the corresponding conductive area  724  on the PCB  402  via the contact ring  708  and the tip area of the spring finger  716 . Referring to  FIG.  7 E , when both the spring finger  716  and the contact ring  708  are electrically coupled to the conductive area  724  of the PCB  402  (i.e., in a stressed state), the spring finger  716  is stressed to adopt a curvature of the arm  718  and has a plurality of stress points  726  (e.g., points  726 A and  726 B at an intersection where the spring finger  716  starts, points  726 C and  726 D on two edges of the spring finger  716 ). 
       FIG.  8 A  illustrates another example touch sensor  414  disposed in proximity to an upper interior surface  600  of a voice-activated electronic device  104  in accordance with some implementations. More specifically, the touch sensor  414  is disposed next to a peripheral wall of the upper portion  306  of the electronic device  104 .  FIG.  8 B  is a cross sectional view  820  of a voice-activated electronic device  104  including a touch sensor  414  shown in  FIG.  8 A  in accordance with some implementations.  FIG.  8 C  is an example stress distribution diagram  850  of an example touch sensor  414  that is assembled in a voice-activated electronic device  104  (i.e., in a stressed state) shown in  FIG.  8 B  in accordance with some implementations. The touch sensor  414  includes a sensing portion  604  and a contact portion  606  extending from the sensing portion  604 . In this example, the sensing portion  604  has a planar or non-planar shape that is conformal to a shape of the upper interior surface  600  locally at a peripheral sensor area  602 . When it is disposed in proximity to the peripheral sensor area  602 , the sensing portion  604  comes into contact with the peripheral sensor area  602  or is separated by a substantially small gap from the peripheral sensor area  602 . As such, the sensing portion  604  is configured to detect a touch on a corresponding area of an upper exterior surface of the housing corresponding to the peripheral sensor area  602 . 
     The sensing portion  604  of the touch sensor  414  has at least one cutout opening  802  configured to receive a light guide  614 . The light guide  616  rises from the upper interior surface  600  when the touch sensor  414  is disposed in proximity to the upper interior surface  600 . A size of the cutout opening  802  matches a size of the light guide  614 . When the light guide  614  is coupled in the cutout opening  802 , the sensing portion  604  can be automatically aligned with a boss structure  612  fixed on the upper interior surface  600 . The cutout opening  802  optionally has a shape that is consistent with or distinct from a shape of the light guide  616 . In some implementations, a plurality of LEDs are mounted on the PCB  402 . When the fastener  720  couples the PCB  402  to the boss structure  612 , the plurality of LEDs are automatically aligned with the light guide array  610  and the light guides  614  and  616 . Light generated by these LEDs are guided to the upper interior surface  600  to be visible to the outside. In some implementations, a first visual pattern enabled by the one or more light guides  610  indicates a voice processing status of the electronic device  104 . A second visual pattern enabled by the second light guide  614  indicates a location of the corresponding touch sensor  414 , and is configured to guide a user of the electronic device  104  to touch on a correct location for the purposes of activating one or more predetermined functions (e.g., increasing a volume, decrease a volume). 
     Alternatively, in some implementations not shown in  FIG.  8 A , the light guide  614  does not rise out of the opening  802  of the touch sensor  414 . Rather, the light guide  616  is disposed in proximity and next to the touch sensor  414 , and is configured to receive light emitted by the LED mounted on the PCB and provide illumination via an LED opening on the housing to indicate the corresponding location on the exterior surface of the housing to which the touch sensor  414  is adjacent. 
     The contact portion  606  extends from an edge of the sensing portion  604 , and has an opening  706  located near its tip area and a contact ring  708  in which the opening  706  is defined. When the touch sensor  414  is so disposed to allow the light guide  616  to rise out of a corresponding opening  802 , the opening  706  of the contact portion  606  is automatically aligned with the boss structure  612  fixed on the upper interior surface  600 , and the boss structure  612  at least partially rises out of the opening  706  of the contact portion  606 . The contact portion  606  further includes a spring finger  716  physically separated from the contact ring  708  and an arm  718  that connects to the contact ring  708 . The spring finger  716  is bent out of a plane of the contact portion  606 , and deviated further away from a plane of the sensing portion  604  compared with the arm  718 . Optionally, the arm  718  is substantially planar (i.e., flat). In some implementations, the spring finger  716  is physically modified to result in the second stiffness or the second bending curvature of the spring finger  716 . For example, the spring finger  716  may be bent with an angle at its intersection with the arm  718 . Alternatively, a thickness of the spring finger  716  may be adjusted at its intersection  732  with the arm  718 , e.g., by placing one or more beads on a rear end of the spring finger  716  near its intersection  732  with the arm  718 . 
     It is noted that in some implementations, the contact ring  708  and a tip area of the spring finger  716  are bent or flattened with respect to bodies of the arm  718  and the spring finger  716  according to a shape of the flat recessed periphery  712  of the boss structure  612 , thereby configuring the contact ring  708  and the tip area of the spring finger  716  to come into close contact with the flat recessed periphery  712 . In a natural state shown in  FIG.  8 A , before the PCB  402  is assembled, the contact ring  708  comes into contact with the flat recessed periphery  712  of the boss structure  612 , and the spring finger  716  deflects from the arm  718  of the contact portion  606  and does not contact the flat recessed periphery  712 . In a stressed state, after the PCB  402  is assembled, the contact ring  708  is held between the flat recessed periphery  712  of the boss structure  612  and the first surface  402 A of the PCB  402 , forming electrically conductive path between the touch sensor  414  and the PCB  402 , and the spring finger  716  also comes into contact with the conductive area  724  of the PCB  402  and is pushed thereby to the arm  718  of the contact portion  606 . Under some circumstances, the fastener  720  is loosened from the boss structure  612  to cause the contact ring  708  to be electrically decoupled from the conductive area  724  of the PCB  402 . This often happens when touches constantly occur on an exterior surface of the upper portion  306  corresponding to the touch sensor  414  for an extended duration of time. The tip area of the spring finger  716  is configured to be controlled by a stiffness of the spring finger  716  to contact the conductive area  724  of the PCB  402  and maintain a corresponding conductive path between the touch sensor  414  and the PCB  402 . 
     In some implementations, the stiffness and bending curvature of the spring finger in the natural state are configured to create a force in a target force range when the contact portion  606  is electrically coupled to the corresponding conductive area  724  on the PCB  402  via the contact ring  708  and the tip area of the spring finger  716 . Referring to  FIG.  8 C , when both the spring finger  716  and the contact ring  708  are electrically coupled to the conductive area  724  of the PCB  402  (i.e., in a stressed state), the spring finger  716  is stressed to adopt a curvature of the arm  718  and has a plurality of stress regions  804  near an intersection  732  where the spring finger  716  starts to separate from the arm  718 . 
     Controlled Sound Path Crossing an Acoustically Porous Cover 
       FIGS.  9 A and  9 B  are a cross sectional view  900  and a top view  950  of a region of a voice-activated electronic device  104  in which a microphone  416  is disposed in accordance with some implementations, respectively. The electronic device  104  has a housing  902  and one or more microphones  416  enclosed in the housing  902 . The housing  902  has an exterior surface  902 A and a first microphone aperture  418 . The microphone  416  has a diaphragm  904  facing the first microphone aperture  418 . The diaphragm  904  of the microphone  416  is configured to receive incoming sound via the first microphone aperture  418 , such that the microphone  416  can convert the incoming sound to an electrical signal. Before the electronic device  104  is shipped out of factory, at least part of the exterior surface of housing  902  (e.g., an upper portion  306 ) is wrapped by an acoustically porous cover  422  to provide a clean look. The first microphone aperture  418  is therefore concealed by the acoustically porous cover  422 . 
     During the course of calibrating the microphone  416 , a microphone testing fixture  906  is disposed in contact with the acoustically porous cover  422  to deliver testing sound signals into the first microphone aperture  418 . The test sound signals cannot be delivered entirely into the microphone, because part of the test sound signals are leaked from an edge at an interface of the microphone testing fixture  906  and the acoustically porous cover  422 . Also, due to leakage at the edge of this interface, sound signals collected by the microphone  416  do not entirely come from the microphone testing fixture  906 . Noise signals in an ambient enter the housing  902  via the edge and interfere with the test sounds signals provided by the microphone testing fixture  906 . As such, the edge has to be substantially sealed at an interface of the microphone testing fixture  906  and the acoustically porous cover  422  to provide a desirable sound delivery efficiency without compromising the clean look of the electronic device  104 . 
     In various implementations of this application, the exterior surface  902 A of the housing  902  includes a sealing area  908  surrounding but not including the first microphone aperture  418 , and the acoustically porous cover  422  is affixed to the sealing area  908  of the exterior surface  902 A via an adhesive  910 . The adhesive  910  covers the sealing area  908  and permeates a thickness of the acoustically porous cover  422  above the sealing area, thereby enabling formation of a controlled sound path to the microphone  416  by coupling of a microphone testing fixture  906  to a region of the acoustically porous cover  422  corresponding to the sealing area  908 . In some implementations, the adhesive  910  is configured to be applied on the sealing area  908  of the housing  902  and covered by the acoustically porous cover  422 . The adhesive  910  permeates the thickness of the acoustically porous cover  422  and is hardened in response to heat treatment under a predetermined condition. Preferably, the adhesive  910  permeates part of the thickness of the acoustically porous cover  422 , rather than an entire thickness, such that the adhesive is not visible or felt by touch from the exterior surface of the acoustically porous cover  422 . In some implementations, the acoustically porous cover  422  is flexible and substantially transparent to audible sound. Referring to  FIG.  9 B , in an example, the sealing area  908  includes a circular ring area enclosing the first microphone aperture  418 . 
     In some implementations, the sealing area  908  is defined according to a shape and a dimension of the microphone testing fixture  906 . When the microphone testing fixture  906  is disposed in contact with the acoustically porous cover  422 , the acoustically porous cover  422  is deformed, and the deformed cover  422  and the adhesive  910  are configured to substantially cut off any leakage at the edge of the interface of the microphone testing fixture  906  and the acoustically porous cover  422 . That said, in an example, when the microphone testing fixture  906  is coupled to the controlled sound path, a portion of sound generated by the microphone testing fixture  906  is collected by the microphone  416 . In accordance with desirable sound delivery efficiency, the portion of sound is greater than a predetermined portion (e.g., 90%) of the sound generated by the microphone testing fixture  906 . Alternatively, from another perspective, when the microphone testing fixture  906  is coupled to the controlled sound path, a portion of sound collected by the microphone  416  comes from an ambient source other than the microphone testing fixture  906 . In accordance with desirable sound delivery efficiency, the portion of sound is less than a predetermined portion (e.g., 20%) of the sound collected by the microphone  416 . 
     In some implementations, the microphone  416  is disposed at a predetermined location with reference to the microphone testing fixture  906  while the microphone testing fixture  906  is not pressed onto the exterior surface of the housing  902 . The microphone testing fixture  906  sweeps through frequencies in a tone range, and a first frequency response is recorded at the microphone  416 . The microphone testing fixture  906  is then pressed onto the first microphone aperture  418  of the housing  902 . The microphone testing fixture  906  sweeps through frequencies in the tone range again, and a second frequency response is recorded at the microphone  416 . The second frequency response is compared with the first frequency response to determine whether the interface of the microphone testing fixture  906  and the acoustically porous cover  422  (also called the cover-fixture interface) can provide a desirable sound delivery efficiency. In some implementation, a difference of the first and second frequency responses is greater than a predetermined attenuation threshold (e.g., 10 dB) to provide the desirable sound delivery efficiency. A direct outcome of failing to provide the desirable sound delivery efficiency is that the microphone  416  cannot detect hot words effectively (e.g., misses 50% of the hot words) in a smart home environment where the electronic device  104  is located. 
     In some implementations, a PCB  402  is enclosed in the housing  902  and has a first surface  402 A facing an interior surface  902 A of the housing  902 , a second surface  402 B opposing the first surface  402 A, and a second microphone aperture  418 ′ aligned with the first microphone aperture  418  of the housing  902 . The microphone  416  is coupled to the second surface  402 B of the PCB  402 , and the diaphragm  904  of the microphone  416  faces the second microphone aperture  418 ′ of the PCB  402  directly. The diaphragm  904  of the microphone  416  is configured to receive sound via the second microphone aperture  418 ′ of the PCB  402 . A sound control structure  912  or  912 ′ is coupled to the interior surface of the housing and the first surface  402 A of the PCB  402 . The sound control structure  912  or  912 ′ forms a sound channel connecting the first microphone aperture  418  of the housing  902  and the second microphone aperture  418 ′ of the PCB  402  and extending to the controlled sound path  420  that passes across the acoustically porous cover  422 . Further, in some implementations, the sound control structure  912  includes a hollow cylinder that is concentric with the sealing area  908  on the exterior surface  902 A of the housing  902  and the controlled sound path  420  that passes across the acoustically porous cover  422 . 
     Alternatively, in some implementations, the microphone  416  is disposed on the first surface  402 A of the PCB  402  and faces the interior surface of the housing  902 . The sound control structure  912  is coupled to the interior surface of the housing  902  and the microphone  416 , and forms a sound channel connecting the first microphone aperture  418  of the housing  902  and the microphone  416  and extending to the controlled sound path  420  that passes across the acoustically porous cover  422 . 
       FIGS.  10 A- 10 C  are enlarged cross sectional views of example microphone aperture areas  1000 ,  1010  and  1020  of a voice-activated electronic device  104  in accordance with some implementations. In some implementations, the adhesive  910  is configured to be applied on the sealing area  908  of the housing  902  and covered by the acoustically porous cover  422 . Preferably, the adhesive  910  permeates part of the thickness of the acoustically porous cover  422 , rather than an entire thickness, such that the adhesive is not visible or felt by touch from the exterior surface of the acoustically porous cover  422 . During the course of calibrating the microphone  416 , the adhesive  910  permeates at least a predetermined portion of the entire thickness of the acoustically porous cover  422 , and the microphone testing fixture  906  is configured to be pressed onto the region of the acoustically porous cover  422  corresponding to the sealing area  908  to compress microcavities in part of the acoustically porous cover  422  that is not permeated with the adhesive  910 , thereby enabling formation of the controlled sound path  420  of the microphone  416 . 
     Each of the microphone aperture areas  1000 ,  1010  and  1020  has a respective thickness of the acoustically porous cover  422  and a respective predetermined portion of the thickness of the cover  422 . The acoustically porous cover  422  made of a thicker textile/fabric demands a larger compression force from the microphone testing fixture  906  to properly seal an interface between them. It is also desirable to increase a thickness of the adhesive  910  (i.e., the respective determined portion). The adhesive  910  is often transformed after being applied onto the sealing area  908 , and the thickness of the adhesive  910  should not exceed the thickness of the acoustically porous cover  422  before or after the adhesive is transformed. If the thickness of the adhesive  910  exceeds the thickness of the acoustically porous cover  422  prior to transformation, the adhesive  910  may leave a trace on the region of the acoustically porous cover  422  corresponding to the sealing area  908  after transformation, thereby compromising the clean look of the electronic device  104 . If the thickness of the adhesive  910  exceeds the thickness of the acoustically porous cover  422  after transformation, the adhesive  910  is visible and comprises the clean look of the electronic device  104  directly. As such, the thickness of the adhesive  910  is preferred to be increased to fill the fabric (i.e., the microcavities in the fabric) of the acoustically porous cover  422  for improving sealing of the cover-fixture interface while maintaining the clean look of the electronic device  104 . 
     Referring to  FIG.  10 A , the acoustically porous cover  422  in the microphone aperture area  1000  corresponds to a first type of fabric material. The thickness of the acoustically porous cover  422  is approximately equal to 0.5 mm, and the portion of the thickness filled with the adhesive  910  is approximately equal to 0.075 mm. The microphone aperture area  1000  passes a microphone seal test involving the microphone testing fixture  906 , and has a clean look from its exterior surface of the housing  902 . That said, for the acoustically porous cover  422  made of the first type of fabric material, a combination of a cover thickness of 0.5 mm and an adhesive thickness of 0.075 mm enables a desirable sound delivery efficiency while keeping the clean look of the electronic device  104 . 
     Referring to  FIGS.  10 B and  10 C , the acoustically porous cover  422  in the microphone aperture areas  1010  and  1020  corresponds to a second type of fabric material that is distinct from the first type of material. In the microphone aperture area  1010 , the thickness of the acoustically porous cover  422  is approximately equal to 0.63 mm, and the portion of the thickness filled with the adhesive  910  is approximately equal to 0.1 mm. The microphone aperture area  1010  failed a microphone seal test, because the cover-fixture interface is leaky and the portion of sound collected by the microphone  416  does not reach a predetermined portion (e.g., 90%) of sound generated by the microphone testing fixture  906 . In contrast, in the microphone aperture area  1020 , the thickness of the acoustically porous cover  422  is approximately equal to 0.63 mm, and the portion of the thickness filled with the adhesive  910  is approximately equal to 0.2 mm, allowing the microphone aperture area  1020  to pass the microphone seal test. As such, for the acoustically porous cover  422  made of the second type of fabric material, a combination of a cover thickness of 0.63 mm and an adhesive thickness of 0.2 mm (not 0.1 mm) enables a desirable sound delivery efficiency while keeping the clean look of the electronic device  104 . 
     The terminology used in the description of the various described implementations herein is for the purpose of describing particular implementations only and is not intended to be limiting. As used in the description of the various described implementations and the appended claims, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will also be understood that the term “and/or” as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items. It will be further understood that the terms “includes,” “including,” “comprises,” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. 
     As used herein, the term “if” is, optionally, construed to mean “when” or “upon” or “in response to determining” or “in response to detecting” or “in accordance with a determination that,” depending on the context. Similarly, the phrase “if it is determined” or “if [a stated condition or event] is detected” is, optionally, construed to mean “upon determining” or “in response to determining” or “upon detecting [the stated condition or event]” or “in response to detecting [the stated condition or event]” or “in accordance with a determination that [a stated condition or event] is detected,” depending on the context. 
     Although various drawings illustrate a number of logical stages in a particular order, stages that are not order dependent may be reordered and other stages may be combined or broken out. While some reordering or other groupings are specifically mentioned, others will be obvious to those of ordinary skill in the art, so the ordering and groupings presented herein are not an exhaustive list of alternatives. Moreover, it should be recognized that the stages can be implemented in hardware, firmware, software or any combination thereof. 
     The foregoing description, for purpose of explanation, has been described with reference to specific implementations. However, the illustrative discussions above are not intended to be exhaustive or to limit the scope of the claims to the precise forms disclosed. Many modifications and variations are possible in view of the above teachings. The implementations were chosen in order to best explain the principles underlying the claims and their practical applications, to thereby enable others skilled in the art to best use the implementations with various modifications as are suited to the particular uses contemplated. 
     Clause 1. An electronic device, comprising: 
     a housing having an exterior surface and an aperture; 
     a microphone enclosed in the housing and having a diaphragm, wherein the diaphragm of the microphone faces the aperture and is configured to receive sound via the aperture; and 
     an acoustically porous cover at least partially covering the exterior surface of the housing, wherein the acoustically porous cover conceals the aperture of the housing; 
     wherein the exterior surface of the housing includes a sealing area surrounding but not including the aperture, and the acoustically porous cover is affixed to the sealing area of the exterior surface via an adhesive; 
     wherein the adhesive covers the sealing area and permeates a thickness of the acoustically porous cover above the sealing area, thereby enabling formation of a controlled sound path to the microphone by coupling of a microphone testing fixture to a region of the acoustically porous cover corresponding to the sealing area. 
     Clause 2. The electronic device of clause 1, wherein the aperture of the housing includes a first aperture, further comprising: 
     a printed circuit board (PCB) that is enclosed in the housing and has a first surface facing an interior surface of the housing, a second surface opposing the first surface, and a second aperture aligned with the first aperture of the housing, wherein the microphone is coupled to the second surface of the PCB, and the diaphragm of the microphone faces the second aperture of the PCB directly and is configured to receive sound via the second aperture of the PCB; and 
     a sound control structure coupled to the interior surface of the housing and the first surface of the PCB, wherein the sound control structure forms a sound channel connecting the first aperture of the housing and the second aperture of the PCB and extending to the controlled sound path that passes across the acoustically porous cover. 
     Clause 3. The electronic device of clause 1 or 2, wherein the sound control structure includes a hollow cylinder that is concentric with the sealing area on the exterior surface of the housing and the controlled sound path that passes across the acoustically porous cover. 
     Clause 4. The electronic device of any of the preceding clauses, wherein the aperture of the housing includes a first aperture, further comprising: 
     a sound control structure coupled to the interior surface of the housing and the microphone, wherein the sound control structure forms a sound channel connecting the first aperture of the housing and the microphone and extending to the controlled sound path that passes across the acoustically porous cover. 
     Clause 5. The electronic device of clause 4, further comprising: 
     a printed circuit board (PCB) that is enclosed in the housing and has a first surface facing an interior surface of the housing, wherein the microphone is mounted on the first surface of the PCB, and the diaphragm of the microphone faces the first aperture of the housing directly. 
     Clause 6. The electronic device of any of the preceding clauses, wherein the acoustically porous cover is flexible and substantially transparent to audible sound. 
     Clause 7. The electronic device of any of the preceding clauses, wherein: 
     the controlled sound path in the acoustically porous cover is configured to match a dimension of the microphone testing fixture and guide sound generated by the microphone towards the microphone testing fixture; 
     when the microphone testing fixture is coupled to the controlled sound path, a portion of sound generated by the microphone testing fixture is collected by the microphone; and 
     the portion of sound is greater than a predetermined portion of the sound generated by the microphone testing fixture. 
     Clause 8. The electronic device of any of the preceding clauses, wherein the adhesive is not visible from an external surface of the acoustically porous cover. 
     Clause 9. The electronic device of any of the preceding clauses, wherein the adhesive is configured to be applied on the sealing area of the housing and covered by the acoustically porous cover, and the adhesive permeates the thickness of the acoustically porous cover and is hardened in response to heat treatment under a predetermined condition. 
     Clause 10. The electronic device of any of the preceding clauses, wherein the adhesive permeates at least a predetermined portion of an entire thickness of the acoustically porous cover, and the microphone testing fixture is configured to be pressed onto the region of the acoustically porous cover to compress microholes in part of the entire thickness of the acoustically porous cover that is not permeated with the adhesive, thereby enabling formation of the controlled sound path of the microphone. 
     Clause 11. The electronic device of any of the preceding clauses, wherein the sealing area includes a circular ring area.