PATENT DOCUMENT

Publication Number: US-9858948-B2
Application Number: US-201615197506-A
Country: US
Kind Code: B2

Title: Electronic equipment with ambient noise sensing input circuitry

Abstract:
An electronic device may include one or more microphones that monitor ambient noise and generate ambient noise data. The electronic device may include processing circuitry that receives the ambient noise data and compares the ambient noise data to a baseline ambient noise profile to detect changes in the ambient noise. Changes in the ambient noise may be caused by user gestures. The electronic device may compare the changes in the ambient noise to characteristic changes in ambient noise that are associated with user gestures to determine the user gesture made by a user. The processing circuitry may modify the operation of the electronic device based on the user gesture. An ambient noise input device may include surface features or movable components that cause the characteristic changes in the ambient noise. Ambient noise input devices may provide feedback to guide a user to provide input using ambient noise sensing.

Claims:
What is claimed is: 
     
       1. An electronic device that operates in the presence of ambient noise, the electronic device comprising:
 a microphone that measures the ambient noise; and 
 processing circuitry that, based on the measured ambient noise, identifies a user gesture that comprises movement of a user&#39;s hand relative to the electronic device without physically contacting the electronic device and without physically contacting a surface on which the electronic device rests, wherein the processing circuitry modifies the operation of the electronic device in response to the user gesture. 
 
     
     
       2. The electronic device defined in  claim 1 , wherein the processing circuitry determines a change in the ambient noise and identifies the user gesture based on the change in the ambient noise. 
     
     
       3. The electronic device defined in  claim 2 , wherein the processing circuitry determines the change in the ambient noise by comparing the measured ambient noise to a baseline ambient noise profile. 
     
     
       4. The electronic device defined in  claim 2 , wherein the user gesture causes the change in the ambient noise. 
     
     
       5. The electronic device defined in  claim 2 , further comprising:
 an additional microphone that measures the ambient noise, wherein the processing circuitry identifies the user gesture by comparing ambient noise measurements from the microphone and the additional microphone. 
 
     
     
       6. The electronic device defined in  claim 2 , further comprising:
 memory that stores a plurality of different predetermined ambient noise changes that are each associated with a different user gesture, wherein the processing circuitry identifies the user gesture by comparing the change in the ambient noise to the plurality of different predetermined ambient noise changes. 
 
     
     
       7. A method of sensing ambient noise with an electronic device that includes a microphone and processing circuitry, the method comprising:
 generating ambient noise information with the microphone; 
 detecting a change in the ambient noise information using the processing circuitry; 
 identifying a user gesture associated with the change in the ambient noise information using the processing circuitry, wherein the user gesture comprises movement of a user&#39;s hand relative to the electronic device without physically contacting the electronic device and without physically contacting a surface on which the electronic device rests; and 
 with the processing circuitry, adjusting an operational parameter of the electronic device in response to the user gesture. 
 
     
     
       8. The method defined in  claim 7 , wherein determining the user gesture further comprises:
 comparing the change in the ambient noise information to a plurality of predetermined ambient noise changes stored in memory in the electronic device, wherein each of the predetermined ambient noise changes corresponds to a different user gesture. 
 
     
     
       9. The method defined in  claim 7 , further comprising:
 generating additional ambient noise information with an additional microphone in the electronic device; and 
 determining the user gesture based on the ambient noise information and the additional ambient noise information. 
 
     
     
       10. The method defined in  claim 7 , wherein detecting the change in the ambient noise information comprises comparing the ambient noise information to a baseline ambient noise profile, and wherein the change in the ambient noise is at least partially caused by the user gesture. 
     
     
       11. The method defined in  claim 7 , wherein the electronic device comprises a display and the user gesture comprises a user sliding a finger on a surface, wherein adjusting the operational parameter comprises scrolling through content displayed on the display. 
     
     
       12. The method defined in  claim 7 , wherein adjusting the operational parameter comprises an action selected from group consisting of: providing an audible cue to the user through a speaker in the electronic device, performing an action in a gaming application, zooming into a display screen displayed on a display of the electronic device, zooming out of a display screen displayed on a display of the electronic device, and switching between different display screens displayed on a display of the electronic device. 
     
     
       13. An electronic device that gathers user input comprising:
 a microphone that detects changes in ambient noise relative to a baseline ambient noise profile; 
 processing circuitry that identifies user gestures based on the detected changes in the ambient noise; 
 a light source that provides visual feedback in response to identification of the user gestures by the processing circuitry; and 
 a tone generator that generates a tone that supplements the baseline ambient noise profile when the processing circuitry cannot identify the user gestures. 
 
     
     
       14. The electronic device defined in  claim 13 , wherein the feedback comprises a visible outline projected onto a surface on which the electronic device rests. 
     
     
       15. The electronic device defined in  claim 14 , wherein the visible outline indicates an area in which the user gestures can be identified by the processing circuitry. 
     
     
       16. The electronic device defined in  claim 15 , wherein the area is determined during a calibration process in which the microphone detects the changes in the ambient noise caused by the user gestures. 
     
     
       17. The electronic device defined in  claim 13  further comprising an output device that directs a user to move the electronic device to a different location when the processing circuitry cannot identify the user gestures.

Description:
This application claims the benefit of provisional patent application No. 62/234,568, filed Sep. 29, 2015, which is hereby incorporated by reference herein in its entirety. 
    
    
     BACKGROUND 
     This relates to electronic devices and, more particularly, to electronic devices with input-output circuitry for receiving user input. 
     Electronic devices such as cellular telephones, computers, and other devices often include input-output components that allow a user to provide input to the electronic device. For example, electronic devices may include touch sensors or buttons that allow a user to provide commands to the electronic device. 
     Challenges can arise in providing input-output circuitry for an electronic device. If care is not taken, providing an electronic device with the ability to detect different types of user input may increase the size and complexity of the input-output circuitry and the electronic device. 
     SUMMARY 
     An electronic device may be provided with one or more microphones. The microphones may detect ambient noise that is produced by nearby people and objects. The microphones may generate a baseline auditory profile that is representative of the ambient noise. 
     The microphones may detect increases and decreases in volume, frequency, direction, and other characteristics of the ambient noise. Processing circuitry may process the changes and determine the cause of the changes. The electronic device may associate certain changes in the ambient noise with certain user input functions, and may cause a change in the operation of the electronic device based on the changes in the ambient noise. 
     The electronic device may detect a gesture made by a user based on changes in ambient noise. The device may determine characteristics of the gesture such as location, direction, proximity to the device, intensity, and which of a user&#39;s fingers or hands made the gesture. The electronic device may determine features of the gesture by comparing the changes in ambient noise to predetermined, characteristic ambient noise changes that are each associated with a particular gesture. 
     The microphones in the electronic device may be mounted in a device housing. The housing may include openings through which the ambient noise passes to reach the microphones. The openings may include resonant cavities that help to transmit the ambient noise to the microphones with emphasis on particular frequencies or bands of frequencies. The microphones may detect the presence of a user outside of the housing through the openings in the housing. The electronic device may include interior walls having acoustic steering elements that modulate sound waves that enter the housing. 
     The electronic device may be a wearable electronic device that detects changes in ambient noise through a user&#39;s fingers, hands, and arms. The electronic device may determine user gestures based on the changes. A first electronic device may generate ambient noise information in response to detected changes in ambient noise and transmit the signals to a second electronic device. The second electronic device may process the ambient noise information and modify the operation of the second electronic device based on the ambient noise information. 
     Multiple electronic devices may operate together in a system to detect changes in ambient noise. A system may include a first electronic device having a speaker that generates a tone that serves as a baseline ambient noise level and a second electronic device having a microphone that detects changes in the baseline ambient noise level generated by the first or second electronic device. 
     A system may include an ambient noise modulation device having surface features that cause characteristic changes in ambient noise as a user moves their hand relative to the device. The system may include an electronic device may have microphones that detect the characteristic changes in ambient noise and associate the changes with corresponding gestures made over the ambient noise modulation device. The ambient noise modulation device may itself detect the characteristic changes, and transmit the changes or commands based on the changes to the electronic device. 
     A system may include a stylus with a microphone that receives different ambient noise sound waves in response to pressure applied to a tip of the stylus. The stylus may communicate the changes in ambient noise to another electronic device that associates the changes with user inputs and takes corresponding action. 
     An electronic device that identifies user gestures using associated changes in ambient noise may provide a user with visual or other feedback indicative of whether or not the device is able to perform ambient noise sensing. The electronic device may have a light source that projects a visual outline onto a surface on which the device rests to indicate an area around the device in which user gestures produce detectable changes in ambient noise. A user may make numerous gestures during calibration operations so that the electronic device can identify an optimum area surrounding the device for ambient noise sensing. The optimum area can be identified by monitoring gestures performed by a user during a calibration process. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of illustrative electronic devices that include microphones in accordance with an embodiment. 
         FIG. 2A  is a diagram of an illustrative ambient noise profile in accordance with an embodiment. 
         FIG. 2B  is a diagram of an illustrative ambient noise profile and illustrative changes in the ambient noise profile in accordance with an embodiment. 
         FIG. 3  is a schematic diagram of illustrative circuitry for use in an electronic device in accordance with an embodiment. 
         FIG. 4  is a perspective view of an illustrative electronic device in an environment that includes a user and changes in the ambient noise in the environment in accordance with an embodiment. 
         FIG. 5  is a perspective view of an illustrative electronic device in an environment that includes a user and changes in the ambient noise in the environment in accordance with an embodiment. 
         FIG. 6  is a perspective view of an illustrative electronic device having a housing and openings in a surface of the housing in accordance with an embodiment. 
         FIG. 7A  is a cross-sectional view of an illustrative electronic device having microphones mounted near openings in a housing of the electronic device in accordance with an embodiment. 
         FIG. 7B  is a cross-sectional view of an illustrative electronic device having acoustic steering elements mounted in a housing of the electronic device in accordance with an embodiment. 
         FIG. 8  is a side view of an illustrative electronic device that detects changes in ambient noise caused by a user in accordance with an embodiment in accordance with an embodiment. 
         FIG. 9  is a perspective view of multiple electronic devices that communicate changes in ambient noise in accordance with an embodiment in accordance with an embodiment. 
         FIG. 10  is a flow chart of illustrative steps that may be performed in connection with ambient noise sensing and processing in accordance with an embodiment in accordance with an embodiment. 
         FIG. 11  is a perspective view a first device that produces characteristic changes in ambient noise based on user input and a second device that operates based on the changes in accordance with an embodiment in accordance with an embodiment. 
         FIG. 12  is a perspective view of a device having surface features that modulate ambient noise in accordance with an embodiment in accordance with an embodiment. 
         FIG. 13  is a cross-sectional view of a device having surface features that modulate ambient noise and a user&#39;s hand positioned above the surface features in accordance with an embodiment in accordance with an embodiment. 
         FIG. 14  is a perspective view of a stylus that causes changes in ambient noise in accordance with an embodiment. 
         FIG. 15  is a cross-sectional view of a stylus that detects changes in ambient noise in accordance with an embodiment. 
         FIG. 16  is perspective view of an electronic device having an indicator that provides feedback on the ability of the electronic device to perform ambient noise sensing in accordance with an embodiment. 
         FIG. 17  is a perspective view of an electronic device having an indicator that provides guidance to a user during ambient noise sensing calibration operations in accordance with an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Electronic devices may be provided with audio transducers (e.g., microphones) that generate signals in response to sound waves and associated processing circuitry that analyzes the signals to determine deviations from a baseline level of noise in an environment in which the electronic device operates. 
     Illustrative electronic devices of the type that may use ambient noise processing to determine changes in ambient noise are shown in  FIG. 1 . As shown in  FIG. 1 , electronic device  10 A, electronic device  10 B, and electronic device  10 C may each be provided with a plurality of microphones  54  (sometimes referred to herein as ambient noise sensors). Each electronic device  10  may be provided with one or more microphones  54  on one or more surfaces of the electronic device  10 . In the illustrative example of  FIG. 1 , each electronic device  10  includes multiple microphones on two side surfaces of the electronic device and multiple microphones on a front surface of the electronic device. If desired, one or all of electronic devices  10 A,  10 B, and  10 C may be provided with one or more microphones in these or other locations. For example, an illustrative electronic device of the type shown in  FIG. 1  may have first and second opposing surfaces that form front and back surfaces of the electronic device. One or both of the first and second opposing surfaces may include one or more microphones mounted on or adjacent to the surface. If desired, an electronic device  10  may have one or more side surfaces and one or more microphones mounted on or adjacent to the side surfaces (e.g., microphones formed along a peripheral edge that wraps around the electronic device). One or more of electronic devices  10 A,  10 B, and  10 C may include multiple microphones arranged in an array on or beneath an exterior surface of the electronic device. As shown in the illustrative example of  FIG. 1 , each electronic device may include a housing  12  in and/or on which microphones  54  and other device components are mounted, as well as a display  14  for displaying content to a user. 
     As shown in the illustrative example of  FIG. 1 , electronic devices  10 A,  10 B, and  10 C may be placed on a surface  52  such as a table or countertop. Electronic device  10  may operate in an environment in which ambient noise is present in the form of sound waves, noises, and other auditory signals 
     The ambient noise may originate from the day-to-day movement and functions of people, machines, and other objects. For example, the rustling of papers and a running fan may create a baseline level of ambient noise in an office. The sounds of nearby traffic and people walking along a sidewalk may produce background noise on a city street. The chirping of birds and the movement of leaves in the wind, an air-conditioner hiss, refrigerator hum, near or distant voices, dogs barking, rustling of leaves or clothing, footsteps, passing cars, trucks, airplanes, jets, sounds transmitted through an open window or through the walls, the clatter of dishes or glasses in a restaurant or bar, music playing next door or in the next room, and in a seemingly silent environment, even a user&#39;s own breathing may provide sufficient ambient noise sources to enable ambient noise sensing. 
     may contribute to ambient noise in a park. These examples, however, are merely illustrative. Ambient noise may originate from a variety of different sources depending on the surrounding environment in which an electronic device is operating. 
     As the environment around the electronic device  10  changes (e.g., a user moves closer to or farther away from the device, a user or other object contacts surface  52 , an object blocks some or all of the microphones on one or more surfaces of the device, etc.), the ambient noise that reaches the electronic device  10  may also change. The electronic device may be able to detect these changes in ambient noise using microphones and process data from the microphones using ambient noise processing circuitry to determine the nature of the changes. 
       FIG. 2A  is an illustrative profile of a baseline ambient noise level. As shown in  FIG. 2A , the ambient noise may include sounds at a range of frequencies. For example, a baseline ambient noise profile  38  such as that shown in  FIG. 2A  may represent average ambient noise levels for frequencies ranging from 0 hertz (Hz) to 10,000 Hz. Such a baseline ambient noise profile may include a low-frequency peak  39  at approximately 1,000 Hz (as an example) and a peak  42  at approximately 6,000 Hz. Peaks  39  and  42  are, however, merely illustrative. Depending on the environment surrounding the electronic device (e.g., objects that may block or redirect the ambient noise) and the source of the sounds that contribute to the ambient noise profile, the baseline ambient noise level  38  may include peaks or troughs having numerous amplitudes at a variety of different frequencies. 
     If desired, baseline ambient noise  38  may be determined using one or more microphones  54  in an electronic device  10 . For example, a microphone  54  may be powered on and generating microphone signals (sometimes referred to herein as ambient noise signals, ambient noise data, or ambient noise measurements) in response to the ambient noise while the electronic device is otherwise idle (e.g., in a standby mode). Processing circuitry may receive and process the microphone signals to generate an ambient noise profile such as that shown in  FIG. 2A . If desired, the ambient noise profile may represent the average contributions of various frequencies of sound to the overall ambient noise level over a given period of time. This, however, is merely illustrative. If desired, a baseline ambient noise profile  38  such as that shown in  FIG. 2A  may be pre-loaded onto an electronic device  10 , loaded onto electronic device  10  as a software or hardware component, or otherwise obtained in electronic device  10  without the use of microphones  54 . 
     Predetermined ambient noise level  38  may serve as a baseline ambient noise level that is used to determine changes in the ambient noise in a given environment. For example, a microphone  54  may measure ambient noise levels, and generate ambient noise data (sometimes referred to herein as ambient noise information, ambient noise measurements, ambient noise readings, etc.) based on the measured ambient noise. The measured ambient noise levels may include deviations from an average ambient noise profile, such as that shown in  FIG. 2A . Processing circuitry in the electronic device  10  may compare the ambient noise data to the baseline ambient noise information to determine changes in the ambient noise. The processing circuitry may determine characteristics of the changes in the ambient noise (e.g., the frequency, amplitude, and duration of the change) based on the comparisons, and determine the nature of the change. For example, the processing circuitry may determine that the change was caused by a user of the electronic device (e.g., a user gesture, a user input, a user input command, a user input gesture, etc.), and may determine the relative location of the user, the gesture that the user made to cause the change, and the intensity, duration, and direction of the gesture based on the characteristics of the change in the ambient noise. 
       FIG. 2B  is an illustrative diagram of ambient noise levels in an environment and characteristic changes in the ambient noise that may occur. For example, a baseline level  38  of ambient noise that is measured by an electronic device  10  may demonstrate a peak  44  at low frequencies in response to changes in the environment surrounding electronic device  10 . For example, if an object is moved into close proximity to device  10 , there may be an increased low-frequency peak  44  (e.g., a higher amplitude peak) at around 1000 Hz (as an example). Low-frequency peak  44  may result from an object that is in close proximity to electronic device  10  (e.g., a user) forming resonant cavities that amplify certain frequencies that are present in the ambient noise. As shown in  FIG. 2B , baseline ambient noise level  38  may also demonstrate decreases in the amplitude of high-frequency components of the ambient noise, as shown by reduced amplitude  50  at approximately 6,000 Hz. An object in close proximity to electronic device  10  may serve as a bandwidth filter and limit the frequencies in the ambient noise that are received at a microphone  54 . 
     In some suitable scenarios, certain frequencies in the ambient noise may be amplified (as shown by peak  44 ) and other frequencies in the ambient noise may be limited (as shown by damping  50 ) in response to the same environmental change (e.g., a user in close proximity to the electronic device  10 ). This, however, is merely illustrative. The ambient noise  38  that is received may change in other ways independent of or in combination with the low frequency peaking and high frequency damping described above. For example, peaks  46  and trough  48  in ambient noise level  38  may result from various changes in the area surrounding electronic device  10  while electronic device  10  is sampling ambient noise. For example, a user may move a hand over one or more microphones  54  in the electronic device, creating resonant cavities that cause spikes about certain frequencies, while possibly muffling other frequencies. In one suitable example, a user may move a hand or finger closer to or farther away from one or more microphones  54 , inducing changes in the ambient noise profile by blocking ambient noise from certain sources while increasing the relative contribution of noise from other sources. In some scenarios, a user may change the ambient noise profile  38  by producing sounds that constructively or destructively interfere with frequencies that are present in the baseline ambient noise level. 
     Certain environmental changes such as those described above may be associated with characteristic changes in the ambient noise profile  38 . For example, spikes, peaks, muffling, and damping at various frequencies may be characteristic changes in ambient noise that are associated with respective changes (e.g., user gestures, user movement, and user input) in the area surrounding electronic device  10 . Processing circuitry in the electronic device can determine that a change has occurred by detecting associated characteristic changes in the ambient noise. In this way, ambient noise sensing and processing may be used to detect user gestures and other actions in the vicinity of an electronic device. 
     A schematic diagram of an illustrative circuitry  10  that may form part or all of an electronic device is shown in  FIG. 3 . As shown in  FIG. 3 , circuitry  10  (sometimes referred to herein as electronic device  10 ) may include control circuitry such as storage and processing circuitry  40 . Storage and processing circuitry  40  may include one or more different types of storage such as hard disk drive storage, nonvolatile memory (e.g., flash memory or other electrically-programmable-read-only memory), volatile memory (e.g., static or dynamic random-access-memory), etc. Processing circuitry in storage and processing circuitry  40  may be used in controlling the operation of device  10 . The processing circuitry may be based on one or more microprocessors, microcontrollers, digital signal processors, baseband processor integrated circuits, application specific integrated circuits, etc. 
     To support interactions with external equipment, storage and processing circuitry  40  may be used in implementing communications protocols. Communications protocols that may be implemented using storage and processing circuitry  40  include internet protocols, wireless local area network protocols (e.g., IEEE 802.11 protocols—sometimes referred to as WiFi®), protocols for other short-range wireless communications links such as the Bluetooth® protocol, etc. 
     If desired, storage and processing circuitry  40  may include ambient noise processing circuitry  41 . Ambient noise processing circuitry  41  may include a specialized integrated circuit such as an ambient noise processing integrated circuit that receives ambient noise signals from microphones  54  in device  10 . By providing electronic device  10  with ambient noise processing circuitry  41 , ambient noise processing operations may be carried out even when other components of processing circuitry  40  (e.g., a CPU or other processors) are inactive. In one suitable example, the processing and power requirements associated with ambient noise processing may be partially or completely offloaded from other processing components onto ambient noise processing circuitry  41 , thereby allowing ambient noise processing to run in the background even when other functions of device  10  are inactive. If desired, device  10  may be operable in a low power mode in which some or all of storage and processing circuitry  40  is inactive (e.g., powered down) while ambient noise processing circuitry  41  is actively processing ambient noise signals to determine when the low power mode should be deactivated and some or all of the functions of storage and processing circuitry  40  should be restored. 
     Input-output circuitry  32  may be used to allow input to be supplied to device  10  from a user or external devices and to allow output to be provided from device  10  to the user or external devices. 
     Input-output circuitry  32  may include wired and wireless communications circuitry  34 . Communications circuitry  34  may include radio-frequency (RF) transceiver circuitry formed from one or more integrated circuits, power amplifier circuitry, low-noise input amplifiers, passive RF components, one or more antennas, and other circuitry for handling RF wireless signals. Wireless signals can also be sent using light (e.g., using infrared communications). 
     Input-output circuitry  32  may include input-output devices  36  such as buttons, joysticks, click wheels, scrolling wheels, a touch screen (e.g., a display  14  as described in connection with  FIG. 1  may be a touch screen display), other touch sensors such as track pads or touch-sensor-based buttons, vibrators, image capture devices such as a camera module having an image sensor and a corresponding lens system, keyboards, status-indicator lights, key pads, speakers, and other equipment for gathering input from a user or other external source and/or generating output for a user or for external equipment. Output components in device  10  may produce an output (e.g., display content that is displayed on a display screen, sound that is produced by a speaker, haptic feedback that is produced by a vibrator, etc.) for a user of device  10 . 
     Sensor circuitry such as sensors  35  of  FIG. 3  may include an ambient light sensor for gathering information on ambient light, proximity sensor components (e.g., light-based proximity sensors and/or proximity sensors based on other structures), accelerometers, gyroscopes, magnetic sensors, and other sensor structures. Sensors  35  of  FIG. 3  may, for example, include one or more microelectromechanical systems (MEMS) sensors (e.g., accelerometers, gyroscopes, microphones, force sensors, pressure sensors, capacitive sensors, or any other suitable type of sensor formed using a microelectromechanical systems device). 
     Input-output circuitry  32  of  FIG. 3  may include one or more microphones  54 . As described in connection with  FIG. 1 , one or more microphones (audio transducers)  54  may convert sound waves into electrical signals that are transmitted to storage and processing circuitry  40  (e.g., ambient noise processing circuitry  41 ) for processing. If desired, device  10  may include a plurality of microphones  54  formed in an array or other suitable configuration or pattern that each receive different baseline ambient noise levels and different changes in the ambient noise levels in response to changes in the environment. 
     Input-output circuitry  32  of  FIG. 3  may include one or more audio output components  33  (e.g., speakers, tone generators, ultrasonic frequency generators, etc.) that generate sound waves. In one suitable arrangement, audio output components  33  may generate sound waves that make up some or all of the ambient noise baseline  38  detected by microphones  54 . The sounds generated by audio components  33  may be audible (e.g., within the range of human hearing), ultrasonic, or a combination of both, if desired. Audio components  33  may be able to produce a more consistent and predictable baseline against which changes can be measured, which may simplify determination of characteristic changes associated with certain environmental conditions (e.g., user gestures). If desired, a first electronic device  10  (e.g., electronic device  10 A as shown and described in connection with  FIG. 1 ) may generate a baseline audio profile using audio output components  33 , while a second electronic device  10  (e.g., electronic device  10 B as shown and described in connection with  FIG. 1 ) may detect the baseline audio profile and changes in the baseline audio profile due to user gestures or other environmental conditions. This, however is merely illustrative. If desired, the baseline audio profile against which changes in ambient noise are measured may not include any auditory signals generated by audio output components  33  in electronic device  10 . 
     If desired, one of more electronic devices  10  (e.g., electronic devices  10 A,  10 B, and  10 C described in connection with  FIG. 1 ) may include none, some, or all of the components described above in connection with an illustrative electronic device  10 . In at least one suitable example, multiple electronic devices  10  having similar or different components may be used together in ambient noise detection and processing operations. 
     If desired, an electronic device  10  (e.g., one or more of electronic devices  10 A,  10 B, and  10 C) may be a computer such as a computer that is integrated into a display such as a computer monitor, a laptop computer, a tablet computer, a somewhat smaller portable device such as a wrist-watch device, pendant device, or other wearable or miniature device, a cellular telephone, a media player, a tablet computer, a gaming device, a navigation device, a computer monitor, a television, or other electronic equipment. 
     If desired, electronic devices  10  may include a housing  12  in which one or more microphones  54  and associated processing circuitry are mounted. If desired, the housing  12  may include upper and lower portions that are coupled with a hinge that allows the upper portion to rotate relative to the lower portion. The housing  12  may be machined or molded as a single structure (e.g., a unibody housing). An electronic device  10  may include a display  14  mounted in the housing  12 . The display  14  may form parts of the front, rear, and side surface of the electronic device  10 . The display  14  may be substantially filled with active display pixels or may have an active portion and an inactive portion. The display  14  may have openings (e.g., openings in the inactive or active portions of display) such as an opening to accommodate buttons and an opening to accommodate speakers. 
     Electronic devices  10 A,  10 B, and  10 C may each be similar electronic devices (e.g., cellular telephones) or may each be different (e.g., a cellular telephone, a laptop computer, and a wearable electronic device, for example). If desired, any one or all of electronic devices  10 A,  10 B, and  10 C may include some or all of the electronic device components described above. Although  FIG. 1  shows three electronic devices  10 A,  10 B, and  10 C, this is merely illustrative. In general, one, two, three, or more than three electronic devices may be used alone or together for ambient noise detection and processing. 
     An illustrative example of an electronic device that may use ambient noise sensing and processing is shown in  FIG. 4 . In the illustrative example of  FIG. 4 , an electronic device  10  having a first microphone  54 - 1  and a second microphone  54 - 2  is provided on a surface  52  with a user  55  nearby. In the example of  FIG. 4 , microphones  54 - 1  and  54 - 2  may be actively receiving sound waves that make up the ambient noise profile around the electronic device  10 , and may be generating ambient noise data based on the ambient noise. User  55  may be present near surface  52  and device  10 . For example, a user may be holding their hand above surface  52 . Electronic device  10  may sense that a user has placed their hand in proximity to the surface  52  and device  10  based on a change in ambient noise caused by the user&#39;s hand, and re-adjust the baseline ambient noise profile based on this change (after one, three, five, ten, less than then, or more than 10 seconds, for example). Alternatively, processing circuitry in the electronic device may be configured to detect that a user has simply moved their hand near the device  10 , and disregard any associated change in ambient noise as not being associated with a user gesture. 
     A user may make gestures that change the ambient noise in the environment surrounding device  10 . For example, a user may move finger  56 - 1  downwards onto surface  52  as shown by arrow  58 - 1 , causing a change  60 - 1  in the ambient noise. In one suitable scenario, a user may simply place their finger on the table (e.g., without creating any audible sound). In such a scenario, the placement of a user&#39;s finger  56 - 1  on the surface  52  may cause a change in the ambient noise that is received at one or both of microphones  54 - 1  and  54 - 2 . For example, the placement of finger  56 - 1  on surface  52  may block some of the ambient noise from reaching microphones  54 - 1  and  54 - 2 , resulting in peaks or muffling at certain frequencies in the ambient noise profile. Microphones  54 - 1  and  54 - 2  may detect such changes in the ambient noise profile and, in response to the changes, generate different ambient noise data than that which is generated in accordance with the baseline ambient noise profile. The changes in the ambient noise data may be processed by processing circuitry in the electronic device  10  to determine the change in the ambient noise. By comparing the change in the ambient noise to known characteristic changes in the ambient noise that are associated with known user gestures, the electronic device  10  may be able to determine that the change in ambient noise was caused by finger  56 - 1 , rather than finger  56 - 2  or finger  56 - 3 . 
     The illustrative example described above in which finger  56 - 1  causes the change in the ambient noise is, however, merely illustrative. As shown in  FIG. 4 , for example, a user  55  may move finger  56 - 2  downward onto surface  52  (in a tapping motion, for example), as shown by arrow  58 - 2 . This downward movement may cause a change  60 - 2  in the ambient noise, which may be measured by microphones  54 - 1  and  54 - 2 . The change in ambient noise data caused by the change  60 - 2  in the ambient noise data may be processed by processing circuitry in electronic device  10  such that the gesture made by user  55  (e.g., placing finger  56 - 2  on the surface  52 ) may be differentiated from other user gestures (e.g., gestures involving fingers  56 - 1  or  56 - 2 ). Similarly, the placement of finger  56 - 3  on surface  52  as shown by arrow  58 - 3  may cause a change  60 - 3  in the ambient noise that is detected and processed by microphones  54 - 1  and  54 - 2  to determine that the change was caused by finger  56 - 3  moving towards surface  52 , rather than another gesture made by another finger. In general, each of changes  60 - 1 ,  60 - 2 , and  60 - 3  may be different such that electronic device can differentiate between the different changes and the gestures associated with each respective change. 
     The examples described above in which the changes  60 - 1 ,  60 - 2 , and  60 - 3  are caused simply by a user placing a finger on a table are merely illustrative. If desired, a user  55  may move a finger (such as finger  56 - 1 , for example) downward in direction  58 - 1  and contact surface  52  with enough force to cause an increased change  60 - 1  in the ambient noise profile. In this way, electronic device  10  may be able to detect the force or magnitude associated with gestures made by a user. In one example, the tapping of a user&#39;s finger  56 - 1  on the table may generate additional sounds that increase certain frequencies in the ambient noise profile or that add new frequencies to the ambient noise profile, thereby generating a different change  60  in the ambient noise detected by the microphones  54 . 
     In another suitable example, a user may move a finger  56  in one of directions  58  without actually contacting surface  52 , while still generating a change  60  in the ambient noise. This change in ambient noise may be detected by microphones  54  and processed by electronic device  10  to determine the gesture associated with the change, which of the user&#39;s fingers  56  made the gesture, the intensity of the gesture, the direction from which the change occurred, and other characteristics of the change. 
     As shown in the example of  FIG. 4 , electronic device  10  may include a first microphone  54 - 1  and a second microphone  54 - 2 . Microphones  54 - 1  and  54 - 2  may be formed in different locations and on different surfaces of electronic device  10 , as shown in  FIG. 4 . This, however, is merely illustrative. If desired, one or more microphones  54  may be formed on the same surface of electronic device  10  (e.g., two or more microphones formed in an array), or may be formed on adjacent portions of different surfaces of electronic device  10 . By forming microphones  54 - 1  and  54 - 2  in different locations, each microphone may detect different changes in the ambient noise, even if the change is caused by the same event or user gesture. 
     In one example, microphone  54 - 1  may generate a first set of ambient noise data, and microphone  54 - 2  (e.g., an additional microphone) may generate a second set of ambient noise data (e.g., additional ambient noise data). The first and second sets of ambient noise data may reflect different changes in ambient noise detected by each of the microphones. By comparing the first and second sets of ambient noise data, characteristics of the change in ambient noise may be determined. For example, both first and second microphones  54 - 1  and  54 - 2  may detect a spike in the ambient noise at a given frequency. The intensity of the spike detected by microphone  54 - 1  may be greater than that detected by microphone  54 - 2 , indicating that the event that caused the spike (e.g., a user gesture), occurred closer to microphone  54 - 1  than microphone  54 - 2 . In another example, microphone  54 - 2  may detect a change in ambient noise, while microphone  54 - 1  may not experience any change in the ambient noise. Based on comparisons between the two ambient noise signals, the electronic device may be able to determine that the event that caused the change involved an obstruction of the ambient noise in the plane of the second microphone, but no obstruction of the ambient noise in the plane of the first microphone. In this way, the different changes in ambient noise detected by different microphones on or in the electronic device may be used to determine characteristics such as location, duration, and intensity of the user gesture or other event that caused the change. 
     If desired, microphone  54 - 1  may measure a first ambient noise level that is used to generate a first baseline ambient noise profile, and microphone  54 - 2  may measure a second ambient noise level that is used to generate a second baseline ambient noise profile. In this way, each of microphones  54 - 1  and  54 - 2  may generate a baseline that accounts for the differences in ambient noise that each microphone may experience based on the different locations or orientations of the microphones. This, however, is merely illustrative. If desired, the baseline ambient noise readings from each of microphones  54 - 1  and  54 - 2  may be averaged to generate a single ambient noise profile against which readings from microphone  54 - 1  and  54 - 2  are compared to determine changes in the ambient noise. 
     Microphones  54 - 1  and  54 - 2  may also detect other user gestures associated with ambient noise signatures. For example, microphones may be able to detect proximity-based user gestures, such as a user moving their hand above the electronic device (e.g., closer to or farther away), moving their hand over the electronic device (e.g., swiping), or towards and away from an edge of the electronic device (e.g., a U-shaped gesture). Microphones  54  may detect these user gestures based on their ambient noise signatures and respond accordingly. Examples of responses that the electronic device may perform include swiping through (switching between) different display screens, zooming in and out of display screens, adjusting the volume of a speaker or brightness of a display, or performing application-specific functions, such as controls within a gaming application. 
     An illustrative example of an electronic device that may use ambient noise sensing and processing to determine changes in ambient noise is shown in  FIG. 5 . As shown in  FIG. 5 , electronic device  10  may operate in an environment that includes a surface  52  on which the electronic device  10  rests and a user  55  having a hand  57 . In the illustrative example of  FIG. 5 , a user  55  may move their hand  57  in one or more directions. For example, a user may move their hand to the left (as shown by arrow  62 - 1 ), forward (as shown by arrow  62 - 2 ), to the right (as shown by arrow  62 - 3 ) and back (as shown by arrow  62 - 4 ). If desired, each of movements  64 - 1  to  64 - 4  may occur in a plane that is substantially parallel to surface  52 . A user may also move their hand in directions that are substantially transverse to the plane of surface  52 , such as upward (as shown by arrow  62 - 5 ), and downward (as shown by arrow  62 - 6 ). In one suitable example, a user may make the above-mentioned movements without touching or otherwise physically contacting surface  52  or device  10 . 
     As a user moves their hand in directions  64 - 1  to  64 - 6  described above, the ambient noise received at microphones  54 - 1  and  54 - 2  on device  10  may change. For example, as a user moves their hand from a position over device  10  in a direction downward and closer to the device  10  (as shown by arrow  62 - 6 ), the ambient noise received at microphones  54 - 1  and  54 - 2  may include a spike at low frequencies and damping at higher frequencies as the higher frequencies are filtered out and the lower frequencies are amplified due to the resonant cavity formed by the proximity of the user&#39;s hand to the device  10  and surface  52 . Based on these characteristic changes in the ambient noise, electronic device  10  may determine that a user&#39;s hand has been moved closer to the electronic device and respond accordingly. 
     In another suitable example, microphones  54 - 1  and  54 - 2  may detect similar changes in ambient noise, but at different times. For example, if a user  55  moves hand  57  in direction  62 - 3 , microphone  54 - 1  may detect a characteristic change in the ambient noise that indicates that hand  57  passed over microphone  54 - 1  at a first time, while microphone  54 - 2  may detect a characteristic change in the ambient noise that indicates that hand  57  passed over microphone  54 - 2  at a second time that is temporally after the first time. By comparing the temporal differences in the ambient noise changes, processing circuitry in the electronic device may be able to determine that a user performed a left-to-right swiping gesture over the electronic device  10 . 
     In another suitable example, microphones  54 - 1  and  54 - 2  may experience a similar change in ambient noise at approximately the same time. For example, both microphone  54 - 1  and microphone  54 - 2  may experience a similar change in ambient noise for a similar duration of time between otherwise normal ambient noise readings. Such a change may indicate, for example, that a user  55  moved hand  57  over device  10  in direction  62 - 2 , causing similar changes in ambient noise at microphones  54 - 1  and  54 - 2  at approximately the same time. In this way, electronic device  10  may be able to determine that a user performed a back-to-front swiping gesture over device  10 . 
     If desired, similarities and differences between the ambient noise readings generated by microphones  54 - 1  and  54 - 2  may be used to determine other gestures, such as diagonal gestures and gestures with multiple directional components. For example, differences in the magnitude, frequency, duration, and relative timing of the changes in ambient noise detected by microphones  54 - 1  and  54 - 2  may be compared to known characteristic changes in ambient noise associated with different known user gestures to determine the gesture that was made by the user. 
     Electronic device  10  may modify the operation of one or more device components in response to ambient noise information from one or microphones  54 . For example, processing circuitry in the electronic device may change an operational parameter of the electronic device such as changing a brightness level, changing a volume level, locking or unlocking the device, or another suitable response. If desired, the processing circuitry may adjust an output of an output component of the electronic device (e.g., a display, a speaker, a haptic feedback component, etc.) in response to a user movement (e.g., a user gesture or a user input command) by changing the content displayed on the display or changing the sound produced by the speaker. In one suitable example, the display may present display content (e.g., a graphical user interface) that includes a cursor or other symbol that a user may use to select and control components of the graphical user interface. The processing circuitry may change the location of the cursor on the display or select a portion of the graphical user interface (in accordance with a clicking operation, for example) in response to changes in the ambient noise caused by the user input. If desired, a user dragging, sliding, or otherwise moving one or more fingers across a surface may correspond to a change in the ambient noise that that is recognized by the device and causes the device to move a cursor across the screen. A user tapping or otherwise placing one or more fingers on a surface may cause a change in the ambient noise that causes the processing circuitry to select a component of a graphical user interface (in accordance with a clicking operation, for example). The processing circuitry may cause the electronic device to scroll up or down through content that is displayed on the display in response to changes in the ambient noise caused by a user dragging or swiping one or more fingers across a surface. In one suitable arrangement, the processing circuitry may increase or decrease the volume of music or another speaker output in response to ambient noise changes caused by a user moving their hand closer to or farther from the electronic device. If desired, processing circuitry in electronic device  10  may cause an audio playback operation to move forward or backwards (e.g., fast-forward or rewind) in response to a user swiping their hand over the electronic device. Processing circuitry may adjust a volume level for a speaker or brightness level for a display in response to a user moving their hand up and down over the electronic device. Processing circuitry may interpret an ambient noise-based user input as denoting a change in the outward-inward position of a user relative to (i.e., nearer to or farther from) the electronic device along a depth dimension (i.e., along a z axis perpendicular to x and y axes that are parallel to a plane defined by a surface of the device). In the context of a game or photo-viewing application, for example, movement of a user&#39;s hand may represent travel forward or back in time. These examples, however, are merely illustrative. An electronic device  10  having a microphone  54  and processing circuitry may associate numerous changes in ambient noise with various user gestures and make one or more suitable changes to device operation in response to the user gestures. 
     An illustrative electronic device  10  having a housing  12  that includes openings  68  is shown in  FIG. 6 . As shown in  FIG. 6 , openings  68  may form part of a speaker grille  66  under which one or more microphones and/or one or more speakers may be mounted. This, however, is merely illustrative. If desired, openings  68  may be discrete openings formed in housing  12  in electronic device  10  that are used only for directing sound to microphones mounted in the housing near the openings. In the illustrative example of  FIG. 6 , electronic device  10  is shown as a laptop computer having upper and lower housing portions, with the openings  68  formed as part of the lower housing portion. This arrangement is merely illustrative. If desired, openings  68  may be formed in any desired portion of a device housing  12 . 
     A cross-sectional view of housing  12  and openings  68  taken along line A-A in  FIG. 6  is shown in  FIG. 7A . As shown in  FIG. 7A , openings  68  may extend partially or completely through housing  12  to form cavities  70  (sometimes referred to herein as paths, transmission pathways, or sound-directing structures). If desired, cavities  70  may be resonant cavities that resonate ambient noise or changes in ambient noise that enter openings  68  and are transmitted through housing  12 . An array of microphones  54 - 1 ,  54 - 2 ,  54 - 3 ,  54 - 4 ,  54 - 5 , and  54 - 6  may be formed beneath openings  68  such that ambient noise is directed to the microphones  54  through the openings  68  and cavities  70 . When device  10  is simply sitting in an environment (e.g., no user is using the device), each of the microphones  54  in the array may receive ambient noise that is substantially identical and generate similar baseline ambient noise signals. 
     In the illustrative example of  FIG. 7A , openings  68  are shown as circular openings, and cavities  70  are shown as having a conical cross-sectional profile. This is merely illustrative. If desired, openings  68  may have any desired shape, such as rectangular, square, triangular, elliptical, semicircular, or any other suitable polygonal shape. If desired, cavities  70  may be rectangular, may have walls that diverge from openings  68  as the cavity extends through the housing, may have patterned walls, or may have any other suitable cross-sectional profile. If desired, each of the openings  68  and cavities  70  that are formed in a housing  12  may have the same shape, or housing  12  may include openings  68  and cavities  70  having different shapes. For example, housing  12  may include a first group of openings and cavities that have a first shape that is configured to serve as a resonant cavity for a first frequency, or sound that arrives from a first direction, may have a second group of openings and cavities that have a second shape that is configured to serve as a resonant cavity for a second frequency, or sound that arrives from a second direction, and may have a third group of openings and cavities that have a third shape that is configured to serve as a resonant cavity for a third frequency, or sound that arrives from a third direction. 
     As shown in  FIG. 7A , a user  55  may place their hand over a portion of the openings  68  in housing  12 . Such a gesture by a user may change the ambient noise that is received at the microphones  54 . The microphones  54  may detect these changes in ambient noise, and may determine that a user has placed their hand on the electronic device based on these changes (e.g., by comparing the changes in ambient noise to known changes in ambient noise that are associated with a user placing a hand on the device). 
     A user  55  may make gestures while using device  10 . For example, a user may place one or more fingers  56 - 1  and/or  56 - 2  over one or more openings  68  in housing  12 , which may cause a change  60  in the ambient noise that is received at the microphones  54  in the array. In the illustrative example of  FIG. 7A , a change  60  in the ambient noise is caused by a user placing finger  56 - 1  over an opening  68 . When user  55  places finger  56 - 1  in this location, the ambient noise that is transmitted to microphones  54 - 5  and  54 - 6  (as shown by arrows  76 ) is changed. In such an example, the gesture made by a user  55  using finger  56 - 1  may have little to no effect on the ambient noise received at microphones  54 - 1 ,  54 - 2 ,  54 - 3 , and  54 - 4 . This may be because the gesture was localized to an area not directly above these microphones, and/or because the sound-directing effects of cavities  70  direct the change to only some of the microphones in the array. By comparing the ambient noise data generated by each of the microphones, the location, duration, intensity, and specific finger of the user  55  associated with the gesture can be determined. 
     In the example described above, changes in ambient noise associated with a user placing a finger over an opening  68  in housing  12  are described. This, however, is merely illustrative. If desired, microphones  54  (e.g., microphones that receive sound through openings  68  and passageways  70 ) may detect changes in ambient noise due to other user gestures. For example, movement of a user&#39;s hand in sideways directions  62 - 1  and  62 - 3 , forward and backward directions  62 - 2  and  62 - 4 , and up and down in directions  62 - 5  and  62 - 6  may cause changes in ambient noise that are detected by microphones  54 - 1 ,  54 - 2 ,  54 - 3 ,  54 - 4 ,  54 - 5 , and  54 - 6 . By using processing circuitry to measure the changes in ambient noise data generated by each microphone and comparing the changes, electronic device  10  may recognize user gestures and activate, deactivate, or otherwise modify a function of the electronic device  10 . 
     If desired, electronic device  10  may be provided with internal walls within housing  12  (sometimes referred to herein as acoustic walls, barriers, acoustic isolation structures, or acoustic steering elements) between one or more microphones  54 . As shown in the illustrative example of  FIG. 7B , acoustic isolation structures  112  may be interposed between two microphones  54  to prevent changes in ambient noise  60  that are transmitted (as indicated by arrow  76 ) to first microphone  54 - 1  from reflecting within housing  12  and being received at a second microphone  54 - 2 . Such an arrangement may be implemented when each of openings  68  and passages  70  has substantially the same size and shape (and therefore transmit and direct ambient noise to respective microphones  54  in similar ways) as a way to prevent cross-talk between the respective microphones. In this way, electronic device  10  may be able to more accurately determine the source (e.g., location, directionality, distance, or type of gesture) associated with changes in ambient noise  60  received at a given microphone. This, however, is merely illustrative. Acoustic isolation structures  112  may serve to isolate microphones  54 - 1  and  54 - 2  that are configured to receive different ambient noise changes (e.g., having different frequencies, arriving from different directions, resulting from different gestures, etc.). In this instance, acoustic walls  112  may prevent changes in ambient noise that are intended to be received at one microphone  54 - 1  from being redirected within housing  12  and inadvertently arriving at microphone  54 - 2 , or vice-versa. 
     Acoustic walls  112  may have one or more patterned surfaces. Patterned surfaces on acoustic walls  112  may serve to provide acoustic isolation properties to walls  112  (e.g., by simply blocking a passageway between microphones  54 - 1  and  54 - 2 ) or may have acoustic properties that amplify or further encode the ambient noise received at microphones  54 - 1  and  54 - 2 . In one illustrative example, walls  112  may have protrusions  114  that project from walls  112  to redirect sound waves that begin to move away from microphone  54 - 1  (due to being reflected within housing  12 , for example) back towards microphone  54 - 1 . In this way, wall  112  may serve as an acoustic steering element that redirects or amplifies soundwaves back towards microphone  54 - 1  (or  54 - 2 ) to increase the amount of ambient noise that is received at the microphone and available for sampling. 
     In another suitable example, protrusions  114  may be configured to encode or modulate ambient noise that is received through openings  68  and passageways  70 . For example, a first sound encoding element  112  may have structures  114  that modify incident sound waves in a first way (e.g., a change in frequency, a change in direction, a change in amplitude, etc.) while a second sound encoding element may have structures  114  that modify the incident sound waves in a second way (e.g., a different change in frequency, direction, amplitude, etc.). If desired, acoustic steering elements  112  may be configured to cause constructive or destructive interference between sound ways that are received through openings  68 . In one example, a microphone  54  may be configured to only respond to sound waves that have been modulated in a particular manner. In another example, microphone  54  may be able to gather additional information based on the modulation of the sound waves (e.g., which acoustic modulator  112  the sound wave was directed by). This additional information may provide further details regarding changes in ambient noise  60 , such as which openings  68  received the ambient noise sound waves, the direction that the sound waves were traveling when they entered the device, or other features of changes in ambient noise  60 . 
     In the illustrative example  FIG. 7B , protrusions  114  have a wave-shaped profile. This, however, is merely illustrative. If desired, protrusions  114  may have a triangular, rectangular, hexagonal, octagonal, circular or semi-circular, scalloped, corrugated, or other suitable profile. Protrusions  114  may be formed in any suitable configuration on an internal wall  112  (which may be formed in any suitable configuration within housing  12 ). Internal walls  112  may be formed between individual openings  68  and/or microphones  54 , or may separate groups of microphones or openings. In general, internal walls  112  and protrusions  114  may be provided within device housing  12  in any suitable arrangement to modulate ambient noise that is received at microphones  54 . 
     One or more different types of microphones  54  may be used for ambient noise sensing. The type of microphone may be selected to have a specific directionality (i.e., to be sensitive to sound waves from certain directions) or frequency sensitivity. Microphone  54  may have a unidirectional, bidirectional, omnidirectional, cardioid, sub-cardioid, super-cardioid, hyper-cardioid, hypo-cardioid, shotgun, or other suitable response pattern. 
     An illustrative example of an electronic device  10  that may detect ambient noise using a microphone  54  and perform ambient noise processing to determine changes in the ambient noise is shown in  FIG. 8 . In the illustrative example of  FIG. 8 , device  10  is a wearable electronic device such as a watch that is worn on the wrist of a user  55 . Microphone  54  is positioned on a bottom surface of the device  10  such that some or all of the microphone faces the body of the user. In such an example, the ambient noise received at microphone  54  may include peaks or troughs at certain frequencies due to the close proximity of microphone  54  to user  55 . If desired, the baseline ambient noise profile used by device  10  to determine changes in ambient noise may be based on the modified ambient noise levels received at microphone  54  simply due to the fact that user  55  is wearing device  10 . 
     In the illustrative example of  FIG. 8 , microphone  54  may detect changes in the ambient noise and generate ambient noise data that reflects the changes. In one scenario, microphone  54  may be able to detect when a user  55  places their hand on surface  52  due to changes in the ambient noise received at the microphone. For example, a microphone  54  and processing circuitry in device  10  may recognize that a user&#39;s hand is resting on a surface based on a characteristic ambient noise profile that differs from an ambient noise profile that is detected when a user is walking or has their hand at their side. In response to determining that the user has rested their hand on the surface  52 , device  10  may switch operational modes (e.g., may enter an ambient noise sensing and processing mode) that allows device  10  to detect changes in ambient noise associated with user gestures on or around surface  52 . 
     In one suitable example, device  10  may be able to detect user gestures through user  55 , as shown by path  78 . For example, user  55  may move one of fingers  56 - 1  in direction  58 - 1  to place the finger on surface  52 . This movement of finger  56 - 1  may cause movements of the user&#39;s wrist and hand, which may cause changes  60  in the ambient noise received at microphone  54 . Processing circuitry may process these changes in the data provided by microphone  54  (by comparing them to a baseline ambient noise profile and/or characteristic changes associated with known user gestures, for example), to determine the gesture made by the user. Because movement of finger  56 - 2  in direction  58 - 2  may cause different changes in the ambient noise received at microphone  54 , processing circuitry may be able to differentiate between gestures made with finger  56 - 1  and  56 - 2 . If desired, the duration and/or force of the gesture may be determined based on the duration and/or magnitude of the change in ambient noise detected by microphone  54 . Movement of fingers  56 - 1  and/or  56 - 2  in directions  62 - 1 ,  62 - 2 ,  62 - 3 , and/or  62 - 4  may cause changes in the ambient noise received at microphone  54 . Processing circuitry in device  10  may be able to determine the direction, velocity, and force associated with these gestures, and accordingly modify the operation of electronic device  10  or another electronic device based on these characteristics. 
     The examples described above in which microphone  54  detects user gestures based on changes in ambient noise are merely illustrative. If desired, movement of a user&#39;s hand in directions  62 - 1 ,  62 - 2 ,  62 - 3 , and/or  62 - 4  may generate additional sound waves that may be detected by microphone  54 . Similarly, a user may tap fingers  56 - 1  and  56 - 2  on surface  52  with sufficient force to produce sound waves that are detected by microphone  54 . If desired, sound waves such as these may cause microphone  54  to generate data that differs from a baseline sound level, which may be used to determine user gestures and modify the operation of electronic device  10  or other devices. 
     The illustrative examples described above in which device  10  is provided with one microphone  54  are merely illustrative. If desired, device  10  may be provided with a plurality of microphones  54 , each of which may detect changes in the ambient noise received at device  10  and generate corresponding ambient noise data. Processing circuitry in device  10  or another electronic device may use the data from the multiple microphones to determine the source of the changes in ambient noise and any associated user gestures. If desired, a plurality of microphones  54  may be formed in an array on the bottom surface of device  10 , or multiple microphones  54  may be formed on multiple different surfaces of device  10 . 
     An illustrative example of a plurality of electronic devices  10 A,  10 B, and  10 C each having at least one microphone  54  for monitoring ambient noise and detecting changes in the ambient noise is shown in  FIG. 9 . As described above in connection with  FIGS. 1-8 , each of devices  10 A,  10 B, and  10 C may detect changes in ambient noise such as changes  60 - 1  and  60 - 2  associated with a user placing one or both of fingers  56 - 1  and  56 - 2  on or near surface  52  by moving fingers  56 - 1  and  56 - 2  in directions  58 - 1  and  58 - 2 , respectively. Similarly, each of devices  10 A,  10 B, and  10 C may detect changes in ambient noise caused by movement of a user in directions  62 - 1 ,  62 - 2 ,  62 - 3 ,  62 - 4 ,  62 - 5 , and  62 - 6 . By processing changes in the ambient noise data generated by microphones  54 , devices  10 A,  10 B, and  10 C may determine user gestures associated with the changes in ambient noise and modify operational parameters associated with the device. 
     If desired, a first device such as device  10 A may be used to change the operation of a second device, such as device  10 B. For example, device  10 A may detect changes in ambient noise using microphone  54  in device  10 A, and generate corresponding ambient noise data. Device  10 A may then wirelessly transmit the data as a transmission  74  to device  10 B, which may process the data to determine the user gestures associated with the changes in ambient noise. Device  10 B may then modify operational parameters of device  10 B based on the user gestures. In this way, a first device may be used to detect changes in ambient noise, while a second device may change its function based on the changes in ambient noise and associated gestures made by a user. If desired, the first device (e.g. device  10 A) may generate and process the data, and simply send commands to the second device (e.g., device  10 B) as a wireless transmission  74 . In one arrangement, the second device  10 B may process the data from the first device  10 A, and transmit commands based on the processed data to a third device  10 C. This, however, is merely illustrative. In general, any combination of devices  10 A,  10 B, and  10 C may be used to monitor ambient noise and detect changes in the ambient noise, process data signals generated in response to the ambient noise, and modify device operations based on user gestures or other events associated with the ambient noise. 
     In the illustrative example of  FIG. 9 , some or all of electronic devices  10 A,  10 B, and  10 C may include one or more speakers  33 . Speaker  33  may be used to generate a tone (i.e., speaker  33  may be a tone generator or other audio output component) or other audio signal that may make up some or all of the ambient noise that is used as the baseline ambient noise level by microphones  54  and processing circuitry in devices  10 A,  10 B, and  10 C. For example, device  10 B may include a speaker  33  that generates a tone  72 , and device  10 C may detect tone  72  using microphone  54 . If desired, tone  72  may include sound waves of a single frequency or band of frequencies (e.g., an ultrasonic tone), or may include a plurality of different frequencies. Because tone  72  may be provided consistently, it may serve as a stable baseline against which changes may be measured by device  10 B. 
     Although described above in connection with  FIGS. 10B and 10C , any one or combination of devices  10 A,  10 B, and/or  10 C may be used to generate and/or detect a baseline tone  72  generated by a speaker  33  in any one of devices  10 A,  10 B, and  10 C. In general, a device  10  may generate a baseline noise profile based on auditory signals  72 , or may have a predetermined baseline profile that corresponds to known background signals  72  stored in memory in device  10 . 
     Electronic device  10  may identify a variety of user gestures based on changes in ambient noise that are detected by microphone  54  and processed by processing circuitry in the electronic device. For example, a different change in ambient noise may be associated with the placement of each one of a user&#39;s fingers  56  on or near a surface  52  (e.g., a tapping motion). Device  10  may be able to differentiate between each of these changes in ambient noise to determine which finger  56  was placed on the surface as well as the duration, location, and force associated with the placement or tap. In this way, a user may make a clicking gesture simply by tapping their finger on a surface, and the electronic device may respond accordingly by performing a clicking action. A variety of different clicking or similar actions may be performed, such as a double click, right click, left click, two-finger click, three-finger click, four-finger click, five-finger click, and other clicking gestures, each of which may cause a unique change in the ambient noise that can be detected and processed by device  10 . 
     In one suitable arrangement, different changes in ambient noise may be generated based on different movements of a user&#39;s hand  57  or fingers  56  along surface  52 . For example, the ambient noise detected by microphone  54  may change as a user one or both  FIGS. 56-1 and 56-2  move along surface  52  (in directions  62 - 1 ,  62 - 2 ,  62 - 3 , and  62 - 4 , for example). The change in ambient noise may be different based on whether one or both fingers are used, as well as the direction in which the movement occurs. These changes in ambient noise may be associated with a scrolling or dragging gesture. In response to determining that the change in ambient noise corresponds to a scrolling or dragging gesture, the electronic device  10  may scroll up or down in an application window that is displayed on a display  14 , or move an application window from one location on the display to another location on the display. 
     In one exemplary configuration, a user may bring fingers  56 - 1  and  56 - 2  together or farther apart (in a pinching motion, for example). Such a gesture may cause a characteristic change in the ambient noise that is received at microphone  54  such that device  10  can determine that a pinching motion has been made by the user. The change in ambient noise may reflect the direction, duration, force, or other characteristics of the gesture. Accordingly, the electronic device may alter its operation in response to the gesture by zooming in or out with respect display content that is displayed on display  14 . 
     The changes in ambient noise, associated user gestures, and corresponding actions taken by electronic device  10  described above are merely illustrative. In general, one or more microphones  54  and processing circuitry in the electronic device may detect and process changes in ambient noise that correspond to a variety of user gestures that can be used to control or otherwise modify the function of electronic device  10 . 
     If desired, an electronic device  10  may use one more sensors  35  to detect user gestures in combination with ambient noise data generated by microphone  54 . In an example in which electronic device  10  is a wearable electronic device, device  10  may use an accelerometer in combination with a microphone  54  to detect user gestures. For example, device  10  may use data generated by the accelerometer to detect movement of device  10  in directions  62 - 1 ,  62 - 2 ,  62 - 3 ,  62 - 4 ,  62 - 5 , and  62 - 6 , and may use microphone  54  to detect user gestures such as tapping, sliding, pinching, spreading, and other movements of fingers  56  on a surface  52 . In this way, device  10  may detect user gestures that involve movement of the device using a sensor component that detects movement, and may detect user gestures that involve little or no movement of the device using a microphone that detects changes in ambient noise. 
     A flow chart of illustrative steps that may be performed in accordance with ambient noise monitoring and processing are shown and described in connection with  FIG. 10 . 
     At optional step  100 , an electronic device  10  may monitor ambient noise using a microphone  54  and generate a baseline ambient noise profile that may be used to detect deviations in ambient noise levels from the baseline. In one example, step  100  may be skipped if electronic device  10  has a pre-established ambient noise profile for a given environment. In another suitable example, the baseline ambient noise profile may include characteristic auditory signatures that are present in whole or in part due to the presence of a nearby device having a textured surface that produces the characteristic auditory signatures. 
     At step  102 , the microphone  54  may generate ambient noise data based on the ambient noise that is received in the electronic device. As changes in the ambient noise occur, the ambient noise data may change and deviate from the ambient noise baseline profile. A nearby device having a textured surface may at least partially modulate the ambient noise to produce the changes. 
     At step  104 , processing circuitry in the electronic device  10  may compare the ambient noise data generated by microphone  54  to the baseline ambient noise profile to determine if a change in the ambient noise has occurred. The differences between the ambient noise data and the ambient noise profile may be used to determine characteristics of the change in the ambient noise. The characteristic changes in the ambient noise may be caused by a nearby device having a textured surface. For example, the textured surface may cause the ambient noise profile to change in a predetermined, characteristic way when a user moves over the textured surface. 
     At step  106 , the processing circuitry may compare the changes in the ambient noise to predetermined characteristic changes in the ambient noise that are stored, for example, in memory in the electronic device. Each characteristic change in the ambient noise may be associated with a corresponding user input. The characteristic change may be associated with a given user input made over the textured surface of a nearby device. 
     At step  108 , the processing circuitry may determine that the change in the ambient noise is similar to or the same as one of the characteristic changes in the ambient noise stored in the memory. Based on the user input associated with the characteristic change, the processing circuitry may determine that the same user input is associated with the detected change in ambient noise and associate the user input with the detected change. The user input may be associated with a characteristic change in the ambient noise that occurs when a user performs a particular gesture over a known textured surface or portion of a textured surface on a nearby device. The processing circuitry may be able to identify the gesture made and the location of the gesture relative to the textured surface based on the detected change in ambient noise. 
     At optional step  110 , the processing circuitry may modify the operation of electronic device  10  based on the user input associated with the change in ambient noise. In one suitable example, the processing circuitry may take no action based on the user input associated with the change in ambient noise. 
     In the above description of  FIG. 10  above, the textured surface that modulates the ambient noise is described as being on a nearby device. This, however, is merely illustrative. If desired, the textured surface may be on the electronic device itself. 
     An example of first and second devices that may be used together for ambient noise sensing and detecting changes in the ambient noise is shown in  FIG. 11 . A first electronic device  10 A and a second electronic device  10 D may both operate in an environment in which ambient noise (sometimes referred to herein as ambient sound, ambient sound waves, or an ambient sound event) is present. Device  10 A may have a plurality of microphones  54  for detecting ambient noise, and a display  14  for displaying images and/or other information to a user. Microphones  54  and display  14  may be mounted in housing  12 . In general, electronic device  10 A shown in  FIG. 11  may be one of electronic devices  10 A- 10 C shown and described in connection with  FIG. 1 . 
     Device  10 D may operate together with electronic device  10 A to monitor ambient noise and detect changes in the ambient noise. In one illustrative embodiment, device  10 D includes a housing  12  with surface features or textures that affect the ambient noise around electronic device  10 A. In such an example, device  10 D may simply serve as an ambient noise modulation device with a predetermined surface patterns that create a known ambient noise profile around electronic device  10 A (e.g., device  10 D may not be an electronic device). Electronic device  10 A may detect the ambient noise profile at least partially created by device  10 D and detect changes in the ambient noise profile caused by movement of components within device  10 D or movement of external objects relative to device  10 D. Device  10 D may rest on surface  52 . 
     In another suitable example, device  10 D may be an electronic device. In scenarios in which electronic device  10 D is provided with electronic circuitry, device  10 D may include some or all of the components shown and described in connection with device  10  of  FIG. 3 . In general, electronic device  10 D may include one or more microphones  54  that detect ambient noise. Electronic device  10 D may include a processor (e.g., storage and processing circuitry  40 ) for analyzing ambient noise that is detected by microphones  54 . Electronic device  10 D may process ambient noise profiles and send the processed data to device  10 A in the form of executable instructions (e.g., a user input command), or may send information related to the ambient noise profile (e.g., raw or processed data) to the electronic device  10 A for further processing. In scenarios in which device  10 D does include electronic components, device  10 D may include physical features that affect the ambient noise received by device  10 A. For example, electronic device  10 D may include physical patterns, textures, movable parts, or other physical components that affect the ambient noise profile detected by electronic device  10 D. 
     In one suitable example, device  10 D may include one or more textured regions  80 - 1 ,  80 - 2 ,  80 - 3 ,  80 - 4 , and  80 - 5  (sometimes collectively referred to herein as portions  80 , planar member portions  80 , textured surfaces  80 , areas  80 , ambient noise-modulating surfaces  80 , or patterns  80 ) as shown in  FIG. 12 . Some or all of textured regions  80  may be formed from housing  12  as raised portions of housing  12 , depressions in housing  12 , patterns that are etched or engraved into housing  12 , or other suitable modifications to housing  12 . Alternatively or in addition to ambient noise-modulating surfaces  80  formed from housing  12 , some or all of the features in areas  80  may be separate structures that are attached to the surface of housing  12 . For example, ambient noise-modulating features may be formed on the surface of housing  12  using sheets formed of plastic, ceramic, metal, or other suitable materials that are attached to housing  12  using a suitable attachment method (e.g., adhesive). 
     Ambient noise-modulating regions  80  may have any suitable shape, size, and pattern. For example, regions  80  may include raised portions or depressions having semi-circular, triangular, rectangular, or other suitable cross-sectional profiles, may include straight, zig-zagging, meandering, intersecting, or other suitable patterns of lines, or may include openings (e.g., through-holes or vias) in housing  12 . Regions  80  may include features formed in a grid or an array, or may be randomly distributed. In one suitable arrangement, at least one of surface regions  80  (e.g., region  80 - 1 ) includes an array of similar features that modify ambient noise near devices  10 A and  10 D. The density of features in the array may be chosen accordingly to provide a desired modulation of the ambient noise profile. An array of features in a region  80  may include 1, 5, 10, 25, 50, 100, 1,000, 10,000, 100,000, 1,000,000, or more features. The features in regions  80  may be formed with a resolution that is low enough to be physically detectable by a user (e.g., a user can touch and feel the ambient noise-affecting features) or may be formed with a resolution high enough (as microperforations, for example) that the features are not physically detectable by a user. 
     The patterned physical features in regions  80  may modulate ambient noise in the environment surrounding devices  10 A and  10 D. The ambient noise profile that exists when device  10 D is simply in the same vicinity of electronic device  10 A may be detected by electronic device  10 A as a baseline ambient noise profile. The baseline ambient noise profile may be a predetermined ambient noise profile that electronic device  10 A recognizes as being associated with device  10 D. As a user moves relative to device  10 D, the ambient noise profile may change from the predetermined ambient noise profile recognized by device  10 A. For example, a user may move their hand over region  80 - 1  to cause a change in the ambient noise received at electronic device  10 A. Electronic device  10 A may be programmed to identify such a change in the ambient noise profile as being due to movement relative to region  80 - 1  (rather than due to user movement over another one of regions  80 - 2 ,  80 - 3 ,  80 - 4 , or  80 - 5 , for example) and may respond accordingly. Similarly, electronic device  10 A may be programmed to separately identify changes in the ambient noise profile due to movement relative to regions  80 - 2 ,  80 - 3 ,  80 - 4 , and  80 - 5 . In general, electronic device  10 A may capable of differentiating between the different locations on device  10 D over which a user is moving or making a gesture based on the relative distance between device  10 A and the different locations on device  10 D. If desired, the patterns, textures, and other physical features of regions  80  may provide additional or improved ambient noise signatures as a user moves over each of the regions. These signatures, or characteristic changes in ambient noise, may allow electronic device  10 A to determine where a user is gesturing over device  10 D with increased resolution, accuracy, and detail. In general, the features in region  80  may allow for device  10 A and/or device  10 D to better discriminate changes in ambient noise caused by a user against background fluctuations in the ambient noise profile. 
     Two or more of textured surfaces  80 - 1 ,  80 - 2 ,  80 - 3 ,  80 - 4 , and  80 - 5  may have the same pattern (i.e. a uniform pattern on a surface of housing  12 ), or each of the textured surfaces may be patterned differently. In one illustrative example, textured surfaces  80 - 2 ,  80 - 3 ,  80 - 4 , and  80 - 5  are all patterned substantially identically (e.g., using the same physical feature, pattern, and density), while textured surface  80 - 1  may be patterned differently (e.g., using a different physical feature, pattern, and/or density that the other four textured surfaces  80 ). 
     In one suitable example, ambient noise modulation device  10 D may be a planar member (sometimes referred to herein as a pad or mat) with a rectangular perimeter having four edges. A first planar member portion  80 - 1  may form a central region on the surface of ambient noise modulation device  10 D, and a second planar member portion  80 - 4  may form a strip between the central region and one of the four edges. If desired, third, fourth, and fifth planar member portions  80 - 2 ,  80 - 3 , and  80 - 5  may form third, fourth, and fifth strips between the central region and each of the other edges of planar member that forms ambient noise modulation device  10 D. 
     Electronic device  10 A may recognize changes in the ambient noise profile (using a microphone  54 , for example) as being associated with movement relative to a given one of regions  80 - 1 ,  80 - 2 ,  80 - 3 ,  80 - 4 , or  80 - 5 , and may perform an associated function. For example, movement of a user relative to region  80 - 1  may be used as a mouse or trackpad functionality. Movement of a user relative to region  80 - 1  may cause a cursor to move across a screen  14  on device  10 A, or may be used to select portions of display  14  in accordance with user-selectable options. Gestures made by a user relative to regions  80 - 2 ,  80 - 3 ,  80 - 4 , and/or  80 - 5  may be used for horizontal scrolling across a display  14 , adjusting the volume of speakers included in device  10 A, adjusting the brightness of display  14 , or other suitable functions. User gestures performed over region  80 - 4  may cause device  10 A to perform a click or select function. This, however, is merely illustrative. Movement of a user relative to any one of regions  80  may cause electronic device  10 A to perform any suitable function. The function performed by device  10 A may be pre-programmed, or may be customized by a user. 
     As described above in connection with  FIG. 16 , device  10 D may not include any electronic components (i.e., device  10 D may consist only of a housing  12  with surface features in regions  80  thereon). This, however, is merely illustrative. If desired, device  10 D may include electronic components such as one or more microphones  54 . As shown in  FIG. 12 , microphones  54 - 1 ,  54 - 2 ,  54 - 3 , and  54 - 4  (sometimes collectively referred to herein as microphones  54 ) may be formed at four corners of device  10 D. Microphones  54  may detect ambient noise in the environment of devices  10 A and  10 D. In particular, one or more of microphones  54 - 1 ,  54 - 2 ,  54 - 3 , and  54 - 4  may detect the baseline ambient noise profile that is at least partially determined by the surface features in ambient noise-modulating areas  80  on device  10 D. As a user moves relative to the surface features in region  80 , the microphone(s)  54  in device  10 D may detect changes in the ambient noise profile, and may be able to determine the location of the gesture relative to the various regions  80  due to the different locations and different physical features of the regions  80 . In this way, device  10 D may serve as a standalone user input device that detects changes in ambient noise, processes the changes to determine a user input or gesture that was performed, and transmits the user input or gesture information to electronic device  10 A (using wireless or wired communications, for example) for further processing or to cause device  10 A to perform a function. 
     In one suitable arrangement, some or all of electronic device  10 D may be touch-sensitive. For example, electronic device  10 D may be touch sensitive in one or more regions  80  on the surface of housing  12 . In general, the entire surface on which surface features  80  are formed may be touch sensitive, or only one of the regions  80  (e.g., region  80 - 1 ) may be touch sensitive, while surrounding regions  80  are not touch-sensitive. Touch sensitivity may be provided using capacitive touch sensor electrodes mounted within housing  12 , using resistive force sensing components within housing  12 , using optical touch sensing components (e.g., visible or infrared light emitters and receivers) that transmit light through housing  12  or through openings in housing  12 , or using any other suitable touch sensing arrangement. In arrangements in which device  10 D is provided with a touch sensor, device  10 D may detect touch inputs and transmit the touch inputs to electronic device  10 A. The touch inputs and inputs detected using ambient noise profiles that are modulated by surface features in ambient sound-modulating regions  80  may be used in conjunction with one another (e.g., a single input may have a touch component and an ambient noise sensing component), or may be used separately to perform different inputs (touch inputs may be used to move a cursor on a display  14  of device  10 A, while ambient noise-based inputs may be used to adjust volume and screen brightness, for example). If desired, a given region  80  such as region  80 - 1  may be used for both touch-based inputs and ambient noise-based inputs. 
     In general, device  10 D may be a stand-alone device, or may be incorporated into another device or structure (i.e., another inanimate object). For example, the textured surfaces and other features of device  10 D may be incorporated into the interior or exterior of a vehicle, the surface of an appliance, the surface of a piece of furniture, interior or exterior walls of a building, or any other suitable object. If desired, coded ambient noise modulation surfaces may be formed by applying a spray or coating to a wall, floor, or other suitable surface. In another example, device  10 D may be formed of fabric having a weave or texture that provides ideal ambient noise modulation. Device  10 D may also be a flexible device that can be rolled onto a wall, table, rug, or other surface that may not provide an optimal ambient noise sensing environment on its own. Device  10 D may then be rolled up for folded to provide a portable device. 
     A cross-sectional view of device  10 D taken along line B-B in  FIG. 12  is shown in  FIG. 13 . As described above in connection with  FIG. 12 , a first region  80 - 1  of housing  12  may include a first group of surface features  82 - 1  and a second region  80 - 4  of housing  12  may include a second group of surface features  82 - 4 . As shown in  FIG. 13 , features  82 - 1  may include rounded protrusions having a first size and pitch, while features  82 - 4  may include rounded protrusions having a second size and pitch. Although shown as rounded protrusions in  FIG. 13 , features  82  in regions  80  may generally have any shape, size, pattern, and density, as described above in connection with  FIG. 12 . 
     As a user  55  moves their hand or fingers  56 - 1 / 56 - 2  relative to regions  80 , changes  60  in the ambient noise profile may occur. For example, if a user holds their hand over region  80 - 1 , a first change  60  in the ambient noise profile may occur due to the shape, size, density, or other characteristics of features  82 - 1 . Microphones  54  on electronic device  10 A and/or microphones  54  on device  10 D may detect these changes and determine that the changes in the ambient noise profile are due to the position or movement of an object over region  80 - 1 . Similarly, if a user holds or swipes their hand over region  80 - 4 , a second change  60  in the ambient noise profile may occur. The shape, size, density, and other characteristics of features  82 - 4  may cause the change in the ambient noise profile to be different than that which results when a user performs a gesture over region  80 - 1 . Microphones  54  on device  10 A and/or  10 D may detect these changes, and may be configured to determine the location and type of a gesture relative to device  60  based on the different ambient noise profile changes that result based on whether the gesture was performed over region  80 - 1  or  80 - 4 . In this way, device  10 D may be provided with a “coded” housing surface that causes characteristic changes in ambient noise that are recognized by device  10 A and/or device  10 D as being associated with the position of a user relative to a specific region of device  10 D. 
     In one example, device  10 D may be provided with different types of textures overlaid onto one another. In addition to a uniform array of textured surface features, for example, device  10 D may be provided with a second set of graded surface features that extend along the electronic device. For example, a second set of surface features (e.g., square depressions) may be overlaid upon or interleaved between a first set of semi-spherical surface features. The second set of surface features may have a density or pitch that increases along an axis of device  10 D. With such an arrangement, device  10 D may help to create a characteristic environment for ambient noise sensing and provide different characteristic changes in ambient noise depending on where a user performs a gesture relative to the surface of device  10 D. 
     In some arrangements, the individual textured elements on a textured surface may have different length and width dimensions. The textured elements may be arranged in aligned rows and columns, or may be formed in offset rows and columns. Graded textures may be used without other underlying, overlaid, or interspersed surface textures. Graded textures may include surface features with a pitch that gradually changes (i.e., the distance between individual features increases or decreases) along an axis parallel to the plane defined by the planar surface of device  10 D on which the surface features are formed. If desired, the density of features in a graded texture may increase as distance to an electronic device that is performing ambient sound sensing increases. Such graded textures may provide more robust ambient noise signatures to account for the farther distance from the electronic device. The speed, direction, and other characteristics of a user gesture performed over such textured elements may be determined by processing the unique changes in the ambient sound environment caused by the different dimensional, spatial, and gradient characteristics of the textured surface elements. 
     The examples described above in which changes in ambient noise are caused by the positioning of the hand of a user  55  over device  10 D are merely illustrative. If desired, changes in ambient noise may be caused by direct contact between a user  55  and the surface of device  10 D. For example, a user may place finger  56 - 1  on the surface of housing  12  in region  80 - 1  such that finger  56 - 1  rests on features  82 - 1 . The placement of a user&#39;s finger in this location may cause a change in the ambient noise profile (without generating sound when the finger  56 - 1  contacts housing  12 , for example) that is different than that caused simply by a user  55  positioning their hand above region  80 - 1  or  80 - 4 . Similarly, a user may place a finger  56 - 2  on a feature  82 - 4  in region  80 - 4  to generate yet another unique change in the ambient noise profile. A variety of unique changes may occur in response to a user holding their hand or fingers  56 - 1 / 56 - 2  in a stationary position or by moving their hand or fingers  56 - 1 / 56 - 2  relative to regions  80 - 1  or  80 - 4  with or without contacting the surface of housing  12 . As the surface features in region  80  may provide a consistent, known surface, device  10 A and/or device  10 D may be programmed to recognize a variety of changes in ambient noise as corresponding to specific gestures made in or over given regions  80  of device  10 D. The inputs to which specific ambient noise changes correspond to be may predetermined, or may be programmable by a user. In one suitable example, electronic device  10 A and/or electronic device  10 D can “learn” associations between ambient noise changes and gestures relative to specific regions  80  through a calibration process in which a user performs gestures over one or more regions  80  and the device records the associated change in ambient noise. The user may then, if desired, program the device to associate specific detected changes with specific user inputs or other device functions. 
     In one suitable example, device  10 D may be a stylus. As shown in  FIG. 14 , stylus  10 D may have an elongated housing  12  having first and second opposing ends. In one suitable example, housing  12  has a cylindrical shape that extends along a longitudinal axis of stylus  10 D. A tip portion  88  may be formed at one end of stylus  10 D. An opposing end of stylus  10 D opposite the tip portion  88  (i.e., along the longitudinal axis) may include a plurality of openings  84  in housing  12 . Openings  84  (e.g., holes or vias) may form a grille, grating, or mesh at the opposing end of stylus  10 D that allows sound waves (e.g., ambient noise) to enter housing  12 . A microphone  54  or other electronic component may be mounted within housing  12  at the opposing end of stylus  10 D. In one suitable example, microphone  54  is mounted adjacent the openings  84  in housing  12  such that sound waves that enter housing  12  through openings  84  are received at microphone  54 . This, however, is merely illustrative. If desired, microphone grille  84  and a corresponding microphone  54  may be formed in any suitable location on housing  12 . 
     Stylus  10 D may include an additional plurality of openings  86  that form an additional grille, mesh, or grating in housing  12 . In the illustrative example of  FIG. 14 , openings  86  are formed in housing  12  near tip portion  88 . In one suitable arrangement, stylus  10 D includes an electronic component such as a speaker  33  adjacent mesh  86 . In this way, the plurality of openings may form a speaker grille  86  that allows sound waves generated by speaker  33  to exit housing  12 . In one suitable example, speaker  33  may generate sound that is audible to a user of stylus  10 D. In another suitable arrangement, speaker  33  may be a tone generator that generates sound that is not audible to a user of stylus  10 D (e.g., ultrasonic tones). In general, audio-producing component  33  may produce sound waves that make up all or part of a background ambient noise profile in an environment in which stylus  10 D is operated. In one suitable arrangement, microphone  54  in stylus  10 D may detect the baseline ambient noise profile (all, some, or none of which may be generated by tone generator  33 ) and may detect changes in the ambient noise profile caused by movement of stylus  10 D or movement of a user (e.g., movement of a user relative to stylus  10 D). 
     If desired, stylus  10 D may be used together with an electronic device  10 A. In such an arrangement, either one or both of devices  10 A and  10 D may sense an ambient noise profile and changes in the ambient noise profile. For example, device  10 A may detect changes in ambient noise caused by a user using stylus  10 D. Because the shape, size, surface texture, and other physical characteristics of stylus  10 D may be known (e.g., known or programmed into device  10 A and/or device  10 D), stylus  10 D may produce characteristic changes in ambient noise when moved relative to device  10 A or used in specific ways by a user. Changes in ambient noise caused by a known device (e.g., stylus  10 D) may have predetermined characteristics that may be easier for device  10 A to recognize when compared to changes generated simply by a user&#39;s hand or fingers, which may vary significantly from user to user and generate a wide variety of changes in the ambient noise. 
     In another suitable example, device  10 D may detect changes in ambient noise. For example, microphone  54  may be used to detect changes in ambient noise caused by movement of stylus  10 D or one or more components of stylus  10 D, or changes in ambient noise caused by movement of a user relative to stylus  10 D (e.g., movement of a user&#39;s hand or fingers along housing  12  of stylus  10 D). In general, electronic device  10 A and stylus  10 D may be in wireless communication with each other to communicate changes in ambient noise detected by either device, to communicate commands to the other electronic device based on changes in ambient noise detected by either device, or to otherwise allow for the transmission of information between electronic device  10 A and electronic device  10 D. If desired, an electronic device  10 D such as a stylus may be used together with a device having a housing surface with coded surface features such as that described above in connection with  FIGS. 5 and 6 . The known arrangement and characteristics of features on the coded housing surface, combined with the known changes in the ambient noise profile generated by stylus  10 D, may allow for similar changes in ambient noise to be detected, even when different users are making a given gesture. 
     If desired, device  10 A may generate a tone that makes up some or all of the ambient noise profile detected by stylus  10 D. For example, device  10 A may be a mobile telephone, a tablet, a wristwatch or other wearable device, or a computer (e.g., a laptop or desktop computer), having a speaker that generates sound (using a tone generator  33 , for example) that is detected by stylus  10 D as the ambient noise profile. This, however, is merely illustrative. If desired, stylus  10 D may generate the baseline ambient noise profile (using speaker  33 , for example), while device  10 A may detect changes in the ambient noise caused by movement of device  10 D relative to device  10 A (based on changes in the detected tone due to the Doppler effect, for example), or movements of a user relative to device  10 A and/or device  10 D. 
     A cross-sectional side view of stylus  10 D taken along line C-C in  FIG. 14  is shown in  FIG. 15 . As described above in connection with  FIG. 14 , stylus  10 D may include a microphone  54  mounted within housing  12  that receives sound through openings  84  in housing  12 . Audio source  33  may generate sound that exits housing  12  through openings  86  in housing  12 . 
     Tip portion  88  of stylus  10 D may be connected to shaft  90  within housing  12 . In one illustrative example, tip  88  and shaft  90  form a single continuous structure, part of which is external to housing  12  (i.e., tip  88 ) and part of which is contained with housing  12  (i.e., shaft  90 ). In another suitable arrangement, tip  88  and shaft  90  may be discrete components coupled together. A disc-shaped head portion  92  (sometimes referred to herein as a plunger, stopper, or disc) may be formed within housing  12  opposite tip portion  88 . Stopper  92  may be formed integrally with shaft  90  and/or head portion  92 , or may be formed separately from shaft  90  and/or head portion  92  and attached to these components. Stopper  92  may be circular and may have a circumference that is the same as or larger than the circumference of cylindrical housing  12  such that stopper  92  contacts inner surfaces of housing  12  to form a seal within housing  12 . In this way, stopper  92  may separate the interior of housing  12  into a first portion  99  and a second portion  98 . This, however, is merely illustrative. In general, head portion  92  may have any suitable shape, and need not physically contact housing  12  to separate the lower portion  98  from upper portion  99 . In general, head portion  92  may at least partially fill the circumference of housing  12  to separate lower portion  98  from upper portion  99 . 
     When pressure is applied to tip portion  88 , tip portion  88  may move towards and away from the end of housing  12  in to which tip portion  88  is inserted. For example, as a user presses tip portion  88  against a surface, tip portion  88  may move within housing  12  such that tip portion  88  is further inserted into housing  12 . When a user pulls stylus  10 D away from a surface against which tip portion  88  is pressed, tip portion  88  may project out of housing  12  due to the reduction of pressure on tip portion  88 . 
     As tip portion  88  is attached to shaft  90  and head portion  92 , movement of tip  88  may cause movement of shaft  90  and head portion  92  within housing  12 . For example, applying pressure to tip portion  88  may cause shaft  90  and stopper  92  to move upwards towards the end of stylus  10 D (in direction  94 ) opposite tip portion  88 , decreasing the size of upper portion  99  and increasing the size of lower portion  98  within housing  12 . Relieving the pressure applied to tip portion  88  may cause shaft portion  90  and head portion  92  to be restored to their original positions (i.e., the position that they are in when no pressure is applied to tip portion  88 ) by moving within housing  12  in direction  96 . In this way, tip portion  88 , shaft  90 , and head portion  92  may form a movable member within housing  12 . 
     Movement of stopper  92  towards the tip end of housing  12  in which tip portion  88  is inserted may increase a dimension such as the size (volume) of upper portion  99  (sometimes referred to herein as cavity  99 , resonant cavity  99 , tube  99 , closed tube  99 , or chamber  99 ) within housing  12  while decreasing the size (volume) of internal cavity  99  within housing  12 . Changes in the dimensions of interior cavity  99  between different values (e.g., first, second, and third different values corresponding to lengths, widths, volumes, etc.) may cause changes in the auditory properties of cavity  99 . For example, movement of stopper  92  in direction  94  may decrease the length and volume of resonant cavity  99 , and increase the resonant frequency of cavity  99 . Movement of stopper  92  in direction  94  may increase the length and volume of resonant cavity  99 , and decrease the resonant frequency of cavity  99 . 
     As the resonant frequency of chamber  99  changes, microphone  54  may detect different peaks in the sound waves that it receives. In one illustrative example, microphone  54  may detect a baseline ambient noise profile when stopper  92  is in a first position (e.g., when no pressure is applied to tip  88 ). When stopper  92  is in this first position, chamber  99  may resonate in response to a first frequency that is present in the baseline ambient noise profile. Accordingly, microphone  54  may detect a peak at this frequency. In this way, stylus  10 D may determine that no pressure is applied to tip  88  in response to microphone  54  detecting a peak at the first resonant frequency. 
     When stopper  92  moves in direction  94  in response to pressure applied to tip  88 , resonant cavity  99  may become shorter and resonate at a second frequency that is different than the first resonant frequency. When the ambient noise profile includes components at the second resonant frequency, cavity  99  may resonate, and microphone  54  may detect peaks at the second resonant frequency. Stylus  10 D may determine that a first amount of pressure is being applied to tip  88  in response to microphone  54  detecting peaks at the second resonant frequency. 
     As more pressure is applied to tip  88  and stopper  92  continues to move within housing  12  in direction  94 , the length of cavity  99  may continue to shorten, further changing the resonant frequency of the cavity. Cavity  99  may resonate at a third resonant frequency when stopper  92  is moved to a third position within cavity  99 . An ambient noise profile that includes frequencies at the third resonant frequency of cavity  99  may cause cavity  99  to resonate. Microphone  54  may detect peaks at the resonant frequency of cavity  99 , thereby indicating that stopper  92  is in a third position due to a second amount of pressure that is applied to tip  88 . 
     As described above, movement of head  92  within housing  12  may cause chamber  99  to resonate in response to different frequency components within the ambient noise profile. When an ambient noise profile includes a variety of frequency components, cavity  99  may resonate when stopper  92  is moved to a position within cavity  99  that adjusts the resonant frequency of cavity  99  to one of the variety of frequencies in the ambient noise profile. By detecting peaks at the resonant frequency with microphone  54 , stylus  10 D may determine the position of stopper  92  within housing  12 , and therefore determine an amount of pressure that is applied to tip  88 . If desired, the resonant frequency of chamber  99  at a variety of lengths may be predetermined and programmed into device  10 D. In this way, stylus  10 D may automatically associate peaks detected by microphone  54  with specific amounts of pressure applied to tip  88 . In another example, a calibration process may be performed in which the position of stopper  92  within housing  12  is changed to a variety of different positions, and the peaks in the ambient noise profile detected by microphone  54  are associated with the position of stopper  92  and an amount of pressure applied to tip  88  when the various peaks are detected. Calibrating stylus  10 D to associate resonant peaks in the ambient noise profile with positions of stopper  92  within housing  12  may allow for stylus  10 D to determine an amount of pressure applied to tip  88  based on ambient noise. 
     In one suitable arrangement, the ambient noise received at microphone  54  may be ambient noise generated within the environment in which stylus  10 D is used. In another suitable example, tone generator  33  may generate one or more tones that make up all or some of the ambient noise profile received at microphone  54 . In this way, an ambient noise profile that includes sound at some or all of the possible resonant frequencies for chamber  99  may be generated, allowing for increased resolution when detecting the amount of pressure applied to tip  88 . If desired, speaker  33  may be used to generate an ambient noise profile during calibration operations for stylus  10 D, or another electronic device such as electronic device  10 A (e.g., a laptop, mobile telephone, wristwatch device, tablet, or other suitable electronic device) may generate tones that make up some or all of the ambient noise profile detected by microphone  54 . 
     Stylus  10 D may use the determined pressure applied to tip  88  to implement device operations in stylus  10 D or device  10 A. In one suitable arrangement, stylus  10 D may take a specific action in response to detecting a given tip pressure based on ambient noise sensed using microphone  54 , such as powering the stylus  10 D on or off, causing speaker  33  to produce a given sound, or activating or deactivating one or more functions of stylus  10 D (e.g., touch sensitivity, visual indicators on or produced by stylus  10 D, auditory indicators produced by stylus  10 D, communication with one or more other electronic devices, etc.). In another suitable example, stylus  10 D may communicate a pressure reading for tip  88  based on ambient noise received at microphone  54  to electronic device  10 A for further processing or to cause device  10 A to perform a given function. In an illustrative example in which device  10 A includes a display  14  with touch sensitivity, device  10 A may perform different functions based on the amount of pressure that stylus  10 D senses at tip  88  (i.e., the amount of pressure that a user applies to tip  88  against the display). Device  10 A may change the way it generates or displays visual content, the way it presents audio content, the volume of speakers in device  10 A, the brightness, contrast, or touch sensitivity of display  14 , or other suitable characteristics and functions of device  10 A. In general, device  10 D may affect changes in the operation of drawing, painting, messaging, email, internet browsing or other applications running on device  10 A in response to the amount of pressure sensed at tip  88  based on ambient noise measurements. 
     An electronic device  10 A that performs ambient noise sensing may provide visual indicators  104  to direct a user to perform gestures or movements in a particular location near device  10 A. In the example of  FIG. 16 , electronic device  10 A includes a light source  102  that generates indicator  118  (sometimes referred to herein as an indicator graphic, projection, ambient noise sensing area, visual indicator, visible indicator, or visual outline) that is projected onto a surface on which electronic device  10 A rests. The ambient noise sensing area  118  illuminated by light source  116  may indicate the ideal area around electronic device  10 A in which changes in ambient noise are most likely to be detected by microphones  54 . In the illustrative example of  FIG. 16 , the ambient noise sensing area is a rectangular region on the surface  52  on which device  10 A rests. This, however, is merely illustrative. Visual ambient noise sensing area indicator  118  may have any suitable shape, size or graphic. For example, indicator  118  may have a triangular, circular, or any other suitable shape, may be illuminated using solid lines, dashed lines, or dots at one or more corners of the ambient noise sensing area, may include illumination in some or all of the area bound by the lines or dots that define the edges of the area, and may include light of one or more colors. 
     In one suitable arrangement, indicator  118  may include a graphic such as a virtual keyboard that is projected onto surface  52 . When a user places a finger on the portion of indicator  118  that corresponds to a key, a characteristic change in ambient noise may be detected by microphones  54 . Microphones  54  may be able to determine the location at which a user placed their finger based on the characteristic change in ambient noise, and may associate the location with a particular key in the keyboard. In this way, a user may be able to type or provide other input to device  10 A by simply touching illuminated locations of the surface  52  on which device  10 A rests. By relating characteristic changes in ambient noise to specific locations relative to device  10 A, device  10 A may use a “map” of ambient noise changes to determine where a user has touched surface  52  and perform a suitable function in response to the user input. 
     The examples above in which indicator  118  is a projection on surface  52  are merely illustrative. If desired, light source  116  may provide information regarding an ideal ambient noise sensing region by turning the illumination on or off (e.g., on when a user is making gestures that microphones  54  can detect, and off when microphones  54  cannot detect the user gestures with suitable accuracy), by providing illumination in different colors depending on whether or not microphones  54  can detect the user gestures (e.g., a continuous scale from red, indicating that microphones  54  cannot detect the user gestures, to green, indicating that microphones  54  can detect the user gestures), by switching between flashing or solid illumination depending on whether a user is providing gestures within the ideal ambient noise sensing region, or any other suitable illumination pattern or scheme. 
     An ideal ambient noise sensing region in which changes in ambient noise are best detected by microphones  54  may be a predetermined region that is programmed into device  10 A, or may be determined using calibration operations as shown in  FIG. 17 . Calibration operations for determining an ideal ambient noise sensing region may include using microphones  54  to detect changes in ambient noise as a user makes gestures in various locations around device  10 A. In one illustrative example, electronic device  10 A may direct a user to make a gesture at various locations around device  10 A using visual indicators  120  (sometimes referred to herein as guide spots, calibration guides, or calibration locations). An example of calibration operations of this type are shown in  FIG. 17 . In this example, light source  116  generates a plurality of visual indicators  120  that indicate locations at which a user should make a gesture so that microphones  54  can detect associated changes in ambient noise. 
     As shown in  FIG. 17 , light source  116  may generate visual indicators such as visual indicators  120 - 1 ,  120 - 2 ,  120 - 3 ,  120 - 4 , and  120 - 5 . When visual indicator  120 - 1  is projected onto surface  52 , a user may perform a gesture at the location on surface  52  illuminated by indicator  120 - 1 . The gesture may include a tap, a touch, moving a finger or hand closer to or farther away from surface  52 , swiping a hand or finger over indicator  120 - 1 , or any other suitable gesture. Microphones  54  may detect the change in ambient noise that occurs as the gesture is performed, and may associate the detected change in ambient noise with performing the given gesture at the given location. A user may then proceed to make specific gestures at each of the locations on surface  52  illuminated by indicators  120 - 2 ,  120 - 3 ,  120 - 4 , and  120 - 5 . At each location, microphones  54  may detect the changes in ambient noise and associate the changes with the given gesture being performed at the specific area illuminated by the indicator. If desired, one or more of indicators  120 - 1 ,  120 - 2 ,  120 - 3 ,  120 - 4 , and  120 - 5  may be illuminated simultaneously. In another example, only one of the indicators  120  may be illuminated at any given time, such that a user receives clear instructions to perform a gesture at a given location. 
     The calibration operations may involve providing instructions to a user using indicators other than visual indicators  120 . For example, device  10 A may provide auditory guidance to a user regarding what gesture should be performed, when the gesture should be performed, whether or not the gesture and/or associated ambient noise change were detected by microphone  54 , or other suitable directions for calibrating device  10 A for ambient noise detection. Device  10 A may also provide guidance during calibration operations using additional visual indicators on display  14 . For example, display  14  may provide written or otherwise visual instructions to a user during calibration operations. The information provided by visual instructions on display  14  may be similar to or different that the instructions described above that may be provided using auditory cues. In one illustrative example, guidance provided by device  10 A during calibration operations may include instructing a user to make a gesture closer to or farther away from device  10 A. 
     If desired, calibration operations may not require the use of indicators  120 . For example, calibration operations may begin at the request of a user, or may be initiated automatically. In one example, the calibration operation may include a test gesture made by a user. The device  10 A may instruct the user on when and where to make the gesture, as well as to what gesture should be made (for example, by providing visual instructions on display  14 , or by providing auditory cues using a speaker  33  on device  10 A). Based on changes in ambient noise detected by microphones  54  in response to the test gesture, device  10 A may determine whether or not the environment is suitable for ambient noise sensing. Based on the ambient noise changes detected by microphone  54 , device  10 A may provide user guidance to enhance ambient noise sensing. User guidance may include instructing a user to change the location, intensity, or type of gesture, or to change the environment surrounding device  10 A (e.g., instructing a user to move somewhere quieter). If desired, device  10 A may make determinations regarding whether or not the environment surrounding device  10 A is suitable for ambient noise sensing without a test gesture. For example, device  10 A may sample the ambient noise profile around device  10 A prior to any user gestures, and determine whether or not the ambient noise profile is suitable for ambient noise sensing. Based on the detected ambient noise, device  10 A may provide feedback to a user to enhance ambient noise sensing at device  10 A (e.g., instructing a user to move to a quieter or noisier location, instructing a user to make a gesture closer or farther away from the device  10 A, instructing a user to make a different type of gesture, etc.). If desired, an indication of whether or not an environment is suitable for ambient noise sensing may be provided by a visual indicator (e.g., light source  116 ) in device  10 A. The visual indication may be a visual signal such as a light source that changes from red to green in response to a determination that the environment surrounding device  10 A is appropriate for ambient noise sensing. 
     In another illustrative example, calibration operations may allow a user to define an ambient noise sensing region. After calibration operations have been initiated (by a user, for example), the user may outline a desired area for the ideal ambient noise sensing region. The outline may be provided by a user touching each corner of the desired region, outlining the region by tracing an outline of the region on surface  52  with their finger, or by touching the location that is desired for the center of the region while electronic device  10 A determines the area surrounding the center in which ambient noise changes can be suitably detected by microphones  54 . In such an example, electronic device  10 A may associate ambient noise changes with gestures at given locations around device  10 A, and may use these associations to determine the outline defined by the user. This, however, is merely illustrative. In general, device  10 A may determine the outline of the desired ambient noise sensing region defined by the user using any suitable detection means, such as light-based detection, proximity detection, or capacitive sensing. 
     During ambient noise sensing calibration operations, the locations of indicators  120  may change based on whether or not microphones  54  can detect changes in ambient noise caused by gestures at each of the locations illuminated by indicators  120 . For example, a first set of indicators  120  may be displayed at the start of the calibration operations. If a user performs a desired gesture (e.g., a touch) at location  120 - 3 , device  10 A may determine if microphones  54  were able to detect changes in ambient noise associated with the gesture. If device  10 A determines that microphones  54  were not able to detect the change in ambient noise with suitable accuracy, intensity, resolution, or volume, then the location of indicator  120 - 3  may change to a location at which microphones  54  may be able to better detect the change in ambient noise. Similar operations may be performed for each other location indicated by illumination  120 . In this way, the calibration operations may include real time determination of the boundaries of the ideal ambient noise sensing region in which microphones  54  can best detect changes in ambient noise. After the ideal ambient noise sensing region is determined, light source  116  may project ambient noise sensing region indicator  118  onto surface  52  to illuminate the ideal ambient noise sensing region for a user. 
     Electronic device  10 A may take actions other than or in addition to adjusting indicators  120  based on the detected changes in ambient noise. In one example, electronic device  10 A may activate or deactivate a speaker  33  in response to the detected ambient noise. For example, if electronic device  10 A determines that microphones  54  cannot sufficiently detect changes in ambient noise (e.g., the background ambient noise profile is too quiet, too loud, includes too much variation, etc.), electronic device  10 A may begin generating a tone using tone generator  33  to supplement the existing ambient noise profile. In this way, electronic device  10 A can change the ambient noise surrounding the device to ensure that changes in ambient noise (caused by user gestures, for example) can be detected. 
     In one suitable arrangement, electronic device  10 A may detect and store the baseline ambient noise profile in the environment surrounding the device. As the environmental baseline ambient noise profile changes, electronic device  10 A may activate tone generator  33  to generate supplemental noise such that the noise detected at microphone  54  (i.e., the combination of the noise profile from the surrounding environment and the noise generated by tone generator  33 ) is the same as the originally-detected baseline ambient noise profile. The repeated detection of the noise profile at microphone  54  and adjustment of the sounds generated by speaker  33  may occur as part of an iterative feedback or self-assessment loop in device  10 A. In this way, ambient noise sensing may continue in changing environments without having to perform continuous calibration operations. 
     If desired, ambient noise-based user gestures may be used to interact with a user interface on an electronic device such as device  10 A. For example, a set of user gestures may be used in a gaming application, with each user gesture in the set corresponding to an action that a user may take in the game. The electronic device may respond accordingly based on the user gesture. The electronic device may display a visual application on display screen  14 , may provide audible cues through a speaker  33 , may provide haptic feedback, or other suitable content while the gaming application is in use. 
     In a blackjack game scenario, display  14  may display a user&#39;s hand of cards and provide audio cues to alert a player of when their turn to play has come. A user may tap twice on a surface on which device  10 A rests to indicate that they wish to be dealt another card, may swipe to the left or right to indicate that they do not wish to be dealt another card, may perform a combination of a swipe and a tap to indicate that they wish to split the cards in their hand, or may tap three times to indicate that the game should continue on to another player (e.g., a human or computer player). When multiple human players are participating in the game, each player may have their own device  10  that is in communication with the other devices  10 , or one device may be passed between players, with each player performing a gesture to indicate that their cards should be displayed on display  14  (e.g., a swipe gesture over the display  14 ). 
     In a racing game scenario, the device  10 A may rest on a table or other surface, while a user moves their hands along a latitudinal axis parallel to length dimension of the electronic device to steer a car presented to the user on the display  14 . To control the speed of the car, a user may move their hands closer or farther away from the electronic device along a latitudinal axis that is parallel to a width dimension of the electronic device. 
     The foregoing is merely illustrative and various modifications can be made to the described embodiments. The foregoing embodiments may be implemented individually or in any combination.

Metadata:
Filing Date: 20160629
Publication Date: 20180102
Grant Date: 20180102
Priority Date: 20150929
Inventors: ARMSTRONG-MUNTNER JOEL S.
ALLEC NICHOLAS PAUL JOSEPH
MU XIAOYI
Assignee: APPLE INC
CPC Classifications: [{"code": "H04R3/005", "inventive": true, "first": false, "tree": "[]"}, {"code": "G10L25/51", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F3/167", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04R2499/11", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04R29/001", "inventive": true, "first": false, "tree": "[]"}, {"code": "G10L25/51", "inventive": true, "first": true, "tree": "[]"}, {"code": "G10L25/51", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F3/167", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04R1/2807", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04R2410/05", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04R1/028", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04R1/2807", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04R1/028", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F3/167", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04R2410/05", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04R2499/11", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04R3/005", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04R29/001", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04R2499/11", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04R3/005", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 58407186