Patent Publication Number: US-11653170-B2

Title: In-ear speaker

Description:
PRIORITY 
     This application claims the benefit under 35 U.S.C. § 119(e) of U.S. Provisional Patent Application No. 62/991,491, filed 18 Mar. 2020, which are incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     This disclosure generally relates to an in-ear speaker used for determining a dynamic head-related transfer function for a subject. 
     BACKGROUND 
     A head-related transfer function (HRTF) may be used to characterize how an ear of a subject receives sound from a point in space. Specifically, an HRTF for a subject may be used to synthesize a binaural sound that appears to the subject to originate from a given point in three-dimensional (3D) space. Conventionally, an HRTF may be measured for a subject by placing a microphone inside the ear of the subject to receive sounds emitted from a series of speakers within an anechoic chamber. Each of the series of speakers may be disposed in a circular, or semi-circular, arrangement proximate to the microphone inside the ear of the subject to emit a respective sound such that the microphone may capture the sound emitted from each speaker individually. However, this process may be time-consuming as the HRTF requires measurements in small increments (e.g., one measurement for each 5° to 30° in a horizontal plane) such that each speaker in the series may emit a respective sound for each increment. In addition, this process may prove arduous for the subject as each HRTF measurement requires the subject to remain still while the microphone inside the ear of the subject receives the respective sound emitted from each speaker of the series of speakers individually. Furthermore, this process may not account for changes in position of the subject (e.g., tilting head, rotating head, and the like) as the subject is required to remain still throughout the process, thus limiting the scope of binaural sounds that the HRTF measurements may synthesize for the subject. 
     SUMMARY OF PARTICULAR EMBODIMENTS 
     In particular embodiments, a dynamic head-related transfer function (HRTF) for a subject may be determined using an in-ear speaker, a series of audio sensors, and a series of image sensors. The in-ear speaker may be worn inside the ear of a subject within a soundproof chamber, or “capture space,” such that the in-ear speaker may emit a sound outwardly away from the ear of the subject into the surrounding capture space. In one embodiment, the sound emitted from the in-ear speaker may be or include a sine wave sweep, increasing or decreasing in frequency such that a range of multiple frequencies (e.g., from 20 Hz to 20 kHz) may be emitted throughout the capture space. To emit the sound, an audio source of the in-ear speaker may first generate a source audio signal. A crossover network coupled to the audio source may filter the source audio signal into multiple frequency signals. One or more speakers coupled to the crossover network may respectively emit the sound and an audio-transport tube having an input end coupled to the speakers may receive the sound. An audio reflector coupled to an output end of the audio-transport tube may receive the sound and reflect the sound throughout the capture space. 
     Innovative aspects of the subject matter described in this specification may be embodied in a system and method for generating, by an audio source of the in-ear speaker, a source audio signal; emitting, by one or more speakers of the in-ear speaker, the sound based on the source audio signal; receiving, by an audio-transport tube of the in-ear speaker, the sound, the audio-transport tube having an input end coupled to the one or more speakers to receive the sound; reflecting, by an audio reflector of the in-ear speaker, the sound, the audio reflector coupled to an output end of the audio-transport tube. 
     In one or more of the disclosed embodiments, the method further includes capturing, by a microphone of the in-ear speaker, the sound, the microphone coupled to the audio reflector. 
     In one or more of the disclosed embodiments, the microphone is enclosed within the audio reflector. 
     In one or more of the disclosed embodiments, the audio reflector is configured to be worn inside an ear of the subject. 
     In one or more of the disclosed embodiments, the audio reflector includes an open end and a closed end, the open end directed away from the ear of the subject, the closed end comprised of a rigid surface worn inside the ear of the subject and configured to reflect the sound away from the ear of the subject through the open end. 
     In one or more of the disclosed embodiments, the method further includes preventing, by an absorptive material removably coupled to the audio reflector, an inner-ear of the subject from receiving the sound, the absorptive material configured to be worn inside the inner-ear of the subject. 
     In one or more of the disclosed embodiments, the method further includes converting, by an audio converter coupled to the audio source, a digital source audio signal into the source audio signal. 
     In one or more of the disclosed embodiments, each of the one or more speakers is disposed within a speaker funnel inside the enclosure. 
     In one or more of the disclosed embodiments, the one or more speakers comprise a singular speaker. 
     In one or more of the disclosed embodiments, the one or more speakers comprise a speaker array coupled to a crossover network, the crossover network coupled to the audio source and configured to filter the source audio signal from the audio source into a plurality of frequency signals, the speaker array comprised of a plurality of speakers configured to respectively emit a frequency signal of the plurality of frequency signals. 
     The embodiments disclosed herein are only examples, and the scope of this disclosure is not limited to them. Particular embodiments may include all, some, or none of the components, elements, features, functions, operations, or steps of the embodiments disclosed herein. Embodiments according to the invention are in particular disclosed in the attached claims directed to a method, a storage medium, a system and a computer program product, wherein any feature mentioned in one claim category, e.g. method, can be claimed in another claim category, e.g. system, as well. The dependencies or references back in the attached claims are chosen for formal reasons only. However, any subject matter resulting from a deliberate reference back to any previous claims (in particular multiple dependencies) can be claimed as well, so that any combination of claims and the features thereof are disclosed and can be claimed regardless of the dependencies chosen in the attached claims. The subject-matter which can be claimed comprises not only the combinations of features as set out in the attached claims but also any other combination of features in the claims, wherein each feature mentioned in the claims can be combined with any other feature or combination of other features in the claims. Furthermore, any of the embodiments and features described or depicted herein can be claimed in a separate claim and/or in any combination with any embodiment or feature described or depicted herein or with any of the features of the attached claims. 
     Embodiments of the invention may include or be implemented in conjunction with an artificial reality system. Artificial reality is a form of reality that has been adjusted in some manner before presentation to a user, which may include, e.g., a virtual reality (VR), an augmented reality (AR), a mixed reality (MR), a hybrid reality, or some combination and/or derivatives thereof. Artificial reality content may include completely generated content or generated content combined with captured content (e.g., real-world photographs). The artificial reality content may include video, audio, haptic feedback, or some combination thereof, and any of which may be presented in a single channel or in multiple channels (such as stereo video that produces a three-dimensional effect to the viewer). Additionally, in some embodiments, artificial reality may be associated with applications, products, accessories, services, or some combination thereof, that are, e.g., used to create content in an artificial reality and/or used in (e.g., perform activities in) an artificial reality. The artificial reality system that provides the artificial reality content may be implemented on various platforms, including a head-mounted display (HMD) connected to a host computer system, a standalone HMD, a mobile device or computing system, or any other hardware platform capable of providing artificial reality content to one or more viewers. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    illustrates selected elements of an example system environment for determining a dynamic reverse head-related transfer function for a subject. 
         FIG.  2    illustrates selected elements of an example in-ear speaker. 
         FIGS.  3 A and  3 B  illustrate selected elements of an example in-ear speaker being worn by a subject. 
         FIG.  4    illustrates selected elements of an example enclosure of an in-ear speaker. 
         FIG.  5    illustrates selected elements of an example speaker funnel of an enclosure. 
         FIGS.  6 A and  6 B  illustrate selected elements of an example audio reflector of an in-ear speaker. 
         FIG.  7    illustrates selected elements of an example method for emitting a sound from an in-ear speaker worn by a subject. 
         FIG.  8    illustrates selected elements of an example computer system. 
     
    
    
     DESCRIPTION OF EXAMPLE EMBODIMENTS 
       FIG.  1    illustrates selected elements of an example system environment for determining a dynamic reverse head-related transfer function for a subject. In the example illustrated in  FIG.  1   , system environment  100  includes capture space  110  and computing device  170 . Capture space  110  includes a series of audio sensors  120 - 1  through  120 -N (collectively referred to herein as “audio sensors  120 ”), a series of image sensors  130 - 1  through  130 -N (collectively referred to herein as “image sensors  130 ”), and a subject  160  wearing an in-ear speaker  140  in the right ear of subject  160  shown in  FIG.  1   . In-ear speaker  140  is coupled to a microphone  150  that is also worn in the right ear of subject  160  shown in  FIG.  1   . Computing device  170  includes a head-related transfer function (HRTF) database  180  for storing measured dynamic HRTF for the subject  160 . In other embodiments, system environment  100  may include additional, fewer, and/or any combination of components suitable for determining a dynamic HRTF for a subject. 
     In one embodiment, capture space  110  may comprise a room, or other enclosed space, generally operable to absorb reflections of sound. In particular, capture space  110  may absorb reverberant sound waves such that sensor devices within capture space  110  may exclusively detect direct sound waves. These “free-field” conditions may be used to measure a transfer function associated with a sound source. For example, in-ear speaker  140  may emit an acoustic pressure wave within capture space  110  such that a series of audio sensors  120  disposed throughout capture space  110  may capture the sound. The captured sound or waveform may be used, in part, to compute a dynamic HRTF for a subject. In the embodiment illustrated in  FIG.  1   , capture space  110  may include a series of audio sensors  120  and a series of image sensors  130 . For example, capture space  110  may include microphones and cameras disposed evenly throughout capture space  110  to detect a sound generated by in-ear speaker  140  and capture images of subject  160 , respectively. In one embodiment, capture space  110  may be or include a dome having audio sensors  120  and image sensors  130  disposed evenly throughout the dome surrounding subject  160 . In another embodiment, capture space  110  may be or include an audio/visual capture stage which includes audio sensors  120  and image sensors  130  embedded in the walls and directed toward subject  160 . In other embodiments, capture space  110  may be or include an anechoic chamber, a semi-anechoic chamber, and/or any combination of soundproof environments suitable for absorbing reflections of sound. 
     In one embodiment, in-ear speaker  140  may comprise a system, device, or apparatus generally operable to emit a sound (e.g., an acoustic pressure wave) outwardly away from the head of a subject. Specifically, in-ear speaker  140  may be worn inside an ear (e.g., left ear, right ear, or both ears) of subject  160  such that in-ear speaker  140  may emit a sound outwardly away from the ear of subject  160  into the surrounding capture space  110 . In one embodiment, each sound emitted by in-ear speaker  140  may be or include a “sine wave sweep,” increasing in frequency (e.g., ranging from 20 Hz to 20 kHz) such that the various frequencies are emitted into the surrounding capture space  110 . For example, in-ear speaker  140  may include a crossover network (not shown in figure) configured to partition a source audio signal into high, middle, and low-frequency sound waves through respective transducers. These high, middle, and low-frequency sound waves may be emitted by the in-ear speaker  140  throughout capture space  110  such that audio sensors  120  may capture the sound waves for processing. In other embodiments, sounds emitted by in-ear speaker  140  may be or include a log sweep, linear sweep, white noise, pink noise, and/or any combination of sounds suitable for serving as a reference signal. In-ear speaker  140  is described in further detail with respect to  FIGS.  2 - 6   . 
     In one embodiment, microphone  150  may comprise a system, device, or apparatus generally operable to capture the sound emitted by in-ear speaker  140 . In particular, microphone  150  may be coupled to in-ear speaker  140  inside an ear of subject  160  such that microphone  150  may capture a sound adjacent to the ear canal of subject  160  before the sound reflects and exits the ear to be modified by anthropometric features of subject  160 . For example, various frequencies of an input signal may become boosted or attenuated as the sound leaves the in-ear speaker  140  and reflects off the head, ears, and body of subject  160 . Because the sounds are captured prior to becoming modified, sound captured by microphone  150  may serve as a “reference signal” in determining a dynamic HRTF for subject  160 . That is, computing device  170  may use reference signals captured by microphone  150  as input signals during processing to determine a dynamic HRTF for subject  160 . In one embodiment, microphone  150  may be or include a microelectromechanical system (MEMS) microphone. In other embodiments, microphone  150  may be or include a dynamic microphone, a condenser microphone, a piezoelectric microphone, or any combination of transducers suitable for receiving and converting sound waves into electrical signals. 
     In one embodiment, each audio sensor  120 - 1  through  120 -N may comprise a system, device, or apparatus generally operable to capture sound emitted by in-ear speaker  140 . Specifically, audio sensors  120  may be disposed throughout capture space  110  (e.g., embedded in the walls) such that a diaphragm, or other acoustic sensor, of each audio sensor  120  is directed toward subject  160  (and in-ear speaker  140 ). Each audio sensor  120  may capture sounds emitted by in-ear speaker  140  after the sounds have exited the ear and have become modified by the anthropometric features of subject  160 . For example, various frequencies of a sound may become modified in response to reflecting off the pinna of the ear and other parts of the body of subject  160  while exiting the ear. Because sounds are captured after becoming modified, sounds captured by each audio sensor  120  may serve as output signals in determining a dynamic HRTF for subject  160 . That is, computing device  170  may use audio recordings of sounds captured by each audio sensor  120  as output signals during processing to determine a dynamic HRTF for subject  160 . In one embodiment, audio sensors  120  may be or include a series of omnidirectional microphones. In other embodiments, audio sensors  120  may be or include a series of dynamic microphones, condenser microphones, piezoelectric microphones, ambisonic microphones, higher-order-ambisonic microphones, or any combination of transducers suitable for receiving and converting sound waves into electrical signals. 
     In one embodiment, each image sensor  130 - 1  through  130 -N may comprise a system, device, or apparatus generally operable to capture one or more images of subject  160 . In particular, image sensors  130  may be disposed throughout capture space  110  (e.g., embedded in the walls) such that a lens, or other light sensor, of each image sensor  130  is directed toward subject  160 . Each image sensor  130  may capture one or more images (e.g., still images, video images, and the like) depicting the body pose of subject  160 , or the orientation of subject  160  in relation to capture space  110 . In one embodiment, image sensors  130  may capture one or more images of subject  160  while in-ear speaker  140  is emitting a sound such that a body pose of subject  160  may be mapped to both the audio recordings of the sound captured by audio sensors  120  and the reference signal captured by microphone  150 . In one embodiment, image sensors  130  may be or include a series of digital cameras. In another embodiment, image sensors  130  may be or include a series of depth sensors, range imaging cameras, time-of-flight (ToF) cameras, and the like. In other embodiments, image sensors  130  may be or include a series of thermographic cameras, infrared cameras, and/or any combination of image sensors suitable for receiving and converting images into electrical signals. 
     In one embodiment, computing device  170  may comprise a system, device, or apparatus generally operable to determine a dynamic HRTF for subject  160 . Computing device  170  may receive audio recordings captured by audio sensors  120  of a sound, or sounds, emitted by in-ear speaker  140 . In addition, computing device  170  may receive a reference signal, or reference signals, captured by microphone  150  and one or more images captured by image sensors  130 . The one or more images may depict a body pose of subject  160  in relation to the surrounding capture space  110  while in-ear speaker  140  is emitting the sound. By allowing subject  160  to change body pose, a dense set of measurements may be achieved and used to determine a dynamic HRTF for subject  160 . In one embodiment, computing device  170  may be or include a desktop computer. In other embodiments, computing device  170  may be or include a server system, microcontroller unit, tablet computer, notebook computer, and/or any combination of computing devices suitable for determining a dynamic HRTF for a subject. 
     In one embodiment, computing device  170  may use the one or more images captured by image sensors  130  to generate a model, or a “pose representation,” of the body pose of subject  160  to be used for determining a dynamic HRTF. Conventional HRTF measurements may not account for changes in position of the subject (e.g., tilting head, rotating head, and the like) as the subject is required to remain still throughout the process, thus limiting the scope of binaural sounds that the HRTF measurements may synthesize for the subject. For example, a conventional HRTF dataset may be represented using the functions HRTF_L(azimuth_i, elevation_i) and HRTF_R(azimuth_i, elevation_i) for left (L) and right (R) ears of a subject, respectively. In this example, “i” may serve as an index used to represent each speaker in a series of speakers where azimuth_i and elevation_i describe angles that indicate a position of each speaker in relation to a subject. In contrast, computing device  170  may use a pose representation of a body pose of subject  160  to yield a dense set of measurements that accounts for changes in position of subject  160 . For example, a dynamic HRTF dataset may be represented using the functions: HRTF_L(azimuth_i, elevation_i, radius_i, pose_j) and HRTF_R(azimuth_i, elevation_i, radius_i, pose_j) for left (L) and right (R) ears of subject  160 , respectively. In this example, “i” may serve as an index used to represent each audio sensor  120  in capture space  110  where azimuth_i and elevation_i describe angles that indicate a position of each audio sensor  120  in relation to subject  160 . Additionally, radius_i may describe a distance between subject  160  and each audio sensor  120  and pose_j may describe body pose of subject  160  (i.e., as indicated using a pose representation). Here, “j” may serve as an additional index used to represent each body pose of subject  160  for multiple body poses that correspond to a specific azimuth_i, elevation_i, and radius_i of a given audio sensor  120 . By allowing subject  160  to change body pose, dynamic HRTF measurements effectively increase the scope of binaural sounds that HRTF measurements may synthesize for a subject. In one embodiment, the pose representation of the body pose may be or include a three-dimensional (3D) virtual reconstruction of the body pose of subject  160 . For example, a pose representation may be generated using a 3D mesh from which an azimuth, elevation, radius, and body pose of subject  160  in relation to each audio sensor  120  may be derived. 
     In one embodiment, computing device  170  may process the audio recordings of the sounds captured by audio sensors  120  with the reference signal captured by microphone  150  and the pose representation to determine an HRTF for each audio sensor  120 - 1  through  120 -N within capture space  110 . That is, computing device  170  may determine an HRTF for the position of each audio sensor  120  within capture space  110  for a given body pose of subject  160 . In the example illustrated in  FIG.  1   , computing device  170  may first determine an HRTF for the position of each audio sensor  120  within capture space  110  for body pose “A” of subject  160 . In one embodiment, computing device  170  may process the audio recordings of the sounds captured by audio sensors  120  with the pose representation and reference signal captured by microphone  150  (e.g., using deconvolution) where the audio recordings may serve as an output signal and the reference signal may serve as an input signal. For example, computing device  170  may determine an HRTF (H 1 (ω)) for audio sensor  120 - 1  (shown in  FIG.  1   ) using the equation below: 
     
       
         
           
             
               
                 H 
                 1 
               
               ( 
               ω 
               ) 
             
             = 
             
               
                 
                   Y 
                   1 
                 
                 ( 
                 ω 
                 ) 
               
               
                 X 
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     In the equation above, Y 1 (ω) is the output signal (i.e., audio recording captured by audio sensor  120 - 1 ) and X(ω) is the input signal (i.e., reference signal captured by microphone  150 ). Because both input and output signals are known, computing device  170  may solve for H 1 (ω), thereby determining an HRTF for the position of audio sensor  120 - 1  in capture space  110 . In one embodiment, computing device  170  may store HRTF (H 1 (ω)) in HRTF database  180  with data indicating a pose representation associated with the HRTF (e.g., indicating body pose “A” of subject  160 ). 
     In another example, computing device  170  may determine an HRTF (H 2 (ω)) for audio sensor  120 - 2  (shown in  FIG.  1   ) using the equation below: 
     
       
         
           
             
               
                 H 
                 2 
               
               ( 
               ω 
               ) 
             
             = 
             
               
                 
                   Y 
                   2 
                 
                 ( 
                 ω 
                 ) 
               
               
                 X 
                 ⁡ 
                 ( 
                 ω 
                 ) 
               
             
           
         
       
     
     In the equation above, Y 2 (ω) is the output signal (i.e., audio recording captured by audio sensor  120 - 2 ) and X(ω) is the input signal (i.e., reference signal captured by microphone  150 ). Again, because both input and output signals are known, computing device  170  may solve for H 2 (ω), thereby determining an HRTF for the position of microphone  120 - 2  in capture space  110 . In one embodiment, computing device  170  may store HRTF (H 2 (ω)) in HRTF database  180  with data indicating the pose representation associated with the HRTF. For example, computing device  170  may store the HRTF for each audio sensor  120  as a data structure that includes: an HRTF measurement; azimuth, elevation, and radius values of the audio sensor  120  in relation to subject  160 ; and pose representation coordinates indicating a body pose “A” of subject  160 . In one embodiment, computing device  170  may determine an HRTF for each audio sensor  120 - 1  through  120 -N within capture space  110 . That is, computing device  170  may determine an HRTF for the position of each audio sensor  120  within capture space  110  for a given pose representation. 
     In one embodiment, computing device  170  may process audio recordings of additional sounds captured by audio sensors  120  with an additional reference signal captured by microphone  150  embedded within in-ear speaker  140  and the pose representation to determine an HRTF for each audio sensor  120 - 1  through  120 -N within capture space  110 . That is, computing device  170  may determine an HRTF for the position of each audio sensor  120  within capture space  110  for an additional body pose of subject  160 . In the example illustrated in  FIG.  1   , computing device  170  may determine an HRTF for the position of each audio sensor  120  within capture space  110  for additional body pose “B” of subject  160 . In response to subject  160  changing body pose, in-ear speaker  140  may emit an additional sound from an ear (e.g., left ear, right ear, or both ears) of subject  160  while subject  160  is oriented in the additional body pose. Microphone  150  may capture an additional reference signal before the additional sound exits the ear and becomes modified by anthropometric features of subject  160 . Similarly, audio sensors  120  may capture the additional sound after the additional sound exits the ear and becomes modified by the anthropometric features of subject  160 . In addition, image sensors  130  may capture an additional one or more images of subject  160  while in-ear speaker  140  is emitting the additional sound. The additional body pose of subject  160  may be mapped to both the audio recordings of the additional sound captured by audio sensors  120  and the additional reference signal captured by microphone  150 . 
     In one embodiment, computing device  170  may modify the pose representation of the body pose of subject  160  based on the additional one or more images captured by image sensors  130 . In particular, computing device  170  may modify the pose representation to represent the additional body pose of subject  160  as shown in the additional one or more images. In the example shown in  FIG.  1   , computing device  170  may modify the pose representation to represent additional body pose “B” of subject  160 . Computing device  170  may process audio recordings of the additional sound captured by audio sensors  120  with the additional reference signal captured by microphone  150  and the pose representation to determine an HRTF for each audio sensor  120  as described above with respect to body pose “A.” In one embodiment, computing device  170  may store the HRTF for each audio sensor  120  in HRTF database  180  with data indicating the pose representation associated with the HRTF. For example, computing device  170  may store the HRTF for each audio sensor  120  as a data structure that includes: an HRTF measurement; azimuth, elevation, and radius values of the audio sensor  120  in relation to subject  160 ; and pose representation coordinates indicating additional body pose “B” of subject  160 . 
     In one embodiment, HRTF database  180  may comprise a system, device, or apparatus generally operable to store HRTF measurements for each audio sensor  120  in capture space  110 . In particular, HRTF database  180  may store HRTF measurements and associated metadata for the position of each audio sensor  120  within capture space  110 . For example, each entry stored in HRTF database  180  may correspond to an audio sensor  120 , or position of the audio sensor  120  within capture space  110 , and include: an HRTF measurement; azimuth, elevation, and radius values of the audio sensor  120  in relation to subject  160 ; and pose representation coordinates indicating a given body pose of subject  160 . Here, each audio sensor  120  within capture space  110  may include multiple entries in HRTF database  180 . Specifically, each audio sensor  120  may include multiple HRTF measurements in HRTF database  180  that each correspond to a respective body pose of subject  160 . Because HRTF database  180  includes multiple HRTF measurements that correspond to each respective body pose of subject  160 , computing device  170  may access HRTF database  180  to determine an HRTF measurement for a given position within capture space  110  that corresponds to a given body pose of subject  160 , thereby determining a dynamic HRTF for subject  160 . 
       FIG.  2    illustrates selected elements of an example in-ear speaker. As described above with respect to  FIG.  1   , in-ear speaker  140  may comprise a system, device, or apparatus generally operable to emit a sound outwardly away from the head of subject  160 . In particular, in-ear speaker  140  may be worn inside the ear of subject  160  such that in-ear speaker  140  emits sounds outwardly away from the ear of subject  160  into the surrounding capture space  110 . In the embodiment illustrated in  FIG.  2   , in-ear speaker  140  includes an audio source  210 , a crossover network  230 , one or more speakers  240 , an audio-transport tube  250 , and an audio reflector  260 . Audio source  210  includes an audio converter  220 . Audio reflector  260  includes a microphone  150 . In other embodiments, in-ear speaker  140  may include additional, fewer, and/or any combination of components suitable for emitting a sound outwardly away from the head of subject  160 . 
     In one embodiment, audio source  210  may comprise a system, device, or apparatus generally operable to generate a digital signal, or a “source audio signal,” to be converted into an analog signal and used as a sound. For example, audio source  210  may generate a digital sine wave to be converted into an analog signal and used as a sine wave sweep emitted from in-ear speaker  140  as a sound. In the embodiment illustrated in  FIG.  2   , audio source  210  includes an audio converter  220  to convert the digital source audio signal into an analog source audio signal to be sent to crossover network  230 . In one embodiment, audio source  210  may be or include a computing device. In other embodiments, audio source  210  may be or include a sine oscillator circuit, microcontroller unit, and/or any combination of audio sources suitable for generating a digital source audio signal. 
     In one embodiment, audio converter  220  may comprise a system, device, or apparatus generally operable to convert a digital signal generated by audio source  210  into an analog source audio signal. Specifically, audio converter  220  may be coupled to audio source  210  to receive a digital source audio signal and convert the digital source audio signal into an analog source audio signal. For example, audio converter  220  may convert a finite precision number such as a fixed-point binary number comprising the digital source audio signal into a physical quantity such as a sound pressure comprising the analog source audio signal. That is, audio converter  220  may receive digital output from audio source  210  and convert the digital output into analog line-level output capable of being filtered by crossover network  230  and emitted by speakers  240 . In one embodiment, audio converter  220  may be or include a sound card coupled to audio source  210 . In other embodiments, audio converter  220  may be or include a digital-to-analog converter (DAC), a network of weighted resistors, and/or any combination of electronic components suitable for converting a digital signal into an analog source audio signal. 
     In one embodiment, crossover network  230  may comprise a system, device, or apparatus generally operable to filter a source audio signal into respective frequency signals. In particular, crossover network  230  may receive the analog source audio signal from audio converter  220  (e.g., via a 3.5 mm headphone jack) and split the source audio signal into two or more respective frequencies such that each respective frequency may be emitted by speakers  240 . For example, crossover network  230  may receive a source audio signal from audio converter  220  and filter the received source audio signal into a high-frequency, a middle-frequency, and a low-frequency signal using a combination of high-pass, band-pass, and low-pass filters, respectively. In the embodiment illustrated in  FIG.  2   , crossover network  230  may be coupled to speakers  240  such that crossover network  230  may provide the respective high-frequency, middle-frequency, and low-frequency signals to speakers  240 . In one embodiment, crossover network  230  may be or include an active crossover network, a passive crossover network, a digital crossover network, a mechanical crossover network, and/or any combination of crossover networks suitable for filtering a source audio signal into respective frequency signals. In the embodiment illustrated in  FIG.  2   , crossover network  230  may be enclosed within enclosure  200  of in-ear speaker  140 . In another embodiment, crossover network  230  may be located outside of enclosure  200 . In other embodiments, in-ear speaker  140  may not include crossover network  230  as illustrated in  FIG.  2   . 
     In one embodiment, speakers  240  may comprise a system, device, or apparatus generally operable to emit a sound comprised of multiple frequency signals. Specifically, speakers  240  may be comprised of one or more speakers having various specifications (e.g., size, frequency response, impedance, sensitivity, and the like) such that each speaker in speakers  240  may be optimized to emit a respective frequency. In the embodiment illustrated in  FIG.  2   , each speaker of speakers  240  may receive a frequency signal from crossover network  230  in accordance with the frequency in which the speaker is optimized to emit. For example, a speaker configured to optimize high-frequencies may receive a high-frequency signal from crossover network  230 . Similarly, a speaker configured to optimize middle-frequencies may receive a middle-frequency signal from crossover network  230 . Speakers  240  may be enclosed within enclosure  200  to dampen leakage such that sounds emitted from speakers  240  are prevented from diffusing throughout the surrounding capture space  110 . Specifically, the sound pressure comprising a sound may be contained within enclosure  200  and directed toward an opening of audio-transport tube  250  such that the sound may be reflected by audio reflector  260 . In one embodiment, speakers  240  may be or include a speaker array comprised of a series of speakers coupled to crossover network  230 . In another embodiment, speakers  240  may be or include a singular speaker. In other embodiments, speakers  240  may be or include a series of balanced armature drivers formed into an array, a singular balanced armature driver, a series of dynamic drivers formed into an array, a singular dynamic driver, and/or any combination of transducers suitable for converting electrical audio signals into sound waves. 
     In one embodiment, audio-transport tube  250  may comprise a system, device, or apparatus generally operable to transport sounds to audio reflector  260  from speakers  240 . Specifically, audio-transport tube  250  may couple speakers  240  to audio reflector  260  such that audio reflector  260  may receive the sounds generated by speakers  240  and reflect the sounds throughout capture space  110 . In one embodiment, audio-transport tube  250  may include one or more bends such that each bend modifies an overall frequency response of audio-transport tube  250 . In one embodiment, audio-transport tube  250  may be comprised of a flexible material (e.g., plastic, carbon fiber, rubber, and the like) having elastic properties such that the formation of one or more bends in audio-transport tube  250  may vary depending on an orientation and/or movement of subject  160 . Here, the overall frequency response of audio-transport tube  250  may be variable in that the flexible material allows audio-transport tube  250  to bend and contort into various shapes. In another embodiment, audio-transport tube  250  may be comprised of a rigid material (e.g., hardened steel, tungsten carbide, glass, and the like) having stiff properties such that the number of bends in audio-transport tube  250  may remain constant despite an orientation and/or movement of subject  160 . Here, the overall frequency response of audio-transport tube  250  may be constant in that the rigid material prevents audio-transport tube  250  from bending, or otherwise contorting, after manufacturing. In other embodiments, audio-transport tube  250  may be comprised of any combination of flexible material and rigid material suitable for transporting sounds to audio reflector  260  from speakers  240 . Audio-transport tube  250  is described further with respect to  FIGS.  3 A and  3 B . 
     In one embodiment, audio reflector  260  may comprise a system, device, or apparatus generally operable to reflect sounds throughout capture space  110 . In particular, audio reflector  260  may receive a sound from speakers  240  via audio-transport tube  250  and reflect the sound outwardly away from the head of subject  160 . Upon reaching audio reflector  260  via audio-transport tube  250 , the sound may reflect, or bounce, off audio reflector  260  inside an ear of subject  160 . Audio reflector  260  may direct the reflected sound pressure outwardly away from the ear of subject  160 , thus reflecting the sound throughout capture space  110 . In one embodiment, audio reflector  260  may be removably coupled to an absorptive material (e.g., foam) preventing sound pressure from entering the inner-ear of a subject that may damage the eardrum and/or generate unwanted inner-ear frequency response. In one embodiment, audio reflector  260  may be configured to diffuse sounds throughout capture space  110 . For example, audio reflector  260  may receive a sound from speakers  240  and diffuse the sound outwardly away from the head of subject  160 . Audio reflector  260  is described further with respect to  FIGS.  3 A,  3 B,  6 A, and  6 B . 
     In one embodiment, microphone  150  may comprise a system, device, or apparatus generally operable to capture sound (e.g., sound pressure waves) emitted by in-ear speaker  140 . Specifically, microphone  150  may be coupled to audio reflector  260  such that microphone  150  may capture sounds within the ear of a subject before the sounds exit the ear and become modified by anthropometric features of the subject. Because the sounds are captured prior to becoming modified, sounds captured by microphone  150  may serve as reference signals in determining a dynamic HRTF for a subject as described above with respect to  FIG.  1   . In addition, the reference signal captured by microphone  150  may be used to account for the overall frequency response of audio-transport tube  250  caused by the one or more bends and to remove delay associated sounds captured by audio sensors  120 . In one embodiment, microphone  150  may be or include a microelectromechanical system (MEMS) microphone. In other embodiments, microphone  150  may be or include a dynamic microphone, a condenser microphone, a piezoelectric microphone, or any combination of transducers suitable for receiving and converting sound waves into electrical signals. 
       FIGS.  3 A and  3 B  illustrate selected elements of an example in-ear speaker being worn by a subject. In the example illustrated in  FIGS.  3 A and  3 B , in-ear speaker  140  may include audio reflector  260 , absorptive material  300 , audio-transport tubes  250 , and enclosure  200 . Enclosure  200  may be coupled to shoulder harness  320  and may include crossover network  230  and speakers  240  enclosed within (not shown in figures). In other embodiments, in-ear speaker  140  may include additional, fewer, and/or any combination of components suitable for emitting a sound outwardly away from the head of subject  160 . 
       FIG.  3 A  illustrates a side view of in-ear speaker  140  being worn by subject  160 . In the example illustrated in  FIG.  3 A , enclosure  200  may be coupled to shoulder harness  320  worn by subject  160  proximate to the base of the neck. Audio-transport tubes  250  may be coupled to enclosure  200 . Specifically, audio-transport tubes  250  may be coupled to speakers  240  enclosed within enclosure  200  to receive a sound emitted by speakers  240 . Audio-transport tubes  250  may direct the sound received from speakers  240  from enclosure  200  to audio reflector  260 . In the embodiment illustrated in  FIGS.  3 A and  3 B , audio-transport tubes  250  may loop behind an ear  310  of subject  160  to direct the sound to audio reflector  260 . Upon reaching audio reflector  260  via audio-transport tube  250 , the sound pressure comprising the sound may reflect, or bounce, off audio reflector  260  inside the ear  310  of subject  160 , thus directing the sound pressure outwardly away from the ear  310 . 
     In the example illustrated in  FIG.  3 A , audio reflector  260  may be removably coupled to absorptive material  300  inside the ear  310  of subject  160 . Specifically, absorptive material  300  may include an outward-facing end having a concave, or cupped, center contoured to receive a peg (not shown in figure) of audio reflector  260 . Additionally, absorptive material  300  may include an inward-facing end contoured to be worn inside an inner-ear of subject  160 . The inward-facing end of absorptive material  300  may prevent the inner-ear of subject  160  from receiving the sound reflected by audio reflector  260 . In particular, the inward-facing end of absorptive material  300  may prevent sound pressure from entering the inner-ear of subject  160  that may damage the eardrum, thus ensuring the safety of subject  160  while in-ear speaker  140  emits a sound. 
       FIG.  3 B  illustrates a rear view of in-ear speaker  140  being worn by subject  160 . In the example illustrated in  FIG.  3 B , enclosure  200  may be coupled to shoulder harness  320  between the shoulders of subject  160  proximate to the base of the neck. Enclosure  200  may include headphone jack  330 , or similar multi-channel audio coupler, used to receive a source audio signal from audio converter  220  (shown in  FIG.  2   ). Specifically, crossover network  230  (shown in  FIG.  2   ) enclosed within enclosure  200  may receive the analog source audio signal from audio converter  220  and split the source audio signal into two or more respective frequencies such that each respective frequency may be emitted by a speaker within speakers  240  (shown in  FIG.  2   ). Speakers  240  may be enclosed within enclosure  200  such that sounds emitted from speakers  240  are prevented from diffusing throughout the surrounding capture space  110 . That is, sound pressure may be contained within enclosure  200  and directed toward openings of audio-transport tubes  250  such that the sound may be reflected by audio reflector  260 . 
       FIG.  4    illustrates selected elements of an example enclosure of an in-ear speaker. In the example illustrated in  FIG.  4   , enclosure  200  includes enclosure top portion  400 , speaker housing caps  420  (individually referred to herein as “speaker housing cap  420 ”), speaker housing sections  430  (individually referred to herein as “speaker housing section  430 ”), speaker funnels  440  (individually referred to herein as “speaker funnel  440 ”), and enclosure bottom portion  460 . Speaker housing caps  420  may include speaker housing cap holes  410  (individually referred to herein as “speaker housing cap hole  410 ”). Speaker funnels  440  may include speaker funnel outputs  450  (individually referred to herein as “speaker funnel output  450 ”). Enclosure top portion  400  may include screw holes  480 . Enclosure bottom portion  460  may include speaker funnel output holes  470  (individually referred to herein as “speaker funnel output hole  470 ”) and screw holes  490 . It is noted that although crossover network  230  and speakers  240  are not illustrated in  FIG.  4   , enclosure  200  may enclose crossover network  230  and speakers  240  as described with respect to  FIGS.  2  and  3    above. In other embodiments, enclosure  200  may include additional, fewer, and/or any combination of components suitable for preventing sounds from diffusing throughout the surrounding capture space  110 . 
     In one embodiment, enclosure top portion  400  may be removably coupled to enclosure bottom portion  460  to enclose speaker housing caps  420 , speaker housing sections  430 , and speaker funnels  440  within enclosure  200 . In particular, enclosure top portion  400  may be removably coupled to enclosure bottom portion  460  by coupling screw holes  480  of enclosure top portion  400  to screw holes  490  of enclosure bottom portion  460  using screws (not shown in figure). In one embodiment, enclosure top portion  400  and enclosure bottom portion  460  may be comprised of a rigid material (e.g., opaque thermoplastic, amorphous polymer, and the like) that provides impact resistance, strength, and heat resistance. For example, enclosure top portion  400  and enclosure bottom portion  460  may each be comprised of acrylonitrile butadiene styrene (ABS) plastic that may be 3D printed to form enclosure top portion  400  and enclosure bottom portion  460 . In one embodiment, enclosure top portion  400 , speaker housing caps  420 , speaker housing sections  430 , speaker funnels  440 , and enclosure bottom portion  460  may be comprised of the same material. In other embodiments, enclosure top portion  400 , speaker housing caps  420 , speaker housing sections  430 , speaker funnels  440 , and enclosure bottom portion  460  may be comprised of two or more materials. 
     In one embodiment, speaker housing caps  420 , speaker housing sections  430 , and speaker funnels  440  may be removably coupled together within enclosure  200 . Specifically, speaker housing caps  420  may be removably coupled to speaker housing sections  430  and speaker housing sections  430  may be removably coupled to speaker funnels  440 . In the embodiment illustrated in  FIG.  4   , each speaker funnel  440  may include one or more speakers  240 . Speaker housing cap holes  410  of speaker housing caps  420  may allow crossover network  230  (not shown in figure) enclosed in enclosure  200  to provide frequency signals (e.g., high-frequency, middle-frequency, and low-frequency signals) to each speaker of speakers  240  (not shown in figure) enclosed in speaker funnels  440 . For example, one or more wires carrying respective frequency signals may be threaded through speaker housing cap hole  410  of speaker housing cap  420  and coupled to respective speakers of speakers  240  housed within speaker funnel  440 . Each speaker funnel  440  may include one or more speakers  240  such that in-ear speaker  140  may output a high signal-to-noise ratio (SNR) to aid in processing the audio recordings of sounds captured by audio sensors  120  as described with respect to  FIG.  1   . For example, speaker funnel  440  may house one or more speakers  240  that include four tweeter speakers and two woofer speakers that each emit respective frequencies to generate a sound. Sounds emitted by each speaker of speakers  240  may exit speaker funnels  440  at speaker funnel outputs  450  and enter respective openings of audio-transport tubes  250  via speaker funnel output holes  470 . Removably coupling speaker housing caps  420 , speaker housing sections  430 , and speaker funnels  440  together may prevent sounds emitted by speakers  240  from diffusing throughout enclosure  200  and, in turn, from diffusing throughout the surrounding capture space  110 . Speaker funnel  440  is described in further detail with respect to  FIG.  5   . 
       FIG.  5    illustrates selected elements of an example speaker funnel of an enclosure. In one embodiment, speaker funnel  440  may comprise a system, device, or apparatus generally operable to house speakers  240  within enclosure  200 . In particular, speaker funnel  440  may include one or more slots that are each contoured to house a speaker of speakers  240 . In the example illustrated in  FIG.  5   , speaker funnel  440  may include two sets of tweeter slots  500  (individually referred to herein as “tweeter slot  500 ”) and two woofer slots  510  (individually referred to herein as “woofer slot  510 ”). In one embodiment, speaker funnel  440  may include two of each slot in order to increase sound pressure level, measured in decibels, output from each speaker funnel  440  without causing destructive interference amongst sound waves comprising each sound. Increasing the sound pressure level output from each speaker funnel  440  may increase SNR which aids in processing the audio recordings of sounds captured by audio sensors  120  as described with respect to  FIG.  1   . In other embodiments, speaker funnel  440  may include additional, fewer, and/or any combination of slots suitable for housing speakers  240 . 
     In one embodiment, each tweeter slot  500  may be contoured to house a speaker that is optimized to emit high-frequency to middle-frequency signals received from crossover network  230 . In the embodiment illustrated in  FIG.  5   , speaker funnel  440  may include two differently-sized tweeter slots  500 . Specifically, the smaller tweeter slots  500  shown in  FIG.  5    may be contoured to house speakers optimized to emit high-frequencies while the larger tweeter slots  500  may be contoured to house speakers optimized to emit middle to low-frequencies. In one embodiment, each tweeter slot  500  may house a balanced armature driver optimized to emit a high-frequency to middle-frequency signal. In another embodiment, each tweeter slot  500  may house a dynamic driver optimized to emit a high-frequency to middle-frequency signal. In the embodiment illustrated in  FIG.  5   , each speaker funnel  440  of enclosure  200  may include a total of four tweeter slots  500 . In other embodiments, each speaker funnel  440  of enclosure  200  may include additional, fewer, or any number of tweeter slots  500  suitable for emitting high-frequency to middle-frequency signals and increasing SNR. 
     In one embodiment, each woofer slot  510  may be contoured to house a speaker that is optimized to emit low-frequency signals received from crossover network  230 . In the embodiment illustrated in  FIG.  5   , speaker funnel  440  may include two woofer slots  510 . In one embodiment, each woofer slot  510  may house a balanced armature driver optimized to emit a low-frequency signal. In another embodiment, each woofer slot  510  may house a dynamic driver optimized to emit a low-frequency signal. In the embodiment illustrated in  FIG.  5   , each speaker funnel  440  of enclosure  200  may include a total of two woofer slots  510 . In other embodiments, each speaker funnel  440  may include additional, fewer, or any number of woofer slots  510  suitable for emitting low-frequency signals and increasing SNR. 
       FIGS.  6 A and  6 B  illustrate selected elements of an example audio reflector of an in-ear speaker. As described above with respect to  FIG.  2   , audio reflector  260  may comprise a system, device, or apparatus generally operable to reflect sounds throughout capture space  110  (shown in  FIG.  1   ). Specifically, audio reflector  260  may receive a sound from speakers  240  (shown in  FIG.  2   ) via audio-transport tube  250  (shown in  FIG.  2   ) and reflect the sound outwardly away from the head of subject  160  (shown in  FIG.  1   ). In the example illustrated in  FIGS.  6 A and  6 B , audio reflector  260  may have a slightly elliptical shape contoured to be worn inside the ear of a subject and may include audio reflector opening  600 , microphone  150 , an open end  610 , a closed end  620 , and a peg  630 . In one embodiment, audio reflector  260  may be coupled to audio-transport tube  250  via audio reflector opening  600 . In other embodiments, audio reflector  260  may include additional, fewer, and/or any combination of components suitable for reflecting sounds throughout capture space  110 . 
       FIG.  6 A  illustrates a front three-quarter view of audio reflector  260 . In the example illustrated in  FIG.  6 A , audio reflector  260  may be contoured into a truncated cone shape having an open end  610  and a closed end  620 . The open end  610  may be directed away from the ear of a subject. The closed end  620  may be or include a rigid surface worn inside the ear of a subject and configured to reflect, or diffuse, a sound away from the ear of the subject through open end  610 . Specifically, audio reflector  260  may receive a sound from audio-transport tube  250  via audio reflector opening  600 . As shown in  FIGS.  3 A and  3 B , audio-transport tube  250  may be looped behind an ear  310  of subject  160 . Therefore, audio reflector opening  600  may be oriented such that audio-transport tube  250  may couple with audio reflector opening  600  proximate to the upper portion of an ear of a subject. In addition, audio reflector  260  may be oriented such that sound received from audio-transport tube  250  may be directed toward microphone  150  located on the rigid surface of closed end  620 . That is, the sound pressure comprising a sound may reflect, or bounce, off closed end  620  of audio reflector  260  inside the ear of a subject. Audio reflector  260  may direct the reflected sound pressure outwardly away from the ear of the subject, thus reflecting the sound throughout capture space  110 . In addition, the microphone  150  may capture the sounds within the ear of the subject before the sounds exit the ear and become modified by anthropometric features of the subject. 
       FIG.  6 B  illustrates a rear three-quarter view of audio reflector  260 . In the example illustrated in  FIG.  6 B , audio reflector  260  may include a peg  630  extending from the back side of closed end  620 . In one embodiment, peg  630  may be removably coupled with absorptive material  300  (shown in  FIG.  3 A ) inside an ear of a subject. In particular, peg  630  may be contoured to removably couple with an outward-facing end of absorptive material  300  having a concave, or cupped, center contoured to receive peg  630  as described with respect to  FIG.  3 A . Peg  630  may ensure that audio reflector  260  remains positioned within the ear of the subject while the inward-facing end of absorptive material  300  may prevent the inner-ear of subject  160  from receiving the sound reflected by audio reflector  260 . 
       FIG.  7    illustrates selected elements of an example method for emitting a sound from an in-ear speaker worn by a subject. The method may begin at step  710 , where an audio source of the in-ear speaker generates a source audio signal. At step  720 , one or more speakers of the in-ear speaker may emit a sound based on the source audio signal. The one or more speakers may comprise a singular speaker and/or a speaker array coupled to a crossover network. At step  730 , an audio-transport tube of the in-ear speaker may receive the sound. The audio-transport tube has an input end coupled to the one or more speakers to receive the sound. At step  740 , an audio reflector of the in-ear speaker may reflect the sound, where the audio reflector is coupled to an output end of the audio-transport tube. 
     Particular embodiments may repeat one or more steps of the method of  FIG.  7   , where appropriate. Although this disclosure describes and illustrates particular steps of the method of  FIG.  7    as occurring in a particular order, this disclosure contemplates any suitable steps of the method of  FIG.  7    occurring in any suitable order. Moreover, although this disclosure describes and illustrates an example method for emitting a sound from an in-ear speaker worn by a subject including the particular steps of the method of  FIG.  7   , this disclosure contemplates any suitable method for emitting a sound from an in-ear speaker worn by a subject including any suitable steps, which may include all, some, or none of the steps of the method of  FIG.  7   , where appropriate. Furthermore, although this disclosure describes and illustrates particular components, devices, or systems carrying out particular steps of the method of  FIG.  7   , this disclosure contemplates any suitable combination of any suitable components, devices, or systems carrying out any suitable steps of the method of  FIG.  7   . 
       FIG.  8    illustrates selected elements of an example computer system. In particular embodiments, one or more computer systems  800  perform one or more steps of one or more methods described or illustrated herein. In particular embodiments, one or more computer systems  800  provide functionality described or illustrated herein. In particular embodiments, software running on one or more computer systems  800  performs one or more steps of one or more methods described or illustrated herein or provides functionality described or illustrated herein. Particular embodiments include one or more portions of one or more computer systems  800 . Herein, reference to a computer system may encompass a computing device, and vice versa, where appropriate. Moreover, reference to a computer system may encompass one or more computer systems, where appropriate. 
     This disclosure contemplates any suitable number of computer systems  800 . This disclosure contemplates computer system  800  taking any suitable physical form. As example and not by way of limitation, computer system  800  may be an embedded computer system, a system-on-chip (SOC), a single-board computer system (SBC) (such as, for example, a computer-on-module (COM) or system-on-module (SOM)), a desktop computer system, a laptop or notebook computer system, an interactive kiosk, a mainframe, a mesh of computer systems, a mobile telephone, a personal digital assistant (PDA), a server, a tablet computer system, an augmented/virtual reality device, or a combination of two or more of these. Where appropriate, computer system  800  may include one or more computer systems  800 ; be unitary or distributed; span multiple locations; span multiple machines; span multiple data centers; or reside in a cloud, which may include one or more cloud components in one or more networks. Where appropriate, one or more computer systems  800  may perform without substantial spatial or temporal limitation one or more steps of one or more methods described or illustrated herein. As an example, and not by way of limitation, one or more computer systems  800  may perform in real time or in batch mode one or more steps of one or more methods described or illustrated herein. One or more computer systems  800  may perform at different times or at different locations one or more steps of one or more methods described or illustrated herein, where appropriate. 
     In particular embodiments, computer system  800  includes a processor  802 , memory  804 , storage  806 , an input/output (I/O) interface  808 , a communication interface  810 , and a bus  812 . Although this disclosure describes and illustrates a particular computer system having a particular number of particular components in a particular arrangement, this disclosure contemplates any suitable computer system having any suitable number of any suitable components in any suitable arrangement. 
     In particular embodiments, processor  802  includes hardware for executing instructions, such as those making up a computer program. As an example, and not by way of limitation, to execute instructions, processor  802  may retrieve (or fetch) the instructions from an internal register, an internal cache, memory  804 , or storage  806 ; decode and execute them; and then write one or more results to an internal register, an internal cache, memory  804 , or storage  806 . In particular embodiments, processor  802  may include one or more internal caches for data, instructions, or addresses. This disclosure contemplates processor  802  including any suitable number of any suitable internal caches, where appropriate. As an example, and not by way of limitation, processor  802  may include one or more instruction caches, one or more data caches, and one or more translation lookaside buffers (TLBs). Instructions in the instruction caches may be copies of instructions in memory  804  or storage  806 , and the instruction caches may speed up retrieval of those instructions by processor  802 . Data in the data caches may be copies of data in memory  804  or storage  806  for instructions executing at processor  802  to operate on; the results of previous instructions executed at processor  802  for access by subsequent instructions executing at processor  802  or for writing to memory  804  or storage  806 ; or other suitable data. The data caches may speed up read or write operations by processor  802 . The TLBs may speed up virtual-address translation for processor  802 . In particular embodiments, processor  802  may include one or more internal registers for data, instructions, or addresses. This disclosure contemplates processor  802  including any suitable number of any suitable internal registers, where appropriate. Where appropriate, processor  802  may include one or more arithmetic logic units (ALUs); be a multi-core processor; or include one or more processors  802 . Although this disclosure describes and illustrates a particular processor, this disclosure contemplates any suitable processor. 
     In particular embodiments, memory  804  includes main memory for storing instructions for processor  802  to execute or data for processor  802  to operate on. As an example, and not by way of limitation, computer system  800  may load instructions from storage  806  or another source (such as, for example, another computer system  800 ) to memory  804 . Processor  802  may then load the instructions from memory  804  to an internal register or internal cache. To execute the instructions, processor  802  may retrieve the instructions from the internal register or internal cache and decode them. During or after execution of the instructions, processor  802  may write one or more results (which may be intermediate or final results) to the internal register or internal cache. Processor  802  may then write one or more of those results to memory  804 . In particular embodiments, processor  802  executes only instructions in one or more internal registers or internal caches or in memory  804  (as opposed to storage  806  or elsewhere) and operates only on data in one or more internal registers or internal caches or in memory  804  (as opposed to storage  806  or elsewhere). One or more memory buses (which may each include an address bus and a data bus) may couple processor  802  to memory  804 . Bus  812  may include one or more memory buses, as described below. In particular embodiments, one or more memory management units (MMUs) reside between processor  802  and memory  804  and facilitate accesses to memory  804  requested by processor  802 . In particular embodiments, memory  804  includes random access memory (RAM). This RAM may be volatile memory, where appropriate. Where appropriate, this RAM may be dynamic RAM (DRAM) or static RAM (SRAM). Moreover, where appropriate, this RAM may be single-ported or multi-ported RAM. This disclosure contemplates any suitable RAM. Memory  804  may include one or more memories  804 , where appropriate. Although this disclosure describes and illustrates particular memory, this disclosure contemplates any suitable memory. 
     In particular embodiments, storage  806  includes mass storage for data or instructions. As an example, and not by way of limitation, storage  806  may include a hard disk drive (HDD), a floppy disk drive, flash memory, an optical disc, a magneto-optical disc, magnetic tape, or a Universal Serial Bus (USB) drive or a combination of two or more of these. Storage  806  may include removable or non-removable (or fixed) media, where appropriate. Storage  806  may be internal or external to computer system  800 , where appropriate. In particular embodiments, storage  806  is non-volatile, solid-state memory. In particular embodiments, storage  806  includes read-only memory (ROM). Where appropriate, this ROM may be mask-programmed ROM, programmable ROM (PROM), erasable PROM (EPROM), electrically erasable PROM (EEPROM), electrically alterable ROM (EAROM), or flash memory or a combination of two or more of these. This disclosure contemplates mass storage  806  taking any suitable physical form. Storage  806  may include one or more storage control units facilitating communication between processor  802  and storage  806 , where appropriate. Where appropriate, storage  806  may include one or more storages  806 . Although this disclosure describes and illustrates particular storage, this disclosure contemplates any suitable storage. 
     In particular embodiments, I/O interface  808  includes hardware, software, or both, providing one or more interfaces for communication between computer system  800  and one or more I/O devices. Computer system  800  may include one or more of these I/O devices, where appropriate. One or more of these I/O devices may enable communication between a person and computer system  800 . As an example, and not by way of limitation, an I/O device may include a keyboard, keypad, microphone, monitor, mouse, printer, scanner, speaker, still camera, stylus, tablet, touch screen, trackball, video camera, another suitable I/O device or a combination of two or more of these. An I/O device may include one or more sensors. This disclosure contemplates any suitable I/O devices and any suitable I/O interfaces  808  for them. Where appropriate, I/O interface  808  may include one or more device or software drivers enabling processor  802  to drive one or more of these I/O devices. I/O interface  808  may include one or more I/O interfaces  808 , where appropriate. Although this disclosure describes and illustrates a particular I/O interface, this disclosure contemplates any suitable I/O interface. 
     In particular embodiments, communication interface  810  includes hardware, software, or both providing one or more interfaces for communication (such as, for example, packet-based communication) between computer system  800  and one or more other computer systems  800  or one or more networks. As an example, and not by way of limitation, communication interface  810  may include a network interface controller (NIC) or network adapter for communicating with an Ethernet or other wire-based network or a wireless NIC (WNIC) or wireless adapter for communicating with a wireless network, such as a WI-FI network. This disclosure contemplates any suitable network and any suitable communication interface  810  for it. As an example, and not by way of limitation, computer system  800  may communicate with an ad hoc network, a personal area network (PAN), a local area network (LAN), a wide area network (WAN), a metropolitan area network (MAN), or one or more portions of the Internet or a combination of two or more of these. One or more portions of one or more of these networks may be wired or wireless. As an example, computer system  800  may communicate with a wireless PAN (WPAN) (such as, for example, a BLUETOOTH WPAN), a WI-FI network, a WI-MAX network, a cellular telephone network (such as, for example, a Global System for Mobile Communications (GSM) network), or other suitable wireless network or a combination of two or more of these. Computer system  800  may include any suitable communication interface  810  for any of these networks, where appropriate. Communication interface  810  may include one or more communication interfaces  810 , where appropriate. Although this disclosure describes and illustrates a particular communication interface, this disclosure contemplates any suitable communication interface. 
     In particular embodiments, bus  812  includes hardware, software, or both coupling components of computer system  800  to each other. As an example and not by way of limitation, bus  812  may include an Accelerated Graphics Port (AGP) or other graphics bus, an Enhanced Industry Standard Architecture (EISA) bus, a front-side bus (FSB), a HYPERTRANSPORT (HT) interconnect, an Industry Standard Architecture (ISA) bus, an INFINIBAND interconnect, a low-pin-count (LPC) bus, a memory bus, a Micro Channel Architecture (MCA) bus, a Peripheral Component Interconnect (PCI) bus, a PCI-Express (PCIe) bus, a serial advanced technology attachment (SATA) bus, a Video Electronics Standards Association local (VLB) bus, or another suitable bus or a combination of two or more of these. Bus  812  may include one or more buses  812 , where appropriate. Although this disclosure describes and illustrates a particular bus, this disclosure contemplates any suitable bus or interconnect. 
     Herein, a computer-readable non-transitory storage medium or media may include one or more semiconductor-based or other integrated circuits (ICs) (such, as for example, field-programmable gate arrays (FPGAs) or application-specific ICs (ASICs)), hard disk drives (HDDs), hybrid hard drives (HHDs), optical discs, optical disc drives (ODDs), magneto-optical discs, magneto-optical drives, floppy diskettes, floppy disk drives (FDDs), magnetic tapes, solid-state drives (SSDs), RAM-drives, SECURE DIGITAL cards or drives, any other suitable computer-readable non-transitory storage media, or any suitable combination of two or more of these, where appropriate. A computer-readable non-transitory storage medium may be volatile, non-volatile, or a combination of volatile and non-volatile, where appropriate. 
     Herein, “or” is inclusive and not exclusive, unless expressly indicated otherwise or indicated otherwise by context. Therefore, herein, “A or B” means “A, B, or both,” unless expressly indicated otherwise or indicated otherwise by context. Moreover, “and” is both joint and several, unless expressly indicated otherwise or indicated otherwise by context. Therefore, herein, “A and B” means “A and B, jointly or severally,” unless expressly indicated otherwise or indicated otherwise by context. 
     The scope of this disclosure encompasses all changes, substitutions, variations, alterations, and modifications to the example embodiments described or illustrated herein that a person having ordinary skill in the art would comprehend. The scope of this disclosure is not limited to the example embodiments described or illustrated herein. Moreover, although this disclosure describes and illustrates respective embodiments herein as including particular components, elements, feature, functions, operations, or steps, any of these embodiments may include any combination or permutation of any of the components, elements, features, functions, operations, or steps described or illustrated anywhere herein that a person having ordinary skill in the art would comprehend. Furthermore, reference in the appended claims to an apparatus or system or a component of an apparatus or system being adapted to, arranged to, capable of, configured to, enabled to, operable to, or operative to perform a particular function encompasses that apparatus, system, component, whether or not it or that particular function is activated, turned on, or unlocked, as long as that apparatus, system, or component is so adapted, arranged, capable, configured, enabled, operable, or operative. Additionally, although this disclosure describes or illustrates particular embodiments as providing particular advantages, particular embodiments may provide none, some, or all of these advantages.