Patent Publication Number: US-2023164488-A1

Title: Headphones

Description:
CROSS REFERENCES TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 17/177,063, filed Feb. 16, 2021, which is a continuation of U.S. application Ser. No. 16/362,404, filed Mar. 22, 2019, which is a continuation of U.S. National Stage application Ser. No. 16/335,846, filed Mar. 22, 2019, now U.S. Pat. No. 10,848,847, and is a bypass continuation of International Patent Application No. PCT/US2017/052978, filed Sep. 22, 2017, which claims the benefit of U.S. Provisional Application Ser. No. 62/398,854, filed Sep. 23, 2016; the disclosures of which are hereby incorporated by reference in their entirety for all purposes. 
    
    
     FIELD 
     The described embodiments relate generally to various headphone features. More particularly, the various features help improve the overall user experience by incorporating an array of sensors and new mechanical features into the headphones. 
     BACKGROUND 
     Headphones have now been in use for over 100 years, but the design of the mechanical frames used to hold the earpieces against the ears of a user have remained somewhat static. For this reason, some over-head headphones are difficult to easily transport without the use of a bulky case or by wearing them conspicuously about the neck when not in use. Conventional interconnects between the earpieces and band often use a yoke that surrounds the periphery of each earpiece, which adds to the overall bulk of each earpiece. Furthermore, headphones users are required to manually verify that the correct earpieces are aligned with the ears of a user any time the user wishes to use the headphones. Consequently, improvements to the aforementioned deficiencies are desirable. 
     SUMMARY 
     This disclosure describes several improvements on circumaural and supra-aural headphone frame designs. 
     An earpiece is disclosed and includes the following: an earpiece housing; a speaker disposed within a central portion of the earpiece housing; and a pivot mechanism disposed at a first end of the earpiece housing, the pivot mechanism comprising: a stem, and a spring configured to oppose a rotation of the earpiece housing with respect to the stem, the spring comprising a first end coupled to the stem and a second end coupled to the earpiece housing. 
     Headphones are disclosed and include the following: a first earpiece; a second earpiece; a headband assembly, comprising a headband spring; a first pivot assembly joining the first earpiece to a first side of the headband assembly, the first pivot assembly comprising: a first stem, and a first pivot spring configured to oppose a rotation of the first earpiece relative to the first stem, the first pivot spring comprising a first end coupled to the first earpiece and a second end coupled to the first stem; and a second pivot assembly joining the second earpiece to a second side of the headband assembly, the second pivot assembly comprising: a second stem, and a second pivot spring configured to oppose a rotation of the second earpiece relative to the second stem, the second pivot spring comprising a first end coupled to the second earpiece and a second end coupled to the second stem. 
     Headphones are disclosed and include the following: a first earpiece; a second earpiece; a headband assembly, comprising a headband spring; first and second pivot assemblies joining opposing sides of the headband assembly to respective first and second earpieces, each of the pivot assemblies substantially enclosed within respective first and second earpieces, a stem of each of the pivot assemblies coupling its respective pivot assembly to the headband assembly. 
     Headphones are disclosed and include the following: a first earpiece; a second earpiece; and a headband coupling the first and second earpieces together and being configured to synchronize a movement of the first earpiece with a movement of the second earpiece such that a distance between the first earpiece and a center of the headband remains substantially equal to a distance between the second earpiece and the center of the headband. 
     Headphones are disclosed and include the following: a headband having a first end and a second end opposite the first end; a first earpiece coupled to the headband a first distance from the first end; a second earpiece coupled to the headband a second distance from the second end; and a cable routed through the headband and mechanically coupling the first earpiece to the second earpiece, the cable being configured to maintain the first distance substantially the same as the second distance by changing the first distance in response to a change in the second distance. 
     Headphones are disclosed and include the following: a first earpiece; a second earpiece; a headband assembly coupling the first and second earpieces together and comprising an earpiece synchronization system, the earpiece synchronization system configured to change a first distance between the first earpiece and the headband assembly concurrently with a change in a second distance between the second earpiece and the headband assembly. 
     Headphones are disclosed and include the following: a first earpiece; a second earpiece; a headband coupling the first earpiece to the second earpiece; earpiece position sensors configured to measure an angular orientation of the first and second earpieces with respect to the headband; and a processor configured to change an operational state of the headphones in accordance with the angular orientation of the first and second earpieces. 
     Headphones are disclosed and also include: a headband; a first earpiece pivotally coupled to a first side of the headband and having a first axis of rotation; a second earpiece pivotally coupled to a second side of the headband and having a second axis of rotation; earpiece position sensors configured to measure an orientation of the first earpiece relative to the first axis of rotation and an orientation of the second earpiece relative to the second axis of rotation; and a processor configured to: place the headphones in a first operational state when the first earpiece is biased in a first direction from a neutral state of the first earpiece and the second earpiece is biased in a second direction opposite the first direction from a neutral state of the second earpiece, and place the headphones in a second operational state when the first earpiece is biased in the second direction from the neutral state of the first earpiece and the second earpiece is biased in the first direction from a neutral state of the second earpiece. 
     Headphones are disclosed and include the following: a headband; a first earpiece comprising a first earpiece housing; a first pivot mechanism disposed within the first earpiece housing, the first pivot mechanism comprising: a first stem base portion that protrudes though an opening defined by the first earpiece housing, the first stem base portion coupled to a first portion of the headband, and a first orientation sensor configured to measure an angular orientation of the first earpiece relative to the headband; a second earpiece comprising a second earpiece housing; a second pivot mechanism disposed within the second earpiece housing, the second pivot mechanism comprising: a second stem base portion that protrudes though an opening defined by the second earpiece housing, the second stem base portion coupled to a second portion of the headband, and a second orientation sensor configured to measure an angular orientation of the second earpiece relative to the headband; and a processor that sends a first audio channel to the first earpiece when sensor readings received from the first and second orientation sensors are consistent with the first earpiece covering a first ear of a user and is configured to send a second audio channel to the first earpiece when the sensor readings are consistent with the first earpiece covering a second ear of the user. 
     Headphones are disclosed and include the following: a first earpiece having a first earpad; a second earpiece having a second earpad; and a headband joining the first earpiece to the second earpiece, the headphones being configured to move between an arched state in which a flexible portion of the headband is curved along its length and a flattened state, in which the flexible portion of the headband is flattened along its length, the first and second earpieces being configured to fold towards the headband such that the first and second earpads contact the flexible headband in the flattened state. 
     Headphones are disclosed and include the following: a first earpiece; a second earpiece; and a headband assembly coupled to both the first and second earpieces, the headband assembly comprising: linkages pivotally coupled together, and an over-center locking mechanism coupling the first earpiece to a first end of the headband assembly and having a first stable position in which the linkages are flattened and a second stable position in which the linkages form an arch. 
     Headphones are disclosed and include the following: a first earpiece; a second earpiece; and a flexible headband assembly coupled to both the first and second earpieces, the flexible headband assembly comprising: hollow linkages pivotally coupled together and defining an interior volume within the flexible headband assembly, and bi-stable elements disposed within the interior volume and configured to oppose transition of the flexible headband assembly between a first state in which a central portion of the hollow linkages are straightened and a second state in which the hollow linkages form an arch. 
     Other aspects and advantages of the invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the described embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The disclosure will be readily understood by the following detailed description in conjunction with the accompanying drawings, wherein like reference numerals designate like structural elements, and in which: 
         FIG.  1 A  shows a front view of an exemplary set of over ear or on-ear headphones; 
         FIG.  1 B  shows headphone stems extending different distances from a headband assembly; 
         FIG.  2 A  shows a perspective view of a first side of headphones with synchronized headphone stems; 
         FIGS.  2 B- 2 C  show cross-sectional views of the headphones depicted in  FIG.  2 A  in accordance with section lines A-A and B-B, respectively; 
         FIG.  2 D  shows a perspective view of an opposite side of the headphones depicted in  FIG.  2 D ; 
         FIG.  2 E  shows a cross-sectional view of the headphones depicted in  FIG.  2 D  in accordance with section line C-C; 
         FIGS.  2 F- 2 G  show perspective views of a second side of headphones with synchronized headphone stems and a unitary spring band; 
         FIGS.  2 H- 2 I  show cross-sectional views of the headphones depicted in  FIGS.  2 F- 2 G  in accordance with section lines D-D and E-E, respectively; 
         FIG.  3 A  shows exemplary headphones having a headband assembly configured to synchronize adjustment of the positions of its earpieces; 
         FIG.  3 B  shows a cross-sectional view of a headband assembly when the headphones are expanded to their largest size; 
         FIG.  3 C  shows a cross-sectional view of the headband assembly when the headphones are contracted to a smaller size; 
         FIGS.  3 D- 3 F  show perspective top and cross-sectional views of a headband assembly configured to synchronize earpiece position; 
         FIGS.  3 G- 3 H  show a top view of an earpiece synchronization assembly; 
         FIGS.  3 I- 3 J  show a flattened schematic view of another earpiece synchronization system similar to the one depicted in  FIGS.  3 G- 3 H ; 
         FIGS.  3 K- 3 L  show cutaway views of headphones  360  that are suitable for incorporation of either one of the earpiece synchronization systems depicted in  FIGS.  3 G- 3 J ; 
         FIGS.  3 M- 3 N  show perspective views of the earpiece synchronization system depicted in  FIGS.  3 G- 3 H  in retracted and extended positions as well as a data synchronization cable; 
         FIG.  3 O  shows a portion of a canopy structure and how an earpiece synchronization system can be routed through reinforcement members of the canopy structure that includes; 
         FIGS.  4 A- 4 B  show front views of headphones  400  having off-center pivoting earpieces; 
         FIG.  5 A  shows an exemplary pivot mechanism that includes torsion springs; 
         FIG.  5 B  shows the pivot mechanism depicted in  FIG.  5 A  positioned behind a cushion of an earpiece; 
         FIG.  6 A  shows a perspective view of another pivot mechanism that includes leaf springs; 
         FIG.  6 B- 6 D  show a range of motion of an earpiece using the pivot mechanism depicted in  FIG.  6 A ; 
         FIG.  6 E  shows an exploded view of the pivot mechanism depicted in  FIG.  6 A ; 
         FIG.  6 F  shows a perspective view of another pivot mechanism; 
         FIG.  6 G  shows yet another pivot mechanism; 
         FIGS.  6 H- 6 I  show the pivot mechanism depicted in  FIG.  6 G  with one side removed in order to illustrate rotation of a stem base in different positions; 
         FIG.  6 J  shows a cutaway perspective view of the pivot assembly of  FIG.  6 G  disposed within an earpiece housing; 
         FIGS.  6 K- 6 L  show partial cross-sectional side views of the pivot assembly positioned within the earpiece housing with helical springs in relaxed and compressed states; 
         FIG.  7 A  shows multiple positions of a spring band suitable for use in a headband assembly; 
         FIG.  7 B  shows a graph illustrating how spring force varies based on spring rate as a function of displacement of the spring band depicted in  FIG.  7 A ; 
         FIGS.  8 A- 8 B  show a solution for preventing discomfort caused by headphones wrapping too tightly around the neck of a user; 
         FIGS.  8 C- 8 D  show how separate and distinct knuckles can be arranged along the lower side of a spring band to prevent the spring band from returning to a neutral position; 
         FIGS.  8 E- 8 F  show how springs joining a headband assembly to earpieces can cooperate with spring band  700  to set the actual amount of force applied to a user by headphones; 
         FIGS.  9 A- 9 B  show another way in which to limit the range of motion of a pair of headphones using a low spring-rate band; 
         FIG.  10 A  shows a top view of an exemplary head of a user wearing headphones; 
         FIG.  10 B  shows a front view of the headphones depicted in  FIG.  10 A ; 
         FIGS.  10 C- 10 D  show top views of the headphones depicted in  FIG.  10 A  and how earpieces of the headphones are able to rotate about respective yaw axes; 
         FIGS.  10 E- 10 F  show flow charts describing control methods that can be carried out when roll and/or yaw of the earpieces with respect to the headband is detected; 
         FIG.  10 G  shows a system level block diagram of a computing device  1070  that can be used to implement the various components described herein; 
         FIGS.  11 A- 11 C  show foldable headphones; 
         FIGS.  11 D- 11 F  show how earpieces of foldable headphones can be folded towards an exterior-facing surface of a deformable band region; 
         FIGS.  12 A- 12 B  show a headphones embodiment that can be transitioned from an arched state to a flattened state by pulling on opposing sides of a spring band; 
         FIGS.  12 C- 12 D  show side views of a foldable stem region in arched and flattened states, respectively; 
         FIG.  12 E  shows a side view of one end of the headphones depicted in  FIG.  12 D ; 
         FIGS.  13 A- 13 B  show partial cross-sectional views of headphones using an off-axis cable to transition between an arched state and a flattened states; 
         FIGS.  14 A- 14 C  show partial cross-sectional views of headphones having a foldable stem region constrained at least in part by an elongating pin that delays flattening of the headphones through a first portion of the travel of the earpieces of the headphones; 
         FIGS.  15 A- 15 F  show various views of headband assembly  1500  from different angles and in different states; 
         FIGS.  16 A- 16 B  show a headband assembly in folded and arched states; and 
         FIGS.  17 A- 17 B  show views of another foldable headphones embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Headphones have been in production for many years, but numerous design problems remain. For example, the functionality of headbands associated with headphones has generally been limited to a mechanical connection functioning only to maintain the earpieces of the headphones over the ears of a user and provide an electrical connection between the earpieces. The headband tends to add substantially to the bulk of the headphones, thereby making storage of the headphones problematic. Stems connecting the headband to the earpieces that are designed to accommodate adjustment of an orientation of the earpieces with respect to a user&#39;s ears also add bulk to the headphones. Stems connecting the headband to the earpieces that accommodate elongation of the headband generally allow a central portion of the headband to shift to one side of a user&#39;s head. This shifted configuration can look somewhat odd and depending on the design of the headphones can also make the headphones less comfortable to wear. 
     While some improvements such as wireless delivery of media content to the headphones has alleviated the problem of cord tangle, this type of technology introduces its own batch of problems. For example, because wireless headphones require battery power to operate, a user who leaves the wireless headphones turned on could inadvertently exhaust the battery of the wireless headphones, making them unusable until a new battery can be installed or for the device to be recharged. Another design problem with many headphones is that a user must generally figure out which earpiece corresponds to which ear to prevent the situation in which the left audio channel is presented to the right ear and the right audio channel is presented to the left ear. 
     A solution to the unsynchronized positioning of the earpieces is to incorporate an earpiece synchronization component taking the form of a mechanical mechanism disposed within the headband that synchronizes the distance between the earpieces and respective ends of the headband. This type of synchronization can be performed in multiple ways. In some embodiments, the earpiece synchronization component can be a cable extending between both stems that can be configured to synchronize the movement of the earpieces. The cable can be arranged in a loop where different sides of the loop are attached to respective stems of the earpieces so that motion of one earpiece away from the headband causes the other earpiece to move the same distance away from the opposite end of the headband. Similarly, pushing one earpiece towards one side of the headband translates the other earpiece the same distance towards the opposite side of the headband. In some embodiments, the earpiece synchronization component can be a rotating gear embedded within the headband can be configured to engage teeth of each stem to keep the earpieces synchronized. 
     One solution to the conventional bulky connections between headphones stems and earpieces is to use a spring-driven pivot mechanism to control motion of the earpieces with respect to the band. The spring-driven pivot mechanism can be positioned near the top of the earpiece, allowing it to be incorporated within the earpiece instead of being external to the earpiece. In this way, pivoting functionality can be built into the earpieces without adding to the overall bulk of the headphones. Different types of springs can be utilized to control the motion of the earpieces with respect to the headband. Specific examples that include torsional springs and leaf springs are described in detail below. The springs associated with each earpiece can cooperate with springs within the headband to set an amount of force exerted on a user wearing the headphones. In some embodiments, the springs within the headband can be low spring-rate springs configured to minimize the force variation exerted across a large spectrum of users with different head sizes. In some embodiments, the travel of the low-rate springs in the headband can be limited to prevent the headband from clamping to tightly about the neck of a user when being worn around the neck. 
     One solution to the large headband form-factor problem is to design the headband to flatten against the earpieces. The flattening headband allows for the arched geometry of the headband to be compacted into a flat geometry, allowing the headphones to achieve a size and shape suitable for more convenient storage and transportation. The earpieces can be attached to the headband by a foldable stem region that allows the earpieces to be folded towards the center of the headband. A force applied to fold each earpiece in towards the headband is transmitted to a mechanism that pulls the corresponding end of the headband to flatten the headband. In some embodiments, the stem can include an over-center locking mechanism that prevents inadvertent return of the headphones to an arched state without requiring the addition of a release button to transition the headphones back to the arched state. 
     A solution to the power management problems associated with wireless headphones includes incorporating an orientation sensor into the earpieces that can be configured to monitor an orientation of the earpieces with respect to the band. The orientation of the earpieces with respect to the band can be used to determine whether or not the headphones are being worn over the ears of a user. This information can then be used to put the headphones into a standby mode or shut the headphones down entirely when the headphones are not determined to be positioned over the ears of a user. In some embodiments, the earpiece orientation sensors can also be utilized to determine which ears of a user the earpieces are currently covering. Circuitry within the headphones can be configured to switch the audio channels routed to each earpiece in order to match a determination regarding which earpiece is on which ear of the user. 
     These and other embodiments are discussed below with reference to  FIGS.  1 - 17 B ; however, those skilled in the art will readily appreciate that the detailed description given herein with respect to these figures is for explanatory purposes only and should not be construed as limiting. 
     Symmetric Telescoping Earpieces 
       FIG.  1 A  shows a front view of an exemplary set of over ear or on-ear headphones  100 . Headphones  100  includes a band  102  that interacts with stems  104  and  106  to allow for adjustability of the size of headphones  100 . In particular, stems  104  and  106  are configured to shift independently with respect to band  102  in order to accommodate multiple different head sizes. In this way, the position of earpieces  108  and  110  can be adjusted to position earpieces  108  and  110  directly over the ears of a user. Unfortunately, as can be seen in  FIG.  1 B , this type of configuration allows stems  104  and  106  to become mismatched with respect to band  102 . The configuration shown in  FIG.  1 B  can be less comfortable for a user and additionally lack cosmetic appeal. To remedy these issues, the user would be forced to manually adjust stems  104  and  106  with respect to band  102  in order to achieve a desirable look and comfortable fit.  FIGS.  1 A- 1 B  also show how stems  104  and  106  extend down to a central portion of earpieces  108  in order to allow earpieces  108  to rotate to accommodate the curvature of a user&#39;s head. As mentioned above the portions of stems  104  and  106  that extend down around earpieces  108  increase the diameters of earpieces  108 . 
       FIG.  2 A  shows a perspective view of headphones  200  with a headband  202  configured to solve the problems depicted in  FIGS.  1 A- 1 B . Headband  202  is depicted without a cosmetic covering to reveal internal features. In particular, headband  202  can include a wire loop  204  configured to synchronize the movement of stems  206  and  208 . Wire guides  210  can be configured to maintain a curvature of wire loop  204  that matches the curvature of leaf springs  212  and  214 . Leaf springs  212  and  214  can be configured to define the shape of headband  202  and to exert a force upon the head of a user. Each of wire guides  210  can include openings through which opposing sides of wire loop  204  and leaf springs  212  and  214  can pass. In some embodiments, the openings for wire loop  204  can be defined by low-friction bearings to prevent noticeable friction from impeding the motion of wire loop  204  through the openings. In this way, wire guides  210  define a path along which wire loop  204  extends between stem housings  216  and  218 . Wire loop  204  is coupled to both stem  206  and stem  208  and functions to maintain a distance  120  between an earpiece  122  and stem housing  116  substantially the same as a distance  124  between earpiece  126  and stem housing  118 . A first side  204 - 1  of wire loop  204  is coupled to stem  206  and a second side  204 - 2  of wire loop  204  is coupled to stem  208 . Because opposite sides of the wire loop are attached to stems  206  and  208  movement of one of the stems results in movement of the other stem in the same direction. 
       FIG.  2 B  shows a cross-sectional view of a portion of stem housing  116  in accordance with section line A-A. In particular,  FIG.  2 B  shows how a protrusion  228  of stem  206  engages part of wire loop  204 . Because protrusion  228  of stem  206  is coupled with wire loop  204 , when a user of headphones  100  pulls earpiece  222  farther away from stem housing  216 , wire loop  204  is also pulled causing wire loop  204  to circulate through headband  202 . The circulation of wire loop  204  through headband  202  adjusts the position of earpieces  226 , which is similarly coupled to wire loop  204  by a protrusion of stem  208 . In addition to forming a mechanical coupling with wire loop  204 , protrusion  228  can also be electrically coupled to wire loop  204 . In some embodiments, protrusion  228  can include an electrically conductive pathway  230  that electrically couples wire loop  204  to electrical components within earpiece  222 . In some embodiments, wire loop  204  can be formed from an electrically conductive material, so that signals can be transferred between components within earpieces  222  and  226  by way of wire loop  204 . 
       FIG.  2 C  shows another cross-sectional view of stem housing  116  in accordance with section line B-B. In particular,  FIG.  2 C  shows how wire loop  204  engages pulley  232  within stem housing  216 . Pulley  232  minimizes any friction generated by the movement of earpiece  222  closer or farther away from stem housing  216 . Alternatively, wire loop  204  can be routed through a static bearing within stem housing  216 . 
       FIG.  2 D  shows another perspective view of headphones  200 . In this view, it can be seen that first side  204 - 1  and second side  204 - 2  of wire loop  204  shift laterally as they cross from one side of headband  202  to the other. This can be accomplished by the openings defined by wire guides  210  being gradually offset so that by the time sides  204 - 1  and  204 - 2  reach stem housing  218 , second side  204 - 2  is centered and aligned with stem  208 , as depicted in  FIG.  2 E . 
       FIG.  2 E  shows how second side  204 - 2  is engaged by protrusion  234 . Because stems  206  and  208  are attached to respective first and second sides of wire loop  204 , pushing earpiece  226  towards stem housing  218  also results in earpiece  222  being pushed towards stem housing  216 . Another advantage of the configuration depicted in  FIGS.  2 A- 2 E  is that regardless of the direction of travel of stems  206  and  208 , wire loop  204  always stays in tension. This keeps the amount of force needed to extend or retract earpieces  222  and  226  consistent regardless of direction. 
       FIGS.  2 F- 2 G  show perspective views of headphones  250 . Headphones  250  are similar to headphones  200  with the exception that only a single leaf spring  252  is used to connect stem housing  254  to stem housing  256 . In this embodiment, wire loop  258  can be positioned to either side of leaf spring  252 . Instead of being positioned directly below one side of wire loop  258 , stems  260  and  262  can be positioned directly between the two sides of wire loop  258  and connected to one side of wire loop  258  by an arm of stems  260  and  262 . 
       FIGS.  2 H and  2 I  show cross-sectional views of an interior portion of stem housings  254  and  256 .  FIG.  2 H  shows a cross-sectional view of stem housing  254  in accordance with section line D-D.  FIG.  2 H  shows how stem  260  can include a laterally protruding arm  268  that engages wire loop  258 . In this way, laterally protruding arm  268  couples stem  260  to wire loop  258  so that when earpiece  264  is moved earpiece  266  is kept in an equivalent position.  FIG.  2 I  shows a cross-sectional view of stem housing  256  in accordance with section line E-E.  FIG.  2 I  shows how wire loop  258  can be routed within stem housing  256  by pulleys  270  and  272 . By routing wire loop  258  above stem  262  any interference between wire loop  258  and stem  206  can be avoided. 
       FIGS.  3 A- 3 C  show another headphones embodiment configured to solve problems described in  FIGS.  1 A- 1 B .  FIG.  3 A  shows headphones  300 , which includes headband assembly  302 . Headband assembly  302  is joined to earpieces  304  and  306  by stems  308  and  310 . A size and shape of headband assembly  302  can vary depending on how much adjustability is desirable for headphones  300 . 
       FIG.  3 B  shows a cross-sectional view of headband assembly  302  when headphones  300  are expanded to their largest size. In particular,  FIG.  3 B  shows how headband assembly  302  includes a gear  312  configured to engage teeth defined by the ends of each of stems  308  and  310 . In some embodiments, stems  308  and  310  can be prevented from pulling completely out of headband assembly  302  by spring pins  314  and  316  by engaging openings defined by stems  308  and  310 . 
       FIG.  3 C  shows a cross-sectional view of headband assembly  302  when headphones  300  are contracted to a smaller size. In particular,  FIG.  3 C  shows how gear  312  keeps the position of stems  308  and  310  synchronized on account of any movement of stem  308  or stem  310  being translated to the other stem by gear  312 . In some embodiments, a stiffness of the housing defining the exterior of headband assembly  302  can be selected to match the stiffness of stems  308  and  310  to provide a user of headphones  300  with a headband having a more consistent feel. 
       FIG.  3 D  shows an alternative embodiment of stems  308  and  310 . A cover concealing the ends of stems  308  and  310  has been removed to more clearly show the features of the mechanism synchronizing the positions of the stems. Stem  308  defines an opening  318  extending through a portion of stem  308 . One side of opening  318  has teeth configured to engage gear  320 . Similarly, stem  310  defines an opening  322  extending through a portion of stem  310 . One side of opening  322  has teeth configured to engage gear  320 . Because opposing sides of openings  318  and  322  engage gear  320 , any motion of one of stems  308  and  310  causes the other stem to move. In this way, earpieces positioned at the ends of each of stem  308  and stem  310  are synchronized. 
       FIG.  3 E  shows a top view of stems  308  and  310 .  FIG.  3 E  also shows an outline of a cover  324  for concealing the geared openings defined by stems  308  and  310  and controlling the motion of the ends of stems  308  and  310 .  FIG.  3 F  shows a cross-sectional side view of stems  308  and  310  covered by cover  324 . Gear  320  can include bearing  326  for defining the axis of rotation for gear  320 . In some embodiments, the top of bearing  326  can protrude from cover  324 , allowing a user to adjust the earpiece positions by manually rotating bearing  326 . It should be appreciated that a user could also adjust the earpiece positions by simply pushing or pulling on one of stems  308  and  310 . 
       FIG.  3 G  shows a flattened schematic view of another earpiece synchronization system that utilizes a loop  328  within a headband  330  (the rectangular shape is used merely to show the location of headband  330  and should not be construed as for exemplary purposes only) to keep a distance between each of earpieces  304  and  306  and headband  330  synchronized. Stem wires  332  and  334  couple respective earpieces  304  and  306  to loop  328 . Stem wires  332  and  334  can be formed of metal and soldered to opposing sides of loop  328 . Because stem wires  332  and  334  are coupled to opposing sides of loop  328 , movement of earpiece  306  in direction  336  results in stem wire  332  moving in direction  338 . Consequently, moving earpiece  306  into closer proximity with headband  330  also moves stem wire  332 , which results in earpiece  304  being brought into closer proximity with headband  330 . In addition to showing a new location of earpieces  304  and  306  after being moved into closer proximity to headband  330 ,  FIG.  3 H  shows how moving earpiece  304  in direction  340  automatically moves earpiece  306  in direction  342  and farther away from headband  330 . While not depicted it should be appreciated that headband  330  could include various reinforcement members to keep loop  328  and stem wires  332  and  334  in the depicted shapes. 
       FIGS.  3 I- 3 J  show a flattened schematic view of another earpiece synchronization system similar to the one depicted in  FIGS.  3 G- 3 H .  FIG.  3 I  shows how the ends of stems  344  and  346  can be coupled directly to each other without an intervening loop. By extending stems  344  and  346  into a pattern, having a similar shape as loop  328 , a similar outcome can be achieved without the need for an additional loop structure. Movement of stems  344  and  346  is assisted by reinforcement members  348 ,  350  and  352 , which help to prevent buckling of stems  344  and  346  while the position of earpieces  304  and  306  are being adjusted. Reinforcement members  348 - 352  can define channels through which stems  344  and  346  smoothly pass. These channels can be particularly helpful in locations where stems  344  and  346  curve. While not defining a curved channel, reinforcement member  352  still serves an important purpose of limiting the direction of travel of the ends of stems  344  and  346  to directions  354  and  356 . Movement in direction  356  results in earpieces moving toward headband  330 , as depicted in  FIG.  3 J . Movement in direction  354  results in earpieces  304  and  306  moving farther away from headband  330 . 
       FIGS.  3 K- 3 L  show cutaway views of headphones  360  that are suitable for incorporation of either one of the earpiece synchronization systems depicted in  FIGS.  3 G- 3 J .  FIG.  3 K  shows headphones  360  with earpieces retracted and stem wires  332  and  334  extending out of headband  330  to engage and synchronize a position of stem assembly  362  with a position of stem assembly  364 . Stem  334  is depicted coupled to support structure  366  within stem assembly  364 , which allows extension and retraction of stem  334  to keep stem assembly  362  synchronized with stem assembly  364 . As depicted, stem assembly  362  is disposed within a channel defined by headband  330 , which allows stem assembly  362  to move relative to headband  330 .  FIG.  3 K  also shows how data synchronization cable  368  can extend through headband  330  and wrap around a portion of both stem wire  334  and stem wire  332 . By wrapping around stem wires  332  and  334 , data synchronization cable  368  is able to act as a reinforcement member to prevent buckling of stem wires  332  and  334 . Data synchronization cable  368  is generally configured to exchange signals between earpieces  304  and  306  in order to keep audio precisely synchronized during playback operations of headphones  360 . 
       FIG.  3 L  shows how the coil configuration of data synchronization cable  368  accommodates extension of stem assemblies  362  and  364 . Data synchronization cable  368  can have an exterior surface with a coating that allows stem wires  332  and  334  to slide through a central opening defined by the coils.  FIG.  3 L  also shows how earpieces  304  and  306  maintain the same distance from a central portion of headband  330 . 
       FIGS.  3 M- 3 N  show perspective views of the earpiece synchronization system depicted in  FIGS.  3 G- 3 H  in retracted and extended positions as well as a data synchronization cable  368 .  FIG.  3 M  shows how stem wire  332  includes an attachment feature  370  that at least partially surrounds a portion of loop  328 . In this way, stem wire  332 , stem wire  334  and support structures  366  move along with loop  328 .  FIG.  3 M  also shows a dashed line illustrating how a covering for headband  330  can at least partially conform with loop  328 , stem wire  332  and stem wire  334 . 
       FIG.  3 O  shows a portion of canopy structure  372  and how an earpiece synchronization system can be routed through reinforcement members  374  of canopy structure  372 . Reinforcement members  374  help guide loop  328  and stem wire  332  along a desired path. In some embodiments, canopy structure  372  can include a spring mechanism that helps keep earpieces secured to a user&#39;s ears. 
     Off-Center Pivoting Earpieces 
       FIGS.  4 A- 4 B  show front views of headphones  400  having off-center pivoting earpieces.  FIG.  4 A  shows a front view of headphones  400 , which includes headband assembly  402 . In some embodiments, headband assembly  402  can include an adjustable band and stems for customizing the size of headphones  400 . Each end of headband assembly  402  is depicted being coupled to an upper portion of earpieces  404 . This differs from conventional designs, which place the pivot point in the center of earpieces  404  so that earpieces can naturally pivot in a direction that allows earpieces  404  to move to an angle in which earpieces  404  are positioned parallel to a surface of a user&#39;s head. Unfortunately, this type of design generally requires bulky arms that extend to either side of earpiece  404 , thereby substantially increasing the size and weight of earpieces  404 . By locating pivot point  406  near the top of earpieces  404 , associated pivot mechanism components can be packaged within earpieces  404 . 
       FIG.  4 B  shows an exemplary range of motion  408  for each of earpieces  404 . Range of motion  408  can be configured to accommodate a majority of users based on studies performed on average head size measurements. This more compact configuration can still perform the same functions as the more traditional configuration described above, which includes applying a force through the center of the earpiece and establishing an acoustic seal. In some embodiments, range of motion  408  can be about 18 degrees. In some embodiments, range of motion  408  may not have a defined stop but instead grow progressively harder to deform as it gets farther from a neutral position. The pivot mechanism components can include spring elements configured to apply a modest retaining force to the ears of a user when the headphones are in use. The spring elements can also bring earpieces back to a neutral position once headphones  400  are no longer being worn. 
       FIG.  5 A  shows an exemplary pivot mechanism  500  for use in the upper portion of an earpiece. Pivot mechanism  500  can be configured to accommodate motion around two axes, thereby allowing adjustments to both roll and yaw for earpieces  404  with respect to headband assembly  402 . Pivot mechanism  500  includes a stem  502 , which can be coupled to a headband assembly. One end of stem  502  is positioned within bearing  504 , which allows stem  502  to rotate about yaw axis  506 . Bearing  504  also couples stem  502  to torsional springs  508 , which oppose rotation of stem  502  with respect to earpiece  404  about roll axis  510 . Each of torsional springs  508  can also be coupled to mounting blocks  512 . Mounting blocks  512  can be secured to an interior surface of earpiece  404  by fasteners  514 . Bearing  504  can be rotationally coupled to mounting blocks  512  by bushings  516 , which allow bearing  504  to rotate with respect to mounting blocks  512 . In some embodiments, the roll and yaw axes can be substantially orthogonal with respect to one another. In this context, substantially orthogonal means that while the angle between the two axes might not be exactly 90 degrees that an angle between the two axes would stay between 85 and 95 degrees. 
       FIG.  5 A  also depicts magnetic field sensor  518 . Magnetic field sensor  518  can take the form of a magnetometer or Hall Effect sensor capable of detecting motion of a magnet within pivot mechanism  500 . In particular, magnetic field sensor  518  can be configured to detect motion of stem  502  with respect to mounting blocks  512 . In this way, magnetic field sensor  518  can be configured to detect when headphones associated with pivot mechanism  500  are being worn. For example, when magnetic field sensor  518  takes the form of a Hall Effect sensor, rotation of a magnet coupled with bearing  504  can result in the polarity of the magnetic field emitted by that magnet saturating magnetic field sensor  518 . Saturation of the Hall Effect sensor by a magnetic field causes the Hall Effect sensor to send a signal to other electronic devices within headphones  400  by way of flexible circuit  520 . 
       FIG.  5 B  shows a pivot mechanism  500  positioned behind a cushion  522  of earpiece  404 . In this way, pivot mechanism  500  can be integrated within earpiece  404  without impinging on space normally left open to accommodate the ear of a user. Close-up view  524  shows a cross-sectional view of pivot mechanism  500 . In particular, close-up view  524  shows a magnet  526  positioned within a fastener  528 . As stem  502  is rotated about roll axis  510 , magnet  526  rotates with it. Magnetic field sensor  518  can be configured to sense rotation of the field emitted by magnet  526  as it rotates. In some embodiments, the signal generated by magnetic field sensor  518  can be used to activate and/or deactivate headphones  400 . This can be particularly effective when the neutral state of earpiece  404  corresponds to the bottom end of each earpiece  404  is oriented towards the user at an angle that causes earpiece  404  to be rotated away from the users head when worn by most users. By designing headphones  400  in this manner, rotation of magnet  526  away from its neutral position can be used as a trigger that headphones  400  are in use. Correspondingly, movement of magnet  526  back to its neutral position can be used as an indicator that headphones  400  are no longer in use. Power states of headphones  400  can be matched to these indications to save power while headphones  400  are not in use. 
     Close up view  524  of  FIG.  5 B  also shows how stem  502  is able to twist within bearing  504 . Stem  502  is coupled to threaded cap  530 , which allows stem  502  to twist within bearing  504  about yaw axis  506 . In some embodiments, threaded cap  530  can define mechanical stops that limit the range of motion through which stem  502  can twist. A magnet  532  is disposed within stem  502  and is configured to rotate along with stem  502 . A magnetic field sensor  534  can be configured to measure the rotation of a magnetic field emitted by magnet  532 . In some embodiments, a processor receiving sensor readings from magnetic field sensor  534  can be configured to change an operating parameter of headphones  400  in response to the sensor readings indicating a threshold amount of change in the angular orientation of magnet  532  relative to the yaw axis has occurred. 
       FIG.  6 A  shows a perspective view of another pivot mechanism  600  that is configured to fit within a top portion of earpieces  404  of headphones. The overall shape of pivot mechanism  600  is configured to conform to space available within the top portion of the earpieces. Pivot mechanism  600  utilizes leaf springs instead of torsion springs to oppose motion in the directions indicated by arrows  601  (e.g., a roll direction) of earpieces  404 . Pivot mechanism  600  includes stem  602 , which has one end disposed within bearing  604 . Bearing  604  allows for rotation of stem  602  about yaw axis  605 . Bearing  604  also couples stem  602  to a first end of leaf spring  606  through spring lever  608 . A second end of each of leaf springs  606  is coupled to a corresponding one of spring anchors  610 . Spring anchors  610  are depicted as being transparent so that the position at which the second end of each of leaf springs  606  engages a central portion of spring anchors  610  can be seen. This positioning allows leaf springs  606  to bend in two different directions. Spring anchors  610  couple the second end of each leaf spring  606  to earpiece housing  612 . In this way, leaf springs  606  create a flexible coupling between stem  602  and earpiece housing  612 . Pivot mechanism  600  can also include cabling  614  configured to route electrical signals between two earpieces  404  by way of headband assembly  402  (not depicted). 
       FIGS.  6 B- 6 D  show a range of motion of earpiece  404 .  FIG.  6 B  shows earpiece  404  in a neutral state with leaf springs  606  in an undeflected state.  FIG.  6 C  shows leaf springs  606  being deflected in a first direction and  FIG.  6 D  shows leaf spring  606  being deflected in a second direction opposite the first direction.  FIGS.  6 C- 6 D  also show how the area between cushion  522  and earpiece housing  612  can accommodate the deflection of leaf springs  606 . 
       FIG.  6 E  shows an exploded view of pivot mechanism  600 .  FIG.  6 E  depicts mechanical stops that govern the amount of rotation possible about yaw axis  605 . Stem  602  includes a protrusion  616 , which is configured to travel within a channel defined by an upper yaw bushing  618 . As depicted, the channel defined by upper yaw bushing  618  has a length that allows for greater than 180 degrees of rotation. In some embodiments, the channel can include a detent configured to define a neutral position for earpiece  404 .  FIG.  6 E  also depicts a portion of stem  602  that can accommodate yaw magnet  620 . A magnetic field emitted by magnet  620  can be detected by magnetic field sensor  622 . Magnetic field sensor  622  can be configured to determine an angle of rotation of stem  602  with respect to the rest of pivot mechanism  600 . In some embodiments, magnetic field sensor  622  can be a Hall Effect sensor. 
       FIG.  6 E  also depicts roll magnet  624  and magnetic field sensor  626 , which can be configured to measure an amount of deflection of leaf springs  606 . In some embodiments, pivot mechanism  600  can also include strain gauge  628  configured to measure strain generated within leaf spring  606 . The strain measured in leaf spring  606  can be used to determine which direction and how much leaf spring is being deflected. In this way, a processor receiving sensor readings recorded by strain gauge  628  can determine whether and in which direction leaf springs  606  are bending. In some embodiments, readings received from strain gauge can be configured to change an operating state of headphones associated with pivot mechanism  600 . For example, the operating state can be changed from a playback state in which media is being presented by speakers associated with pivot mechanism  600  to a standby or inactive state in response to the readings from the strain gauge. In some embodiments, when leaf springs  606  are in an undeflected state this can be indicative of headphones associated with pivot mechanism  600  not being worn by a user. In other embodiments, the strain gauge can be positioned upon a headband spring. For this reason, ceasing playback based on this input can be very convenient as it allows a user to maintain a location in a media file until putting the headphones back on the head of the user at which point the headphones can be configured to resume playback of the media file. Seal  630  can close an opening between stem  602  and an exterior surface of an earpiece in order to prevent the ingress of foreign particulates that could interfere with the operation of pivot mechanism  600 . 
       FIG.  6 F  shows a perspective view of another pivot mechanism  650 , which differs in some ways from pivot mechanism  600 . Leaf springs  652  have a different orientation than leaf springs  606  of pivot mechanism  600 . In particular, an orientation of leaf springs  652  is about 90 degrees different than an orientation of leaf springs  606 . This results in a thick dimension of leaf springs  652  opposing rotation of an earpiece associated with pivot mechanism  650 .  FIG.  6 F  also shows flexible circuit  654  and board-to-board connector  656 . Flexible circuit can electrically couple a strain gauge positioned upon leaf spring  652  to a circuit board or other electrically conductive pathways on pivot mechanism  650 . Electrical signals can be routed through a distal end  658  of pivot mechanism  650 , which allows electrical signals to be routed between the earpieces. 
       FIG.  6 G  shows another pivot assembly  660  attached to earpiece housing  612  by fasteners  662  and bracket  663 . Pivot assembly  660  can include multiple helical springs  664  arranged side by side. In this way, helical coils  664  can act in parallel increasing the amount of resistance provided by pivot assembly  660 . Helical springs  664  are held in place and stabilized by pins  666  and  668 . Actuator  670  translates any force received from rotation of stem base  672  to helical springs  664 . In this way, helical springs  664  can establish a desired amount of resistance to rotation of stem base  672 . 
       FIGS.  6 H- 6 I  show pivot assembly  660  with one side removed in order to illustrate rotation of stem base  672  in different positions. In particular,  FIGS.  6 H- 6 I  shows how rotation of stem base  672  results in rotation of actuator  670  and compression of helical springs  664 . 
       FIG.  6 J  shows a cutaway perspective view of pivot assembly  660  disposed within earpiece housing  612 . In some embodiments, stem base  672  can include a bearing  674 , as depicted, to reduce friction between stem base  672  and actuator  670 .  FIG.  6 J  also shows how bracket  663  can define a bearing for securing pin  666  in place. Pins  666  and  668  are also shown defining flattened recesses for keeping helical springs  664  securely in place. In some embodiments, the flattened recess can include protrusions that extends into central openings of helical springs  664 . 
       FIGS.  6 K- 6 L  show partial cross-sectional side views of pivot assembly  660  positioned within earpiece housing with helical springs  664  in relaxed and compressed states. In particular, the motion undergone by actuator  670  when shifting from a first position in  FIG.  6 K  to a second position of maximum deflection is clearly depicted.  FIGS.  6 K and  6 L  also depict mechanical stop  676  which helps limit an amount of rotation earpiece housing can achieve relative to stem base. 
     Low Spring-Rate Band 
       FIG.  7 A  shows multiple positions of a spring band  700  suitable for use in a headband assembly. Spring band  700  can have a low spring rate that causes a force generated by the band in response to deformation of spring band  700  to change slowly as a function of displacement. Unfortunately, the low spring rate also results in the spring having to go through a larger amount of displacement before exerting a particular amount of force. Spring band  700  is depicted in different positions  702 ,  704 ,  706  and  708 . Position  702  can correspond to spring band  700  being in a neutral state at which no force is exerted by spring band  700 . At position  704 , a spring band  700  can begin exerting a force pushing spring band  700  back toward its neutral state. Position  706  can correspond to a position at which users with small heads bend spring band  700  when using headphones associated with spring band  700 . Position  708  can correspond to a position of spring band  700  in which the users with large heads bend spring band  700 . The displacement between positions  702  and  706  can be sufficiently large for spring band  700  to exert an amount of force sufficient to keep headphones associated with spring band  700  from falling off the head of a user. Further, due to the low spring rate the force exerted by spring band  700  at position  708  can be small enough so that use of headphones associated with spring band  700  is not high enough to cause a user discomfort. In general, the lower the spring rate of spring band  700 , the smaller the variation in force exerted by spring band  700 . In this way, use of a low spring-rate spring band  700  can allow headphones associated with spring band  700  to give users with different sized heads a more consistent user experience. 
       FIG.  7 B  shows a graph illustrating how spring force varies based on spring rate as a function of displacement of spring band  700 . Line  710  can represent spring band  700  having its neutral position equivalent to position  702 . As depicted, this allows spring band  700  to have a relatively low spring rate that still passes through a desired force in the middle of the range of motion for a particular pair of headphones. Line  712  can represent spring band  700  having its neutral position equivalent to position  704 . As depicted, a higher spring rate is required to achieve a desired amount of force being exerted in the middle of the desired range of motion. Finally, line  714  represents spring band  700  having its neutral position equivalent to position  706 . Setting spring band  700  to have a profile consistent with line  714  would result in no force being exerted by spring band  700  at the minimum position for the desired range of motion and over twice the amount of force exerted compared with spring band  700  having a profile consistent with line  710  at the maximum position. While configuring spring band  700  to travel through a greater amount of displacement prior to the desired range of motion has clear benefits when wearing headphones associated with spring band  700 , it may not be desirable for the headphones to return to position  702  when worn around the neck of a user. This could result in the headphones uncomfortably clinging to the neck of a user. 
       FIG.  8 A- 8 B  show a solution for preventing discomfort caused by headphones  800  utilizing a low spring-rate spring band from wrapping too tightly around the neck of a user. Headphones  800  include a headband assembly  802  joining earpieces  804 . Headband assembly  802  includes compression band  806  coupled to an interior-facing surface of spring band  700 .  FIG.  8 A  shows spring band  700  in position  708 , corresponding to a maximum deflection position of headphones  800 . The force exerted by spring band  700  can act as a deterrent to stretching headphones  800  past this maximum deflection position. In some embodiments, an exterior facing surface of spring band  700  can include a second compression band configured to oppose deflection of spring band  700  past position  708 . As depicted, knuckles  808  of compression band  806  serve little purpose when spring band is in position  708  because none of the lateral surfaces of knuckles  808  are in contact with adjacent knuckles  808 . 
       FIG.  8 B  shows spring band  700  in position  706 . At position  706 , knuckles  808  come into contact with adjacent knuckles  808  to prevent further displacement of spring band  700  towards position  704  or  702 . In this way, compression band  806  can prevent spring band  700  from squeezing the neck of a user of headphones  800  while maintaining the benefits of the low-spring rate spring band  700 .  FIGS.  8 C- 8 D  show how separate and distinct knuckles  808  can be arranged along the lower side of spring band  700  to prevent spring band  700  from returning past position  706 . 
       FIGS.  8 E- 8 F  show how the use of springs to control the motion of headband assembly  802  with respect to earpieces  804  can change the amount of force applied to a user by headphones  800  when compared to the force applied by spring band  700  alone.  FIG.  8 E  shows forces  810  exerted by spring band  700  and forces  812  exerted by springs controlling the motion of earpieces  804  with respect to headband assembly  802 .  FIG.  8 F  shows exemplary curves illustrating how forces  810  and  812  supplied by at least two different springs can vary based on spring displacement. Force  810  does not begin to act until just prior to the desired range of motion because of the compression band preventing spring band  700  from returning all the way to a neutral state. For this reason, the amount of force imparted by force  810  begins at a much higher level, resulting in a smaller variation in force  810 .  FIG.  8 F  also illustrates force  814 , the result of forces  810  and  812  acting in series. By arranging the springs in series, a rate at which the resulting force changes as headphones  800  change shape to accommodate the size of a user&#39;s head is reduced. In this way, the dual spring configuration helps to provide a more consistent user experience for a user base that includes a great diversity of head shapes. 
       FIGS.  9 A- 9 B  show another way in which to limit the range of motion of a pair of headphones  900  using a low spring-rate band  902 .  FIG.  9 A  shows cable  904  in a slack state on account of earpieces  906  being pulled apart. The range of motion of low spring-rate band  902  can be limited by cable  904  achieving a similar function to the function of compression band  806 , engaging as a result of function of tension instead of compression. Cable  904  is configured to extend between earpieces  906  and is coupled to each of earpieces  906  by anchoring features  908 . Cable  904  can be held above low spring-rate band  902  by wire guides  910 . Wire guides  910  can be similar to wire guides  210  depicted in  FIGS.  2 A- 2 G , with the difference that wire guides  910  are configured to elevate cable  904  above low spring-rate band  902 . Bearings of wire guides  910  can prevent cable  904  from catching or becoming undesirably tangled. It should be noted that cable  904  and low spring-rate band  902  can be covered by a cosmetic cover. It should also be noted that in some embodiments, cable  904  could be combined with the embodiments shown in  FIGS.  2 A- 2 G  to produce headphones capable of synchronizing earpiece position and controlling the range of motion of the headphones. 
       FIG.  9 B  shows how when earpieces  906  are brought closer together cable  904  tightens and eventually stops further movement of earpieces  906  closer together. In this way, a minimum distance  912  between earpieces  906  can be maintained that allows headphones  900  to be worn comfortably around the neck of a broad population of users without squeezing the neck of the user too tightly. 
     Left/Right Ear Detection 
       FIG.  10 A  shows a top view of an exemplary head of a user  1000  wearing headphones  1002 . Earpieces  1004  are depicted on opposing sides of user  1000 . A headband joining earpieces  1004  is omitted to show the features of the head of user  1000  in greater detail. As depicted, earpieces  1004  are configured to rotate about a yaw axis so they can be positioned flush against the head of user  1000  and oriented slightly towards the face of user  1000 . In a study performed upon a large group of users it was found that on average, earpieces  1004  when situated over the ears of a user were offset above the x-axis as depicted. Furthermore, for over 99% of users the angle of earpieces  1004  with respect to the x-axis was above the x-axis. This means that only a statistically irrelevant portion of users of headphones  1002  would have head shapes causing earpieces  1004  to be oriented forward of the x-axis.  FIG.  10 B  shows a front view of headphones  1002 . In particular,  FIG.  10 B  shows yaw axes of rotation  1006  associated with earpieces  1004  and how earpieces  1004  are both oriented toward the same side of headband  1008  joining earpieces  1004 . 
       FIGS.  10 C- 10 D  show top views of headphones  1002  and how earpieces  1004  are able to rotate about yaw axes of rotation  1006 .  FIGS.  10 C- 10 D  also show earpieces  1004  being joined together by headband  1008 . Headband  1008  can include yaw position sensors  1010 , which can be configured to determine an angle of each of earpieces  1004  with respect to headband  1008 . The angle can be measured with respect to a neutral position of earpieces with respect to headband  1008 . The neutral position can be a position in which earpieces  1004  are oriented directly toward a central region of headband  1008 . In some embodiments, earpieces  1004  can have springs that return earpieces  1004  to the neutral position when not being acted upon by an external force. The angle of earpieces relative to the neutral position can change in a clockwise direction or counter clockwise direction. For example, in  FIG.  10 C  earpiece  1004 - 1  is biased about axis of rotation  1006 - 1  in a counter clockwise direction and earpiece  1004 - 2  is biased about axis of rotation  1006 - 2  in a clockwise direction. In some embodiments, sensors  1010  can be time of flight sensors configured to measure angular change of earpieces  1004 . The depicted pattern associated and indicated as sensor  1010  can represent an optical pattern allowing accurate measurement of an amount of rotation of each of the earpieces. In other embodiments, sensors  1010  can take the form of magnetic field sensors or Hall Effect sensors as described in conjunction with  FIGS.  5 B and  6 E . In some embodiments, sensors  1010  can be used to determine which ear each earpiece is covering for a user. Because earpieces  1004  are known to be oriented behind the x-axis for almost all users, when sensors  1010  detect both earpieces  1004  oriented to towards one side of the x-axis headphones  1002  can determine which earpieces are on which ear. For example,  FIG.  10 C  shows a configuration in which earpiece  1004 - 1  can be determined to be on the left ear of a user and earpiece  1004 - 2  is on the right ear of the user. In some embodiments, circuitry within headphones  1002  can be configured to adjust the audio channels so the correct channel is being delivered to the correct ear. 
     Similarly,  FIG.  10 D  shows a configuration in which earpiece  1004 - 1  is on the right ear of a user and earpiece  1004 - 2  is on the left ear of a user. In some embodiments, when earpieces are not oriented towards the same side of the x-axis, headphones  1002  can request further input prior to changing audio channels. For example, when earpieces  1004 - 1  and  1004 - 2  are both detected as being biased in a clockwise direction, a processor associated with headphones  1002  can determine headphones  1002  are not in current use. In some embodiments, headphones  1002  can include an override switch for the case where the user wants to flip the audio channels independent of the L/R audio channel routing logic associated with yaw position sensors  1010 . In other embodiments, another sensor or sensors can be activated to confirm the position of headphones  1002  relative to the user. 
       FIGS.  10 E- 10 F  show flow charts describing control methods that can be carried out when roll and/or yaw of the earpieces with respect to the headband is detected.  FIG.  10 E  shows a flow chart that describes a response to detection of rotation of earpieces with respect to a headband of headphones about a yaw axis. The yaw axes can extend through a point located near the interface between each earpiece and the headband. When the headphones are being used by a user, the yaw axes can be substantially parallel to a vector defining the intersection of the sagittal and coronal anatomical planes of the user. At  1052 , rotation of the earpieces about the yaw axes can be detected by a rotation sensor associated with a pivot mechanism. In some embodiments, the pivot mechanism can be similar to pivot mechanism  500  or pivot mechanism  600 , which depict yaw axes  506  and  605 . At  1054 , a determination can be made regarding whether a threshold associated with rotation about the yaw axis has been exceeded. In some embodiments, the yaw threshold can be met anytime the earpieces pass through a position where the ear-facing surfaces of the two earpieces can be facing directly towards one another. At  1056 , in the case where at least one of the earpieces passes through the threshold and both earpieces are determined to be oriented in the same direction, the audio channels being routed to the two earpieces can be swapped. In some embodiments, the user can be notified of the change in audio channels. In some embodiments, an amount of roll detected by the pivot mechanism can be factored into a determination of how to assign the audio channels. 
       FIG.  10 F  shows a flow chart that describes a response to detection of rotation of earpieces with respect to a headband of headphones about roll axes. The roll axes can pass through a point near the interface between each earpiece and the headband. When the headphones are being used by a user, the roll axes can be substantially parallel to a vector defining the intersection of the sagittal and axial anatomical planes of the user. At  1062 , rotation of the earpieces about the yaw axes can be detected by a rotation sensor associated with a pivot mechanism. In some embodiments, the pivot mechanism can be similar to pivot mechanism  500  or pivot mechanism  600 , which depict roll axis  510  and roll direction  601 , respectively. At  1064 , a determination can be made regarding whether a threshold associated with rotation about the roll axis has been exceeded. In some embodiments, the threshold can be met anytime the spring(s) controlling the rotation of the earpieces with respect to the headband are required to exert a force. In some embodiments, a position sensor such as a Hall Effect sensor can be configured to measure an angle of the earpieces with respect to the roll axis. At  1066 , an operational state of the headphones is changed when the roll angle of the earpieces with respect to the headband indicates the headphones have gone from being in use to out of use or vice versa. 
       FIG.  10 G  shows a system level block diagram of a computing device  1070  that can be used to implement the various components described herein, according to some embodiments. In particular, the detailed view illustrates various components that can be included in headphones  1002  illustrated in  FIGS.  10 A- 10 D . As shown in  FIG.  10 G , the computing device  1070  can include a processor  1072  that represents a microprocessor or controller for controlling the overall operation of computing device  1070 . The computing device  1070  can include first and second earpieces  1074  and  1076  joined by a headband assembly, the earpieces including speakers for presenting media content to the user. Processor  1072  can be configured to transmit first and second audio channels to first and second earpieces  1074  and  1076 . In some embodiments, first orientation sensor(s)  1078  can be configured to transmit orientation data of first earpiece  1074  to processor  1072 . Similarly, second orientation sensor(s)  1080  can be configured to transmit orientation data of second earpiece  1076  to processor  1072 . Processor  1072  can be configured to swap the 1st Audio Channel with the 2nd Audio Channel in accordance with information received from first and second orientation sensors  1078  and  1080 . A data bus  1082  can facilitate data transfer between at least battery/power source  1084 , wireless communications circuitry  1086 , wired communications circuitry  1088  computer readable memory  1090  and processor  1072 . In some embodiments, processor  1072  can be configured to instruct battery/power source  1084  in accordance with information received by first and second orientation sensors  1078  and  1080 . Wireless communications circuitry  1086  and wired communications circuitry  1088  can be configured to provide media content to processor  1072 . In some embodiments, processor  1072 , wireless communications circuitry  1086  and wired communications circuitry  1088  can be configured to transmit and receive information from computer-readable memory  1090 . Computer readable memory  1090  can include a single disk or multiple disks (e.g. hard drives) and includes a storage management module that manages one or more partitions within computer readable memory  1090 . 
     Foldable Headphones 
       FIGS.  11 A- 11 B  show headphones  1100  having a deformable form factor.  FIG.  11 A  shows headphones  1100  including deformable headband assembly  1102 , which can be configured to mechanically and electrically couple earpieces  1104 . In some embodiments, earpieces  1104  can be ear cups and in other embodiments, earpieces  1104  can be on-ear earpieces. Deformable headband assembly  1102  can be joined to earpieces  1104  by foldable stem regions  1106  of headband assembly  1102 . Foldable stem regions  1106  are arranged at opposing ends of deformable band region  1108 . Each of foldable stem regions  1106  can include an over-center locking mechanism that allows each of earpieces  1104  to remain in a flattened state after being rotated against deformable band region  1108 . The flattened state refers to the curvature of deformable band region  1108  changing to become flatter than in the arched state. In some embodiments, deformable band region  1108  can become very flat but in other embodiments, the curvature can be more variable (as shown in the following figures). The over-center locking mechanism allows earpieces  1104  to remain in the flattened state until a user rotates the over-center locking mechanism back away from deformable band region  1108 . In this way, a user need not find a button to change the state, but simply perform the intuitive action of rotating the earpiece back into its arched state position. 
       FIG.  11 B  shows one of earpieces  1104  rotated into contact with deformable band region  1108 . As depicted, rotation of just one of earpieces  1104  against deformable band region  1108  causes half of deformable band region  1108  to flatten.  FIG.  11 C  shows the second one of earpieces rotated against deformable band region  1108 . In this way, headphones  1100  can be easily transformed from an arched state (i.e.  FIG.  11 A ) to a flattened state (i.e.  FIG.  11 C ). In the flattened state headphones, the size of headphones  1100  can be reduced to a size equivalent to two earpieces arranged end to end. In some embodiments, deformable band region can press into cushions of earpieces  1104 , thereby substantially preventing headband assembly  1102  from adding to the height of headphones  1100  in the flattened state. 
       FIGS.  11 D- 11 F  show how earpieces  1104  of headphones  1150  can be folded towards an exterior-facing surface of deformable band region  1108 .  FIG.  11 D  shows headphones  11 D in an arched state. In  FIG.  11 E , one of earpieces  1104  is folded towards the exterior-facing surface of deformable band region  1108 . Once earpiece  1104  is in place as depicted, the force exerted in moving earpiece  1104  to this position can place one side of deformable headband assembly  1102  in a flattened state while the other side stays in the arched state. In  FIG.  11 F , the second earpiece  1104  is also shown folded against the exterior-facing surface of deformable band region  1108 . 
       FIGS.  12 A- 12 B  show a headphones embodiment in which the headphones can be transitioned from an arched state to a flattened state by pulling on opposing ends of a spring band.  FIG.  12 A  shows headphones  1200 , which can be, for example, headphones  1100  shown in  FIG.  11   , in a flattened state. In the flattened state, earpieces  1104  are aligned in the same plane so that each of ear pads  1202  face in substantially the same direction. In some embodiments, headband assembly  1102  contacts opposing sides of each of ear pads  1202  in the flattened state. Deformable band region  1108  of headband assembly  1102  includes spring band  1204  and segments  1206 . Spring band  1204  can be prevented from returning headphones  1200  to the arched state by locking components of foldable stem regions  1106  exerting pulling forces on each end of spring band  1204 . Segments  1206  can be connected to adjacent segments  1206  by pins  1208 . Pins  1208  allow segments to rotate relative to one another so that the shape of segments  1206  can be kept together but also be able to change shape to accommodate an arched state. Each of segments  1206  can also be hollow to accommodate spring band  1204  passing through each of segments  1206 . A central or keystone segment  1206  can include fastener  1210 , which engages the center of spring band  1204 . Fastener  1210  isolates the two side of spring band  1204  allowing for earpieces  1104  to be sequentially rotated into the flattened state as depicted in  FIG.  11 B . 
       FIG.  12 A  also shows each of foldable stem regions  1106  which include three rigid linkages joined together by pins that pivotally couple upper linkage  1212 , middle linkage  1214  and lower linkage  1216  together. Motion of the linkages with respect to each other can also be at least partially governed by spring pin  1218 , which can have a first end coupled to a pin  1220  joining middle linkage  1214  to lower linkage  1216  and a second end engaged within a channel  1222  defined by upper linkage  1212 . The second end of spring pin  1218  can also be coupled to spring band  1204  so that as the second end of spring pin  1218  slides within channel  1222  the force exerted upon spring band  1204  changes. Headphones  1200  can snap into the flattened state once the first end of spring pin  1218  reaches an over-center locking position. The over-center locking position keeps earpiece  1104  in the flattened position until the first end of spring pin  1218  is moved far enough to be released from the over-center locking position. At that point, earpiece  1104  returns to its arched state position. 
       FIG.  12 B  shows headphones  1200  arranged in an arched state. In this state, spring band  1204  is in a relaxed state where a minimal amount of force is being stored within spring band  1204 . In this way, the neutral state of spring band  1204  can be used to define the shape of headband assembly  1102  in the arched state when not being actively worn by a user.  FIG.  12 B  also shows the resting state of the second end of spring pins  1218  within channels  1222  and how the corresponding reduction in force on the end of spring band  1204  allows spring band  1204  to help headphones  1200  assume the arched state. It should be noted that while substantially all of spring band  1204  is depicted in  FIGS.  12 A- 12 B  that spring band  1204  would generally be hidden by segments  1206  and upper linkages  1212 . 
       FIGS.  12 C- 12 D  show side views of foldable stem region  1106  in arched and flattened states, respectively.  FIG.  12 C  shows how forces  1224  exerted by spring pin  1218  operate to keep linkages  1212 ,  1214  and  1216  in the arched state. In particular, spring pin  1218  keeps the linkages in the arched state by preventing upper linkage  1212  from rotating about pin  1226  and away from lower linkage  1216 .  FIG.  12 D  shows how forces  1228  exerted by spring pin  1218  operate to keep linkages  1212 ,  1214  and  1216  in the flattened state. This bi-stable behavior is made possible by spring pin  1218  being shifted to an opposite side of the axis of rotation defined by pin  1226  in the flattened state. In this way, linkages  1212 - 1216  are operable as an over-center locking mechanism. In the flattened state, spring pin  1218  resists transitioning the headphones from moving from the flattened state to the arched state; however, a user exerting a sufficiently large rotational force on earpiece  1104  can overcome the forces exerted by spring pin  1218  to transition the headphones between the flat and arched states. 
       FIG.  12 E  shows a side view of one end of headphones  1200  in the flattened state. In this view, ear pads  1202  are shown with a contour configured to conform to the curvature of the head of a user. The contour of ear pads  1202  can also help to prevent headband assembly  1102  and particularly segments  1206  making up headband assembly  1102  from protruding substantially farther vertically than ear pads  1202 . In some embodiments, the depression of the central portion of ear pads  1202  can be caused at least in part by pressure exerted on them by segments  1206 . 
       FIGS.  13 A- 13 B  show partial cross-sectional views of headphones  1300 , which use an off-axis cable to transition between an arched state and a flattened state.  FIG.  13 A  shows a partial cross-sectional view of headphones  1300  in an arched state. Headphones  1300  differ from headphones  1200  in that when earpieces  1104  are rotated towards headband assembly  1102  a cable  1302  is tightened in order to flatten deformable band region  1108  of headband assembly  1102 . Cable  1302  can be formed from a highly elastic cable material such as Nitinol™, a Nickel Titanium alloy. Close-up view  1303  shows how deformable band region  1108  can include many segments  1304  that are fastened to spring band  1204  by fasteners  1306 . In some embodiments, fasteners  1306  can also be secured to spring band  1204  by an O-ring to prevent any rattling of fasteners  1306  while using headphones  1300 . A central one of segments  1304  can include a sleeve  1308  that prevents cable  1302  from sliding with respect to the central one of segments  1304 . The other segments  1304  can include metal pulleys  1310  that keep cable  1302  from experiencing substantial amounts of friction as cable  1302  is pulled on to flatten headphones  1300 .  FIG.  13 A  also shows how each end of cable  1302  is secured to a rotating fastener  1312 . As foldable stem region  1106  rotates, rotating fasteners  1312  keeps the ends of cable  1302  from twisting. 
       FIG.  13 B  shows a partial cross-sectional view of headphones  1300  in a flattened state. Rotating fasteners  1312  are shown in a different rotational position to accommodate the change in orientation of cable  1302 . The new location of rotating fasteners  1312  also generates an over-center locking position that prevents headphones  1300  from being inadvertently returned to the arched state as described above with respect to headphones  1200 .  FIG.  13 B  also shows how the curved geometry of each of segments  1304  allows segments  1304  to rotate with respect to one another in order to transition between the arched and flattened states. In some embodiments, cable  1302  can also be operative to limit a range of motion of spring band  1204  similar in some ways to the embodiment shown in  FIGS.  9 A- 9 B . 
       FIG.  14 A  shows headphones  1400  that are similar to headphones  1300 . In particular, headphones  1400  also use cable  1302  to flatten deformable band region  1108 . Furthermore, a central portion of cable  1302  is retained by the central segment  1304 . In contrast, lower linkage  1216  of foldable stem region  1106  is shifted upward with respect to lower linkage  1216  depicted in  FIG.  12 A . When earpiece  1104  is rotated about axis  1402  towards deformable band region  1108 , spring pin  1404  is configured to elongate as shown in  FIG.  14 B  during a first portion of the rotation. In some embodiments, elongation of spring pin  1404  can allow earpiece to rotate about 30 degrees from an initial position. Once spring pins  1404  reach their maximum length further rotation of earpieces  1104  about axes  1402  results in cable  1302  being pulled, which causes deformable band region  1108  to change from an arched geometry to a flat geometry as shown in  FIG.  14 C . The delayed pulling motion changes the angle from which cable  1302  is initially pulled. The changed initial angle can make it less likely for cable  1302  to bind when transitioning headphones  1400  from the arched state to the flattened state. 
       FIGS.  15 A- 15 F  show various views of headband assembly  1500  from different angles and in different states. Headband assembly  1500  has a bi-stable configuration that accommodates transitioning between flattened and arched states.  FIGS.  15 A- 15 C  depict headband assembly  1500  in an arched state. Bi-stable wires  1502  and  1504  are depicted within a flexible headband housing  1506 . Headband housing can be configured to change shape to accommodate at least the flattened and arched states. Bi-stable wires  1502  and  1504  extend from one end of headband housing  1506  to another and are configured to apply a clamping force through earpieces attached to opposing ends of headband assembly  1500  to a user&#39;s head to keep an associated pair of headphone securely in place during use.  FIG.  15 C  in particular shows how headband housing  1506  can be formed from multiple hollow links  1508 , which can be hinged together and cooperatively form a cavity within which bi-stable wires  1502  are able to transition between configurations corresponding to the arched and flattened states. Because links  1508  are only hinged on one side, the links are only able to move to the arched state in one direction. This helps avoid the unfortunate situation where headband assembly  1500  is bent the wrong direction, thereby position the earpieces in the wrong direction. 
       FIGS.  15 D- 15 F  show headband assembly in a flattened state. Because the ends of bi-stable wires  1502  and  1504  have passed an over-center point where the ends of wires  1502  and  1504  are higher than a central portion of bi-stable wires  1502  and  1504 , the bi-stable wires  1502  now help keep headband assembly  1500  in the flattened state. In some embodiments, bi-stable wires  1502  can also be used to carry signals and/or power through headband assembly  1500  from one earpiece to another. 
       FIGS.  16 A- 16 B  show headband assembly  1600  in folded and arched states.  FIG.  16 A  shows headband assembly  1600  in the arched state. Headband assembly, similarly to the embodiment shown in  FIGS.  15 C and  15 F  includes multiple hollow links  1602  that cooperatively form a flexible headband housing that define an interior volume. Passive linkage hinge  1604  can be positioned within a central portion of the interior volume and link bi-stable elements  1606  together.  FIG.  16 A  shows bi-stable elements  1606  and  16008  in arched configurations that resist forces acting to squeeze opposing sides of headband assembly  1600 . Once opposing sides of headband assembly  1600  are pushed together, in the directions indicated by arrows  1610  and  1612 , with enough force to overcome the resistance forces generated by bi-stable elements  1606  and  1608 , headband assembly  1600  can transition from the arched state depicted in  FIG.  16 A  to the flattened state depicted in  FIG.  16 B . Passive linkage hinge  1604  accommodates headphone assembly  1600  being folding around a central region  1614  of headband assembly  1600 .  FIG.  16 B  shows how passive linkage hinge  1604  bends to accommodate the flattened state of headband assembly  1600 . Bi-stable elements  1606  and  1608  are shown configured in folded configurations in order to bias the opposing sides of headband assembly  1600  toward one another, thereby opposing an inadvertent change in state. The folded configuration, depicted in  FIG.  16 B , has the benefit of taking up a substantially smaller amount of space by allowing the open area defined by headband assembly  1600  for accommodating the head of a user to be collapsed so that headband assembly  1600  can take up less space when not in active use. 
       FIGS.  17 A- 17 B  show various views of foldable headphones  1700 . In particular,  FIG.  17 A  shows a top view of headphones  1700  in a flattened state. Headband  1702 , which extends between earpieces  1704  and  1706 , includes wires  1708  and springs  1710 . In the depicted flattened state, wires  1708  and spring  1710  are straight and in a relaxed state or neutral state.  FIG.  17 B  shows a side view of headphones  1700  in an arched state. Headphones  1700  can be transitioned from the flattened state depicted in  FIG.  17 A  to the arched state depicted in  FIG.  17 B  by rotating earpieces  1704  and  1706  away from headband  1702 . Earpieces  1704  and  1706  each include an over-center mechanism  1712  that applies tension to the ends of wires  1708  to keep wires  1708  in tension in order to maintain an arched state of headband  1702 . Wires  1708  help maintain the shape of headband  1702  by exerting forces at multiple locations along springs  1710  through wire guides  1714 , which are distributed at regular intervals along headband  1702 . 
     While each of the aforementioned improvements has been discussed in isolation it should be appreciated that any of the aforementioned improvements can be combined. For example, the synchronized telescoping earpieces can be combined with the low spring-rate band embodiments. Similarly, off-center pivoting earpiece designs can be combined with the deformable form-factor headphones designs. In some embodiments, each type of improvement can be combined together to produce headphones with all the described advantages. 
     Headphones are disclosed and include the following: a first earpiece; a second earpiece; and a headband coupling the first and second earpieces together and being configured to synchronize a movement of the first earpiece with a movement of the second earpiece such that a distance between the first earpiece and a center of the headband remains substantially equal to a distance between the second earpiece and the center of the headband. 
     In some embodiments, the headband comprises a loop of cable routed therethrough. 
     In some embodiments, a first stem of the first earpiece is coupled to the loop of cable and a second stem of the second earpiece is coupled to the loop of cable. 
     In some embodiments, the loop of cable is configured to route an electrical signal from the first earpiece to the second earpiece. 
     In some embodiments the headband includes two parallel leaf springs defining a shape of the headband. 
     In some embodiments, the headband includes a gear disposed in a central portion of the headband and engaged with gear teeth of stems associated with the first and second earpieces. 
     In some embodiments the headband includes a loop of wire disposed within the headband, a first stem wire coupling the first earpiece to a first side of the loop of wire, and a second stem wire coupling the second earpiece to a second side of the loop of wire. 
     In some embodiments, the headphones also include a data synchronization cable extending from the first earpiece to the second earpiece through a channel defined by the headband, the data synchronization cable carrying signals between electrical components of the first and second earpieces. 
     In some embodiments, a first portion of the data synchronization cable is coiled around the first stem wire and a second portion of the data synchronization cable is coiled around the second stem wire. 
     Headphones are disclosed and include the following: a headband having a first end and a second end opposite the first end; a first earpiece coupled to the headband a first distance from the first end; a second earpiece coupled to the headband a second distance from the second end; and a cable routed through the headband and mechanically coupling the first earpiece to the second earpiece, the cable being configured to maintain the first distance substantially the same as the second distance by changing the first distance in response to a change in the second distance. 
     In some embodiments, the cable is arranged in a loop and the first earpiece is coupled to a first side of the loop and the second earpiece is coupled to a second side of the loop. 
     In some embodiments, the headphones also include stem housings coupled to opposing ends of the headband, each of the stem housings enclosing a pulley about which the cable is wrapped. 
     In some embodiments, the headphones also include wire guides distributed across the headband and defining a path of the cable through the headband. 
     Headphones are disclosed and include the following: a first earpiece; a second earpiece; a headband assembly coupling the first and second earpieces together and comprising an earpiece synchronization system, the earpiece synchronization system configured to change a first distance between the first earpiece and the headband assembly concurrently with a change in a second distance between the second earpiece and the headband assembly. 
     In some embodiments, the headphones also include first and second members coupled to opposing ends of the headband assembly, each of the first and second members being configured to telescope relative to a channel defined by a respective end of the headband assembly. 
     In some embodiments, the headphones as recited in claim  34 , wherein the earpiece synchronization system includes a first stem wire coupled to the first earpiece and a second stem wire coupled to the second earpiece. 
     In some embodiments, the first stem wire is coupled to the second stem wire in a channel disposed within a central region of the headband assembly. 
     In some embodiments, the headphones also include a reinforcement member disposed within the headband assembly and defining the channel within which the first and second stem wires are coupled together. 
     In some embodiments, the earpiece synchronization system includes a first stem wire having a first end coupled to the first earpiece and a second end coupled to a second end of the second stem wire and wherein a first end of the second stem wire is coupled to the second earpiece. 
     In some embodiments, the second end of the first stem wire is oriented in the same direction as the second end of the second stem wire. 
     Headphones are disclosed and include the following: a first earpiece; a second earpiece; a headband coupling the first earpiece to the second earpiece; earpiece position sensors configured to measure an angular orientation of the first and second earpieces with respect to the headband; and a processor configured to change an operational state of the headphones in accordance with the angular orientation of the first and second earpieces. 
     In some embodiments, changing the operational state of the headphones comprises switching audio channels routed to the first and second earpieces. 
     In some embodiments, the earpiece position sensors are configured to measure a position of the first and second earpieces relative to respective yaw axes of the earpieces. 
     In some embodiments, the earpiece position sensors comprise a time of flight sensor. 
     In some embodiments, the headphones also include a pivot mechanism joining the first earpiece to the headband, wherein the earpiece position sensors comprise a Hall Effect sensor positioned within the pivot mechanism and configured to measure the angular orientation of the first earpiece. 
     In some embodiments, the operational state is a playback state. 
     In some embodiments, the headphones also include a secondary sensor disposed within the first earpiece and configured to confirm sensor readings provided by the earpiece position sensors. 
     In some embodiments, the secondary sensor is a strain gauge. 
     Headphones are disclosed and also include: a headband; a first earpiece pivotally coupled to a first side of the headband and having a first axis of rotation; a second earpiece pivotally coupled to a second side of the headband and having a second axis of rotation; earpiece position sensors configured to measure an orientation of the first earpiece relative to the first axis of rotation and an orientation of the second earpiece relative to the second axis of rotation; and a processor configured to: place the headphones in a first operational state when the first earpiece is biased in a first direction from a neutral state of the first earpiece and the second earpiece is biased in a second direction opposite the first direction from a neutral state of the second earpiece, and place the headphones in a second operational state when the first earpiece is biased in the second direction from the neutral state of the first earpiece and the second earpiece is biased in the first direction from a neutral state of the second earpiece. 
     In some embodiments, in the first operational state a left audio channel is routed to the first earpiece and in the second operational state the left audio channel is routed to the second earpiece. 
     In some embodiments, the earpiece position sensors are time of flight sensors. 
     In some embodiments, the headphones also include a pivot mechanism configured to accommodate rotation of the first earpiece about the first axis of rotation and about a third axis of rotation substantially orthogonal to the first axis of rotation. 
     In some embodiments, one of the earpiece position sensors is positioned on a bearing accommodating rotation of the first earpiece about the first axis of rotation. 
     In some embodiments, the earpiece position sensors comprise a magnetic field sensor and a permanent magnet. 
     In some embodiments, the magnetic field sensor is a Hall Effect sensor. 
     In some embodiments, the pivot mechanism comprises a leaf spring that accommodates rotation of the earpiece about the third axis of rotation. 
     In some embodiments, the earpiece position sensors comprise a strain gauge positioned on the leaf spring for measuring rotation of the first earpiece about the third axis of rotation. 
     Headphones are disclosed and include the following: a headband; a first earpiece comprising a first earpiece housing; a first pivot mechanism disposed within the first earpiece housing, the first pivot mechanism comprising: a first stem base portion that protrudes though an opening defined by the first earpiece housing, the first stem base portion coupled to a first portion of the headband, and a first orientation sensor configured to measure an angular orientation of the first earpiece relative to the headband; a second earpiece comprising a second earpiece housing; a second pivot mechanism disposed within the second earpiece housing, the second pivot mechanism comprising: a second stem base portion that protrudes though an opening defined by the second earpiece housing, the second stem base portion coupled to a second portion of the headband, and a second orientation sensor configured to measure an angular orientation of the second earpiece relative to the headband; and a processor that sends a first audio channel to the first earpiece when sensor readings received from the first and second orientation sensors are consistent with the first earpiece covering a first ear of a user and is configured to send a second audio channel to the first earpiece when the sensor readings are consistent with the first earpiece covering a second ear of the user. 
     In some embodiments, the first pivot mechanism accommodates rotation of the first earpiece about two substantially orthogonal axes of rotation. 
     In some embodiments, the first and second orientation sensors are magnetic field sensors. 
     Headphones are disclosed and include the following: a first earpiece having a first earpad; a second earpiece having a second earpad; and a headband joining the first earpiece to the second earpiece, the headphones being configured to move between an arched state in which a flexible portion of the headband is curved along its length and a flattened state, in which the flexible portion of the headband is flattened along its length, the first and second earpieces being configured to fold towards the headband such that the first and second earpads contact the flexible headband in the flattened state. 
     In some embodiments, the headband includes foldable stem regions at each end of the headband, the foldable stem regions coupling the headband to the first and second earpieces and allowing the earpieces to fold toward the headband. 
     In some embodiments, the foldable stem region comprises an over-center locking mechanism that prevents the headphones from inadvertently transitioning from the flattened state to the arched state. 
     In some embodiments, the headband is formed from multiple hollow linkages. 
     In some embodiments, the headphones also include a data synchronization cable electrically coupling the first and second earpieces and extending through the hollow linkages. 
     Headphones are disclosed and include the following: a first earpiece; a second earpiece; and a headband assembly coupled to both the first and second earpieces, the headband assembly comprising: linkages pivotally coupled together, and an over-center locking mechanism coupling the first earpiece to a first end of the headband assembly and having a first stable position in which the linkages are flattened and a second stable position in which the linkages form an arch. 
     In some embodiments, the headband assembly further comprises one or more wires extending through the linkages. 
     In some embodiments, one or more of the linkages comprises a pulley for carrying the one or more wires. 
     In some embodiments, one of the linkages defines a channel of the over-center locking mechanism. 
     In some embodiments, the headphones transition from the second stable position to the first stable position when the first and second earpieces are folded toward the headband assembly. 
     In some embodiments, the first earpiece comprises an earpad having an exterior-facing surface defining a channel sized to receive a portion of the headband assembly in the first stable position. 
     Headphones are disclosed and include the following: a first earpiece; a second earpiece; and a flexible headband assembly coupled to both the first and second earpieces, the flexible headband assembly comprising: hollow linkages pivotally coupled together and defining an interior volume within the flexible headband assembly, and bi-stable elements disposed within the interior volume and configured to oppose transition of the flexible headband assembly between a first state in which a central portion of the hollow linkages are straightened and a second state in which the hollow linkages form an arch. 
     In some embodiments, the bi-stable elements have a first geometry when the flexible headband assembly is in the first state and a second geometry different from the first geometry when the flexible headband assembly is in the second state. 
     In some embodiments, the bi-stable elements comprise wires extending through the hollow linkages. 
     In some embodiments, the headphones also include an over-center mechanism through which the wires extend. 
     In some embodiments, the wires are in tension when the flexible headband assembly is in the first state and in a neutral state when the flexible headband assembly is in the second state. 
     In some embodiments, each of the hollow linkages has a rectangular geometry. 
     In some embodiments, the hollow linkages are coupled together by pins. 
     In some embodiments, one or more of the hollow linkages includes a pulley configured to guide one or more of the bi-stable elements through the flexible headband assembly. 
     In some embodiments, the flexible headband assembly further comprises a spring band extending through the flexible headband assembly.