Abstract:
The subject technology can be embodied in a retaining structure which is configured to engage with external structures to hold an earpiece in position. The retaining structure includes a first portion forming a loop and having an upper end and a lower end. The upper end of the first portion is coupled to a top surface of a body of the earpiece and the lower end of the first portion is coupled to a bottom surface of the earpiece. The retaining structure also includes a second portion having an upper end and a lower end, wherein the lower end of the second portion is coupled to the loop formed by the first portion, and the upper end of the second portion extends from the earpiece. The top and bottom surfaces are located on substantially opposite sides of the body in a direction along a plane of the retaining structure.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application is related to co-filed application titled “Earpiece With Movable Joint,” filed on Sep. 5, 2014 and bearing attorney docket number 02103-0945001, the entire content of which is incorporated herein by reference. 
       TECHNICAL FIELD 
       [0002]    This disclosure generally relates to earpieces for use with electronic devices. 
       BACKGROUND 
       [0003]    Earpieces can be placed within human ears, e.g., as part of earphones, Bluetooth devices, etc., to deliver sound to the ears. 
       SUMMARY 
       [0004]    In one aspect, this document features a retaining structure which is configured to engage with external structures to hold an earpiece in position. The retaining structure includes a first portion forming a loop and having an upper end and a lower end. The upper end of the first portion is coupled to a top surface of a body of the earpiece and the lower end of the first portion is coupled to a bottom surface of the earpiece. The retaining structure also includes a second portion having an upper end and a lower end, wherein the lower end of the second portion is coupled to the loop formed by the first portion, and the upper end of the second portion extends from the earpiece. The top and bottom surfaces are located on substantially opposite sides of the body in a direction along a plane in which the retaining structure is disposed. 
         [0005]    In another aspect, this document features an eartip for an earpiece. The eartip includes a body including an acoustic passage, and a retaining structure configured to engage with external structural features of a human ear to hold the eartip in position. The body is configured to be coupled to an external acoustic driver, and the retaining structure includes a first portion forming a loop and having an upper end and a lower end. The upper end of the first portion is coupled to a top surface of the body and the lower end of the first portion is coupled to a bottom surface of the body. The retaining structure also includes a second portion having an upper end and a lower end, wherein the lower end of the second portion is coupled to the loop formed by the first portion, and the upper end of the second portion extends from the eartip. The body includes a sealing structure to be inserted into the ear canal of the ear. The first portion of the retaining structure is compliant in a direction parallel to a direction of insertion of the sealing structure into the ear canal, and the sealing structure has a lower compliance than the retaining structure in the direction parallel to the direction of insertion. 
         [0006]    In another aspect, the document describes a retaining structure configured to engage with external structures to hold an earpiece in position. The retaining structure includes a first portion that forms a loop in a plane and has an upper end and a lower end. The upper end of the first portion is coupled to a top surface of a body of the earpiece and the lower end of the first portion is coupled to a bottom surface of the earpiece. The retaining structure also includes a second portion that has an upper end and a lower end, wherein the lower end of the second portion is coupled to the loop formed by the first portion, and the upper end of the second portion extends from the earpiece in the plane of the loop. The top and bottom surfaces are located on substantially opposite sides of the body in a direction along the plane of the loop. A compliance of the first portion in directions out of the plane of the loop is configured such that the retaining structure is allowed to bend in a manner that allows the retaining structure to effectively pivot around the body. 
         [0007]    Implementations of the above aspects can include one or more of the following features. 
         [0008]    The upper end of the second portion can be coupled to the loop of the first portion via a bridging portion that connects the first and second portions. The first portion can include a lower arm that extends below the body in the direction along the plane in which the retaining structure is disposed. The lower end of the first portion can be configured to provide out-of-plane compliance with respect to the plane in which the retaining structure is disposed when engaged with portions of the external structures. An axis of an acoustic passage within the body can be substantially out of the plane in which the retaining structure is disposed. A shape of the first portion can be configured to provide balanced compliance together with a sealing structure of the body. The external structural features can be features of a human ear. The retaining structure can be configured to hold the body in position proximate to an ear canal of the human ear. 
         [0009]    The sealing structure can be compliant in a direction orthogonal to the direction of insertion. The second portion can be coupled to the loop via a bridging portion. A portion of the loop can extend below the bottom surface of the body along a plane in which the retaining structure is disposed. An axis of the acoustic passage can be substantially out of the plane in which the retaining structure is disposed. The retaining structure can be configured to hold the sealing structure in position against an opening of the ear canal of the human ear. 
         [0010]    The lower end of the first portion can extend below the body along the plane of the loop. The external structural features can be features of a human ear, and the retaining structure can be configured to hold the body in position proximate to an ear canal of the human ear and to provide compliance with the features of the human ear. The upper end of the second portion can be coupled to the loop of the first portion via a bridging portion that connects the first and second portions. A portion of the loop can extend below the bottom surface of the earpiece along the plane of the loop. The first portion can be configured to hold the body in position proximate to an ear canal of a human ear. 
         [0011]    In another aspect, this document describes an earpiece that includes a body, a retaining structure, and a movable joint structure. The body includes an acoustic passage for conducting sound waves. The retaining structure is configured to engage with external structural features to hold the body in position, and the movable joint structure is configured to couple the body to the retaining structure. The movable joint structure is also configured to allow angular motion of the body with respect to the retaining structure. 
         [0012]    In another aspect, this document describes an earpiece that includes a body and a retaining structure. The body includes an acoustic passage for conducting sound waves, wherein the acoustic passage is disposed within the body. The body also includes a movable joint structure disposed on an outer surface of the body. The retaining structure is configured to engage with external structural features to hold the body in position, wherein the movable joint structure is configured to couple the body to the retaining structure, and allow angular motion of the body with respect to the retaining structure. 
         [0013]    In another aspect, this document describes an earpiece that includes a body and a retaining structure. The body includes an acoustic passage for conducting sound waves, and the retaining structure is configured to engage with external structural features to hold the body in position. The retaining structure includes a movable joint structure that is configured to couple the retaining structure to the body, and allow angular motion of the body with respect to the retaining structure. 
         [0014]    Implementations of the above can include one or more of the following features. 
         [0015]    The movable joint structure can include a hinge. The movable joint structure can be configured to allow the angular motion along a plane perpendicular to an axis of the angular motion. The axis passes though the movable joint structure. The movable joint structure can be configured to allow the angular motion along a first plane substantially perpendicular to a second plane in which the retaining structure is disposed. The body can include a tip substantially conical in shape, the tip being configured to engage with the ear canal in a sealing configuration. A range of the angular motion can be ±90°. The body can be configured to house an acoustic driver module having a diameter between 4 mm and 5 mm. The body and the retaining structure can be removably coupled to the movable joint structure. A sealing structure can be disposed over the body, the sealing structure being configured to engage with the ear canal in a sealing configuration. The movable joint structure can be configured to have a stiffness that impedes the angular motion. The external structural features can include features of a human ear. The retaining structure can be configured to hold the body in position proximate to an ear canal of the human ear. A volume of the body can be less than 0.5 cubic centimeters. 
         [0016]    Various implementations described herein may provide one or more of the following advantages. Discomfort and/or pain (for example at the anti-tragus or cymba concha of the ear) experienced by a wearer can be reduced, thereby allowing for comfortable use for long periods. Earpieces can be made more compliant for users with less common ear-features (e.g., smaller concha) without reducing the appeal of the earpieces to the majority of users. The bodies of the earpieces can be made smaller. By providing a design in which independently selected constituent parts can be joined together to form an earpiece, the number of combinations available from a given number of constituent parts can be increased. In some cases, the earpieces can be made side-independent, e.g., the same earpiece can be used for the left or right ear. 
         [0017]    Two or more of the features described in this disclosure, including those described in this summary section, may be combined to form implementations not specifically described herein. 
         [0018]    The details of one or more implementations are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description and drawings, and from the claims. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0019]      FIG. 1  is an exterior view of a human ear. 
           [0020]      FIGS. 2A-2D  are different views of a first example earpiece. 
           [0021]      FIG. 2E  shows an example of an earpiece as worn by a user. 
           [0022]      FIGS. 3A-3F  are different views of a second example earpiece. 
           [0023]      FIGS. 4A and 4B  show examples of earpieces as worn by users. 
       
    
    
     DETAILED DESCRIPTION 
       [0024]    This document describes earpieces that are configured to reduce discomfort for users. An earpiece can include a tip or nozzle that fits into the concha or ear canal, and a retaining structure that is configured to hold the tip in place using the concha and the anti-helix of the user as support. In some cases, interaction between the tip and the retaining structure may push the tip inward towards the ear canal such that the tip and earbud body pushes against one or more of the tragus, anti-tragus, and inner portion of ear canal. This can cause discomfort or even pain in some users. The present disclosure describes earpieces in which the tip and the retaining structure are coupled in a way that may reduce discomfort to the wearer. In the example implementations described herein, the left and right earpieces may mirror each other, but have the same structure and function. 
         [0025]      FIG. 1  shows an exterior view of a human right ear  100 , with features of the ear identified. For example,  FIG. 1  shows the helix  110 , anti-helix  120 , base-of-the-helix  130 , concha  140 , cymba-concha  150 , tragus  160 , and anti-tragus  170 . However, different ears have different sizes and geometries. In this regard, the precise structure of the human ear varies from individual to individual. For example, some ears have additional features that are not shown in  FIG. 1 , and some ears may lack some of the features that are shown in  FIG. 1 . Likewise, some features of different ears may be more or less prominent than those shown in  FIG. 1 . 
         [0026]      FIGS. 2A and 2B  show two different views of an example earpiece  200  that is configured to fit in the human ear  100 . The earpiece  200  can be connected to an audio generating device, for example, using a connecting cable  202  (as shown in  FIG. 2E ). In some implementations, the earpiece  200  can include a stem for positioning the connecting cable  202 . Some earpieces may lack the stem but may include electronics modules (not shown) for wireless communicating with corresponding audio generation devices. For example, an earpiece may be connected to the audio generation device wirelessly via a BLUETOOTH® transceiver disposed within the earpiece  200 . Other earpieces may lack any connections and function as passive earplugs. In this context, a passive earplug includes an earplug that does not include acoustic features, e.g., they do not provide sound to the ear. 
         [0027]    The earpiece  200  includes an acoustic driver module  215  disposed within a body  205 . The body can include an acoustic passage for conducting sound waves to an ear canal of a user. In some implementations, the acoustic passage for conducting sound to the ear canal of the user can be disposed within a tip of the body  205 . In some implementations, the tip can be covered by a sealing structure  230 , which is configured to form a sealing fit with the exterior opening of the ear canal. Such a sealing fit reduces external noise entering the ear canal, thereby providing a passive noise attenuation arrangement. 
         [0028]    The body  205  is coupled to a retaining structure  210  that engages with external structural features of the user&#39;s ear to provide mechanical stability for holding the earpiece  200  in place. For example, the retaining structure  210  can be configured to engage with a concha of the wearer, to hold the earpiece  200  in place. The retaining structure  210  can have various shapes and sizes. In the example shown in  FIGS. 2A and 2B , the retaining structure  210  includes an outer portion  212  and an inner portion  214 . In such cases, the outer portion  212  is curved to generally follow the curve of the anti-helix and/or the cymba concha at the rear of the concha. The outer portion  212  and the inner portion  214  can lie on one plane and can be connected to one another at least at one end. In some examples, the inner portion may be omitted and a single leg used to retain the earpiece. 
         [0029]    In some implementations, the retaining structure  210  is coupled to the body  205  via a movable joint  220  such as a hinge. The movable joint  220  can be a separate structure to which the body  205  and the retaining structure  210  are coupled, in some cases in a removable way. In such cases, the body  205  and the retaining structure  210  are configured to include respective receptacles that can attach to the movable joint  220 . In some implementations, the movable joint  220  can be an integral part of the body  205  or the retaining structure  210 . In implementations where the movable joint  220  is an integral part of the body  205  (e.g., the movable joint  220  is disposed on the outside of the body  205 ), the movable joint  220  can be configured to couple with the retaining structure  210 , in some cases, in a removable way. In such cases, the retaining structure  210  is configured to include receptacles that can attach to the movable joint  220 . In implementations where the movable joint  220  is an integral part of the retaining structure  210 , the movable joint  220  can be configured to couple with the body  205 , in some cases, in a removable way. In such cases, the body  205  is configured to include receptacles that can attach to the movable joint  220 . 
         [0030]    The movable joint  220  allows the body  205  and the retaining structure  210  to rotate around an axis depicted by the line  222 . The movable joint  220  allows for an angular motion of the body  205  with respect to the retaining structure  210  in a plane substantially perpendicular to the plane in which the outer portion  212  and the inner portion  214  of the retaining structure  210  is disposed. The body  205  can therefore be rotated (with respect to the axis  222 ) towards the exterior opening of the ear canal when the retaining structure  210  engages with the concha and/or the anti-helix.  FIG. 2E  depicts an example of the earpiece  200  worn by a user. 
         [0031]    In some implementations, the movable joint  220  affects the interaction between the body  205  and the retaining structure  210  to impede the retaining structure  210  from pushing the body  205  into the ear canal in a way that is uncomfortable for the wearer. For example, because the retaining structure  210  is not rigidly coupled to the body  205 , a force applied by the retaining structure along a direction into the ear canal can be absorbed, at least in part, by the movable joint  220 , and may result in a rotational motion of the movable joint  220 . As a result, the stiffness of the earpiece along the radial direction (i.e., pushing out towards the anti-helix) can be substantially decoupled from the stiffness of the earpiece along the axial direction (i.e., inwards into the ear canal). This in turn allows for the stiffness or size of the retaining structure  210  to be adjusted separately from the size of the body  205  and/or the stiffness of the movable joint  220 , thereby facilitating a more comfortable custom fit for a wide range of wearers. For example, the retaining structure can be selected in a way such that it fits the concha and/or the anti-helix of the wearer to provide the desired stability. This can be done, for example, by allowing the wearer to select a retaining structure  210  from multiple available choices of varying sizes and stiffness. The body  205  and/or the sealing structure  230  can be selected independently such that the fit is comfortable for the wearer. The rotational stiffness of the movable joint  220  can be configured such that it provides enough axial push to hold the body  205  (and the sealing structure  230 ) in contact with the exterior opening of the ear canal without causing any discomfort to the wearer. By allowing for selecting the body  205  and the retaining structure  210  independently, a wider range of customizability can be achieved. For example, if the retaining structure  210  is available in three different variants (e.g., based on size and/or stiffness), and the body  205  is available in four different variants, a total of twelve combinations is possible. This allows for the product to be suitable for a wide range of wearers with varying ear geometry. 
         [0032]    The movable joint  220  can have a range of angular swing sufficient to adapt to varying angles between the ear canal and helix across different users. In some implementations, the movable joint  220  can be configured such that the body  205  can rotate ±90° with respect to the retaining structure  210 . This allows for the same earpiece to be used in either ear, thus obviating the need for separate mirror image designs. This requires fewer parts to be designed and manufactured and can be advantageous, for example, from a manufacturing cost standpoint. In particular, when multiple variants of the retaining structure  210  and body  205  are manufactured, and the various parts can be removably coupled to the movable joint structure  220 , the side-independence of the earpiece  200  can result in significant savings and streamlining in the manufacturing and packaging processes. 
         [0033]    In some implementations, a small acoustic driver module  215  can be used in the earpiece  200 . The use of a small driver allows for the hinge axis  222  to be placed between the anti-helix and tragus. For example, a driver with a 4-5 mm diameter can be used in the earpiece  200 . A large driver typically occupies the region between the anti-helix and tragus, and the axis of any hinge used with such a driver would be offset outward. A small driver can be housed within the body  205  and can therefore be aligned with the ear canal entrance. For example, the size of the driver can be such that the driver can be housed within a body of volume less than 0.5 cubic centimeter. In some implementations, the volume of the body  205  can be between 0.2 and 0.5 cubic centimeter (e.g., 0.25 cubic centimeter). Due to the small size of the driver, the driver or the body  205  does not have to angled with respect to the ear canal axis, and therefore the same driver (and by extension the same earpiece) can be used for either ear. 
         [0034]    In operation, when the body  205  and the retaining structure  210  are in place, the retaining structure  210  and/or body  205  contact the ear of most people at two or more contact points. In some cases, the outer portion  212  contacts the anti-helix at the rear of the concha, and one end of the retaining structure  210  (i.e., the end at which the outer portion  212  and the inner portion  214  are connected to one another) is underneath the anti-helix. Some portions of the outer portion  212 , or the body  205 , or both are underneath the anti-tragus. The body  205  is inserted partially into the ear canal under the tragus. The contact points hold the earpiece in position, providing greater stability. The movable joint  220  facilitates a substantial decoupling of the force distribution and compliance associated with the retaining structure  210  and body  205 , respectively, thereby providing a more comfortable and customized fit for a wide range of users having various ear geometries. 
         [0035]    In some implementations, a tip of the body  205  is covered by the sealing structure  230 . The sealing structure  230  can include a frusto-conical structure. In some implementations, the frusto-conical structure may have an elliptical or oval cross section, with walls that taper substantially linearly. In some implementations, the sealing structure  230  can be constructed of materials including silicones, TPUs (thermoplastic polyurethanes) and TPEs (thermoplastic elastomers). 
         [0036]    In some implementations, one or more of the body  205 , the retaining structure  210 , the movable joint  220 , and the sealing structure  230  may be made of, for example, a soft silicone rubber having a prerequisite hardness (e.g., 30 Shore A or less). The walls of the sealing structure  230  can be of a uniform thickness which may be very thin, for example, less than one millimeter. The walls of the sealing structure  230  can be configured to taper to the base of the frusto-conical structure so that the walls deflect easily, thereby conforming easily to the contours of the ear and providing a good seal and good passive attenuation without exerting significant radial pressure on the ear canal. In some implementations, different parts of the earpiece  200  can be made of different materials, such as materials with different hardness or moduli, that may be selected based on the function the corresponding portion is intended to serve. For example, the hardness of the retaining structure  210  may be selected for comfort (for example 12 Shore A), whereas the hardness of the body  205  may be slightly higher (for example 20 Shore A) for a better fit and seal. 
         [0037]    In some implementations, an earpiece without a movable joint can also be configured to achieve increased comfort levels for a wearer. For example, a retaining structure of an earpiece can be configured in a way such that an interaction between the retaining structure and the body of the earpiece does not result in undesirable effects such as increased axial pressure on the ear-canal or pressure on the anti-tragus. For example, an earpiece can include a suitably designed compliant eartip that can be coupled to a rigid acoustic driver. Such an eartip can serve as an interface between a rigid driver and the ear, thereby allowing the use of the rigid acoustic driver in an earpiece that is not uncomfortable to wear. Examples of such earpieces are shown in  FIGS. 4A and 4B  where rigid acoustic drivers  410  are coupled to compliant eartips  300 . 
         [0038]      FIGS. 3A-3F  shows different views of such an eartip  300 . For the eartip  300 , the retaining structure  310  is configured such that an interaction between the retaining structure  310  and the body  305  (and by extension, the extended nozzle  307 ) does not axially push the nozzle  307  and/or sealing structure  330  into the ear canal in a way that causes discomfort for most wearers. The nozzle  307  includes an opening  340  at the outer end. The retaining structure  310  can be configured such that the pressure or axial force exerted into the ear canal of a wearer is consistent over a wide range of ear geometries in a way that the pressure does not cause a discomfort for the wearer. This can be accomplished, for example, by balancing compliant features of the nozzle  307  and the retaining structure  310 . In some implementations, the retaining structure  310  can be removably connected to the body  305 , for example, by a hinge structure. 
         [0039]    In some implementations, the eartip  300  has reduced axial push because of an outer portion  312  of the retaining structure  310  connected at a bottom portion  325  of the body  305 . Example dimensions of the retaining structure  310  are shown in  FIG. 3A . An inner portion  314  (or a bridging portion  316  that connects the outer portion  312  with the inner portion  314 ) of the retaining structure  310  is connected to a top portion  320  of the body  305 . In some implementation, the bridging structure  316  can be used to increase stiffness of the outer portion  312  which applies force to the anti-helix. In some implementations, the bridging portion  316  may not be present. 
         [0040]      FIGS. 3C and 3D  show that the retaining structure  310  is disposed along a plane represented by the line  350 . When the eartip  300  is worn by a user, the plane represented by the line  350  matches up with the ear geometry such that the retaining structure  310  is placed into the anti-helix and under the anti-tragus. This can result in the compliance (i.e., an amount of displacement for a given amount of force) of the retaining structure  310  being in a substantially opposite direction to that of the compliance of the nozzle  307  or the sealing structure  330 . The interaction between the retaining structure  310  and the sealing structure  330  can result in a comfortable fit for a wide range of population. In some implementations, an out of plane compliance can also contribute to a comfortable fit. For example, the outer portion  312  of the retaining structure  310  can be configured to be flexible, such that the outer portion  312  bends in and out to provide an even better overall fit. 
         [0041]    In some implementations, the coupling between the retaining structure  310  and the body  305  can be adjusted such that the resulting axial push exerted by the retaining structure  310  is sufficient to create and maintain a seal between the eartip  300  and the ear canal, but not high enough to cause discomfort to the wearer. 
         [0042]    As shown in  FIGS. 3C and 3D , in some implementations, the retaining structure  310  extends below the body  305  by a distance  360 . For example the outer portion  312  can have a lower arm that extends below the body and is attached to the bottom surface  325  of the body  305 . In some implementations, the extension can be along the direction of the plane depicted by the line  350 . In some implementations, the extension may be along a plane different from the plane represented by the line  350 . In some implementations, the out of plane compliance allows a larger portion of the retaining structure  310  to be positioned below the body  305 . Such out of plane compliance of the retaining structure also allows for improved fit with variation of ear canal to anti helix positions. In some implementations, the out of plane compliance can also reduce contact between the body  305  and the anti-helix. 
         [0043]    In general, the retaining structure  310  can perform the functionality of engaging with a lower part of the anti-tragus or the concha (along with engaging with the anti-helix at the top) to provide stability to the eartip  300 . As a result, because the body  305  does not have to engage with the anti-tragus or concha, the body  305  can be made small, for example, in the form of a 6 mm thick circular disk with less than a 12 mm diameter (or an oval disk with principal axes of 10 mm and 14 mm), to reduce contact with the ear, and to provide added compliance to the outer portion  312  of the retaining structure  310 .  FIG. 3A  shows some example dimensions of the body  305 . In some implementations, the body  305  only has to be large enough to accommodate the outlet of an acoustic driver module and couple with a nozzle  307 . In some implementations, the body  305  includes a cavity  335  to receive the outlet of the driver module (e.g., the acoustic driver module shown in  FIGS. 4A and 4B ), and can be made only large enough to accommodate the outlet of the driver within the cavity  335 . The rear end  306  of the body  305  can be shaped to accept the outlet of the driver within the cavity  335 . The cavity  335  can be used, for example, to lock the eartip  300  onto a rigid acoustic driver module. In some implementations, the acoustic driver module (e.g., the driver module  410  shown in  FIGS. 4A and 4B ) can include a structural feature that couples to the cavity  335 . Drivers of various sizes can be coupled to the eartip  300  via the cavity  335 . For example, 8 mm, 12.4 mm, or 14.8 mm diameter drivers can be used. Because contact between the body  305  and the anti-tragus/concha is reduced, any discomfort resulting from an interaction of the body  305  with the ear is also reduced. In addition, compliance between the retaining structure  310  and the sealing structure  330  allow the body  305  to be better positioned in the ear, therefore resulting in reduced contact with the ear structures such as the tragus, anti-tragus, and anti-helix. In some implementations, the reduction in size of the body  305  allows the retaining structure  310  to move more freely. 
         [0044]    In some implementations, a stability of the eartip  300  depends primarily on the retaining structure  310 . The retaining structure  310  can be made compliant enough to engage with a wide range of population with varying ear geometries. For example, the retaining structure  310  can be made compliant enough for users with smaller conchae. Typically such users feel discomfort in wearing earpieces with large bodies. In some implementations, a small body  305 , together with an appropriately shaped retaining structure  310  (e.g., one with a longer outer portion  312  for added compliance), makes the eartip  300  comfortable for such users.  FIGS. 4A and 4B  show two examples of earpieces being worn by users having relatively small conchae. In each of these examples, a relatively large acoustic driver (or speaker)  410  is adapted for the user using the compliant eartip  300  that fits the small concha. 
         [0045]    The retaining structure  310  can be configured to provide sufficient compliance for the eartip  300  to fit a wide range of users with diverse ear geometries. In some implementations, the outer portion  312  can be shaped such that the outer portion  312  provides balanced compliance together with the sealing structure  330 . Because the compliance of the retaining structure  310  is more than that of the body  305  or the sealing structure  330 , the retaining structure  310  is configured to deform rather than push the body  305  or the sealing structure  330  uncomfortably deep into the ear canal. In some implementations, the stiffness (which resists bending) of the retaining structure  310  can be approximately 0.03 N/mm, while the stiffness of the sealing structure  330  (and/or the nozzle  307 ) can be approximately 0.3 N/mm, thereby making the retaining structure approximately ten times more compliant than the sealing structure  330 . The compliance of the outer portion  312  can be adjusted, for example, based on using a material with an appropriate modulus of elasticity, and/or by adjusting the geometry (e.g., area of the cross section of the outer portion  312 ). The compliance of the nozzle  307  and the sealing structure  330  can also depend on geometries of the respective structures. Once the nozzle  307  is sealed against the ear canal (e.g., via the sealing structure  330 ), the compliance can be provided by the material used for the nozzle  307  and/or the sealing structure  330 . 
         [0046]    In some implementations, the lower part of the outer portion  312  (i.e. the portion that is connected to the bottom  325  of the body  305 ) provides additional out-of-plane compliance while reducing contact with the ear (e.g., with the anti-tragus). The out-of-plane compliance can be configured such that the seal between the sealing structure  330  and the ear canal is not compromised, yet a comfortable fit is achieved for the user. 
         [0047]    In operation, the nozzle  307  (together with the sealing structure  330 , where present) is placed in the ear and the eartip  300  is pushed gently inward. Pushing the eartip  300  into the ear causes the outer portion  312  to fit into a position underneath the anti-helix, and causes the opening or nozzle  340  to enter the ear canal by a small amount, depending on the dimensions and geometry of the entrance to the ear canal. In some cases, the eartip  300  can be rotated in one direction (e.g., counter-clockwise) for a better fit. The eartip  300  can then be rotated in the opposite direction (e.g., clockwise) until the eartip  300  cannot be further rotated. This can happen when, for example, the extremity  345  of the retaining structure  310  contacts the base of the helix, the inner portion  314  contacts the base of the helix, or the extremity  345  of the retaining structure  310  becomes wedged behind the anti-helix in the cymba concha region. At the lower end, the retaining structure  310  contacts the bottom portion of the concha and/or the anti-tragus to provide a comfortable and stable fit for the user. The exact way the retaining structure  310  engages with a particular user&#39;s ear can depend on the size and geometry of the user&#39;s ears. Therefore, by having a compliant retaining structure  310  and a small body  305 , the eartip  300  can be made suitably comfortable for a wide range of users, including users with less common ear geometry such as medium to small sized conchae. 
         [0048]    Elements of different implementations described herein may be combined to form other embodiments not specifically set forth above. Elements may be left out of the structures described herein without adversely affecting their operation. Furthermore, various separate elements may be combined into one or more individual elements to perform the functions described herein.