Open-back headphones

Abstract

A flexible arm is positioned between an acoustic module of the open headphones and a battery housing of the open headphones and configured to physically and electrically connect to the acoustic module and the battery housing. The flexible arm includes a flexible printed circuit extending throughout the entire original resting length of the flexible arm and including conductors configured to carry electrical energy between the acoustic module and the battery housing. A first interface structure is coupled to one of the acoustic module and the battery housing. At least one link member is pivotally coupled to the first interface structure. A flexible material encases at least a portion of the flexible printed circuit, at least a portion of the at least one link member, and at least a portion of the first interface structure.

Description

[Technical Field]

[0001] The present disclosure relates to ear-worn headphones.

[0002] Open headphones typically emit sound close to the ear canal rather than in the ear canal. Summary of the Invention

[0003] All examples and features mentioned below can be combined in any technically possible manner.

[0004] In one aspect, the flexible arm is positioned between an acoustic module of the open headphones and a battery housing of the open headphones and is configured to physically and electrically connect to the acoustic module and the battery housing. The flexible arm includes a flexible printed circuit extending throughout the entire original resting length of the flexible arm and including conductors configured to carry electrical energy between the acoustic module and the battery housing. The first interface structure is coupled to one of the acoustic module and the battery housing. At least one link member is pivotally coupled to the first interface structure. A flexible material encases at least a portion of the flexible printed circuit, at least a portion of the at least one link member, and at least a portion of the first interface structure.

[0005] Implementations may include one or any combination of the following features.

[0006] In some implementations, the at least one link member is pivotally coupled to the first interface structure via a pivot pin that passes through respective holes in the at least one link member and the first interface structure.

[0007] In certain implementations, the at least one link member constrains twisting of the flexible arm.

[0008] In some cases, the at least one link member includes a plurality of link members pivotally connected to one another in series.

[0009] In certain cases, the link members are pivotally coupled to one another via a pivot pin that passes through respective holes defined by the link members.

[0010] In some embodiments, at least one link member at least partially surrounds the flexible printed circuit.

[0011] In certain embodiments, the flexible arm also includes a guide member coupled to the at least one link member, and the flexible printed circuit may pass through a channel in the guide member, thereby coupling the flexible printed circuit to the at least one link member.

[0012] In some implementations, the guide member is formed of silicone.

[0013] In certain implementations, the guide member is coupled to the at least one link member via an adhesive.

[0014] In some cases, the flexible arm also includes a second interface structure coupled to the other of the acoustic module and the battery housing, and the at least one link member may be pivotally coupled to the second interface structure.

[0015] In certain cases, the at least one link member includes a plurality of link members pivotally coupled to one another and arranged in series between the first interface member and the second interface member.

[0016] In some embodiments, at least one link member includes a motion limiting mechanism that limits rotational movement of the link member.

[0017] In certain embodiments, at least one link member is formed from a rigid plastic.

[0018] In some implementations, at least one link member is formed of metal (eg, spring steel).

[0019] In certain implementations, the flexible material is overmolded onto the at least one link member over at least a portion of the flexible printed circuit and over at least a portion of the first interface structure.

[0020] In some cases, the flexible material comprises the outer layer of the entire flexible arm.

[0021] In certain cases, the original rest position of the flexible arm is along a curved axis that defines a simple open curve.

[0022] In some embodiments, the first interface structure includes one or more centering features to assist in centering the first interface structure within the cavity of the battery housing.

[0023] In certain embodiments, the first interface structure includes one or more guide members that provide a hard stop that abuts the battery housing to limit inward movement of the first interface structure into the cavity of the battery housing during assembly.

[0024] In some implementations, the flexible material defines a gasket that provides a seal between the first interface member and the acoustic module.

[0025] Various aspects of at least one example are discussed below with reference to the accompanying drawings, which are not intended to be drawn to scale. These drawings are included to provide illustration and a further understanding of various aspects and examples, and are incorporated into and constitute a part of this specification, but are not intended as a definition of the limits of the invention. In the drawings, identical or nearly identical components shown in various figures may be labeled with like letters or numerals. For clarity, not every component may be labeled in every figure. [Brief explanation of the drawings]

[0026] [Figure 1A] FIG. 1 is a side view of an open-type headphone. [Figure 1B] FIG. 2 is a rear view of the open-type headphones. [Figure 1C] FIG. 1C is a cross-sectional view taken along line 1C-1C of FIG. 1B. [Figure 1D] FIG. 1B is a perspective view of the open-back headphones of FIG. 1A. [Figure 2A] FIG. 10 is a front perspective view of an interface structure for a flexible arm. [Figure 2B] FIG. 10 is a rear perspective view of an interface structure for a flexible arm. [Figure 3A] 2A and 2B engaged with a battery housing of an open-type headphone. FIG. [Figure 3B] 2A and 2B engaged with a battery housing of an open-type headphone. FIG. [Figure 4A] 10A-10C are various perspective views of an alternative interface structure for a flexible arm. [Figure 4B] 10A-10C are various perspective views of an alternative interface structure for a flexible arm. [Figure 4C] 10A-10C are various perspective views of an alternative interface structure for a flexible arm. [Figure 5A]4B and 4C are perspective and rear views, respectively, of the interface structure of FIG. 4A engaged with the acoustic module of an open-type headphone. [Figure 5B] 4B and 4C are perspective and rear views, respectively, of the interface structure of FIG. 4A engaged with the acoustic module of an open-type headphone. [Figure 5C] 4B and 4C are perspective and rear views, respectively, of the interface structure of FIG. 4A engaged with the acoustic module of an open-type headphone. [Figure 6A] 1B and 1C are front and rear perspective views, respectively, of a link member of the open-type headphones of FIG. 1A. [Figure 6B] 1B and 1C are front and rear perspective views, respectively, of a link member of the open-type headphones of FIG. 1A. [Figure 7A] FIG. 1 is a perspective view of an open-type headphone having an alternative link member design. [Figure 7B] FIG. 1 is a perspective view of an open-type headphone having an alternative link member design. [Figure 8A] 7B are front and rear perspective views, respectively, of the link member of the open-type headphones of FIG. 7A. [Figure 8B] 7B are front and rear perspective views, respectively, of the link member of the open-type headphones of FIG. 7A. DETAILED DESCRIPTION OF THE INVENTION

[0027] Open-ear headphones must provide high-quality sound, be stable on the ear, be comfortable for extended wear, be discreet, and be stylish. These objectives can be difficult to achieve because they have been considered mutually exclusive in some respects. For example, stability typically leads to clamping to the outer ear, which can be uncomfortable for extended wear and may not be stylish. Also, for high-quality sound, sound must be delivered near the ear canal, not in it, which means the headphone structure must be placed over the ear and therefore be clearly visible to others. Also, for best sound quality, sound should be delivered near the ear canal opening, not in it.

[0028] The open-back headphone embodiments discussed herein are not limited in their application to the details of construction and arrangements of components set forth in the following description or illustrated in the accompanying drawings. The headphones may be implemented in other embodiments and practiced or carried out in various ways. Specific embodiments are provided herein for illustrative purposes only and are not intended to be limiting. In particular, functions, components, elements, and features discussed in connection with any one or more embodiments are not intended to be excluded from a similar role in any other embodiments.

[0029] Examples disclosed herein may be combined with other examples in any manner consistent with at least one of the principles disclosed herein, and further, references to "an example," "some examples," "an alternate example," "various examples," "one example," etc. are not necessarily mutually exclusive and are intended to indicate that a particular feature, structure, or characteristic described may be included in at least one example. Appearances of such terms herein do not necessarily all refer to the same example.

[0030] Additionally, the phraseology and terminology used herein are for descriptive purposes only and should not be considered limiting. Any reference herein to an example, component, element, act, or function of headphones in the singular may also encompass embodiments including the plural, and any reference herein to any example, component, element, act, or function in the plural may also encompass examples including only the singular. Thus, singular or plural references are not intended to limit the systems or methods of the present disclosure, their components, acts, or elements. The use herein of "including," "comprising," "having," "containing," "involving," and variations thereof, is meant to encompass the items listed below and their equivalents, as well as other items. References to "or" may be construed as inclusive, such that all terms described with "or" can refer to either one, more than one, or all of the listed terms.

[0031] In some embodiments herein, the open-type headphones include a flexible arm positioned between an acoustic module and a battery housing of the headphones and configured to physically and electrically connect to the acoustic module and the battery housing. The flexible arm defines an original resting length and position between the acoustic module and the battery housing. The flexible arm includes a flexible printed circuit extending across the entire original resting length of the flexible arm. The flexible printed circuit includes one or more conductors that carry electrical energy between the acoustic module and the battery housing. An interface structure is coupled to the acoustic module or the battery housing. A flexible material encases at least a portion of the flexible printed circuit and at least a portion of the interface structure. In some embodiments, the length of the flexible printed circuit within the flexible arm is longer than the original resting length of the flexible arm. The flexible printed circuit can therefore better accommodate tension or compression on the flexible arm when the flexible arm is bent from its original resting position.

[0032] In some embodiments, the original rest position of the flexible arm is along a bending axis. In one embodiment, the bending axis defines a simple open curve. In one embodiment, the bending axis is generally "C" shaped. In one embodiment, the bending axis bisects the flexible arm, and different portions of the first surface of the flexible printed circuit are located on different sides of the bending axis. In one embodiment, the flexible printed circuit defines at least one simple open curve along the length of the flexible printed circuit within the flexible arm. In one embodiment, the flexible printed circuit defines both a plurality of upward and downward simple open curves along the length of the flexible printed circuit within the flexible arm. In one embodiment, each downward simple open curve is adjacent to one or more upward simple open curves.

[0033] In various embodiments, the flexible arm may also include a series of pinned links disposed between and pivotally attached to the first and second interface structures. The flexible printed circuit may be threaded through internal channels formed in the links, which may provide support and protection for the flexible printed circuit in the area between the interface members. The links may also resist torsional motion, for example, to prevent twisting of the flexible arm. The links may be formed from plastic (e.g., cast urethane) or metal (e.g., spring steel) and may be formed in a molding or stamping operation.

[0034] FIG. 1A is a side view of open-type headphones 100, FIG. 1B is a rear view, FIG. 1C is a cross-sectional view taken along line 1C-1C, and FIG. 1D is a perspective view. The headphones 100 are configured to be worn on a user's ear such that a distal sound-delivery end 102 of the headphones' acoustic module 104 is positioned within the ear's concha and a battery housing 106 is positioned behind the ear. A flexible arm 108 is configured to pass over the outer upper portion of the ear's helix, antihelix, and / or lobule. The arm 108 has an original or rest position and length illustrated in FIGS. 1A-1D. In some embodiments, the original position defines a generally "C" shape as shown in these figures. The arm 108 is configured to flex along at least the length of the arm, thereby slightly increasing the space between the acoustic module 104 and the battery housing 106. This allows headphones 100 to be put on and taken off from the ear without having to be forced onto the outer ear, and also provides a slight clamping force on the ear as the user's head moves, helping to hold headphones 100 in place on the ear. Note that FIGS. 1A-1D illustrate some interference between acoustic module 104 and battery housing 106. However, in most embodiments, there is actually space between the two, as disclosed, for example, in the patents incorporated by reference. In some embodiments, this interference is modeled so that arm 108, if molded into this shape, will tend to "rest" in this position. This modeling helps create some preload on the arm.

[0035] Electrical signals need to be carried through the arm 108. In some embodiments, the electrical signals include or comprise power from the battery 110 in the battery housing 106 to any electrical circuitry and components in the acoustic module 104 and the acoustic transducer 112. In some embodiments, the electrical signals also include audio signals from wireless receiving and processing circuitry (not shown), which may be located in one or more of the arm 108, the battery housing 106, and the acoustic module 104. In some embodiments, these electrical signals are carried by conductors in the flexible printed circuit 114. The flexible printed circuit needs to be able to flex when the arm 108 flexes, yet at the same time, it needs to carry the necessary electrical signals.

[0036] The flexible printed circuit 114 carries power from the battery 110 to data receiving and processing circuitry on the printed circuit board 116. Power and audio signals are provided from the board 116 to the transducer 112. The transducer 112 generates sound pressure in a front acoustic cavity 118 and a rear acoustic cavity 120. Openings / ports in the acoustic module housing 122 provide a path for sound to escape from the housing 122. The flexible printed circuit 114, arm interface structures 124 and 126, and flexible overmold material 128 are described further below.

[0037] Additional details of open headphones, including but not limited to details of their construction, operation, and acoustic performance, are disclosed in U.S. Patent No. 11,140,469, the entire disclosure of which is incorporated herein by reference for all purposes. The aspects of the present open headphones disclosed in this patent will not be further described herein.

[0038] In some embodiments, the flexible arm 108 includes one or more interface structures 124, 126. The interface structures are configured to mechanically couple the arm to one or both of the battery housing and the acoustic module. In some embodiments, the interface structures are relatively rigid but have some compliance. The interface structures can be made of an engineering plastic, such as nylon or acrylonitrile butadiene styrene (ABS), or from rubber or a rubber-like material. In some embodiments, the interface structures are made by injection molding, machining, stamping, or 3D printing. In some embodiments, the interface structures are a single piece. The interface structures help hold the arm in its curved, resting position and provide stiffening reinforcement to the arm. In some embodiments, the interface structures also help anchor a relatively soft overmold that covers the entire arm. In some embodiments, the overmold also covers at least a portion of the battery housing.

[0039] 2A and 2B illustrate the first interface structure 124. The interface structure 124 is a single-piece molded plastic part defining a body 202 extending between a proximal end 204 and a distal end 206, with a pair of pivot arms 208 disposed along the distal end 206 of the body 202. Each of the pivot arms 208 includes a hole 209 for accommodating a pivot pin 130 (FIG. 1C). The body 202 defines an opening 210 extending through its length between the proximal end 204 and the distal end 206. The opening 210 accommodates the flexible printed circuit 114, thereby allowing the flexible printed circuit 114 to pass through the first interface structure 124 and into the battery housing 106.

[0040] The interface structure 124 is configured to couple the flexible arm 108 to the battery housing 106 and to help support and guide the flexible printed circuit 114. As shown in FIGS. 3A and 3B , the body 202 is configured to couple to the battery housing 106. In some embodiments, the body 202 is received within a complementarily shaped cavity 302 ( FIG. 3B ) in the battery housing 106, and / or the battery housing 106 may be made from two (or more) pieces that are snapped or otherwise mated together around the body 202. An adhesive (such as a pressure-sensitive adhesive) may be used to more permanently attach the interface structure 124 to the battery housing 106.

[0041] A pair of guide members 212, shown in the form of protruding bars, are provided along opposing exterior surfaces of the body 202. The guide members 212 provide a hard stop that abuts the battery housing 106, preventing further inward movement during assembly. The guide members 212 provide a reference surface that helps ensure that the interface structure 124 is properly positioned during assembly with the battery housing 106. The interface structure 124 further includes a plurality of centering features 214, shown in the form of protruding ridges that extend outward from the exterior surface of the body 202. These centering features 214 engage the surface of the battery housing 106 within the cavity 302 to help ensure that the body 202 is centered within the cavity 302.

[0042] A second interface structure 126 (FIGS. 4A-4C) couples the flexible arm 108 to the acoustic module 104. The interface structure 126 is a single-piece molded plastic part that defines a body 402, an intermediate narrow portion 404, and an end flared portion 406. The body 402 defines a recess 410 for receiving the flexible printed circuit 114.

[0043] Interface structure 126 is configured to couple flexible arm 108 to acoustic module 104, help support and guide the flexible printed circuit, and anchor the overmold. End enlarged portion 406 is configured to be coupled to acoustic module 104, as shown in FIG. 5A (only a portion of the acoustic module is shown in FIGS. 5A-5C ). In some embodiments, portion 406 is received within a complementary shaped cavity (not shown) in acoustic module 104, and / or acoustic module 104 is made from two (or more) pieces snapped or otherwise mated together around portion 402. In some embodiments, an adhesive (such as a pressure-sensitive adhesive) is used to more permanently attach interface structure 126 to acoustic module 104.

[0044] The interface structure 126 defines a guide 410 for the flexible printed circuit 114. The guide 410 has approximately the same width and thickness as the flexible printed circuit so that the flexible printed circuit is guided into the acoustic module through a slot 412 that extends through the intermediate narrow portion 404 and the end flared portion 406. The guide 410 helps to properly center, align, and support the flexible printed circuit. The guide 410 includes a flat surface formed by a recess formed in the surface of the body 402.

[0045] In some embodiments herein, the overmold material 128 surrounds and encases the flexible printed circuit along at least a majority, and preferably all, of the original rest length of the flexible arm, as well as some, and preferably all, of any internal support and interface structures. In some cases, a sleeve (not shown) may be provided to cover the link member 600 before overmolding the overmold material 128. The sleeve can help prevent the overmold material 128 (e.g., silicone) from entering the link or directly contacting the link.

[0046] Prior to assembly with acoustic module 104 (only a portion of the acoustic module is shown in FIGS. 5A-5C), interface structure 126 is overmolded with flexible overmolding material 128 ( FIGS. 5B and 5C ). Interface structure 126 is shown without overmolding material 128 in FIG. 5A for illustrative purposes. Overmolding material 128 forms a gasket 502 ( FIGS. 5B and 5C ) around intermediate narrow portion 404, which engages acoustic module 104 to form a seal therebetween, for example, to prevent the ingress of liquids or debris into the interior cavity of acoustic module 104.

[0047] 6A and 6B, one or more link members 600 are disposed between and pivotally coupled to the first interface structure 124 and the second interface structure 126. Each link member 600 includes a plurality of link arms 602 and one or more bridge members 604 extending therebetween. In the illustrated embodiment, the bridge members 604 are positioned to define channels 606 between the link arms 602 for receiving the flexible printed circuit 114.

[0048] Each of the link arms 602 includes a hole 612 for receiving a pivot pin 130 ( FIG. 1C ) for coupling the link members 600 to each other and to the first and second interface structures. In the embodiment shown in FIG. 1D , which includes multiple link members 600 arranged in series, the link arm 602 located along the distal end 610 of the link members 600 is configured to fit around a link arm 602 located along the proximal end 608 of an adjacent one of the link members 600. The link arm 602 located along the proximal end 608 of the first link member 600 in the series is configured to fit between the pivot arms 208 ( FIGS. 2A and 2B ) on the first interface structure 124, and the link arm 602 located along the distal end 610 of the last link member 600 in the series is configured to fit around a pair of pivot arms 414 on the second interface structure 126. Pivot pin 130 (FIG. 1C) extends through a hole in link arm 602, pivotally coupling link members 600 together. Similarly, pivot pin 130 extends through holes in each of the first and last link members 600 and first and second interface structures 124, 126, pivotally coupling link members 600 to battery housing 106 and acoustic module 104. In some cases, each of link members 600 may also include a motion-limiting feature, such as a ridge or wedge, extending outward from one of bridge members 606 and providing a mechanical limit to rotation of link member 600. The links may be formed of plastic (e.g., cast urethane).

[0049] 1C and 1D illustrate the manner in which the flexible printed circuit 114 interfaces with the link member 600, the interface structure 124, and the interface structure 126. A first end 132 of the flexible printed circuit 114 is configured to interface with a printed circuit board connected to two terminals of the battery 110 ( FIG. 1C ) in the battery housing 106, while a second end 136 is configured to interface with a printed circuit board (such as the printed circuit board 116 in FIG. 1C ) in the acoustic module 104. To accommodate flexure of the arm 108 while reducing stress on the flexible printed circuit 114, the flexible printed circuit 114 can have a length at the arm 108 that is longer than the nominal rest length of the arm 108. The additional length can be achieved by one or more curves in the flexible printed circuit that are held within the flexible arm 108. Such additional length can be accommodated by a bend formed in the flexible printed circuit 114. In some embodiments, flexure 138 is held in place via an associated one of pivot pins 130. Link member 600 serves to surround and protect flexible printed circuit board 114. In addition, link member 600 restrains twisting of flexible arm 108. Link member 600 can be made by injection molding, machining, or stamping.

[0050] Other implementations Different implementations of link members are shown in FIGS. 7A, 7B, 8A, and 8B. Link member 800 can be fabricated by injection molding, machining, or stamping. In some embodiments, link member 800 may be formed (e.g., stamped) from spring steel. Link member 800 includes a pair of link arms (first link arm 802 and second link arm 804) coupled to each other via a bridge member 806. A third link arm 808 extends from an intermediate portion of bridge member 806. Link arms 802, 804, and 808 include holes 814 for receiving pivot pins 130. Third link arm 808 is configured to fit between first link arm 802 and second link arm 804 of an adjacent link member 800. Pivot pin 130 pivotally connects link members 800. The link arms 802 , 804 , 808 may in turn be pivotally coupled to the pivot arms 208 , 414 on the first and second interface structures 124 , 126 via the pivot pin 130 .

[0051] Link member 800 may also include a motion-limiting mechanism 820 that limits the amount of relative rotational movement. This can help prevent hyperextension of the flexion joint. In the embodiment shown in Figures 8A and 8B, motion-limiting mechanism 820 is in the form of a tab that extends outward from the bridge member between first link arm 802 and second link arm 804.

[0052] The link members 800 are free to rotate relative to one another before the limiting features 820 contact adjacent link members 800. Once the limiting features 820 on each link contact adjacent link members 800, any further rotation will cause the link members 800 to bend, thereby providing a relatively firm resistance to the user as feedback to inhibit (e.g., prevent) any additional rotation that could damage other plastic components or the flexible printed circuit 114.

[0053] In some cases, a guide member 822 may be provided on one or more of the link members 800. The guide member 822 defines a channel 824 (FIG. 8B) for receiving and supporting the flexible printed circuit 114. The guide member 822 may be formed from silicone and may be secured to the link members 800 via, for example, an adhesive or interlocking mechanical features.

[0054] Having described several aspects of at least one embodiment, it will be appreciated that various alterations, modifications, and improvements will readily occur to those skilled in the art. Such alterations, modifications, and improvements are intended to be part of this disclosure and be within the scope of the invention. Accordingly, the foregoing description and drawings are by way of example only, with the scope of the invention to be determined from proper construction of the appended claims and their equivalents.

Claims

1. a flexible arm positioned between an acoustic module of the open headphones and a battery housing of the open headphones, the flexible arm being configured to physically and electrically connect to the acoustic module and the battery housing; a flexible printed circuit including conductors extending through the entire original resting length of the flexible arm and configured to carry electrical energy between the acoustic module and the battery housing; a first interface structure coupled to one of the acoustic module and the battery housing; at least one link member pivotally coupled to the first interface structure; a flexible material encasing the at least one link member, at least a portion of the flexible printed circuit, and at least a portion of the first interface structure.

2. 2. The flexible arm of claim 1, wherein the at least one link member is pivotally coupled to the first interface structure via a pivot pin that passes through respective holes in the at least one link member and the first interface structure.

3. The flexible arm of claim 1 , wherein the at least one link member restrains twisting of the flexible arm.

4. The flexible arm of claim 1 , wherein the at least one link member comprises a plurality of link members pivotally coupled to one another in series.

5. The flexible arm of claim 4 , wherein the plurality of link members are pivotally coupled to one another via a pivot pin that passes through respective holes defined by the plurality of link members.

6. The flexible arm of claim 1 , wherein the at least one link member at least partially surrounds the flexible printed circuit.

7. 2. The flexible arm of claim 1, further comprising a guide member coupled to the at least one link member, the flexible printed circuit passing through a channel in the guide member, thereby coupling the flexible printed circuit to the at least one link member.

8. The flexible arm of claim 7 , wherein the guide member is formed from silicone.

9. The flexible arm of claim 7 , wherein the guide member is coupled to the at least one link member via an adhesive.

10. 10. The flexible arm of claim 1, further comprising a second interface structure coupled to the other of the acoustic module and the battery housing, the at least one link member being pivotally coupled to the second interface structure.

11. The flexible arm of claim 10 , wherein the at least one link member comprises a plurality of link members pivotally coupled to one another and arranged in series between the first interface member and the second interface member.

12. The flexible arm of claim 1 , wherein the at least one link member includes a motion limiting mechanism that limits rotational movement of the link member.

13. The flexible arm of claim 1 , wherein the at least one link member is formed of a rigid plastic.

14. The flexible arm of claim 1 , wherein the at least one link member is formed of metal.

15. The flexible arm of claim 1 , wherein the flexible material is overmolded onto the at least one link member, at least a portion of the flexible printed circuit, and at least a portion of the first interface structure.

16. The flexible arm of claim 1 , wherein the flexible material comprises an outer layer of the entire flexible arm.

17. The flexible arm of claim 1 , wherein the original rest position of the flexible arm is along a curved axis that defines a simple open curve.

18. The flexible arm of claim 1 , wherein the first interface structure includes one or more centering features to assist in centering the first interface structure within a cavity in the battery housing.

19. 2. The flexible arm of claim 1, wherein the first interface structure comprises one or more guide members that provide a hard stop that abuts the battery housing to limit inward movement of the first interface structure into a cavity of the battery housing during assembly.

20. The flexible arm of claim 1 , wherein the flexible material defines a gasket that provides a seal between the first interface member and the acoustic module.

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