PATENT DOCUMENT

Publication Number: US-11265645-B2
Application Number: US-201816140350-A
Country: US
Kind Code: B2

Title: Acoustic chambers damped with side-branch resonators, and related systems and methods

Abstract:
An acoustic enclosure includes a housing at least partially defining an acoustic chamber for an acoustic radiator. The housing further defines an acoustic opening from the acoustic chamber to a surrounding environment. The acoustic enclosure also has a first acoustic resonator and a second acoustic resonator. The first acoustic resonator and the second acoustic resonator are acoustically coupled with the acoustic chamber in parallel relative to each other. Each of the first acoustic resonator and the second acoustic resonator modifies a frequency response of the acoustic chamber. Loudspeakers can include such an enclosure acoustically excited or driven by an electro-acoustic transducer. As well, an electronic device can include such a loudspeaker.

Claims:
We currently claim: 
     
       1. An electronic earbud device comprising:
 an acoustic radiator; 
 circuitry to drive the acoustic radiator to emit sound over a selected frequency bandwidth; 
 a housing at least partially defining an acoustic chamber adjacent the acoustic radiator, wherein the housing further defines an acoustic opening extending from the acoustic chamber to a surrounding environment; 
 an external ear-contact region configured to contact a region of a wearer&#39;s ear when the electronic earbud is donned by a wearer; and 
 a first acoustic resonator and a second acoustic resonator, wherein the first acoustic resonator and the second acoustic resonator are acoustically coupled with and extend directly from respective locations around the acoustic chamber in parallel relative to each other and the acoustic opening, each of the first acoustic resonator and the second acoustic resonator configured to modify a frequency response of the acoustic chamber. 
 
     
     
       2. The electronic earbud device according to  claim 1 , wherein the first acoustic resonator is arranged to resonate at a corresponding first frequency and the second acoustic resonator is arranged to resonate at a corresponding second frequency. 
     
     
       3. The electronic earbud device according to  claim 1 , wherein the first acoustic resonator comprises a first resonant chamber and a first duct extending from the acoustic chamber to the first resonant chamber, wherein the second acoustic resonator comprises a second resonant chamber and a second duct extending from the acoustic chamber to the second resonant chamber. 
     
     
       4. The electronic earbud device according to  claim 1 , wherein the first acoustic resonator comprises a first resonant chamber and a first duct extending from the acoustic chamber to the first resonant chamber, wherein the second acoustic resonator comprises a second resonant chamber and a second duct extending from the first duct to the second resonant chamber. 
     
     
       5. The electronic earbud device according to  claim 1 , wherein the first acoustic resonator comprises a first resonant chamber and a first duct extending from the acoustic chamber to the first resonant chamber, wherein the second acoustic resonator comprises a resonant conduit extending from a proximal end to a distal end, wherein the proximal end is acoustically coupled with the acoustic chamber. 
     
     
       6. The electronic earbud device according to  claim 5 , wherein the distal end is open. 
     
     
       7. The electronic earbud device according to  claim 5 , wherein the distal end is closed. 
     
     
       8. The electronic earbud device according to  claim 1 , wherein the first acoustic resonator comprises a first resonant conduit extending from a proximal end to a distal end, wherein the proximal end of the first resonant conduit is acoustically coupled with the acoustic chamber, wherein the second acoustic resonator comprises a second resonant conduit extending from a proximal end to a distal end. 
     
     
       9. The electronic earbud device according to  claim 8 , wherein the distal end of the first resonant conduit is open, wherein the distal end of the second resonant conduit is open. 
     
     
       10. The electronic earbud device according to  claim 8 , wherein the distal end of the first resonant conduit is open, wherein the distal end of the second resonant conduit is closed. 
     
     
       11. The electronic earbud device according to  claim 8 , wherein the distal end of the first resonant conduit is closed, wherein the distal end of the second resonant conduit is closed. 
     
     
       12. The electronic earbud device according to  claim 8 , wherein the first resonant conduit extends longitudinally within the second resonant conduit. 
     
     
       13. The electronic earbud device according to  claim 12 , wherein the first resonant conduit and the second resonant conduit are spaced apart from each other to define a longitudinally extending gap between the first resonant conduit and the second resonant conduit, wherein the longitudinally extending gap is acoustically coupled with the acoustic chamber at a position adjacent the proximal end of the second resonant conduit. 
     
     
       14. The electronic earbud device according to  claim 1 , wherein the housing comprises a shell member and a complementarily configured insert having an outer surface with a shape that substantially conforms to a shape of an inner surface of the shell member, wherein the shell member is configured to receive the insert in a mating engagement, wherein, when matingly engaged with each other, the shell member and the insert define an outer boundary of at least a portion of the first acoustic resonator. 
     
     
       15. The electronic earbud device according to  claim 14 , wherein the insert defines a through-hole aperture open to the acoustic chamber, and the portion of the first acoustic resonator defined by the shell member and the insert. 
     
     
       16. The electronic earbud device according to  claim 15 , wherein the portion of the first acoustic resonator defined by the shell member and the insert comprises a resonant chamber and wherein the aperture provides a contraction positioned between the acoustic chamber and the resonant chamber. 
     
     
       17. The electronic earbud device according to  claim 15 , wherein the portion of the first acoustic resonator defined by the shell member and the insert comprises a resonant conduit and wherein the aperture further opens to the resonant conduit such that the aperture extends the resonant conduit to the acoustic chamber. 
     
     
       18. The electronic earbud device according to  claim 17 , wherein the shell member defines a through-hole aperture extending from the resonant conduit to a surrounding environment. 
     
     
       19. The electronic earbud device according to  claim 18 , further comprising an acoustic mesh positioned over the through-hole aperture defined by the shell member. 
     
     
       20. The electronic device according to  claim 1 , wherein the acoustic radiator defines a first major surface and an second major surface, and the acoustic chamber is a first acoustic chamber positioned adjacent the first major surface of the acoustic radiator; wherein the housing further defines, at least partially, a second acoustic chamber positioned adjacent the second major surface of the acoustic radiator. 
     
     
       21. The electronic device according to  claim 20 , wherein the second acoustic chamber is acoustically sealed. 
     
     
       22. The electronic device according to  claim 20 , wherein the second acoustic chamber is ported. 
     
     
       23. An electronic earbud device comprising:
 an acoustic radiator; 
 circuitry to drive the acoustic radiator to emit sound over a selected frequency bandwidth; 
 a housing at least partially defining an acoustic chamber adjacent the acoustic radiator, wherein the housing further defines an acoustic opening extending from the acoustic chamber to a surrounding environment; 
 an external ear-contact region configured to contact a region of a wearer&#39;s ear when the electronic earbud is donned by a wearer; and 
 a first acoustic resonator and a second acoustic resonator, wherein the first acoustic resonator and the second acoustic resonator are acoustically coupled with the acoustic chamber in parallel relative to each other and the acoustic opening, each of the first acoustic resonator and the second acoustic resonator configured to modify a frequency response of the acoustic chamber, 
 wherein the housing comprises a shell member and a complementarily configured insert, wherein the shell member is configured to receive the insert in a mating engagement, wherein, when matingly engaged with each other, the shell member and the insert define an outer boundary of at least a portion of the first acoustic resonator, wherein the insert defines a through-hole aperture open to the acoustic chamber, and the portion of the first acoustic resonator defined by the shell member and the insert, wherein the portion of the first acoustic resonator defined by the shell member and the insert comprises a resonant conduit, and wherein the aperture further opens to the resonant conduit such that the aperture extends the resonant conduit to the acoustic chamber. 
 
     
     
       24. An earbud, comprising:
 an acoustic radiator; 
 a housing at least partially defining an acoustic chamber adjacent the acoustic radiator, wherein the housing further defines an acoustic opening extending from the acoustic chamber to a surrounding environment; and 
 a first acoustic resonator and a second acoustic resonator, wherein the first acoustic resonator and the second acoustic resonator extend directly from respective locations around the acoustic chamber in parallel with respect to each other and the acoustic opening.

Description:
FIELD 
     This application and related subject matter (collectively referred to as the “disclosure”) generally concern acoustic chambers damped with one or more side-branch resonators, and related systems and methods. More particularly, but not exclusively, this disclosure pertains to loudspeaker enclosures defining an acoustic chamber acoustically coupled with two or more side-branch resonators, with each respective side-branch resonator being configured to damp a corresponding resonant frequency. 
     BACKGROUND INFORMATION 
     Typical electro-acoustic transducers have an acoustic radiator and typical loudspeakers pair such an acoustic radiator with an acoustic chamber to accentuate and/or to damp selected acoustic frequency bands. Conventional acoustic chambers and acoustic radiators often are large compared to many electronic devices. 
     For example, many commercially available electronic devices have a characteristic length scale equivalent to or smaller than a characteristic length scale of conventional acoustic chambers and acoustic radiators. Representative electronic devices include, by way of example, portable personal computers (e.g., smartphones, smart speakers, laptop, notebook and tablet computers), desktop personal computers, and wearable electronics (e.g., smart watches). 
     Consequently, many electronic devices do not incorporate conventional acoustic radiators and acoustic chambers, given their incompatible size differences. As a further consequence, some electronic devices do not provide an audio experience to users on par with that provided by more conventional, albeit larger, loudspeakers. 
     SUMMARY 
     In some respects, concepts disclosed herein concern acoustic enclosures having an acoustic chamber damped with plural resonant chambers. 
     According to one aspect, an acoustic enclosure includes a housing at least partially defining an acoustic chamber for an acoustic radiator. The housing further defines an acoustic opening from the acoustic chamber to a surrounding environment. The acoustic enclosure also includes a first acoustic resonator and a second acoustic resonator. The first acoustic resonator and the second acoustic resonator are acoustically coupled with the acoustic chamber in parallel relative to each other. Each of the first acoustic resonator and the second acoustic resonator modifies a frequency response of the acoustic chamber. 
     The first acoustic resonator can be arranged to resonate at a corresponding first frequency and the second acoustic resonator can be arranged to resonate at a corresponding second frequency. 
     The first acoustic resonator can include a first resonant chamber and a first duct extending from the acoustic chamber to the first resonant chamber. The second acoustic resonator can include a second resonant chamber and a second duct extending from the acoustic chamber to the second resonant chamber. Alternatively, the second duct can extend from the first duct to the second resonant chamber. 
     As another alternative, the second acoustic resonator can include a resonant conduit extending from a proximal end to a distal end. The proximal end can be acoustically coupled with the acoustic chamber. The distal end can be open to a surrounding environment or closed to a surrounding environment. 
     The first acoustic resonator can include a first resonant conduit extending from a proximal end to a distal end. The proximal end of the first resonant conduit can be acoustically coupled with the acoustic chamber. The second acoustic resonator also can include a second resonant conduit extending from a proximal end to a distal end. The distal end of the first resonant conduit can be open to a surrounding environment, and the distal end of the second resonant conduit can be open to the surrounding environment. Alternatively, the distal end of the first resonant conduit can be open to a surrounding environment, and the distal end of the second resonant conduit can be closed to the surrounding environment. As yet another alternative, both distal ends can be closed to a surrounding environment. In one aspect, the first resonant conduit can extend longitudinally within the second resonant conduit. 
     The first resonant conduit and the second resonant conduit can be spaced apart from each other to define a longitudinally extending gap between the first resonant conduit and the second resonant conduit. The longitudinally extending gap can be acoustically coupled with the acoustic chamber at a position adjacent the proximal end of the second resonant conduit. 
     The housing can include a shell member and a complementarily configured insert. The shell member can be configured to receive the insert in a mating engagement. When matingly engaged with each other, the shell member and the insert can define an outer boundary of at least a portion of the first acoustic resonator. The insert can define a through-hole aperture open to the acoustic chamber and the portion of the first acoustic resonator defined by the shell member and the insert. The portion of the first acoustic resonator defined by the shell member and the insert can include a resonant chamber and the aperture can provide a contraction positioned between the acoustic chamber and the resonant chamber. Alternatively, the portion of the first acoustic resonator defined by the shell member and the insert can include a resonant conduit and the aperture can further open to the resonant conduit such that the aperture extends the resonant conduit to the acoustic chamber. 
     The shell member can define a through-hole aperture extending from the resonant conduit to a surrounding environment. An acoustic mesh can be positioned over the through-hole aperture defined by the shell member. 
     According to another aspect, electronic devices are described. An electronic device can include an electro-acoustic transducer and circuitry to drive the electro-acoustic transducer to emit sound over a selected frequency bandwidth. For example, such circuitry can include a processor and a memory. The memory can contain instructions that, when executed by the processor, cause the electronic device to drive the electro-acoustic transducer to emit sound over the selected frequency bandwidth. A ported acoustic chamber is positioned adjacent the electro-acoustic transducer, and an acoustic resonator has a first side-branch resonator and a second side-branch resonator. The first side-branch resonator and the second-side-branch resonator are acoustically coupled with the acoustic chamber in parallel relative to each other. Such an arrangement can damp respective first and second frequencies corresponding to a tuning of the first side-branch resonator and the second side-branch resonator. 
     Also disclosed are associated methods, as well as tangible, non-transitory computer-readable media including computer executable instructions that, when executed, cause an audio appliance to implement one or more methods disclosed herein. Digital signal processors embodied in software, firmware, or hardware and being suitable for implementing such instructions also are described. 
     The foregoing and other features and advantages will become more apparent from the following detailed description, which proceeds with reference to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Referring to the drawings, wherein like numerals refer to like parts throughout the several views and this specification, aspects of presently disclosed principles are illustrated by way of example, and not by way of limitation. 
         FIG. 1  illustrates a cross-sectional view of a damped acoustic enclosure and a loudspeaker transducer. 
         FIG. 2  illustrates a frequency response of an acoustic enclosure damped with an acoustic resonator and a frequency response of an acoustic enclosure without such damping. 
         FIG. 3A  schematically illustrates an isometric view of a Helmholtz resonator. 
         FIG. 3B  schematically illustrates a cross-sectional view of the Helmholtz resonator shown in  FIG. 3A  along section III-III. 
         FIG. 4A  illustrates a pair of open-ended side-branch resonators acoustically coupled with an acoustic enclosure in parallel relative to each other. 
         FIG. 4B  illustrates a pair of closed-ended side-branch resonators acoustically coupled with an acoustic enclosure in parallel relative to each other. 
         FIG. 4C  illustrates a pair of Helmholtz resonators acoustically coupled with an acoustic enclosure in parallel relative to each other. 
         FIG. 5A  illustrates another pair of open-ended side-branch resonators acoustically coupled with an acoustic enclosure in parallel relative to each other. In  FIG. 5A , one of the resonators is at least partially surrounded by the other of the resonators. 
         FIG. 5B  illustrates another pair of side-branch Helmholtz resonators acoustically coupled with an acoustic enclosure in parallel relative to each other. In  FIG. 5B , one of the resonators is at least partially surrounded by the other of the resonators. 
         FIG. 6  schematically illustrates aspects of an acoustic enclosure incorporating one or more side-branch resonators. 
         FIG. 7  schematically illustrates a plan-view from above showing aspects of an acoustic enclosure incorporating one or more side-branch resonators. 
         FIG. 8  illustrates a cross-sectional view of another damped acoustic enclosure and loudspeaker transducer. 
         FIG. 9  illustrates a cross-sectional view of another damped acoustic enclosure and loudspeaker transducer. 
         FIG. 10  schematically illustrates a plan-view from above showing aspects of an acoustic enclosure incorporating a plurality of side-branch resonators. 
         FIG. 11  illustrates a media device and an associated audio accessory. 
         FIG. 12  illustrates an external, isometric view of a housing for an in-ear earphone. 
         FIG. 13  schematically illustrates anatomy of a typical human ear. 
         FIG. 14  schematically illustrates an in-ear earphone positioned in the human ear shown in  FIG. 13 . 
         FIG. 15  illustrates an exploded, isometric view of a housing for an in-ear earphone. 
         FIG. 16  illustrates a cross-sectional view of the housing shown in  FIG. 15  taken along section line XVI-XVI when assembled with a loudspeaker transducer. 
         FIG. 17  illustrates an isometric view of another housing for an in-ear earphone. 
         FIG. 18  illustrates a cross-sectional view of the housing shown in  FIG. 17  taken along section line XVIII-XVIII assembled with a loudspeaker transducer. 
         FIG. 19  illustrates a block diagram showing aspects of an audio appliance. 
     
    
    
     DETAILED DESCRIPTION 
     The following describes various principles related to acoustic chambers damped with one or more side-branch resonators, and related systems and methods. For example, some disclosed principles pertain to acoustic systems, methods, and components to damp resonance at certain frequencies, extending a frequency response of an acoustic enclosure. That said, descriptions herein of specific appliance, apparatus or system configurations, and specific combinations of method acts, are but particular examples of contemplated appliances, components, systems, and methods chosen as being convenient illustrative examples of disclosed principles. One or more of the disclosed principles can be incorporated in various other appliances, components, systems, and methods to achieve any of a variety of corresponding, desired characteristics. Thus, a person of ordinary skill in the art, following a review of this disclosure, will appreciate that appliances, components, systems, and methods having attributes that are different from those specific examples discussed herein can embody one or more presently disclosed principles, and can be used in applications not described herein in detail. Such alternative embodiments also fall within the scope of this disclosure. 
     I. Overview 
     Electronic devices can include one or more electro-acoustic transducers to emit sound. Given size constraints, some electronic devices incorporate electro-acoustic transducers configured as so-called “micro-speakers.” Examples of micro-speakers include a speakerphone speaker or an earpiece receiver found within an in-ear earphone, headphone, smart-phone, or other similar compact electronic device, such as, for example, a portable time-piece, or a tablet-, notebook-, or laptop-computer. 
     Micro-speakers operate on principles similar, but not necessarily identical, to larger electro-acoustic transducers. For example, as shown in  FIG. 1 , a micro-speaker  10  can incorporate a voice coil  12  and one or more corresponding magnets  14   a ,  14   b   [MOU1]  to cause the voice coil to reciprocate in correspondence with variations in electrical current through the voice coil. Although  FIG. 1  shows inner and outer magnets  14   a ,  14   b , another loudspeaker may have an inner magnet  14   a , and the illustrated structure  14   b  may be iron. Alternatively, another loudspeaker may have an outer magnet  14   b  and the illustrated structure  14   a  may be iron. 
     In any event, such micro-speakers can have a diaphragm  16  or other acoustic radiator so coupled with the voice coil  12  as to cause the acoustic radiator to emit sound as the voice coil reciprocates. However, given their limited physical size, output levels attainable by micro-speakers are limited. Some electronic devices acoustically couple such a micro-speaker with one or more open regions suitable for improving radiated sound, as in the nature of an acoustic chamber  18 . A diameter or major axis of a non-circular micro-speaker diaphragm can measure, for example, between about 3 mm and about 75 mm, such as between about 15 mm and about 65 mm, for example, between about 20 mm and about 50 mm. 
     An acoustic chamber  18  or other acoustic system can be characterized by a range of frequencies (sometimes referred to in the art as a “bandwidth” or a “frequency response”), as shown in  FIG. 2 , over which observed sound-pressure level (SPL)  20 ,  22  losses are less than a selected threshold level. Sometimes, a loss of less than three decibels (−3 dB) SPL is used to characterize the bandwidth provided by a given acoustic enclosure or other system. 
     An acoustic frequency having a quarter-wavelength substantially equal to a characteristic length of a ported acoustic chamber can resonate (e.g., form a standing wave) within the chamber, making radiated sound louder at that frequency than at other frequencies. The frequency at which this occurs is sometimes referred to in the art as the “Quarter Wave Resonance (QWR) frequency,” which represents a unit-of-measure for a given acoustic chamber and can differ among chambers with different geometries. 
     Additionally, an acoustic wave propagating at the QWR frequency (or above) can be 180-degrees out-of-phase relative to a loudspeaker diaphragm or other acoustic radiator exciting an air mass in the acoustic chamber. Consequently, sound loudness can rapidly decay at frequencies beyond the QWR frequency for a given acoustic chamber and negatively affect a perceived quality of sound radiated by the acoustic chamber. Such a decay in sound-pressure level is shown in  FIG. 2  to the right of peak  24  and to the right of peak  27 . 
     Referring again to  FIGS. 1 and 2 , an acoustic chamber  18  providing a relatively wider bandwidth  20  compared to a bandwidth  22  provided by another acoustic chamber (not shown) may be perceived as providing relatively better sound quality than the other chamber. As described more fully herein, one or more side-branch resonators  13   a ,  13   b  acoustically coupled with an acoustic chamber  18  can damp resonance at certain frequencies, as indicated by the arrow  21 , and extend a frequency response, as indicated by the arrow  23 , of the acoustic chamber compared to acoustic chambers that lack such damping. Consequently, an acoustic enclosure and/or an electronic device having an acoustic chamber damped with plural resonators can improve perceived sound quality compared to previous enclosures and/or devices. 
     In certain exemplary embodiments described more fully below, an in-ear earphone can have an acoustic chamber  18  partially bounded by a major surface  16   a  of a loudspeaker diaphragm  16 . The acoustic chamber can have an open port or vent  6  arranged to direct sound into a wearer&#39;s ear canal  7 . The earphone also can define one or more ducts, conduits, channels, grooves, chambers, ports, or combinations thereof, acoustically coupled with the acoustic chamber  18 . The arrangement of the one or more ducts, conduits, channels, grooves, chambers, ports, or combinations thereof, can modify a frequency response of the acoustic chamber  18 , and thus modify sound perceived by the wearer. 
     For example, the arrangement of the one or more ducts, conduits, channels, grooves, chambers, ports, or combinations thereof, can damp the frequency response of the acoustic chamber  18  at one or more, e.g., resonant, frequencies. Such damping can de-emphasize otherwise dominant frequencies and flatten the overall frequency response of the earphone. As well, or alternatively, such damping can extend a frequency response of the earphone. An earphone (or other loudspeaker enclosure) with a flattened and/or extended frequency response may be subjectively perceived by a wearer (or other user) as providing “better” sound quality than an earphone (or other enclosure) having one or more resonant peaks in its frequency response. Accordingly, such damping can provide a perceptually improved listening experience for an earphone wearer (or other user), requiring less equalization or other signal processing by, e.g., a media device. 
     II. Electro-Acoustic Transducers 
     There are numerous types of electro-acoustic transducers or drivers for loudspeakers (or micro-speakers). 
     Referring still to  FIG. 1 , a traditional direct radiator, for example, can include an electrodynamic loudspeaker  10  having a coil  12  of electrically conductive wire (sometimes referred to in the art as a “voice coil”) immersed in a static magnetic field, e.g., associated with the magnets  14   a ,  14   b , and coupled to a diaphragm  16  and a suspension system  15 . The conductive wire (e.g., copper clad aluminum) is sometimes referred to as a “voice coil wire.” 
     One or more magnets  14   a ,  14   b  (e.g., an NdFeB magnet) can be so positioned adjacent the voice coil  12  as to cause a magnetic field of the magnet(s)  14   a ,  14   b  to interact with a magnetic flux corresponding to an electrical current through the voice coil  12 . In the particular embodiment shown in  FIG. 1 , the voice coil  12  is positioned between an inner magnet  14   a  and an outer magnet  14   b . With the configuration in  FIG. 1 , the voice coil  12  is configured to move pistonically to and fro between a distal-most position and a proximal-most position relative to the inner magnet  14   a.    
     With loudspeakers as in  FIG. 1 , the diaphragm  16  and the coil  12  are movable in correspondence with each other. As current alternates in direction through the voice coil  12 , mechanical forces develop between the magnetic fields of the voice coil  12  and the magnet(s)  14   a ,  14   b , urging the voice coil (and thus the diaphragm  16 ) to move, e.g., to reciprocate. As the respective current or voltage potential alternates, e.g., at an audible frequency, the voice coil  12  (and diaphragm  16 ) can move, e.g., reciprocate pistonically, and radiate sound. 
     The transducer module  10  has a frame  17  and a suspension system  15  supportively coupling the acoustic diaphragm  16  with the frame. The diaphragm  16  can be stiff (or rigid) and lightweight. Ideally, the diaphragm  16  exhibits perfectly pistonic motion. The diaphragm, sometimes referred to as a cone or a dome, e.g., in correspondence with its selected shape, may be formed from aluminum, tungsten, paper, plastic, composites, or other materials that provide high stiffness, low mass, and are suitably formable during manufacture. 
     The suspension system  15  generally provides a restoring force to the diaphragm  16  following an excursion driven by interactions of the magnetic fields from the voice coil  12  and the magnet(s)  14   a ,  14   b . Such a restoring force can return the diaphragm  16  to a neutral position, e.g., as shown in  FIG. 1 . The suspension system  15  can maintain the voice coil  12  in a desired range of positions relative to the magnet(s)  14   a ,  14   b . For example, the suspension  15  can provide for controlled axial motion along an axis, z, transverse to the diaphragm  16  (e.g., pistonic motion) of the diaphragm  16  and voice coil  12  while largely preventing lateral motion or tilting that could cause the coil to strike other motor components, such as, for example, the magnet(s)  14   a ,  14   b.    
     A measure of resiliency (e.g., a position-dependent stiffness) of the suspension  15  can be chosen to match a force vs. deflection characteristic of the voice coil  12  and motor (e.g., magnet  14   a ,  14   b ) system. The illustrated suspension system  15  includes a surround extending outward of an outer periphery  15   a  of the diaphragm  16 . The surround member can be formed from a polyurethane foam material, a silicone material, or other pliant material. In some instances, the surround may be compressed into a desired shape by heat and pressure applied to a material in a mold or die. 
     The diaphragm  16  has a first major surface  16   a  partially bounding the acoustic chamber  18 , and an opposed second major surface  16   b . A first end of the voice coil  12  can be chemically or otherwise physically bonded to the second major surface  16   b  of the acoustic diaphragm  16 . For example, in  FIG. 1 , a voice coil  12  is physically coupled with the second major surface  16   b.    
     Alternatively, a voice coil wire can be wrapped around a non-conductive bobbin, sometimes referred to as a “voice coil former.” The voice coil former (not shown) can be integral with or physically attached, e.g., bonded, to the major surface  16   b  of the acoustic diaphragm  16 . Such a voice coil former can provide a platform for transmitting mechanical force and mechanical stability to the diaphragm  16 , generally as described above in connection with the voice coil. 
     The voice coil  12  and/or the voice coil former can have a cross-sectional shape corresponding to a shape of the major surface of the diaphragm  16 . For example, the diaphragm  16  can have a substantially circular, rectilinear, ovular, race-track or other shape when viewed in plan from above (or below). Similarly, the voice coil (or voice coil former) can have a substantially circular, rectilinear, ovular, race-track or other cross-sectional shape. In other instances, the cross-sectional shape of the voice coil former can differ from a shape of the diaphragm when viewed in plan from above (or below). 
     Other forms of driver are contemplated for use in connection with disclosed technologies. For example, piezo-electric drivers, ribbon drivers, and other flexural transducers can suspend an electro-responsive diaphragm within a frame. The diaphragm can change dimension or shape or otherwise deflect responsive to an electrical current or an electrical potential applied across the diaphragm (or other member physically coupled (directly or indirectly) with the diaphragm). As in the case of piezo-electric transducers, the deflection can arise by virtue of internal mechanical forces arising in correspondence to electrical current or potential. As in the case of, for example, electrostatic (or planar-magnetic) transducers, mechanical forces between a diaphragm and a stator arise by virtue of variations in electrostatic fields between the diaphragm and the stator, urging the diaphragm to vibrate and radiate sound. 
     And, although not shown, loudspeaker transducers can include other circuitry (e.g., application-specific integrated circuits (ASICs)) or electrical devices (e.g., capacitors, inductors, and/or amplifiers) to condition and/or drive electrical signals through the voice coil. Such circuitry can constitute a portion of a computing environment or audio appliance described herein. 
     III. Acoustic Enclosures 
     Referring still to  FIG. 1 , the loudspeaker module  10  is positioned in an acoustic enclosure  1 . The acoustic enclosure  1  can be a stand-alone apparatus, as in the case of, for example, a traditional bookshelf speaker or a smart speaker. Alternatively, the acoustic enclosure  1  can constitute a defined region within an encasement of another device, such as, for example, a smart phone or a tablet computer. In still other alternative embodiments, the acoustic enclosure can constitute a portion of an in-ear earphone, on on-ear headphone, or an over-the-ear headphone. 
     In any event, the acoustic enclosure  1  in  FIG. 1  includes a housing  2  defining an open interior region  3 . The loudspeaker diaphragm  16 , or more generally, the acoustic radiator, is positioned in the open interior region  3  and defines a first major surface  16   a  and an opposed second major surface  16   b . In  FIG. 1 , the open interior region  3  is partitioned by several walls  5  and the loudspeaker diaphragm  16  into an acoustic chamber  18  adjacent the first major surface  16   a  and an acoustically-sealed acoustic chamber  19  adjacent the second major surface  16   b . In  FIG. 1 , the acoustic chamber  18  and the acoustically-sealed acoustic chamber  19  are at least partially bounded by the first major surface  16   a  and the second major surface  16   b , respectively. 
     The housing  2  also defines an acoustic port  6  from the acoustic chamber  18  to a surrounding environment  7 . The port  6  and diaphragm  16  can be arranged in a so-called “side firing” arrangement, as in  FIG. 1 . That is to say, a cross-section (or mouth) of the port  6  can be oriented transversely relative to a major surface  16   a ,  16   b  of the diaphragm  16 . For example, in  FIG. 1 , the port  6  is oriented such that a vector normal to the mouth of the port extends orthogonally relative to a vector normal to the loudspeaker diaphragm  16 . 
     Although the illustrated acoustic port  6  has a cover  8  or other protective barrier to inhibit intrusion of dirt, water, or other debris into the acoustic chamber  18 , some acoustic ports have no distinct cover. For example, rather than defining a single aperture as in  FIG. 1 , the housing  2  can define a perforated wall (not shown) extending across the mouth of the port  6 . 
     Although the acoustic port  6  is illustrated in  FIG. 1  generally as being an aperture defined by the housing wall, in some instances, the acoustic port  6  includes an acoustic duct or channel extending from the acoustic chamber  18  to an outer surface  2   a  of the housing  2  or other encasement. For example, aesthetic or other design constraints for an electronic device may cause the acoustic chamber  18  to be spaced apart from the outer surface  2   a  of the housing or other encasement. Consequently, a duct or other acoustic channel (not shown) can extend from the acoustic chamber  18  to the outer surface to acoustically connect the acoustic chamber  18  to the surrounding environment  7 . Although not shown, such a duct can have internal baffles to define a circuitous path from a proximal end adjacent the acoustic chamber  18  to a distal end adjacent the outer surface  2   a.    
     As shown in  FIG. 1 , the acoustic chamber  18  has a characteristic length, L, extending between an interior housing wall  5  and the mouth of the port  6 . In general, a fundamental (or QWR) frequency of an acoustic chamber  18  with a characteristic length, L, is a frequency, f, having a wavelength, λ, equal to 4*L. Stated differently, a resonant frequency, f res , for a typical ported acoustic chamber  18  can be estimated according the following relationship:
 
 f   res   =c/ 4 L  
 
where c is about 343 m/s, the approximate speed of sound in air, at sea level and at a temperature of 20° C.  FIG. 2  shows a representative frequency response  22  for such a ported acoustic chamber  18 . Note the rapid loss of sound pressure level (SPL) at frequencies above f res  where SPL reaches a local maximum 24.
 
     However, the enclosure  1  shown in  FIG. 1  also includes an acoustic resonator  11  acoustically coupled with the acoustic chamber  18 . The resonator can be configured to resonate at a frequency substantially identical to f res  for the acoustic chamber  18 . Alternatively, the resonator  11  can be configured to resonate one or more frequencies different from f res  for the acoustic chamber  18 . 
     An acoustic resonator  11  coupled with the acoustic chamber  18  tends to damp a frequency response of the acoustic chamber  18  at the resonator&#39;s resonant frequency. When the resonant frequency of the resonator  11  matches f res , the local peak  24  ( FIG. 2 ) at f res  can be diminished. Stated differently, the presence and configuration of the acoustic resonator  11  can spread the energy that otherwise would be concentrated at the frequency, f res , over a wider range of frequencies. Consequently, the sound loudness, or level, radiated by the diaphragm  16  and emitted by the acoustic enclosure  1  does not increase at or near the QWR frequency, f res , as dramatically as would otherwise be radiated and emitted at or near that frequency absent the acoustic resonator. Moreover, the damped enclosure  1  can maintain a loudness or level over a wider range of frequencies, or bandwidth,  20  compared to a bandwidth  22  attained without damping. 
     To further illustrate,  FIG. 2  shows a representative frequency response  20  for a ported acoustic chamber damped with a resonator  11  as shown in  FIG. 1  and just described. The response  20  corresponding to the damped acoustic chamber  18  has both a lower peak SPL  26 ,  27  and an extended bandwidth  23  compared to the representative response for an acoustic chamber without damping by an acoustic resonator. 
     More particularly, the peak  24  depicts the increased sound level at the QWR frequency, f res , for the un-damped enclosure. As well, the rapid decay in level at frequencies above f res , depicts fall-off in sound loudness at those higher frequencies. Referring now to the frequency response  20  for the damped acoustic chamber  18 , the sound loudness  28  at f res  is substantially lower than at the peak  24 , yet is similar in magnitude to sound loudness at lower frequencies. Nonetheless, the sound loudness modestly increases over narrow frequency bands above and below f res  (depicted by peaks  26 ,  27 ) for the acoustic chamber  18  damped with the acoustic resonator  11 . 
     Some acoustic resonators  11  coupled with the acoustic chamber  18  include a plurality of constituent resonant structures coupled in series and/or in parallel with each other relative to the acoustic chamber  18 . An acoustic resonator  11  having a plurality of constituent resonant structures  13   a ,  13   b  acoustically coupled with each other in parallel relative to the acoustic chamber  18 , as shown for example in  FIG. 1 , can provide more degrees-of-freedom for tuning the damping provided at one or more selected frequencies compared to damping provided by a single resonant structure. In general, acoustic resonators described herein can include any number and type of constituent resonant structures acoustically coupled with the acoustic chamber  18  and coupled with each other in series and/or in parallel relative to the acoustic chamber  18 . 
     When plural resonant structures are coupled with an acoustic chamber in parallel relative to each other, each resonant structure is sometimes referred to in the art as a “side-branch resonator.” As noted above, each respective side-branch resonator can resonate at a corresponding frequency, damping the acoustic chamber  18  at each respective frequency. And, plural side-branch resonators  13   a ,  13   b  can provide additional degrees-of-freedom for tuning the enclosure compared to a single side-branch resonator. 
     IV. Acoustic Resonators 
     In general, the acoustic resonator  11  shown in  FIG. 1  can be any form of acoustic resonator. According to aspects of this disclosure, the acoustic resonator  11  refers to a plurality of side-branch resonators or other constituent resonant structures acoustically coupled with the acoustic chamber  18  in parallel relative to each other. 
     In turn, each constituent resonant structure in the resonator  11  can have one or more corresponding chambers or cavities configured to resonate at a respective frequency (e.g., a resonant frequency) with greater amplitude than at other frequencies. For example, a geometry of each resonant structure can be tuned to resonate at a corresponding frequency. When taken together, such a plurality of constituent side-branch resonators cause the resonator  11  to resonate at each of the respective frequencies corresponding to the tuned geometries. Accordingly, a resonator having a plurality of constituent, side-branch resonators can damp the acoustic chamber  18  at a corresponding plurality of frequencies, extending the frequency response and improving a perceptual quality of sound emitted by the enclosure  1 . 
       FIGS. 3A and 3B  show an example of a chamber-based resonant structure  30 , sometimes referred to in the art as a Helmholtz resonator. As shown in  FIGS. 3A and 3B , a Helmholtz resonator  30  can have a closed resonant chamber  32  (or cavity) coupled to a surrounding environment  34  by way of an acoustic channel (or duct)  36 . The acoustic channel  36  can extend from a proximal end  35  open to the resonant chamber  32  to a distal end  37  open to the surrounding environment  34 . As well, the acoustic channel  36  can define a contraction (e.g., a smaller cross-sectional area) relative to the resonant chamber  32  and the surrounding environment  34 . 
     A given Helmholtz resonator&#39;s resonant frequency (i.e., the frequency at which the given Helmholtz resonator resonates with a relatively larger amplitude as compared to other frequencies) corresponds the physical arrangement of the Helmholtz resonator. For example, the resonant frequency can correspond to a volume of the resonant chamber (or cavity)  32 , a characteristic width (or diameter) of the acoustic channel  36  at the proximal end  35 , a characteristic width (or diameter) of the acoustic channel  36  at the distal end  37 , a length of the acoustic channel  36  from the proximal end  35  to the distal end  37 , as well as a whether the distal end of the channel has a flange  38  or wall extending, e.g., radially outward, of the distal end  37 . 
     Other resonant structures, e.g., shown in  FIGS. 4A and 4B , can be configured as an acoustic transmission line (sometimes also referred to in the art as a “waveguide”). For example, an acoustic duct (or conduit)  46   a ,  46   b ,  46   c ,  46   d  can function as a waveguide and be tuned to damp one or more resonant frequencies in the acoustic chamber  18 . These other forms of resonant structures (e.g., an open-ended or a closed-ended duct) may be substituted for or combined with a Helmholtz resonator (e.g., acoustically coupled with an acoustic chamber in series or in parallel with a Helmholtz resonator). 
     Referring to  FIG. 4A , a pair of side-branch resonators  41   a ,  42   a  is acoustically coupled with the acoustic chamber in a parallel relative to each other. The first side-branch resonator (or waveguide)  41  has a resonant conduit  46   a  extending from a proximal end  45   a  to a distal end  47   a . An aperture in a wall  48  of the acoustic chamber  18  defines an opening at the proximal end  45   a , coupling the resonant conduit  46   a  with the acoustic chamber  18  (e.g.,  FIG. 1 ). An aperture at the opposed distal end  47   a  vents the conduit  46   a  to a local environment  7 . 
     The resonant conduit  46   a  of the waveguide  41   a  spans a longitudinal length from the proximal end  45   a  to the distal end  47   a . The illustrated waveguide  41   a  can have a circular cross-sectional shape and a substantially uniform cross-sectional dimension t 1 , though the cross-sectional shape, the cross-sectional dimension, or both, can vary with position between the proximal end  45   a  and distal end  47   a . For example, the dimension t 1  can increase with increasing distance from the proximal end and define a “horn” shape (e.g., where the cross-sectional dimension at the distal end  47   a  is comparatively larger than the cross-sectional dimension at the proximal end  45   a ). Alternatively, the dimension t 1  can decrease with increasing distance from the proximal end. And, the duct  46   a  need not have a circular cross-section; the cross-sectional shape can have any regular or irregular shape. 
     The frequencies at which the resonator  41   a  resonates (and thus the frequencies within the frequency response  22  of the enclosure  1  that the resonator  41   a  can damp) correspond to the physical arrangement of the resonator. For example, a resonant frequency for an acoustic waveguide can correspond to the cross-sectional dimension t 1 , the cross-sectional shape, the longitudinal length of the duct  46   a  between the proximal end  45   a  and the distal end  47   a , a contour of the duct (e.g., whether the duct expands or contracts moving longitudinally from the proximal end to the distal end), as well as whether the distal end of the channel  46   a  is open ( FIG. 4A ) or closed (e.g., channel  46   c  in  FIG. 4B ), as well as whether the distal end has a flange  49  or wall extending, e.g., radially outward, from the distal end  47   a.    
     Referring still to  FIG. 4A , a second side-branch resonator  42   a  is illustrated. The illustrated resonant structure  42   a  is shown as an open-ended waveguide having a physical configuration similar to the first side-branch resonator  41   a  just described. For example, the second waveguide  42   a  has a resonant conduit  46   b  extending from a proximal end  45   b  to a distal end  47   b . A second aperture in the wall  48  defines an opening at the proximal end  45   b , coupling the resonant conduit  46   b  with the acoustic chamber  18  ( FIG. 1 ) in parallel relative to the first waveguide  41   a . An aperture at the opposed distal end  47   b  vents the conduit  46   b  to the local environment  7 . As with the resonator  41   a , the resonator  42   a  can have a uniform or a non-uniform cross-sectional shape or dimension. 
     Referring still to  FIG. 4A , each aspect of one side-branch resonator  41   a  can be identical to or different from the corresponding aspect of an adjacent side-branch resonator  42   a . Or, certain aspects of one resonator  41   a  can be identical to the corresponding aspects of the other resonator  42   a , while other aspects of can differ between the resonators. As but one example, both ducts  46   a ,  46   b  can have identical cross-sectional shapes and dimensions, but one duct  46   a  can be shorter or longer than the other duct  46   b.    
     As a consequence, the resonant frequency of each respective side-branch resonator  41   a ,  42   a  may differ from that of the other resonator, damping the frequency response of the acoustic chamber  18  at each of the resonant frequencies. By damping the frequency response of the acoustic chamber at a plurality of resonant frequencies, a plurality of peaks in the frequency response  22  can be flattened, reducing the computational overhead needed to equalize audio playback and physically extending the frequency response of the acoustic chamber. 
     As noted, the waveguides  41   a ,  42   a  ( FIG. 4A ) have open-ended ducts  46   a ,  46   b . By contrast, the side-branch resonators  41   b ,  42   b  ( FIG. 4B ), which are similar in form to the waveguides  41   a ,  42   a , have closed-ended ducts  46   c ,  46   d . The closed ends of the ducts  46   c ,  46   d  cause the waveguides  41   b ,  42   b  to resonate at a different frequency than the waveguides  41   a ,  42   a  having open-ended ducts  46   a ,  46   b  when all other aspects (e.g. dimensions) of the waveguides are identical. For example, even if the waveguides  41   a ,  42   a  have identical lengths and cross-sectional dimensions, shapes and contours, as the waveguides  41   b ,  42   b , the waveguides  41   a ,  42   a  will resonate at a different frequency than the waveguides  41   b ,  42   b  simply by virtue of the difference in their end configurations. 
     Referring now to  FIG. 4C , a pair of Helmholtz resonators  41   c ,  42   c  is shown. Each Helmholtz resonator  41   c ,  42   c  is configured generally as described above in connection with  FIGS. 3A and 3B , though specific aspects (e.g., chamber volume, duct length, etc.) may differ between the resonators  41   c ,  42   c . Such differences can cause each resonator  41   c ,  42   c  to resonate at a respective frequency, and when combined as depicted in  FIG. 4C , to damp the frequency response  22  of the acoustic chamber  18  at the respective frequencies. 
     Aspects of similarity or dissimilarity between side-branch resonators acoustically coupled to the chamber  18  can include dimensional characteristics (e.g., length of the ducts  46   a ,  46   b , cross-sectional dimension or shape, etc.). And, aspects of similarity or dissimilarity can include overall configuration of the waveguides themselves. For example, one side-branch resonator coupled with the acoustic chamber  18  may be an open-ended waveguide as described in connection with  FIG. 4A , another side-branch resonator coupled with the acoustic chamber  18  may be a Helmholtz resonator as described in connection with  FIGS. 3A and 3B , and yet another side-branch resonator coupled with the acoustic chamber  18  may be a closed-ended waveguide as described in connection with  FIG. 4B . For example, the side-branch resonator  42   a  shown in  FIG. 4A  can be replaced with a closed-ended side-branch resonator  41   b  or  42   b  shown in  FIG. 4B . Alternatively, a Helmholtz resonator can replace the side-branch resonator  42   a  shown in  FIG. 4A . As yet another alternative, a Helmholtz resonator can replace the side-branch resonator  42   b  shown in  FIG. 4B . Thus, a pair of side-branch resonators can consist of any of the following combinations: two open-ended waveguides ( FIG. 4A ), two closed-ended waveguides ( FIG. 4B ), two Helmholtz resonators ( FIG. 4C ), one open-ended waveguide and one closed-ended waveguide, one open-ended waveguide and one Helmholtz resonator, or one closed-ended waveguide and one Helmholtz resonator. 
     As well, it should be understood that more than two side-branch resonators can be incorporated in a loudspeaker enclosure to provide tunable damping across a plurality of peaks in a frequency response (e.g., frequency response  22 ). By coupling a plurality of distinct side-branch resonators with an acoustic chamber (e.g., in series or in parallel relative to one of more other side-branch resonators), dimensions (and thus damping frequency) of each side-branch resonator can be adjusted with little or no effect on frequency-damping provided by another side-branch resonator. As a consequence, a plurality of resonant peaks in the frequency response of an acoustic enclosure can be selectively damped by such a plurality of side-branch resonators acoustically coupled with the enclosure. 
     In  FIGS. 4A, 4B, and 4C , each pair of constituent resonant structures  41   a ,  42   a ;  41   b ,  42   b ; and  41   c ,  42   c  is acoustically coupled with the acoustic chamber  18  in parallel relative to each other. Further, the resonant structures are physically juxtaposed relative to each other. Nonetheless, one constituent resonant structure may be partially or wholly positioned within another constituent resonant structure. 
     For example,  FIG. 5A  shows a first side-branch resonator  51   a  at least partially surrounding a second side-branch resonator  52   a . In  FIG. 5A , the side-branch resonators  51   a ,  52   a  are acoustically coupled with an acoustic chamber  18  in parallel relative to each other. Each of the side-branch resonators  51   a ,  52   a  also is open to an external environment  7  and configured as an open-ended waveguide. As indicated by  FIG. 5A , the resonator  51   a  can have an annular cross-sectional shape surrounding the resonator  51   b . Similarly, the resonator  51   b  can have a circular cross-sectional shape. Of course, the cross-sectional shapes need not be annular and circular, respectively. Rather, each resonator can have any selected regular or irregular cross-sectional shape that allows the external resonator  51   a  to extend around a perimeter of the inner resonator  52   a , or vice-versa. Similarly, one or both of the resonators  51   a ,  51   b  can have a closed terminal end, rather than an open terminal end as illustrated in  FIG. 5A . 
       FIG. 5B  illustrates another example of a side-branch resonator  51   c  surrounding another side-branch resonator  51   d . In  FIG. 5B , each side-branch resonator  51   c ,  51   d  is arranged as a Helmholtz resonator (e.g., having a neck region and an enlarged, terminal chamber). Although not illustrated, a Helmholtz resonator can surround or enclose an open-ended or a closed-ended waveguide in a manner shown in  FIGS. 5A and 5B . Similarly, an open-ended or a closed-ended waveguide can surround or enclose a Helmholtz resonator in a manner shown in  FIGS. 5A and 5B . 
     IV. Damped Enclosures 
       FIG. 6  shows a schematic, cross-sectional view of a loudspeaker enclosure  60  having a housing  61  and a port  62  opening from an acoustic chamber  68 . As with the enclosure  1  in  FIG. 1 , the enclosure  60  includes a loudspeaker diaphragm  66  to emit sound and a side-branch resonator  63  acoustically coupled with the acoustic chamber  68 . The arrangement of the resonator  63  damps one or more selected frequencies within the chamber  68 . In  FIG. 6 , the resonator  63  is arranged as a Helmholtz resonator having a neck  65  that opens to a resonant chamber  64  with volume, VI. 
       FIG. 7  illustrates a top-plan view of a loudspeaker enclosure  70  similar to the enclosure  60 . The enclosure  70  has a housing  71  and a port  72  opening to a local environment from an acoustic chamber  78 . A diaphragm  76  emits sound within the chamber  78 . A first side-branch resonator  73   a  is acoustically coupled with the acoustic chamber  78  in parallel relative to a second side-branch resonator  73   b . In  FIG. 7 , each side-branch resonator  73   a ,  73   b  is configured as a Helmholtz resonator having a corresponding neck  75   a ,  75   b  that opens to a corresponding resonant chamber  74   a ,  74   b  from the acoustic chamber  78 . 
     Each side-branch resonator can be configured to resonate at a selected frequency, allowing each side-branch resonator to damp a frequency response of the acoustic chamber  78  at a corresponding frequency. For example, the first resonator  73   a  can resonate at a first frequency and the second resonator  73   b  can resonate at a second frequency. By acoustically coupling the first and the second side-branch resonators  73   a ,  73   b  with the acoustic chamber  78  in parallel relative to each other, the frequency response of the acoustic chamber  78  can be damped at the first frequency and the second frequency, extending a frequency response of the acoustic chamber  78  generally as described above in relation to  FIG. 2 . 
     In  FIG. 7 , an optional side-branch resonator is depicted using dashed lines. The optional side-branch resonator illustrates that more than two side-branch resonators may be acoustically coupled with the acoustic chamber  78  in parallel relative to each other. The inclusion of a selected number of side-branch resonators permits damping a corresponding number of frequencies in the frequency response of the acoustic chamber  78 , and can provide a suitable number of degrees-of-freedom to system designers. 
       FIGS. 8 and 9  illustrate respective side-views of a cross-section through a loudspeaker enclosure generally as in  FIG. 1 . The loudspeaker enclosure  80  is similar to the enclosure  1  in  FIG. 1  in most respects, except that the combined resonator  11  (consisting of the constituent side-branch resonators  13   a ,  13   b ) is omitted. Instead, an open-ended waveguide  83   a  is shown in  FIG. 8 . The open-ended waveguide  83   a  has a duct length I 1  extending from a proximal end opening to the acoustic chamber  18  to a distal end opening to a local environment  7  surrounding the enclosure  80 , damping a frequency response of the acoustic chamber  18  at a corresponding frequency. The waveguide  83   a  has a cross-sectional dimension t 1 . 
     The enclosure  90  shown in  FIG. 9  is similar in most respects to the enclosure  80  shown in  FIG. 8 , except that the open-ended waveguide  83   a  has been removed and replaced with a closed-ended waveguide  93   a . The closed-ended waveguide  93   a  remains a side-branch resonator acoustically coupled with the acoustic chamber  18 , as with the waveguide  83   a . The closed-ended waveguide  93   a  has a duct length I 2  extending from a proximal end opening to the acoustic chamber  18  to a closed distal end, damping a frequency response of the acoustic chamber  18  at a corresponding frequency. The waveguide  93   a  has a cross-sectional dimension t 2 . 
     One or more additional side-branch resonators also are positioned outside the planes depicted in  FIGS. 8 and 9 , and thus are not shown in those drawings. Nonetheless, one or more additional side-branch resonators are included in the enclosure  80  and the enclosure  90 , generally as described above, e.g., in connection with  FIGS. 6 and 7 . Each additional side-branch resonator damps a frequency response of the respective enclosure  80 ,  90  at each of one or more corresponding additional frequencies. 
       FIG. 10  shows a top plan view of another enclosure  100 . The enclosure  100  is arranged similarly to the enclosure shown in  FIG. 7  and has a plurality of side-branch resonators  103   a ,  103   b  acoustically coupled with the acoustic chamber  108  in parallel relative to each other. However, rather than extending from adjacent walls of the acoustic chamber as in  FIG. 7 , the side-branch resonators  103   a ,  103   b  extend from opposed walls of the acoustic chamber, with the diaphragm  106  positioned therebetween. A loudspeaker diaphragm  106  emits sound into the chamber  108 , and a respective frequency resonates within each respective side-branch resonator  103   a ,  103   b , damping a frequency response of the acoustic chamber  108  at corresponding frequencies. 
     In  FIG. 10 , the first side-branch resonator  103   a  has a first region  105   a  and a second region  107   a . The first region  105   a  has a smaller cross-sectional dimension than the second region  107   a , which has a cross-sectional area that expands from a region adjoining the first region  105   a  to an opposed terminal end. The terminal end of the resonator  103   a  is open to a local environment. The second side-branch resonator  103   b  is similar to the first side-branch resonator  103   a , except that the terminal end of the second region  107   b  is closed. As with the resonator  103   a , the first region  105   b  of the second resonator  103   b  extends from the acoustic chamber  108  to the second region  107   b , and the second region  107   b  has a cross-sectional area that expands from a region adjoining the first region  105   b  to the closed terminal end. Also shown in  FIG. 10  using dashed lines is another, optional, side-branch resonator  103   c . As with the enclosure  70  shown in  FIG. 7 , any of the side-branch resonators shown in  FIG. 10  can be replaced with a Helmholtz-style resonator (e.g.,  FIGS. 3A and 3B ) or a differently configured waveguide. 
     V. In-Ear Earphones 
     An acoustic enclosure incorporating one or more side-branch resonators can be incorporated in any of a variety of devices, including portable media devices and accessories used with media devices. For example, in-ear earphones can incorporate one or more side-branch resonators as described herein. 
       FIG. 11  shows a portable media device  110  suitable for use with a variety of accessory devices. The portable media device  110  can include a touch sensitive display  112  configured to provide a touch sensitive user interface for controlling the portable media device  110  and in some embodiments any accessories to which the portable media device  110  is electrically or wirelessly coupled. For example, the media device  110  can include a mechanical button  114 , a tactile/haptic button, or variations thereof, or any other suitable ways for navigating on the device. The portable media device  110  can also include a communication connection, e.g., one or more hard-wired input/output (I/O) ports that can include a digital I/O port and/or an analog I/O port, or a wireless communication connection. The portable media device can include a damped acoustic enclosure arranged as described above. 
     An accessory device can take the form of, for example, an audio device that includes two separate earbuds  120   a  and  120   b  (also referred to in the art as “in-ear earphones” or, more specifically, “intra-canal earphones” or “intra-concha earphones”). Each of the earbuds  120   a  and  120   b  can include wireless receivers, transmitters or transceivers capable of establishing a wireless link  116  with the portable media device  110  and/or with each other. Alternatively, and not shown in  FIG. 11 , the accessory device can take the form of a wired or tethered audio device that includes separate earbuds. Such wired earbuds can be electrically coupled to each other and/or to a connector plug by a number of wires. The connector plug can matingly engage with one or more of the I/O ports and establish a communication link over the wire and between the media device and the accessory. In some wired embodiments, power and/or selected communications can be carried by the one or more wires and selected communications can be carried wirelessly. 
     Intra-concha earphones typically fit in the outer ear and rest just above the inner ear canal. Intra-concha earphones do not typically seal within the ear canal. Sound quality, however, may not be optimal to the user because sound can leak from the ear-phone and not reach the ear canal. In addition, due to the differences in ear shapes and sizes among users, different amounts of sound may leak thus resulting in inconsistent acoustic performance between or among users. 
     Referring now to  FIGS. 15 and 16 , intra-canal earphones, on the other hand, are typically designed to fit within and form a seal with the user&#39;s ear canal. Intra-canal earphones therefore have an acoustic output tube portion that extends from the housing. The open end of the output tube portion can be inserted into the wearer&#39;s ear canal. The tube portion typically forms, or is fitted with, a flexible and resilient tip or cap made of a rubber or silicone material. The tip may be custom molded for the discerning audiophile, or it may be a high-volume manufactured piece. When the tip portion is inserted into the user&#39;s ear, the tip compresses against the ear canal wall and creates a sealed (essentially airtight) cavity inside the canal. Although the sealed cavity allows for maximum sound output power into the ear canal, it can amplify external vibrations, thus diminishing overall sound quality. 
       FIG. 12  schematically illustrates common anatomy  130  of a human ear.  FIG. 13  shows an earbud positioned within an ear  130  of a user during use. For example, when properly positioned in a user&#39;s ear  130 , the earphone housing  150  ( FIGS. 14 and 15 ) can rest in the user&#39;s concha cavum  133  between the user&#39;s tragus  136  and anti-tragus  137 . As shown in  FIG. 13 , a portion of the housing  150  can extend into the ear canal  131 . Those of ordinary skill in the art will understand and appreciate that, although a housing  150  is described in relation to the concha cavum  133 , other external regions of an earphone can be contoured relative to another region of a human ear  130 . For example, other ear-contact regions are possible. 
     The housing  150  illustrated in  FIG. 13  also defines a lateral surface from which a post  135  extends. The post  135  can include a microphone transducer and/or other component(s) such as, for example, a battery or, in context of a wired earbud, one or more wires. Additionally, or alternatively, the post can incorporate one or more side-branch resonators acoustically coupled with an acoustic chamber in the housing  150 , damping the acoustic chamber in a manner as described herein. When the earbud is donned, as in  FIG. 13 , the post  135  can extend generally parallel to a plane defined by the user&#39;s earlobe  139  at a position laterally outward of a gap  138  between the user&#39;s tragus  136  and anti-tragus  137 . 
     Further, the earbud housing  150  defines an acoustic port  152   a . The port  152   a  provides an acoustic pathway from an acoustic chamber  158  ( FIG. 14 ) in an interior region of the housing  150  to an exterior of the housing. For example, as shown in  FIG. 13 , the port  152   a  aligns with and opens to the user&#39;s ear canal  131  when the earbud is donned as described above. A mesh, screen, film, or other protective barrier (not shown) can extend across the port  152   a  to inhibit or prevent intrusion of debris into the interior of the housing. 
     As shown in  FIGS. 14 and 15 , some earbud the housings  150  define a boss or other protrusion  151  from which the port  152   a  opens. The boss or other protrusion  151  can extend into the ear canal  131  ( FIG. 13 ) and can contact the walls of the canal over a contact region. Alternatively, referring again to  FIG. 15 , the boss or other protrusion  151  can provide a structure to which a resiliently flexible cover  152  such as, for example, a silicone cover, can attach and provide an intermediate structure forming a sealing engagement between the walls of the user&#39;s ear canal  131  and the housing  150 . The sealing engagement can enhance perceived sound quality, as by passively attenuating external noise and inhibiting a loss of sound power from the earbud. 
     Referring still to  FIGS. 14 and 15 , an earbud housing  150  incorporating one or more side-branch resonators is shown. The illustrated housing  150  is a two-piece housing having an outer housing member  157  and an inner housing member  159 . The outer housing member  157  matingly receives the inner housing member  159 . The outer housing member  157  and the inner housing member  159  are so complementarily configured relative to each other as to define one or more constituent resonators of the type described above to damp an acoustic chamber  158  defined at least in part by an interior region of the inner housing member  159 . 
     For example, the illustrated outer housing member  157  is a shell having a convex outer surface  153   a  and a concave inner surface  153   b . The inner surface  153   b  defines a recessed groove  154 . The illustrated inner housing member  159  also is a shell having a convex outer surface  153   c  and a concave inner surface  153   d . The inner housing member  159  also defines an aperture  156  extending through the shell from the inner surface  153   d  to the outer surface  153   c.    
       FIG. 15  shows a cross-sectional view of an acoustic enclosure  160  incorporating an earbud housing  150 . As shown in  FIG. 15 , the aperture  156  can be so positioned relative to the inner housing member  159  as to overlie and acoustically couple with the recessed groove  154  defined by the outer housing member  157 , e.g., when the inner shell is seated against the convex inner surface  153   b  of the outer shell. The aperture  156  defines an acoustic port acoustically coupling the inner region  158  of the convex inner surface  153   d  with the recessed groove  154  defined by the outer shell. 
     When the inner shell  159  and the outer shell  157  are assembled together as shown in  FIG. 15 , the port  156  and the groove  154  together define a side-branch resonator acoustically coupled with the acoustic chamber  158 , damping the frequency response of the enclosure  160  when driven by the diaphragm  162 . According to selected dimensions and contours of the groove  154  and the aperture  156 , such a side-branch resonator may exhibit resonance characteristic predominantly similar to a Helmholtz resonator, predominantly similar to a waveguide, or similar to a combination of a Helmholtz resonator and a waveguide. 
     To facilitate tuning of the side-branch resonator, an acoustic mesh  155  can be positioned to overlie the port  156 . Optionally, one or more additional side-branch resonators can be incorporated in the enclosure  160  (or in an earbud stem as described above). And, as shown in  FIG. 15 , the inner housing member  159  can define another aperture (not shown) to acoustically couple the acoustic chamber  158  with an outlet port  152   a , e.g., to a wearer&#39;s ear canal, defined by the outer housing member  157 . And, although only one groove  154  and one port  156  are depicted in  FIG. 15  for sake of clarity, it shall be understood that additional side-branch resonators formed from groove-and-port combinations can be defined by the housings  157 ,  159 . Moreover, the groove  154  need not be defined by the outer housing  157 . Rather, the convex outer surface of the inner shell  159  can define a recessed groove extending from the aperture  156 , and a corresponding region of the inner surface  153   b  can overlie the groove, defining a side-branch resonator. 
     As shown in  FIGS. 16 and 17 , a side-branch resonator may extend outward of an earbud housing. For example, the housing  170  is a shell similar in construction to the outer shell  157  insofar as it defines an outlet port extending through a protrusion  171  and the protrusion  171  has a compliant member  172  to sealingly engage a wearer&#39;s ear canal. However, unlike the outer shell  157 , the housing  170  also defines an aperture  176  extending from an inner surface  173   b  to an outer surface  173   a.    
     As best illustrated in the cross-sectional view of the acoustic enclosure  180  in  FIG. 17 , an acoustic duct  174  extends from the aperture  176  outward of the outer surface  173   a , defining a side-branch resonator acoustically coupled with the acoustic chamber  178  ( FIG. 17 ). More particularly, the illustrated acoustic duct  174  defines a waveguide to acoustically damp an acoustic response of the acoustic chamber  178  when driven by the diaphragm  182 . Nonetheless, the duct  174  can be contoured differently so as to define a Helmholtz resonator (rather than a waveguide) in combination with the port  176 . 
     Referring again to  FIG. 16 , the duct  174  can have an open or a closed terminal end, defining, respectively, an open-ended or a closed-ended waveguide. As well, the acoustic duct  174  can define a longitudinal curve (e.g., it can be “bent”) to further define a concha- or a pinna-engaging member that urges against a wearer&#39;s concha  133  or pinna  132  ( FIG. 12 ), respectively, when the enclosure  180  is donned by a wearer. 
     To enhance a wearer&#39;s comfort, a concha-engaging region of the duct  174  can incorporate a compliant member (not shown). As well, such a compliant member can conform to person-to-person variations in contour among the tragus  136 , anti-tragus  137 , and concha cavum  133 . Such a compliant member (not shown) can accommodate a selected degree of compression that allows secure seating of enclosure  180  within the ear  130  of the user, e.g., within the concha cavum  133 . Although not illustrated, the enclosure  180  can incorporate one or more additional side-branch resonators as described herein. 
     Further, the enclosure  180  can include an externally-extending side-branch resonator similar to the resonator  174 . In that instance, the inner shell  159  and the outer shell  157  define respective apertures extending through the respective shells and positioned in alignment with each other to acoustically couple the duct of the side-branch resonator  174  with the acoustic chamber  158 . 
     The housing of any acoustic enclosure described herein can be formed of any material or combination of materials suitable for acoustic enclosures. For example, some housings are formed of acrylonitrile butadiene styrene (ABS). Other representative materials include polycarbonates, acrylics, methacrylates, epoxies, and the like. A compliant member described herein can be formed of, for example, polymers of silicone, latex, and the like. 
     VI. Electronic Devices with Damped Acoustic Chambers 
     Electronic devices, including those having damped acoustic chambers of the type described above, are described by way of reference to a specific example of an audio appliance. Electronic devices represent but one possible class of computing environments which can incorporate an acoustic enclosure, and more particularly, a damped acoustic chamber, as described herein. Nonetheless, electronic devices, including the portable media device  110  ( FIG. 11 ) are succinctly described in relation to a particular audio appliance  190  to illustrate an example of a system incorporating and benefitting from a damped acoustic chamber. 
     As shown in  FIG. 18 , an audio appliance  190  or other electronic device can include, in its most basic form, a processor  194 , a memory  195 , and a loudspeaker or other electro-acoustic transducer  197 , and associated circuitry (e.g., a signal bus, which is omitted from  FIG. 19  for clarity). The memory  195  can store instructions that, when executed by the processor  194 , cause the circuitry in the audio appliance  190  to drive the electro-acoustic transducer  197  to emit sound over a selected frequency bandwidth. 
     In addition, the audio appliance  190  can have a ported acoustic chamber positioned adjacent the electro-acoustic transducer, together with an acoustic resonator acoustically coupled with the acoustic chamber. As described above, the acoustic resonator can include a first side-branch resonator and a second side-branch resonator acoustically coupled with the acoustic chamber in parallel relative to each other. The acoustic resonator can be arranged to resonate at a selected frequency corresponding to a resonant frequency of the ported acoustic chamber to extend a frequency bandwidth of sound emitted by the electronic device compared to the selected frequency bandwidth emitted by the electro-acoustic transducer. 
     The audio appliance  190  schematically illustrated in  FIG. 18  also includes a communication connection  196 , as to establish communication with another computing environment. As well, the audio appliance  190  includes an audio acquisition module  191  having a microphone transducer  192  to convert incident sound to an electrical signal, together with a signal conditioning module  193  to condition (e.g., sample, filter, and/or otherwise condition) the electrical signal emitted by the microphone. In addition, the memory  195  can store other instructions that, when executed by the processor, cause the audio appliance  190  to perform any of a variety of tasks akin to a general computing environment. 
     VII. Acoustic Signal Conditioning 
     A damped acoustic chamber as described herein can radiate sound over a broader bandwidth and can also require less conditioning of an acoustic signal as compared to a degree of signal conditioning applied to the acoustic signal when played through un-damped acoustic chambers. For example, an amplitude of a signal used to drive a loudspeaker transducer can be diminished at and near the resonant frequency of an un-damped acoustic chamber to de-emphasize that frequency during audio playback. However, such signal conditioning can be computationally intensive. An acoustically damped acoustic chamber described herein can acoustically damp selected frequencies and allow for less signal conditioning and reduce computational overhead during audio playback. Such signal conditioning can be performed in software, firmware, or hardware (e.g., using an ASIC). 
     VIII. Other Embodiments 
     The examples described above generally concern acoustic chambers damped with plural resonant chambers, and related systems and methods. The previous description is provided to enable a person skilled in the art to make or use the disclosed principles. Embodiments other than those described above in detail are contemplated based on the principles disclosed herein, together with any attendant changes in configurations of the respective apparatus described herein, without departing from the spirit or scope of this disclosure. Various modifications to the examples described herein will be readily apparent to those skilled in the art. 
     Directions and other relative references (e.g., up, down, top, bottom, left, right, rearward, forward, etc.) may be used to facilitate discussion of the drawings and principles herein, but are not intended to be limiting. For example, certain terms may be used such as “up,” “down,”, “upper,” “lower,” “horizontal,” “vertical,” “left,” “right,” and the like. Such terms are used, where applicable, to provide some clarity of description when dealing with relative relationships, particularly with respect to the illustrated embodiments. Such terms are not, however, intended to imply absolute relationships, positions, and/or orientations. For example, with respect to an object, an “upper” surface can become a “lower” surface simply by turning the object over. Nevertheless, it is still the same surface and the object remains the same. As used herein, “and/or” means “and” or “or”, as well as “and” and “or.” Moreover, all patent and non-patent literature cited herein is hereby incorporated by reference in its entirety for all purposes. 
     And, those of ordinary skill in the art will appreciate that the exemplary embodiments disclosed herein can be adapted to various configurations and/or uses without departing from the disclosed principles. Applying the principles disclosed herein, it is possible to provide a wide variety of damped acoustic enclosures, and related methods and systems. For example, the principles described above in connection with any particular example can be combined with the principles described in connection with another example described herein. Thus, all structural and functional equivalents to the features and method acts of the various embodiments described throughout the disclosure that are known or later come to be known to those of ordinary skill in the art are intended to be encompassed by the principles described and the features claimed herein. Accordingly, neither the claims nor this detailed description shall be construed in a limiting sense, and following a review of this disclosure, those of ordinary skill in the art will appreciate the wide variety of audio appliances, and related methods and systems that can be devised under disclosed and claimed concepts. 
     Moreover, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the claims. No claim feature is to be construed under the provisions of 35 USC 112(f), unless the feature is expressly recited using the phrase “means for” or “step for”. 
     The appended claims are not intended to be limited to the embodiments shown herein, but are to be accorded the full scope consistent with the language of the claims, wherein reference to a feature in the singular, such as by use of the article “a” or “an” is not intended to mean “one and only one” unless specifically so stated, but rather “one or more”. Further, in view of the many possible embodiments to which the disclosed principles can be applied, I reserve to the right to claim any and all combinations of features and technologies described herein as understood by a person of ordinary skill in the art, including, for example, all that comes within the scope and spirit of the following claims.

Metadata:
Filing Date: 20180924
Publication Date: 20220301
Grant Date: 20220301
Priority Date: 20180924
Inventors: PAVLOV, PETER M.
BRUSS, JOHN R.
LE, DUY P.
Assignee: APPLE INC
CPC Classifications: [{"code": "H04R1/2811", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04R1/2811", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04R1/1075", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04R9/06", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04R1/1083", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04R1/1016", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04R1/1016", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04R1/2849", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04R1/025", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04R9/025", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04R1/2842", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04R1/1075", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04R1/2876", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04R1/025", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04R1/2826", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04R1/2811", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04R1/2826", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04R1/1016", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04R1/025", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04R1/2842", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04R1/1075", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04R9/06", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04R1/2849", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 69885149