PATENT DOCUMENT

Publication Number: US-9743189-B2
Application Number: US-201614988401-A
Country: US
Kind Code: B2

Title: Microspeaker with improved high frequency extension

Abstract:
A decoupled speaker membrane assembly for a microspeaker, the membrane including a first membrane portion, a compliant portion, a second membrane portion and a suspension member. The compliant portion is attached to, and extends radially outward from, an entire perimeter of the first membrane portion. The second membrane portion is attached to, and extends radially outward from the compliant portion such that the second membrane portion is decoupled from the first membrane portion by the compliant portion. The suspension member extends radially outward from the second membrane portion.

Claims:
What is claimed is: 
     
       1. A decoupled speaker membrane assembly for use in a microspeaker, the speaker membrane assembly comprising:
 a first membrane portion; 
 a compliant portion attached to, and extending radially outward from, a perimeter of the first membrane portion, wherein the compliant portion is more compliant than the first membrane portion; 
 a second membrane portion attached to, and extending radially outward from the compliant portion such that the second membrane portion is decoupled from the first membrane portion by the compliant portion; and 
 a suspension member extending radially outward from the second membrane portion. 
 
     
     
       2. The speaker membrane assembly of  claim 1  wherein the first membrane portion is tuned to have a natural resonant frequency at a breakup mode frequency of the decoupled speaker membrane. 
     
     
       3. The speaker membrane assembly of  claim 1  wherein a channel is formed between the first membrane portion and the second membrane portion, and the channel is dimensioned to tune a natural resonant frequency of the first membrane portion to that of a breakup mode frequency of the decoupled speaker membrane. 
     
     
       4. The speaker membrane assembly of  claim 1  wherein the compliant portion comprises a material having a lower Young&#39;s modulus than a material of the first membrane portion and a material of the second membrane portion. 
     
     
       5. The speaker membrane assembly of  claim 1  wherein the second membrane portion is attached to, and extends radially outward from, an entire perimeter of the compliant portion. 
     
     
       6. The speaker membrane assembly of  claim 1  wherein the compliant portion acoustically seals the first membrane portion to the second membrane portion. 
     
     
       7. The speaker membrane assembly of  claim 1  wherein the first membrane portion and the second membrane portion are formed of a same material. 
     
     
       8. The speaker membrane assembly of  claim 1  wherein the compliant portion is formed by a portion of the suspension member extending between the first membrane portion and the second membrane portion, and the first membrane portion and the second membrane portion are attached to a face of the suspension member. 
     
     
       9. The speaker membrane assembly of  claim 1  wherein the first membrane portion and the second membrane portion comprise a plurality of material layers, and at least one of the material layers extends from the first membrane portion to the second membrane portion to form the compliant portion. 
     
     
       10. The speaker membrane assembly of  claim 9  wherein the suspension member is attached to a face of the at least one of the material layers. 
     
     
       11. A decoupled microspeaker diaphragm comprising:
 an inner diaphragm portion; 
 an outer diaphragm portion, the outer diaphragm portion being spaced radially outward from the inner diaphragm portion; and 
 a decoupling membrane positioned between the inner diaphragm portion and the outer diaphragm portion, wherein the decoupling membrane surrounds the inner diaphragm portion and is more compliant than the inner diaphragm portion and the outer diaphragm portion. 
 
     
     
       12. The microspeaker diaphragm of  claim 11  wherein the inner diaphragm portion and the outer diaphragm portion are within a first plane and the decoupling membrane is within a second plane parallel to the first plane. 
     
     
       13. The microspeaker diaphragm of  claim 11  wherein a top side of the decoupling membrane is attached to a bottom side of the inner diaphragm portion and the outer diaphragm portion. 
     
     
       14. The microspeaker diaphragm of  claim 11  wherein the decoupling membrane comprises an inner edge and an outer edge, wherein the inner edge of the decoupling membrane is connected to an outer edge of the inner diaphragm portion, and the outer edge of the decoupling membrane is connected to an inner edge of the outer diaphragm portion. 
     
     
       15. The microspeaker diaphragm of  claim 11  wherein the inner diaphragm portion and the outer diaphragm portion comprise a first material layer and a second material layer, and the decoupling membrane comprises one of the first material layer or the second material layer. 
     
     
       16. The microspeaker diaphragm of  claim 11  wherein the decoupling membrane is a continuous membrane that extends along an entire bottom side of the inner diaphragm portion and the outer diaphragm portion, and the bottom side of the inner diaphragm portion and the outer diaphragm portion is attached to a top side of the decoupling membrane. 
     
     
       17. The microspeaker diaphragm of  claim 11  further comprising:
 a suspension member extending radially outward from the outer diaphragm portion, wherein the inner diaphragm portion and the outer diaphragm portion comprise at least one different material than the suspension member. 
 
     
     
       18. A driver comprising:
 a frame; 
 a membrane assembly for radiating sound, the membrane assembly comprising:
 a first membrane portion; 
 a second membrane portion extending radially outward from, and decoupled from, the first membrane portion by a compliant membrane attached to, and positioned between, the first membrane portion and the second membrane portion; and 
 a suspension member extending radially outward from the second membrane portion, and wherein the compliant membrane is more compliant than the first membrane portion and the second membrane portion; and 
 
 a voice coil connected to a face of the membrane assembly, and wherein the voice coil is positioned concentrically outward to the first membrane portion and the compliant membrane. 
 
     
     
       19. The driver of  claim 18  wherein the driver is a microspeaker driver. 
     
     
       20. The driver of  claim 18  wherein the first membrane portion and the second membrane portion are substantially flat and substantially within a same plane.

Description:
FIELD 
     An embodiment of the invention is directed to a microspeaker having a decoupled sound radiating surface which improves the acoustic performance of a driver within which the membrane may be implemented. Other embodiments are also described and claimed. 
     BACKGROUND 
     Whether listening to an MP3 player while traveling, or to a high-fidelity stereo system at home, consumers are increasingly choosing intra-canal and intra-concha earphones for their listening pleasure. Both types of electro-acoustic transducer devices have a relatively low profile housing that contains a receiver or driver (an earpiece speaker). The low profile housing provides convenience for the wearer, while also providing very good sound quality. 
     These devices, however, do not have sufficient space to house high fidelity speakers. This is also true for portable personal computers such as laptop, notebook, and tablet computers, and, to a lesser extent, desktop personal computers with built-in speakers. Such devices typically require speaker enclosures or boxes that have a relatively low rise (e.g., height as defined along the z-axis) and small back volume, as compared to, for instance, stand alone high fidelity speakers and dedicated digital music systems for handheld media players. 
     The drivers (earpiece speakers) for such devices therefore typically use a low profile diaphragm assembly, which is composed of two parts. Namely, a sound radiating surface (SRS) and a suspension member. The SRS vibrates axially thereby creating pressure waves outside the driver enclosure. The suspension surrounds and suspends the SRS within the enclosure and allows it to vibrate axially. Each of these moving parts, however, have natural structural resonances that can be excited at certain frequencies, which are typically different from one another. As a result, at certain frequencies (the so-called “breakup mode” frequency) portions of the SRS (e.g., the inner portion and the outer portion), and in some cases the suspension member, may move out of phase with one another. In other words, in the case of the SRS, the center or inner portion of the SRS may be moving up while the outer portion or edges of the SRS may be moving down. Such out of phase movements, result in an undesirable sound pressure output (e.g., drop in pressure) at the breakup frequency. One way in which breakup modes have been addressed is to increase the stiffness of the SRS, such as by using a stiffer SRS material or making the SRS thicker. In some cases, however, there are manufacturing constraints and/or undesirable performance trade-offs that come along with a stiffer SRS, and therefore this may not be an option. 
     SUMMARY 
     An embodiment of the invention is a decoupled speaker membrane assembly, which improves sound output at a breakup mode frequency of a driver within which the membrane is incorporated. In some embodiments the membrane is a sound radiating surface (SRS) such as a diaphragm designed for use within a driver such as a loudspeaker, more specifically, a microspeaker. The term “microspeaker” is intended to refer to a speaker having a size range (e.g., a diameter or longest dimension) of from about 10 mm to 75 mm, in some cases, within a size range of from 10 mm to 20 mm. The speaker membrane may be separated into two or more portions (i.e. decoupled), for example an inner portion and an outer portion, by a compliant portion. The inner portion may be concentrically inward to the outer portion and the compliant portion may be a compliant member (e.g., a ring shaped membrane) connecting the inner and outer portions together. The inner portion and the compliant member may act as a mass/spring type system that can be tuned to have a natural resonant frequency at the breakup mode frequency where a drop in sound pressure output would normally occur. In particular, the inner portion may be tuned so that the sound pressure output at the breakup mode frequency increases, and therefore the undesirable sound pressure drop previously experienced at the breakup mode frequency is minimized or eliminated altogether. This, in turn, creates additional acoustic output in the high frequencies beyond what is achieved by a homogenous SRS (e.g., an SRS without separate parts). 
     More specifically, the inner portion and compliant member assembly can be tuned by controlling the size (e.g., area, thickness, etc.) and/or mass of the inner portion and/or the stiffness (or compliance) of the compliant member. In particular, in most cases, the inner portion of the SRS is equal to or smaller in size and mass than the outer portion of the SRS. It should be understood that reducing the mass of the inner portion increases the resonant frequency, while increasing the mass of the inner portion reduces the resonant frequency. Thus, in order to drive the resonant frequency of the inner portion up, which is the goal, the size or mass of the inner portion is reduced, but only to a certain point, otherwise it becomes too small to effectively radiate sound. The size limitations on the inner portion, however, can be compensated for by adjusting the stiffness or compliance of the compliant member in order to achieve the desired resonant frequency. 
     In particular, increasing the stiffness of the compliant member (i.e. reducing the compliance) increases the resonant frequency of the mass/spring system created by the inner portion and compliant member, while reducing the stiffness of the compliant member (i.e. increasing the compliance) reduces the resonant frequency. Thus, the size or mass of the inner portion can be balanced with the stiffness or compliance of the compliant member in order to tune the assembly to the desired resonant frequency. For example, where the size or mass of the center must be increased (such as by increasing the area), for example to improve sound radiation, the resultant lowered resonant frequency can be compensated for by increasing the stiffness of the compliant member, which increases the resonant frequency. Alternatively, if the size or mass of the center portion is decreased (such as by decreasing the area), the stiffness of the compliant member could be increased to further increase the resonant frequency, or decreased to lower the resonant frequency to a desired level. It should be understood that the stiffness of the compliant member and/or inner portion may be controlled by, for example, controlling a thickness of the material, selecting a different material, and/or otherwise chemically or mechanically altering a portion of the material to locally tune the stiffness. If the compliant member is made of aluminum, for example, one such method of chemically altering the mechanical properties could be anodization. In addition, another way to tune the resonant frequency of the inner portion and compliant member assembly could be to modify a width of the channel between the inner and outer portions. For example, a wider channel, and in turn compliant member with larger area, would reduce the stiffness and lower the resonant frequency, while a narrower channel would increase the stiffness and in turn increase the resonant frequency. 
     For example, in one embodiment, the SRS consists of an SRS material attached to a compliant membrane that is continuous with a suspension member. The SRS material may be a relatively stiff material, which is stiffer than the compliant membrane. To decouple inner and outer portions of the SRS and create a high frequency resonator within the SRS, a ring of the SRS material is removed, leaving only the compliant membrane between the remaining inner and outer portions of the SRS material. In this aspect, the inner portion of SRS material and compliant membrane provide the mass/spring assembly, which is tuned to have a natural resonance frequency at the breakup mode frequency as previously discussed. 
     More specifically, a decoupled speaker membrane assembly includes a first membrane portion, a compliant portion, a second membrane portion and a suspension member. The compliant portion may be attached to, and extends radially outward from, an entire perimeter of the first membrane portion. The second membrane portion may be attached to, and extend radially outward from the compliant portion such that the second membrane portion is decoupled from the first membrane portion by the compliant portion. The suspension member may extend radially outward from the second membrane portion. The first membrane portion may be tuned to have a natural resonant frequency at a breakup mode frequency of the speaker membrane. In addition, a channel may be formed between the first membrane portion and the second membrane portion, and the channel may be dimensioned to tune a natural resonant frequency of the first membrane portion to that of a breakup mode frequency of the speaker membrane. Still further, the compliant portion may be more compliant than the first membrane portion and the second membrane portion. In addition, the second membrane portion may be attached to, and extend radially outward from, an entire perimeter of the compliant portion. The compliant portion may acoustically seal the first membrane portion to the second membrane portion. The first membrane portion and the second membrane portion may be formed of a same material. Still further, the compliant portion may be formed by a portion of the suspension member extending between the first membrane portion and the second membrane portion, and the first membrane portion and the second membrane portion may be attached to a face of the suspension member. In addition, the first membrane portion and the second membrane portion may include a plurality of material layers, and at least one of the material layers may extend from the first membrane portion to the second membrane portion to form the compliant portion. The suspension member may be attached to a face of the at least one of the material layers. 
     In another embodiment, the SRS consists of layers of SRS materials, for example, thin layers of aluminum sandwiched around a core material. The core material may be a relatively low mass material (e.g. lower mass density than the aluminum layers) and have good internal damping characteristics. To decouple inner and outer portions of the SRS, a ring of only one of the aluminum layers and the core material may be removed, leaving behind inner and outer SRS portions that are connected together by the remaining aluminum layer. The ring of aluminum creates a compliant region between the inner and outer portions of the SRS. The inner portion and compliant region are tuned to have a natural resonance frequency within the frequency range of the breakup mode frequency in order to minimize or eliminate the drop in sound pressure output as previously discussed. 
     More specifically, a decoupled speaker diaphragm may include an inner diaphragm portion, an outer diaphragm portion and a decoupling membrane. The outer diaphragm portion may be spaced concentrically outward from the inner diaphragm portion. The decoupling membrane may be positioned between the inner diaphragm portion and the outer diaphragm portion. In addition, the decoupling membrane may surround the inner diaphragm portion and be more compliant than the inner diaphragm portion and the outer diaphragm portion. The inner diaphragm portion and the outer diaphragm portion may be within a first plane and the decoupling membrane may be within a second plane parallel to the first plane. In one aspect, a top side of the decoupling membrane may be attached to a bottom side of the inner diaphragm portion and the outer diaphragm portion. In addition, the decoupling membrane may include an inner edge and an outer edge, the inner edge of the decoupling membrane may be connected to an outer edge of the inner diaphragm portion, and the outer edge of the decoupling membrane may be connected to an inner edge of the outer diaphragm portion. In some embodiments, the inner diaphragm portion and the outer diaphragm portion may include a first material layer and a second material layer, and the decoupling membrane includes one of the first material layer or the second material layer. In another aspect, the membrane is a continuous membrane that extends along an entire bottom side of the inner diaphragm portion and the outer diaphragm portion, and the bottom side of the inner diaphragm portion and the outer diaphragm portion is attached to a top side of the decoupling membrane. Still further, the membrane may include a suspension member extending radially outward from the outer diaphragm portion. The inner diaphragm portion and the outer diaphragm portion may, in one embodiment, include at least one different material than the suspension member. 
     In another embodiment, a driver includes a frame, a membrane assembly and a voice coil connected to a face of the membrane assembly. The membrane assembly may be for radiating sound and include a first membrane portion, a second membrane portion decoupled from the first membrane portion by a compliant membrane and a suspension member. The second membrane portion may extend radially outward from the compliant membrane attached to, and positioned between, the first membrane portion and the second membrane portion. The suspension member may extend radially outward from the second membrane portion. The compliant membrane may be more compliant than the first membrane portion and the second membrane portion. The voice coil, which is connected to a face of the membrane assembly, may be positioned concentrically outward to the first membrane portion and the compliant membrane. The driver may be a speaker driver. In addition, the first membrane portion and the second membrane portion may be substantially flat and substantially within a same plane. 
     The above summary does not include an exhaustive list of all aspects of the present invention. It is contemplated that the invention includes all systems and methods that can be practiced from all suitable combinations of the various aspects summarized above, as well as those disclosed in the Detailed Description below and particularly pointed out in the claims filed with the application. Such combinations have particular advantages not specifically recited in the above summary. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The embodiments are illustrated by way of example and not by way of limitation in the figures of the accompanying drawings in which like references indicate similar elements. It should be noted that references to “an” or “one” embodiment in this disclosure are not necessarily to the same embodiment, and they mean at least one. 
         FIG. 1  illustrates a top plan view of one embodiment of a speaker membrane. 
         FIG. 2  illustrates a cross sectional side view along line A-A′ of the membrane of  FIG. 1 . 
         FIG. 3  illustrates a cross sectional side view along line A-A′ of another embodiment of the membrane of  FIG. 1 . 
         FIG. 4  illustrates a cross sectional side view along line A-A′ of another embodiment of the membrane of  FIG. 1 . 
         FIG. 5  illustrates a cross sectional side view of the membrane of  FIG. 1  integrated within a driver. 
         FIG. 6  illustrates a frequency response curve of a driver including the membrane disclosed herein. 
         FIG. 7  illustrates one embodiment of an electronic device in which a membrane as disclosed herein may be implemented. 
         FIG. 8  illustrates a simplified schematic view of one embodiment of an electronic device in which the membrane may be implemented. 
     
    
    
     DETAILED DESCRIPTION 
     In this section we shall explain several preferred embodiments of this invention with reference to the appended drawings. Whenever the shapes, relative positions and other aspects of the parts described in the embodiments are not clearly defined, the scope of the invention is not limited only to the parts shown, which are meant merely for the purpose of illustration. Also, while numerous details are set forth, it is understood that some embodiments of the invention may be practiced without these details. In other instances, well-known structures and techniques have not been shown in detail so as not to obscure the understanding of this description. Furthermore, the particular features, structures, configurations, or characteristics may be combined in any suitable manner in one or more embodiments. The terms “over”, “to”, and “on” as used herein may refer to a relative position of one feature with respect to other features. One feature “over” or “on” another feature or bonded “to” another feature may be directly in contact with the other feature or may have one or more intervening layers. In addition, the use of relative terms throughout the description, such as “top” and “bottom” may denote a relative position or direction. For example, a “top edge”, “top end” or “top side” may be directed in a first axial direction and a “bottom edge”, “bottom end” or “bottom side” may be directed in a second direction opposite to the first axial direction. 
       FIG. 1  illustrates a top plan view of one embodiment of a speaker membrane assembly. In one embodiment, the speaker membrane assembly  100  is dimensioned to generate sound waves when integrated within a driver. The driver may, for example, be an electric-to-acoustic transducer having membrane assembly  100  and circuitry configured to produce a sound in response to an electrical audio signal input (e.g., a loudspeaker). In some embodiments, membrane assembly  100  is configured for use within a 10 mm to 75 mm driver, for example, a 10 mm to 20 mm driver, for example, a microspeaker. In addition, although membrane assembly  100  is shown having a substantially square or rectangular profile, membrane assembly  100  may have any number of other profiles suitable for use in a driver, for example, a circular or elliptical profile. 
     Membrane assembly  100  may include a decoupled membrane, which is configured to extend the high frequency output of the membrane and/or driver within which it is implemented. Membrane assembly  100  may therefore also be referred to herein as a decoupled speaker membrane assembly or a decoupled microspeaker diaphragm. In particular, at some frequency, the size and lack of stiffness of the SRS encourages the appearance of partial vibrations, also known as “breakup”, such that the SRS ceases to move pistonically as a rigid body causing destructive interference and loss of sensitivity. Above the frequency where this occurs, high frequency sensitivity and the speaker&#39;s bandwidth can be limited. This is particularly true in microspeakers with severe constraints on overall thickness (e.g., z-height), because it is difficult to create sufficient stiffness in the diaphragm to move the breakup mode high enough in frequency to leave the audio band. Thus, in one embodiment, the membrane assembly  100  includes a sound radiating surface (SRS) or diaphragm that is separated into two or more concentric portions separated by a compliant region, such that the inner portion (or portions) resonates at, for example, a frequency near the frequency at which the breakup mode occurs. In other words, a high frequency resonator is formed within the SRS. This can be accomplished by, for example, locally tuning the inner portion and/or compliant region to have a natural resonant frequency at, within, or above, the breakup mode frequency. This creates additional sensitivity in the high frequencies beyond that which can be achieved by homogenous diaphragm designs. 
     Representatively, in one embodiment, membrane assembly  100  includes an SRS  104  having an inner portion  104 A and an outer portion  104 B. The SRS  104  may also be referred to herein as a diaphragm or sound radiating membrane. The inner portion  104 A may form a center portion of SRS  104 . The outer portion  104 B may be positioned radially outward to the inner portion  104 A and form an outer portion of SRS  104 . Said another way, the outer portion  104 B may be positioned concentrically outward to the inner portion  104 A. In some embodiments, the outer portion  104 B forms a ring or frame around the inner portion  104 A. The inner portion  104 A and the outer portion  104 B may be spaced a distance from one another such that the two do not directly contact one another. In one embodiment, the inner portion  104 A and outer portion  104 B are radially spaced a distance from one another. In this aspect, the inner portion  104 A is considered decoupled, or otherwise separated from, the outer portion  104 B. It should be understood, however, that although inner portion  104 A and outer portion  104 B are decoupled from one another, both portions are considered sound radiating surfaces that can vibrate in response to an acoustic signal and radiate sound waves for output from a driver within which the SRS  104  is incorporated. Alternatively, where the driver is a microphone, both inner portion  104 A and outer portion  104 B may serve as sound pick up surfaces that vibrate in response to incoming air pressure sound waves. 
     Inner portion  104 A and outer portion  104 B may be made of a same material or different materials depending upon the desired level of stiffness. For example, both inner portion  104 A and outer portion  104 B may be made of a polyester material such as polyethylene naphthalate (PEN) or layers of different materials (e.g., a core layer sandwiched between two aluminum layers) as will be discussed in more detail in reference to  FIG. 4 . Inner portion  104 A will typically have a smaller surface area, size and/or mass than outer portion  104 B. 
     The inner portion  104 A and the outer portion  104 B may be connected by compliant member  106 . Compliant member  106  may also be referred to herein as a decoupling member. Representatively, compliant member  106  may be positioned between inner portion  104 A and outer portion  104 B. In other words, compliant member  106  extends radially outward from inner portion  104 A to outer portion  104 B, or radially inward from outer portion  104 B to inner portion  104 A. Compliant member  106  may, in some embodiments, partially or entirely surround, and be attached to, a perimeter of inner portion  104 A. For example, in the case of a square or rectangular shaped SRS  104  having a similarly shaped inner portion  104 A, compliant member  106  may surround one side, two sides, three sides or all four sides of inner portion  104 A. Alternatively, where SRS  104  has a circular or elliptical profile, compliant member  106  may form a ring partially or entirely around inner portion  104 A. In addition, outer portion  104 B may be positioned around, and attached to, an entire perimeter of compliant member  106 . Still further, in some embodiments, compliant member  106  is a membrane, which acoustically seals inner portion  104 A to outer portion  104 B. In other words, compliant member  106  may be a substantially non-porous sheet of material such that when it is attached to the outer and inner edges, respectively, of inner portion  104 A and outer portion  104 B, air cannot pass between inner portion  104 A and outer portion  104 B. The term “membrane” is intended to refer to a relatively thin, pliable, sheet of material that can occupy an entire space between inner portion  104 A and outer portion  104 B. In other words, there are no openings or gaps between interfacing edges of inner portion  104 A and outer portion  104 B. 
     Compliant member  106  may form a localized compliant region between the inner portion  104 A and outer portion  104 B, which is more compliant, or less stiff, than the rest of the SRS  104  (i.e., inner portion  104 A and outer portion  104 B). In one embodiment, the compliance of compliant member  106  may be controlled by selecting a material having a desired compliance, changing a thickness of the material, changing a surface area of the compliant member  106 , or modifying the material within the region of compliant member  106 , such as by anodizing the region changing the mechanical properties of the local region. It should be understood that the term “compliant” is intended to refer to a member or material used to form the member which has a relatively low modulus of elasticity or modulus of elasticity that is lower than a “stiff” material, such as inner and outer portions  104 A,  104 B of SRS  104 , or a material used to form inner and outer portions  104 A,  104 B of SRS  104 . 
     Various characteristics of the inner portion  104 A and/or compliant member  106  may be used to tune the resonant frequency of SRS  104  and improve a sound output at the breakup mode frequency, as previously discussed. More specifically, the inner portion  104 A and compliant member  106  can be tuned by controlling the size (e.g., area) and/or mass (e.g., thickness) of the inner portion and/or the compliance (or stiffness) of the compliant member. For example, in order to drive the natural resonant frequency of the inner portion  104 A up at the breakup mode frequency, the size, area and/or mass of the inner portion  104 A may be reduced, and/or the stiffness of the compliant member  106  increased. Alternatively, where it is desirable to increase the size, area and/or mass of the inner portion  104 A, for example to improve sound radiation, which in turn lowers the natural resonant frequency, the stiffness of the compliant member  106  may be tuned (e.g., the stiffness increased) to drive the frequency back up to the desired range. It should be noted, however, that while the stiffness of the compliant member  106  may be increased to increase the resonant frequency in some cases, compliant member  106  is still less stiff or more compliant than inner portion  104 A and outer portion  104 B. By making the area around inner portion  104 A, and between inner portion  104 A and outer portion  104 B, more compliant (or less stiff) than the rest of SRS  104 , a natural resonant frequency of the inner portion  104 A can be locally controlled and tuned to a higher frequency at the breakup mode frequency where a sound pressure output typically occurs. 
     In addition, it is contemplated that in some embodiments, the inner portion  104 A and/or compliant member  106  are tuned to increase the breakup mode frequency above the working range of the driver. Since the breakup mode frequency is above the working range of the driver, any undesirable impact in sound output from the driver due to the breakup mode will go substantially unnoticed by the user. For example, in some embodiments where the working range of the driver is intended to operate in a range from about 0.02 kHz to about 20 kHz, the inner resonator or portion  104 A may be tuned to encourage significant output in the upper frequency range. 
     The compliance or stiffness of the compliant member  106  and/or inner portion  104 A may be controlled by, for example, controlling a thickness of the material, selecting a different material, and/or anodizing a portion of the material to locally tune the compliance or stiffness, as previously discussed. In still further embodiments, the compliance or stiffness may be controlled by making compliant member  106  of a material having a different density than the material used to make inner portion  104 A and/or outer portion  104 B. For example, compliant member  106  may be made of a first material, and inner portion  104 A and outer portion  104 B may be made of a second material. In one embodiment, the first material and the second material may be different materials having different stiffnesses and/or different densities. 
     In one embodiment, a suitable material for compliant member  106  may include, but is not limited to a material that is more compliant (or less stiff) than inner portion  104 A and outer portion  104 B of SRS  104 . For example, a suitable material may be a very compliant material having a relatively low Young&#39;s modulus (e.g., a lower Young&#39;s modulus than inner portion  104 A and outer portion  104 B). A representative very compliant material having a relatively low Young&#39;s modulus may include, but is not limited to, a polymer material such as polyurethane (PU). 
     In one embodiment, the material of inner portion  104 A and outer portion  104 B of SRS  104  may be any material capable of forming a relatively stiff axially vibratable membrane. It may be further desirable that the inner and outer portion  104 A,  104 B be made of a relatively light and/or relatively low density material so as not to substantially increase a mass of the SRS  104  and therefore impact a desired high frequency response of the membrane assembly  100 . Representatively, a suitable material for inner portion  104 A and outer portion  104 B may include, but is not limited to, a polyester material. A suitable polyester material may include, but is not limited to, polyethylene naphthalate (PEN). In one embodiment, the SRS  104  may be an integrally formed dome shaped structure made of a PEN thermofoil. 
     In other embodiments, a suitable material for inner portion  104 A and outer portion  104 B may include, but is not limited to, a material having a greater stiffness and/or density than the material used to make compliant member  106 . For example, the material of inner and outer portions  104 A,  104 B may be made of a material which is at least twice as dense as the material used for compliant member  106 . For example, in one embodiment wherein the material for compliant member  106  has a density of from about 0.5 to about 1.5 g cm, the material of inner and outer portions  104 A,  104 B may have a density of from about 2 to about 3 g cm. Representatively, inner and outer portions  104 A,  104 B may be made of an alloy material, more specifically an aluminum alloy material, or layers of an aluminum and core material. 
     In still further embodiments, it is contemplated that in addition to, or instead of, using a different material to make compliant member  106  more compliant than inner portion  104 A and outer portion  104 B, compliant member  106  may be thicker (along the z-axis) than portions  104 A,  104 B. 
     In addition, it is to be understood that another way to tune the resonant frequency of the inner portion  104 A and/or compliant member  106  is by controlling the width of compliant member  106 , or the channel formed by compliant member  106 . For example, a wider compliant member  106 , or channel formed between inner and outer portions  104 A,  104 B by compliant member  106 , reduces the stiffness and lowers the resonant frequency, while a narrower compliant member  106  or channel increases the stiffness and in turn increase the resonant frequency. It should be understood, however, that in most cases, the width (or area) of compliant member  106  is less than that of inner portion  104 A or outer portion  104 B. 
     In addition it should be understood that inner portion  104 A, outer portion  104 B and compliant member  106  are relatively flat, planar members, and therefore have a substantially low profile in the z-height direction. 
     Membrane assembly  100  may further include a suspension member  102  used to suspend SRS  104  within a frame of the driver. In this aspect, suspension member  102  may extend radially outward from the outer portion  104 B and have an outer edge  108  that connects to a frame member of the driver. Suspension member  102  may be formed of a relatively compliant material so that SRS  104  can vibrate when suspended within the frame by suspension member  102 . Representatively, in one embodiment, suspension member  102  may be formed of a same material as suspension member  102 . 
       FIG. 2  illustrates a cross sectional side view along line A-A′ of the membrane assembly of  FIG. 1 . From this view, it can be seen that in some embodiments, the suspension member  102  is one continuous membrane that forms a bottom side of SRS  104 . In particular, a bottom side  202  of each of the inner and outer portions  104 A and  104 B of SRS  104  are positioned on, and attached to (such as by gluing), a top side  204  of suspension member  102 . In this aspect, the suspension member  102  extends across an entire bottom side  202  of the inner and outer portions  104 A and  104 B. The inner portion  104 A and outer portion  104 B are radially spaced from one another along the suspension member  102  and the compliant portion  106  is formed between them. In this embodiment, the compliant portion  106  is therefore formed by the portion of suspension member  102  extending between inner portion  104 A and outer portion  104 B of SRS  104 . In other words, the compliant portion  106  is integrally formed as a single membrane with the suspension member  102 . In this aspect, the inner and outer portions  104 A and  104 B may be substantially within one plane, and the compliant portion  106  (i.e. suspension member  102 ) is substantially within another plane parallel to the plane of the inner and outer portions  104 A,  104 B. The inner portion  104 A and outer portion  104 B may be formed of the same material or different materials, for example, a material or materials that are stiffer than the suspension member  102  (e.g., a polyester material). In this aspect, when inner portion  104 A and outer portion  104 B are attached to suspension member  102  they have the desired stiffness for sound radiation. The compliant portion  106 , which is part of the suspension member  102 , is formed of a different material which is more compliant than the inner and outer portions  104 A,  104 B (e.g. polyurethane). 
       FIG. 3  illustrates a cross sectional side view along line A-A′ of another embodiment of the membrane assembly of  FIG. 1 . The membrane assembly of  FIG. 3  is substantially similar to that of  FIG. 2 , except in this embodiment, the compliant portion  106  is not formed by suspension member  102 . Rather, compliant portion  106  is a ring or frame shaped member that includes an outer edge  304  and an inner edge  306 . The outer edge  304  of compliant portion  106  is connected to the inner edge  310  of outer portion  104 B of SRS  104  and the inner edge  306  is connected to the outer edge  312  of inner portion  104 A of SRS  104 . For example, in one embodiment, a top face portion of inner edge  306  and outer edge  304  of compliant member  106  may be glued to a bottom face  202  of outer edge  312  of inner portion  104 A and inner edge  310  of outer portion  104 B, respectively. Thus, compliant member  106  separates inner portion  104 A from outer portion  104 B in a radial direction such that inner portion  104 A does not directly contact outer portion  104 B. In addition, the suspension member  102  includes an inner edge  302 , which is connected to an outer edge  308  of outer portion  104 B of SRS  104 , and an outer edge  108  that is connected to a driver frame (not shown). In this aspect, suspension member  102  is not directly connected to, or otherwise in direct contact with, compliant portion  106  or inner portion  104 A of SRS  104 . 
       FIG. 4  illustrates a cross sectional side view along line A-A′ of another embodiment of the membrane assembly of  FIG. 1 . The membrane assembly of  FIG. 4  is substantially similar to that of  FIG. 2 , except in this embodiment compliant portion  106  is formed by a layer of the material used to form a bottom face of the SRS  104 . Representatively, SRS  104  is made of a first material layer  402 , a second material layer  404  and a third material layer  406 . The first material layer  402  and the third material layer  406  may, for example, be layers of an aluminum material or other similarly stiff material suitable for forming a speaker diaphragm. The second material layer  404  may be a layer of lightweight core material that is sandwiched between the first and third material layers  402  and  406 . The lightweight core material may be any material having a relatively low mass and good internal damping properties, for example, a polypropylene, or foams such as polymethacrylimide (PMI) or foamed PET, or natural low density materials such as balsa wood. Portions of the first material layer  402  and second material layer  404  may then be removed leaving behind only the third material layer  406  to form compliant portion  106  between inner portion  104 A and outer portion  104 B of SRS  104 . In this aspect compliant portion  106  is formed by at least one material layer (e.g. first material layer  402 ) of SRS  104 . The inner and outer portions  104 A,  104 B of SRS  104  formed by a same material layer as compliant portion  106 , and at least one more additional material layer, in this case, two additional material layers (e.g. second and third material layers  404 ,  406 ). It should be noted that since compliant portion  106  includes less material layers than inner and outer portions  104 A,  104 B, it will be more compliant (or less stiff) than inner and outer portions  104 A,  104 B. The number of layers used to form compliant portion  106  may, however, be modified to achieve the desired resonant frequency. For example, more material layers may be used (e.g. material layer  402  and material layer  404 ) to increase a thickness of compliant portion  106 , and in turn, increase the resonant frequency. 
     In addition, a width (W) of a channel  408  formed between inner portion  104 A, outer portion  104 B and compliant portion  106  may, as previously discussed, be tuned to achieve a desired resonant frequency. For example, width (W) of channel  408  may be increased to reduce the stiffness of compliant portion  106  and lower the resonant frequency. Alternatively, a width (W) of channel  408  may be decreased to increase the stiffness and in turn increase the resonant frequency. It should be understood, however, that in most cases, the width (or area) of compliant member  106  is less than that of inner portion  104 A or outer portion  104 B. 
     To suspend SRS  104  of  FIG. 4  from a driver frame, an outer edge of the first material layer  402  of SRS  104  may be attached to the inner edge  302  of suspension member  102 . The outer edge  108  of suspension member  102  may then be attached to the driver frame, as previously discussed. 
       FIG. 5  illustrates a cross sectional side view of the membrane of  FIG. 1  integrated within a driver. Driver  500  may be any type of electric-to-acoustic transducer that uses a pressure sensitive diaphragm and circuitry to produce a sound in response to an electrical audio signal input (e.g., a loudspeaker). Representatively, membrane assembly  100 , which includes SRS  104 , having inner portion  104 A and outer portion  104 B decoupled by compliant portion  106 , and suspension member  102  as described in reference to  FIG. 1  and  FIG. 2 , may be integrated within driver  500  to produce a sound. The driver  500  may, for example, be a microspeaker driver. The electrical audio signal may be a music signal input to driver  500  by a sound source. The sound source may be any type of audio device capable of outputting an audio signal, for example, an audio electronic device such as a portable music player, home stereo system or home theater system capable of outputting an audio signal. Driver  500  may be integrated within headphones, intra-canal earphones, inter-concha earphones or the like. 
     Representatively, the outer edge  108  of suspension member  102  may be attached to frame  502  to suspend membrane assembly  100  within driver  500 . Frame  502  may be part of a driver enclosure or box whose height (or rise) and speaker back volume (also referred to as an acoustic chamber) are considered to be relatively small. For example, the enclosure height or rise may be in the range of about 1 millimeter (mm) to about 10 mm. The concepts described here, however, need not be limited to driver enclosures whose rises are within these ranges. 
     Driver  500  may include magnet assembly  514  positioned along a face of membrane assembly  100 . Magnet assembly  514  may define a gap within which a portion of coil  506  (also referred to as a voice coil) and the associated former  504 , used to support voice coil  506 , may be positioned. The former  504  and/or coil  506  may be attached to a face or side of the suspension member  102  facing magnet assembly  514 . It is to be understood that in some embodiments, coil  506  and/or former are attached to suspension member  102  such that they are concentrically outward to the inner portion  104   a  and outer portion  104 B of SRS  104  and compliant portion  106 . Said another way, the decoupled portion of SRS  104  is concentrically inward of the voice coil  506  and former  504 . 
     Coil  506 , which is affixed to the former  504 , may be positioned around center magnet piece  508 . It is noted that although former  504  is illustrated, former  504  is optional and may be omitted in some embodiments. Coil  506  may be a pre-wound coil assembly (which includes the wire coil held in its intended position by a lacquer or other adhesive material), which may be bonded directly to former  504 , for example to the outer surface wall of the former. In other embodiments, former  504  may be omitted and coil  506  may be attached directly to a surface of suspension member  102 . 
     Although not shown, coil  506  may have electrical connections to a pair of terminals through which an input audio signal is received, in response to which coil  506  produces a changing magnetic field that interacts with the magnetic field produced by magnet assembly  514  for providing a driving mechanism for driver  500 . 
     As previously discussed, SRS  104  may be coupled to frame  502  by way of suspension member  102 . Suspension member  102  allows substantially vertical movement of SRS  104 , that is in a substantially up and down direction or also referred to as a forward-backward direction, relative to fixed frame  502 . Suspension member  102  may be any compliant material, such as those previously discussed, that is sufficiently flexible to allow movement of SRS  104  in order to produce acoustic or sound waves. The SRS  104  may be more rigid or less flexible, to be more efficient in producing high frequency acoustic waves. In one instance, suspension member  102  is a single-piece flexible membrane, and SRS  104  includes substantially rigid or stiff inner and outer portions  104 A and  104 B that may be attached to the face of suspension member  102  as previously discussed. This may be done by directly gluing inner and outer portions  104 A,  104 B and suspension member  102  together at their respective edges and/or faces. In addition to allowing for axial movement of SRS  104 , suspension member  102  may also serve to maintain SRS  104  in substantial alignment relative to a center vertical axis of former  504  during operation of driver  500 . This alignment also serves to prevent a moving coil from impacting the walls of the magnet system. 
     Former  504  may have a typical, generally cylindrical or ring like structure around which a voice coil can be wound. Alternatively, former  504  may be a flat plate with a central opening therein which extends substantially horizontally outward of a peripheral portion of SRS  104 . Former  504  may be made from any suitably lightweight yet rigid material, so as to keep the weight of the suspended combination with membrane assembly  100  to a minimum, for greater performance and efficiency. An example material is an aluminum alloy. Other suitable materials include titanium, nomex, or kapton, which may be made sufficiently lightweight yet rigid. 
       FIG. 6  illustrates a frequency response curve for a driver having a decoupled membrane. In particular, frequency response chart  600  includes dashed line  602  illustrating a frequency response curve for a driver experiencing a substantial drop in sound pressure at a breakup mode frequency X (e.g., a frequency from 2 kHz to 15 kHz). The solid line  604  represents the response curve of a driver having a decoupled membrane tuned to have a natural resonant frequency at the breakup mode frequency X. In this aspect, it can be seen that due to the tuning of the membrane, there is a peak  608  (or increase) in sound pressure output at the breakup mode frequency X. In this aspect, the drop in sound pressure output at the breakup mode frequency X is now compensated by the peak  608  in sound pressure output at the breakup frequency X, and the sound output of the driver is therefore improved. 
       FIG. 7  illustrates one embodiment of an electronic device in which a membrane as disclosed herein may be implemented. Electronic device  700  may be, for example, a circumaural headphone that includes a left and right circumaural earcup connected by a headband (not shown). It should be noted that  FIG. 7  illustrates only one of the pair of left and right earcups of the headphone. In this aspect, device  700  may include a housing  702  dimensioned to encircle and cover a user&#39;s ear  706  and house the driver, for example driver  500  which includes membrane assembly  100  as discussed in reference to  FIG. 1 - FIG. 5 . In addition, in some cases, an earcup pad  704  may be positioned around the front end of the earcup to ensure a comfortable fit around the user&#39;s ear. The driver  500  may be positioned within housing  702  such that sound (S) emitted from driver  500  may be output to the user&#39;s ear  706 . It should further be recognized, however, that although a circumaural headphones is described, the membrane disclosed herein may be integrated within other types of electronic devices that use a transducer, for example, an inter-canal earphone or intra-concha earphone dimensioned to fit within an ear of a user. 
       FIG. 8  illustrates a simplified schematic view of one embodiment of an electronic device in which a membrane as disclosed herein may be implemented. For example, a circumaural headphone as discussed in reference to  FIG. 7  is an example of a system that can include some or all of the circuitry illustrated by electronic device  800 . 
     Electronic device  800  can include, for example, power supply  802 , storage  804 , signal processor  806 , memory  808 , processor  810 , communication circuitry  812 , and input/output circuitry  814 . In some embodiments, electronic device  800  can include more than one of each component of circuitry, but for the sake of simplicity, only one of each is shown in  FIG. 8 . In addition, one skilled in the art would appreciate that the functionality of certain components can be combined or omitted and that additional or less components, which are not shown in  FIG. 8 , can be included in, for example, device  800 . 
     Power supply  802  can provide power to the components of electronic device  800 . In some embodiments, power supply  802  can be coupled to a power grid such as, for example, a wall outlet. In some embodiments, power supply  802  can include one or more batteries for providing power to earphones, headphones or other type of electronic device associated with the headphone. As another example, power supply  802  can be configured to generate power from a natural source (e.g., solar power using solar cells). 
     Storage  804  can include, for example, a hard-drive, flash memory, cache, ROM, and/or RAM. Additionally, storage  804  can be local to and/or remote from electronic device  800 . For example, storage  804  can include an integrated storage medium, removable storage medium, storage space on a remote server, wireless storage medium, or any combination thereof. Furthermore, storage  804  can store data such as, for example, system data, user profile data, and any other relevant data. 
     Signal processor  806  can be, for example a digital signal processor, used for real-time processing of digital signals that are converted from analog signals by, for example, input/output circuitry  814 . After processing of the digital signals has been completed, the digital signals could then be converted back into analog signals. 
     Memory  808  can include any form of temporary memory such as RAM, buffers, and/or cache. Memory  808  can also be used for storing data used to operate electronic device applications (e.g., operation system instructions). 
     In addition to signal processor  806 , electronic device  800  can additionally contain general processor  810 . Processor  810  can be capable of interpreting system instructions and processing data. For example, processor  810  can be capable of executing instructions or programs such as system applications, firmware applications, and/or any other application. Additionally, processor  810  has the capability to execute instructions in order to communicate with any or all of the components of electronic device  800 . 
     Communication circuitry  812  may be any suitable communications circuitry operative to initiate a communications request, connect to a communications network, and/or to transmit communications data to one or more servers or devices within the communications network. For example, communications circuitry  812  may support one or more of Wi-Fi (e.g., a 802.11 protocol), Bluetooth®, high frequency systems, infrared, GSM, GSM plus EDGE, CDMA, or any other communication protocol and/or any combination thereof. 
     Input/output circuitry  814  can convert (and encode/decode, if necessary) analog signals and other signals (e.g., physical contact inputs, physical movements, analog audio signals, etc.) into digital data. Input/output circuitry  814  can also convert digital data into any other type of signal. The digital data can be provided to and received from processor  810 , storage  804 , memory  808 , signal processor  806 , or any other component of electronic device  800 . Input/output circuitry  814  can be used to interface with any suitable input or output devices, such as, for example, a microphone. Furthermore, electronic device  800  can include specialized input circuitry associated with input devices such as, for example, one or more proximity sensors, accelerometers, etc. Electronic device  800  can also include specialized output circuitry associated with output devices such as, for example, one or more speakers, earphones, etc. 
     Lastly, bus  816  can provide a data transfer path for transferring data to, from, or between processor  810 , storage  804 , memory  808 , communications circuitry  812 , and any other component included in electronic device  800 . Although bus  816  is illustrated as a single component in  FIG. 8 , one skilled in the art would appreciate that electronic device  800  may include one or more bus components. 
     While certain embodiments have been described and shown in the accompanying drawings, it is to be understood that such embodiments are merely illustrative of and not restrictive on the broad invention, and that the invention is not limited to the specific constructions and arrangements shown and described, since various other modifications may occur to those of ordinary skill in the art. For example, although a two part membrane having a localized compliant region is primarily disclosed as being implemented within a speaker driver for earphones or headphones, it is contemplated that the two part membrane disclosed herein may be used within any type of driver and integrated within any type of electronic device that could benefit from an increased breakup mode frequency, for example, a notebook, laptop, smartphone or any other type of device which can be used to output sound to a user. The description is thus to be regarded as illustrative instead of limiting.

Metadata:
Filing Date: 20160105
Publication Date: 20170822
Grant Date: 20170822
Priority Date: 20160105
Inventors: SALVATTI ALEXANDER V.
BOOTHE DANIEL K.
Assignee: APPLE INC
CPC Classifications: [{"code": "H04R9/18", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04R7/127", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04R2499/11", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04R2307/027", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04R2499/15", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04R7/125", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04R7/10", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04R2307/025", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04R9/02", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04R9/06", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04R7/06", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04R7/122", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04R9/06", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04R7/127", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04R9/18", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04R2307/207", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04R2400/11", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04R9/18", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04R7/122", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04R7/127", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04R9/06", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04R2307/207", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04R7/06", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 59227080