# Patent

## Title
Suspension for acoustic device

## Abstract

An acoustic device includes a diaphragm, a frame, and a suspension element that couples the diaphragm to the frame such that the diaphragm is movable in a reciprocating manner relative to the frame. The suspension element includes a first surround element and a second surround element that have respective inner landings between which a region proximal to an outer edge of the diaphragm is disposed. The inner landings are mechanically coupled by an adhesive material disposed along an inner periphery of the suspension element. The adhesive material has a viscoelastic response that increases stiffness as frequency increases, resulting in a shift of a first breakup mode of the acoustic device from a first frequency to a second, higher frequency.

## Background
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is a continuation-in-part of U.S. patent application Ser. No. 14/522,770, entitled “Acoustic Device Suspension,” filed Oct. 24, 2014. The content of this application is incorporated herein by reference in its entirety.


BACKGROUND
This disclosure relates to a suspension for an acoustic device.
SUMMARY
In accordance with a first aspect, an acoustic device includes a diaphragm, a frame, and a suspension element that couples the diaphragm to the frame such that the diaphragm is movable in a reciprocating manner relative to the frame. The suspension element includes a first surround element and a second surround element that have respective inner landings between which a region proximal to an outer edge of the diaphragm is disposed and respective outer landings that are separated by a distance that is greater than a thickness of the diaphragm. The inner landings are mechanically coupled by an adhesive material disposed along an inner periphery of the suspension element. The adhesive material has a viscoelastic response that increases stiffness as frequency increases, resulting in a shift of a first breakup mode of the acoustic device from a first frequency to a second, higher frequency.
In some implementations of the first aspect, the adhesive material has a viscoelastic response that increases stiffness by at least one order of magnitude as the frequency increases.
In some implementations of the first aspect, the inner periphery of the suspension element is defined by respective inner edges of the first surround element and the second surround element.
In some implementations of the first aspect, the first surround element and the second surround element are arranged such that a midline of the inner landings of the surround elements is substantially aligned with a midline of the outer landings of the surround elements.
In some implementations of the first aspect, the acoustic device further includes a spacer element that is disposed between the respective outer landings of the first surround element and the second surround element, and the respective outer landings are separated by a distance that comprises a thickness of the spacer element.
In some implementations of the first aspect, the frame includes a first frame element that is coupled to the outer landing of the first surround element, and a second frame element that is coupled to the outer landing of the second surround element.
In some implementations of the first aspect, the frame further includes a third frame element that couples the first frame element to the second frame element. The distance that separates the respective outer landings of the first surround element and the second surround element is defined at least in part by a dimension of the third frame element, and wherein the first frame element, the second frame element and the third frame element form an integral unit.
In some implementations of the first aspect, the first surround element includes a half-roll that defines a concave surface and a convex surface, the second surround element includes a half-roll that defines a concave surface and a convex surface, and the first surround element and the second surround element are arranged such that the respective concave surfaces face each other and the respective convex surfaces face away from each other.
In accordance with a second aspect, an acoustic device includes a diaphragm, a frame, and a suspension element that couples the diaphragm to the frame such that the diaphragm is movable in a reciprocating manner relative to the frame. The suspension element includes a first surround element and a second surround element that have respective inner landings between which a region proximal to an outer edge of the diaphragm is disposed and respective outer landings. A midline of the inner landings is substantially aligned with a midline of the outer landings. The inner landings are mechanically coupled by an adhesive material disposed along an inner periphery of the suspension element. The adhesive material has a viscoelastic response that increases stiffness as frequency increases, resulting in a shift of a first breakup mode of the acoustic device from a first frequency to a second, higher frequency.
In some implementations of the second aspect, the adhesive material has a viscoelastic response that increases stiffness by at least one order of magnitude as the frequency increases.
In some implementations of the second aspect, the inner periphery of the suspension element is defined by respective inner edges of the first surround element and the second surround element.
In some implementations of the second aspect, a distance that separates the outer landings is greater than a distance that separates the inner landings.
In some implementations of the second aspect, the acoustic device further includes a spacer element that is disposed between the outer landings, and a distance that separates the outer landings comprises a thickness of the spacer element.
In some implementations of the second aspect, the frame includes a first frame element that is coupled to the outer landing of the first surround element, and a second frame element that is coupled to the outer landing of the second surround element.
In some implementations of the second aspect, the frame further includes a third frame element that couples the first frame element to the second frame element, wherein a distance that separates the outer landings is defined at least in part by a dimension of the third frame element, and wherein the first frame element, the second frame element and the third frame element form an integral unit.
In some implementations of the second aspect, the first surround element comprises a half-roll that defines a concave surface and a convex surface, the second surround element comprises a half-roll that defines a concave surface and a convex surface, and the first surround element and the second surround element are arranged such that the respective concave surfaces face each other and the respective convex surfaces face away from each other.
In accordance with a third aspect, an acoustic device includes a diaphragm, a frame, and a suspension element that couples the diaphragm to the frame such that the diaphragm is movable in a reciprocating manner relative to the frame. The suspension element includes a first surround element and a second surround element that have respective inner landings and respective outer landings. The inner landings and the outer landings are separated by distances that are substantially identical. The inner landings are mechanically coupled by an adhesive material disposed along an inner periphery of the suspension element. The adhesive material has a viscoelastic response that increases stiffness as frequency increases, resulting in a shift of a first breakup mode of the acoustic device from a first frequency to a second, higher frequency.
In some implementations of the third aspect, the adhesive material has a viscoelastic response that increases stiffness by at least one order of magnitude as the frequency increases.
In some implementations of the third aspect, the inner periphery of the suspension element is defined by respective inner edges of the first surround element and the second surround element.
In some implementations of the third aspect, the first surround element includes a half-roll that defines a concave surface and a convex surface, the second surround element includes a half-roll that defines a concave surface and a convex surface, and the first surround element and the second surround element are arranged such that the respective concave surfaces face each other and the respective convex surfaces face away from each other.
Advantages of implementations include one or more of the following. Application of the adhesive around the inner periphery of the suspension element stiffens the acoustic device. This has the effect of pushing a first breakup frequency of the acoustic device upwards and increasing the usable frequency range of the acoustic device.
All examples and features mentioned above can be combined in any technically possible way. Other features and advantages will be apparent from the description and the claims.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of an acoustic device with a suspension element that includes a spacer element.
FIG. 2 is a top view of the acoustic device of FIG. 1.
FIGS. 3A, 4A, and 5A each show a cross-sectional view of an acoustic device with a suspension element that includes a spacer element.
FIGS. 3B, 4B, and 5B each show a perspective view of the acoustic devices of FIGS. 3A, 4A, and 5A, respectively.
FIG. 6A shows a cross-sectional view of a suspension element with aligned midlines.
FIG. 6B shows a cross-sectional view of a suspension element with offset midlines.
FIG. 7 illustrates an exemplary force versus displacement curve for an acoustic device that includes a spacer element and aligned midlines and an exemplary force versus displacement curve for the same acoustic device with offset midlines.
FIG. 8 illustrates an exemplary rocking frequency versus separation distance curve for an acoustic device with aligned midlines and an exemplary rocking frequency versus separation distance curve for an acoustic device with offset midlines.
FIG. 9A shows a cross-sectional view of a suspension element with aligned midlines and adhesive applied around an inner periphery of the suspension element.
FIG. 9B shows a cross-sectional view of a suspension element with offset midlines and adhesive applied around an inner periphery of the suspension element.
FIG. 10 illustrates an exemplary sound pressure level versus frequency curve for an acoustic device with the suspension element of FIG. 6A and an acoustic device with the suspension element of FIG. 9A.



DESCRIPTION
FIG. 1 illustrates an acoustic device such as a loudspeaker, driver or transducer. The acoustic device includes a diaphragm 100 (sometimes referred to as a cone, plate, cup or dome) coupled to a frame 102 via a suspension element 104 sometimes referred to as a surround. The diaphragm may be circular or non-circular in shape. For example, and without limitation, the diaphragm could be an ellipse, square, rectangle, oblong, or racetrack. The frame 102 may be coupled to an acoustic enclosure box (not illustrated). The suspension element 104 allows the diaphragm 100 to move in a reciprocating manner relative to the frame 102 and enclosure in response to an excitation signal provided to a motor that outputs a force to diaphragm 100. Movement of the diaphragm causes changes in air pressure which result in production of sound.
In some examples, as shown in FIGS. 1, 2, 3A and 3B, the suspension element 104 is formed by a pair of opposing and generally circular half roll surround elements each having an inner edge 106 and an outer edge 108, separated by a radial width or span. The suspension element 104 includes an inner landing 110 extending radially inward from the inner edge 106 and an outer landing 112 extending radially outward from the outer edge 108 for connection to the diaphragm 100 and frame 102, respectively. The suspension element 104 can be connected to the diaphragm 100 and the frame 102 using any suitable method, including use of an adhesive or by melting the suspension element material to the diaphragm/frame, to name two examples. Each half roll surround element has a convex surface 302 facing away from the interior of the enclosure, and a concave surface 304 (shown in FIGS. 3A and 3B) facing toward the interior of the volume enclosed by the two surround elements. Although the suspension element 104 is shown as a full roll having a single convolution, the suspension element 104 could be, without limitation, an inverted half roll (i.e., flipped over 180 degrees) or a roll having multiple convolutions, and could include variations of concavity and other features. A “convolution” as used herein comprises one cycle of a possibly repeating structure, where the structure typically comprises concatenated sections of arcs. The arcs are generally circular, but can have any curvature. Further, although the suspension element 104 is shown as circular in shape, the suspension element 104 could also be non-circular in shape. For example, without limitation, the suspension element 104 could be an ellipse, toroid, square, rectangle, oblong, racetrack, or other non-circular shapes. In places where the terms circumferential, radial, or other circle-specific terminology is mentioned, it should be understood that we also mean to encompass non-circular geometries.
The suspension element 104 may be made from any suitable material, including, but not limited to, fabric, rubber, foam, metal, or polyurethane plastic, such as thermoplastic polyurethane. In some implementations, the suspension element 104 includes rib and groove features (not shown) which may enhance axial stiffness, free length, force-deflection relationships, and buckling resistance, and may reduce the overall mass of the suspension element. For example, the suspension element 104 may include one or more radial rib features, groove features, and rib-and-groove features. Examples of these features are described in U.S. application Ser. No. 14/086284, which is incorporated herein by reference in its entirety.
In some examples, as shown in FIGS. 3A and 3B, a spacer element 306 is disposed between the respective outer landings 112 of the opposing pair of surround elements such that the outer edges 108 are separated by a first distance that is defined at least in part by the height of the spacer element 306 while the inner edges 106 are separated by a second distance that is defined at least in part by a thickness of the diaphragm 100. In some implementations, the spacer element 306 is formed of a non-porous material and includes vent holes 308, as shown in FIGS. 3A and 3B, while in other implementations, the spacer element is formed of a non-porous material that does not include any vent holes (not shown). In still other implementations, the spacer element 406 is formed of a porous material, as shown in FIG. 4A and 4B. Example spacer element materials include plastic, rubber, foam, fabric, and metal. The vented and porous spacer elements 306, 406 of FIG. 3A, 3B, 4A, and 4B are configured to allow air inside the suspension element 104 to be vented to the external environment. The spacer elements 306, 406 could be a separate component that are coupled to the surround elements using any suitable method (e.g., via an adhesive or by melting the suspension element material to the spacer element, among others). Alternatively, the spacer elements 306, 406 could be formed integrally with the surround elements or with another component (e.g., the frame 102 or other support structure). In some examples, as shown in FIGS. 5A and 5B, the frame of the acoustic device includes an upper frame element 502 and a lower frame element 504 that are separated by a spacer frame element 506. The elements 502, 504, and 506 may be separate and distinct components, as shown in
FIGS. 5A and 5B, or formed as a single integral component (not shown). Referring to FIGS. 5A and 5B, the respective outer landings 112 of the opposing pair of surround elements are coupled to the upper and lower frame elements 502, 504 and separated by a distance that is defined at least in part by the height of the spacer frame element 506.
FIGS. 6A and 6B each show a cross-sectional view of a suspension element of an acoustic device. The suspension elements of FIGS. 6A and 6B could be used, for example, in the acoustic devices shown in FIGS. 1-5. The suspension element of FIG. 6A is formed by a pair of opposing and generally circular half roll surround elements that are arranged such that the midline of the inner landings 610 of the surround elements is aligned with the midline of the outer landings 612 of the surround elements. This is in contrast to the suspension element of FIG. 6B, which is formed by a pair of opposing and generally circular half roll surround elements that are arranged such that the midline of the inner landings 610 is offset from the midline of the outer landings 612.
FIG. 7 illustrates exemplary force versus displacement curves 702, 704 for the acoustic devices of FIGS. 6A and 6B. The solid lined curve 702 in FIG. 7 represents the force-displacement curve for the acoustic device of FIG. 6A; the dash lined curve 704 in FIG. 7 represents the force-displacement curve for the acoustic device of FIG. 6B. As can be seen, the acoustic device of FIG. 6A, which is implemented with a suspension element that has aligned midlines, exhibits more symmetrical force versus displacement in comparison with the acoustic device of FIG. 6B, which is implemented with a suspension element that has offset midlines. The vertical difference between the two curves 702, 704 represents the contribution made by aligning the midlines. Thus, in some examples, in addition to providing a different amount of spacing on the inner edges as compared to the outer edges of the suspension element, it may also be advantageous to align the midlines on the inner and outer edges of the suspension element.
FIG. 8 illustrates rocking frequency versus separation distance curves 802, 804 for the acoustic devices of FIGS. 6A and 6B. The solid lined curve 802 in FIG. 8 represents the rocking frequency-separation distance curve for the acoustic device of FIG. 6A; the dash lined curve 804 in FIG. 8 represents the rocking frequency-separation distance curve for the acoustic device of FIG. 6B. As can be seen, regardless of the actual separation distance, the acoustic device of FIG. 6A, which is implemented with a suspension element that has aligned midlines, exhibits a higher range of acoustic device rocking frequencies relative to the acoustic device of FIG. 6B, which is implemented with a suspension element that has offset midlines.
FIG. 9A shows a cross-sectional view of a suspension element of an acoustic device. The suspension element of FIG. 9A could be used, for example, in the acoustic devices shown in FIGS. 1-5. The suspension element of FIG. 9A is formed by a pair of opposing and generally circular half roll surround elements that are arranged such that the midline of the inner landings 910 of the surround elements is aligned with the midline of the outer landings 912 of the surround elements. An adhesive 930 is applied in a generally uniform manner around an inner periphery of the suspension element, the inner periphery being defined by respective inner edges 906 of the surround elements. Application of the adhesive 930 mechanically couples the inner edges 906 of the surround elements and stiffens the diaphragm 100 and suspension element.
The adhesive 930 may be a bead of glue or other suitable adhesive material that generally exhibits the following viscoelastic properties: stiffer response at higher frequencies and more compliant response at lower frequencies. In some implementations, the adhesive 930 has a Young's modulus that increases by at least one order of magnitude as frequency increases. One example adhesive material exhibits a Young's modulus of approximately 30 MPa at 0.1 kHz and 200-300 MPa at 10 kHz.
FIG. 10 illustrates sound pressure level versus frequency curves 1002, 1004 for the acoustic devices of FIGS. 6A and 9A. The solid lined curve 1002 in FIG. 10 represents the sound pressure level—frequency curve for the acoustic device of FIG. 6A; the dash lined curve 1004 in FIG. 10 represents the sound pressure level—frequency curve for the acoustic device of FIG. 9A. As can be seen, the acoustic device of FIG. 9A, which is implemented with a suspension element that has aligned midlines and adhesive 930 applied around its inner periphery, exhibits a higher breakup frequency relative to the acoustic device of FIG. 6A, which is implemented with a suspension element that has aligned midlines but no adhesive applied around its inner periphery. In some implementations, moving the breakup frequency higher has the effect of moving the resonance of the acoustic device to a higher frequency range that is less audible to the human ear. This has the effect of increasing the usable frequency range of the acoustic device even if the mode is pushed to a less audible portion of the spectrum.
Among the wide variety of variations that are contemplated are variations in the amount of separation provided between the inner landings and the outer landings of the suspension element. For example, in some implementations, the distance separating the outer edges of the suspension element could be approximately three times the distance separating the inner edges of the suspension element, while in some implementations, the distance separating the outer edges of the suspension element is approximately equal to that separating the inner edges of the suspension element. Other relative distances are contemplated, however.
Other variations that are contemplated include applying an adhesive 980 in a generally uniform manner around an inner periphery of a suspension element that has offset midlines, as shown in FIG. 9B. In such implementations, the suspension element is formed by a pair of opposing and generally circular half roll surround elements that are arranged such that the midline of the inner landings 970 is offset from the midline of the outer landings 962. Application of the adhesive 980 mechanically couples the inner edges 956 of the surround elements and stiffens the diaphragm 100 and suspension element with benefits similar to those described above with respect to suspension elements with aligned midlines.
The implementations described herein could apply to an active transducer that includes a motor structure (as shown), but could also apply to a passive radiator, sometimes referred to as a drone.
A number of implementations have been described. Nevertheless, it will be understood that additional modifications may be made without departing from the scope of the inventive concepts described herein, and, accordingly, other embodiments are within the scope of the following claims.

## Claims

1. An acoustic device comprising:
a diaphragm
a frame; and
a suspension element that couples the diaphragm to the frame such that the diaphragm is movable in a reciprocating manner relative to the frame, the suspension element comprising a first surround element and a second surround element that have respective inner landings between which a region proximal to an outer edge of the diaphragm is disposed and respective outer landings that are separated by a distance that is greater than a thickness of the diaphragm, wherein the inner landings are mechanically coupled by an adhesive material disposed along an inner periphery of the suspension element, the adhesive material having a viscoelastic response that increases stiffness as frequency increases, resulting in a shift of a first breakup mode of the acoustic device from a first frequency to a second, higher frequency.

2. The acoustic device of claim 1, wherein the adhesive material has a viscoelastic response that increases stiffness by at least one order of magnitude as the frequency increases.

3. The acoustic device of claim 1, wherein the inner periphery of the suspension element is defined by respective inner edges of the first surround element and the second surround element.

4. The acoustic device of claim 1, wherein:
the first surround element and the second surround element are arranged such that a midline of the inner landings of the surround elements is substantially aligned with a midline of the outer landings of the surround elements.

5. The acoustic device of claim 1, further comprising a spacer element that is disposed between the respective outer landings of the first surround element and the second surround element, and wherein the respective outer landings are separated by a distance that comprises a thickness of the spacer element.

6. The acoustic device of claim 1, wherein the frame comprises:
a first frame element that is coupled to the outer landing of the first surround element; and
a second frame element that is coupled to the outer landing of the second surround element.

7. The acoustic device of claim 6, wherein the frame further comprises:
a third frame element that couples the first frame element to the second frame element, wherein the distance is defined at least in part by a dimension of the third frame element, and wherein the first frame element, the second frame element and the third frame element form an integral unit.

8. The acoustic device of claim 1, wherein:
the first surround element comprises a half-roll that defines a concave surface and a convex surface;
the second surround element comprises a half-roll that defines a concave surface and a convex surface; and
the first surround element and the second surround element are arranged such that the respective concave surfaces face each other and the respective convex surfaces face away from each other.

9. An acoustic device:
a diaphragm
a frame; and
a suspension element that couples the diaphragm to the frame such that the diaphragm is movable in a reciprocating manner relative to the frame, the suspension element comprising a first surround element and a second surround element that have respective inner landings between which a region proximal to an outer edge of the diaphragm is disposed and respective outer landings, wherein a midline of the inner landings is substantially aligned with a midline of the outer landings, and wherein the inner landings are mechanically coupled by an adhesive material disposed along an inner periphery of the suspension element, the adhesive material having a viscoelastic response that increases stiffness as frequency increases, resulting in a shift of a first breakup mode of the acoustic device from a first frequency to a second, higher frequency.

10. The acoustic device of claim 9, wherein the adhesive material has a viscoelastic response that increases stiffness by at least one order of magnitude as the frequency increases.

11. The acoustic device of claim 9, wherein the inner periphery of the suspension element is defined by respective inner edges of the first surround element and the second surround element.

12. The acoustic device of claim 9, wherein a distance that separates the outer landings is greater than a distance that separates the inner landings.

13. The acoustic device of claim 9, further comprising a spacer element that is disposed between the outer landings, and wherein a distance that separates the outer landings comprises a thickness of the spacer element.

14. The acoustic device of claim 9, wherein the frame includes:
a first frame element that is coupled to the outer landing of the first surround element; and
a second frame element that is coupled to the outer landing of the second surround element.

15. The acoustic device of claim 14, wherein the frame further includes:
a third frame element that couples the first frame element to the second frame element, wherein a distance that separates the outer landings is defined at least in part by a dimension of the third frame element, and wherein the first frame element, the second frame element and the third frame element form an integral unit.

16. The acoustic device of claim 9, wherein:
the first surround element comprises a half-roll that defines a concave surface and a convex surface;
the second surround element comprises a half-roll that defines a concave surface and a convex surface; and
the first surround element and the second surround element are arranged such that
the respective concave surfaces face each other and the respective convex surfaces face away from each other.

17. An acoustic device comprising:
a diaphragm
a frame; and
a suspension element that couples the diaphragm to the frame such that the diaphragm is movable in a reciprocating manner relative to the frame, the suspension element comprising a first surround element and a second surround element that have respective inner landings and respective outer landings, wherein a distance that separates the inner landings is substantially identical to a distance that separates the outer landings, and wherein the inner landings are mechanically coupled by an adhesive material disposed along an inner periphery of the suspension element, the adhesive material having a viscoelastic response that increases stiffness as frequency increases, resulting in a shift of a first breakup mode of the acoustic device from a first frequency to a second, higher frequency.

18. The acoustic device of claim 17, wherein the adhesive material has a viscoelastic response that increases stiffness by at least one order of magnitude as the frequency increases.

19. The acoustic device of claim 17, wherein the inner periphery of the suspension element is defined by respective inner edges of the first surround element and the second surround element.

20. The acoustic device of claim 17, wherein:
the first surround element comprises a half-roll that defines a concave surface and a convex surface;
the second surround element comprises a half-roll that defines a concave surface and a convex surface; and
the first surround element and the second surround element are arranged such that the respective concave surfaces face each other and the respective convex surfaces face away from each other.