Acoustic fillers including acoustically active beads and expandable fillers

Abstract

The present disclosure relates to acoustic fillers including acoustically active beads and expandable fillers. Aspects of fillers for occupying a volume are disclosed. The filler includes an expandable filler positioned in the volume such that it occupies a percentage of the volume. The expandable filler can permanently expand from a first size to a second size when an expansion trigger is applied. The filler also includes an acoustic filler composed of a plurality of acoustically active beads, the acoustic filler positioned in the volume with the expandable filler such that the acoustic filler can adsorb gas flowing into the volume. Other embodiments are disclosed and protected by the claims.

Description

Technical Field

[0001] Aspects disclosed herein relate generally to audio speakers, and particularly, but not exclusively, to audio speakers that may utilize a combination of acoustically active fillers and expandable fillers in a back cavity thereof to improve speaker performance. Background Art

[0002] A loudspeaker consists of a back cavity and a membrane or diaphragm that oscillates and emits sound when driven by an electromagnetic transducer. When the membrane is moved, a variety of different forces act on it, distorting its intended acceleration by the electromagnets and thus the sound waves it emits. Reducing these additional membrane forces improves the sound quality.

[0003] One of the forces acting on the membrane is the pressure fluctuations in the back cavity due to the compression and decompression of the air by the moving membrane. These pressure fluctuations can be reduced by increasing the space of the back cavity (e.g., making it larger). However, in handheld devices such as mobile phones, it is only possible to increase the size of the back cavity to a small extent, because these devices should remain small and light.

[0004] In the context of the present disclosure, "acoustically active beads" refers to any entity of various geometric shapes and capable of adsorption and desorption. The adsorbent material may, for example, include zeolites, activated carbon or metal organic frameworks (MOFs). Summary of the invention

[0005] Various aspects of an audio speaker are described herein. The audio speaker includes a housing defining a back cavity located behind a speaker driver, such that the speaker driver can convert an electrical audio signal into sound, and the sound can propagate through gas in the back cavity. A permeable partition divides the back cavity into a back cavity defined between the speaker driver, the housing, and the permeable partition, and an adsorption cavity defined between the housing and the permeable partition. The permeable partition includes a plurality of holes that place the back cavity in fluid communication with the adsorption cavity to allow gas to flow between the back cavity and the adsorption cavity. An expandable filler is positioned in the adsorption cavity so that it occupies a percentage of the volume of the adsorption cavity. The expandable filler can permanently expand from a first size to a second size when an expansion trigger is applied. An acoustic filler is positioned in the adsorption cavity together with the expandable filler to adsorb the gas, and the acoustic filler includes a plurality of acoustically active beads.

[0006] Aspects of a filler for occupying a volume are described herein. The filler includes an expandable filler positioned in the volume such that it occupies a percentage of the volume. The expandable filler can permanently expand from a first size to a second size when an expansion trigger is applied. An acoustic filler is positioned in the volume with the expandable filler such that the acoustic filler can adsorb gas flowing into the volume. The acoustic filler includes a plurality of acoustically active beads.

[0007] Various aspects of a method are described herein, the method comprising inserting an expandable filler into a back cavity of an audio speaker such that the expandable filler occupies a percentage of the back cavity. Inserting an acoustic filler into at least a portion of the back cavity not occupied by the expandable filler such that the acoustic filler can adsorb gas flowing into the back cavity; the acoustic filler comprises a plurality of acoustically active beads. Applying an expansion trigger to the expandable filler and the acoustic filler such that the expandable filler permanently expands from a first size to a second size to reduce movement of the acoustically active beads in the back cavity.

[0008] Various aspects of an expandable material are described herein. The expandable material includes a solvent, a plurality of polymer particles mixed into the solvent, a polymer binder, and a modifier, which is a chemically inert density adjusting compound or a viscosity adjusting compound. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Non-limiting and non-exhaustive aspects of the present invention are described with reference to the following figures, wherein like reference numerals refer to like parts throughout the various views unless otherwise specified.

[0010] Figure 1 It is a pictorial view of aspects of an electronic device.

[0011] FIG. 2A to FIG. 2B are cross-sectional views of various aspects of an audio microspeaker for use in an electronic device.

[0012] Figure 3 is a schematic diagram of aspects of an electronic device including aspects of an audio microspeaker such as FIG. 2A to FIG. 2B Those audio micro speakers shown.

[0013] FIG. 4A to FIG. 4C A cross-sectional view of an aspect of the back cavity of an audio micro speaker, such as FIG. 2A to FIG. 2B As shown in those of , it has acoustically active beads and expandable beads. Figure 4A shows an expandable bead in its unexpanded state, Figure 4B The expandable bead is shown in its expanded state.

[0014] Figure 4C The expansion of a single expandable bead is shown.

[0015] FIG. 5A to FIG. 5B A cross-sectional view of an aspect of the back cavity of an audio micro speaker, such as FIG. 2A to FIG. 2B As shown in those of , where there is a swellable coating on the wall of the back cavity. Figure 5A The coating is shown in its unexpanded state, Figure 5B The coating is shown in its expanded state.

[0016] Figure 6It is used to prepare FIG. 4A to FIG. 4C and FIG. 5A to FIG. 5B A flow chart of aspects of a process for using aspects of an expandable material is shown in FIG.

[0017] Figure 7 Is used for use in FIG. 4A to FIG. 4C and FIG. 5A to FIG. 5B A flow chart of aspects of a process for using an expandable material is shown in FIG.

[0018] FIG. 8A to FIG. 8D A perspective view and a series of side views of a simplified embodiment of a back cavity showing different orientations of the back cavity.

[0019] Fig. 9 The figure shows the situation when the back cavity does not have expandable beads. FIG. 8A to FIG. 8D A graph showing the resonant frequency shift produced by the back cavity orientation is shown.

[0020] Fig.10 The figure shows that when the back cavity has expandable beads, FIG. 8A to FIG. 8D A graph showing the resonant frequency shift produced by the back cavity orientation is shown. DETAILED DESCRIPTION

[0021] The following disclosure describes aspects of a speaker including a back cavity with acoustic filler and expandable filler. Specific details are described to provide an understanding of the various aspects disclosed, but one skilled in the art will recognize that the invention can be practiced without one or more of the details or with other methods, components, materials, etc. In some cases, well-known structures, materials, or operations are not shown or described in detail, but are still included within the scope of the invention.

[0022] References throughout this specification to "one aspect" or "aspects" mean that the features, structures, or characteristics may be included in at least one of the aspects, so that the appearance of "in one aspect" or "in aspects" does not necessarily all refer to the same aspect. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more aspects.

[0023] One way to reduce back cavity pressure fluctuations in handheld devices is to place adsorbent materials such as carbon black or zeolites into the back cavity. It has been shown that these materials can actually increase the back cavity - in other words, their presence in the back cavity enhances speaker performance as if the speaker's back cavity had become larger.

[0024] speaker

[0025] Figure 1Aspects of an electronic device 100 are shown. In one aspect, the electronic device 100 may be a smart phone device, but in other aspects may be any other portable device or fixed device or apparatus, such as a laptop or tablet computer. The electronic device 100 may include various functions to allow the user to access functions related to, for example, calls, voicemails, music, emails, internet browsing, plans, and photos. The electronic device 100 may also include hardware that facilitates such capabilities. For example, an integrated microphone 102 may pick up the user's voice during a call, and an audio speaker 106 (e.g., a micro speaker) may deliver far-end voice to an end user during a call. The audio speaker 106 may also emit sounds associated with music files played by a music player application running on the electronic device 100. The display 104 may present a graphical user interface to the user to allow the user to interact with the electronic device 100 and / or the application running on the electronic device 100. Other conventional features are not shown, but they may certainly be included in the electronic device 100.

[0026] FIG. 2A to FIG. 2B Various aspects of an audio speaker of an electronic device are shown. In aspect, the audio speaker 106 includes a housing, such as a speaker housing 204, that supports a speaker driver 202. The speaker driver 202 can be a speaker for converting an electrical audio signal into sound. For example, the speaker driver 202 can be a miniature speaker having a diaphragm 206 supported by a speaker surround 208 relative to the housing 204. The speaker surround 208 can be bent to allow the diaphragm 206 to move axially along a central axis 210. For example, the speaker driver 202 can have a motor assembly attached to the diaphragm 206 to move the diaphragm 206 axially with a piston-like motion (i.e., forward and backward) along the central axis 210. The motor assembly can include a voice coil 212 that moves relative to a magnetic assembly 214. In aspect, the magnetic assembly 214 includes a magnet, such as a permanent magnet, attached to a top plate on the front surface and a yoke on the rear surface. The top plate and the yoke can be formed of a magnetic material to produce a magnetic circuit with a magnetic gap in which the voice coil 212 swings forward and backward. Thus, when an electrical audio signal is input to the voice coil 212 , a mechanical force may be generated to move the diaphragm 206 to radiate sound forward along the central axis 210 into the surrounding environment outside of the housing 204 .

[0027] The movement of the diaphragm 206 to radiate sound forward toward the surrounding environment can cause the sound to be pushed backward. For example, sound can propagate through the gas that fills the space surrounded by the housing 204. More specifically, the sound can travel through the air in the back cavity 216 behind the diaphragm 206. The back cavity 216 can affect the acoustic performance. Specifically, the size of the back cavity 216 can affect the natural resonance peak of the audio speaker 106. For example, increasing the size of the back cavity 216 can result in a louder bass.

[0028] In aspect, the back cavity 216 within the housing 204 can be separated into several cavities. For example, the back cavity 216 can be separated into a rear cavity 218 and an adsorption cavity 220 by a permeable partition 222. The rear cavity 218 can be located directly behind the speaker driver 202. That is, the speaker driver 202 can be suspended or supported in the rear cavity 218 so that the sound radiated backward from the diaphragm 206 is directly transmitted into the rear cavity 218. Therefore, at least a portion of the rear cavity 218 can be defined by the back side of the diaphragm 206, and similarly defined by the back side of the speaker surround 208. In addition, considering that the permeable partition 222 can extend across the cross-sectional area of ​​the back cavity 216 between several walls of the housing 204, the rear cavity 218 can be further defined by the inner surface of the housing 204 and the first side 224 of the permeable partition 222.

[0029] The back cavity 216 may include a sorption cavity 220 separated from the back cavity 218 by a permeable partition 222, that is, the sorption cavity 220 may be adjacent to the back cavity 218 on the opposite side of the permeable partition 222. In an aspect, the sorption cavity 220 is defined by the inner surface of the housing 204 surrounding the back cavity 216, and may also be defined by the second side 226 of the permeable partition 222. Therefore, the back cavity 218 and the sorption cavity 220 may be adjacent to each other through the permeable partition 222.

[0030] In one embodiment, the adsorption chamber 220 can be in fluid communication with the surrounding environment through a filling port 228. For example, the filling port 228 can be a hole through the wall of the housing 204 that allows the adsorption chamber 220 to be in fluid communication with the surrounding environment. The port can be formed during molding of the housing 204, or formed by a secondary operation, as described further below. In order to isolate the adsorption chamber 220 from the surrounding environment, a plug 230 can be located in the filling port 228, for example, after the adsorption chamber 220 is filled with an adsorption filler 232, to prevent the adsorption filler 232 from leaking into the surrounding environment. Therefore, the adsorption chamber 220 can be partially defined by the surface of the plug 230.

[0031] The audio speaker 106 may have a form factor having any number of shapes and sizes. For example, the audio speaker 106, and therefore the housing 204, may have an outer profile that appears to be a combination of a hexahedron, a cylinder, and the like. For example, one such outer profile may be a thin box. In addition, the housing 204 may have thin walls, and therefore, the cross-sectional area of ​​a plane passing through the housing 204 at any point may have a geometric shape corresponding to the outer profile, including a rectangle, a circle, a triangle, and the like. Therefore, the permeable partition 222 extending through the back cavity 216 within the housing 204 may also have a variety of outer shapes. For example, in the case where the audio speaker 106 is a hexahedron, such as a low-profile box having a rectangular profile that protrudes in a direction orthogonal to the central axis 210, the permeable partition 222 may have a rectangular profile.

[0032] The adsorbent filler 232 may be packaged in the adsorbent cavity 220 by directly filling (e.g., filling) the adsorbent cavity 220 with loose adsorbent material and / or by coating the inner surface of the shell 204 with the adsorbent material. Directly filling the adsorbent cavity 220 may be different from indirectly filling the adsorbent cavity 220 because the loose adsorbent material may be poured, injected, or otherwise transferred into the adsorbent cavity 220 in a loose and unconstrained manner, so that the adsorbent material may move freely within the adsorbent cavity 220. That is, the adsorbent material may be constrained only by the walls defining the adsorbent cavity 220, such as the inner surface of the shell 204, rather than by a separate constrained piece (e.g., a bag, a pouch, a box, etc.) filled with the adsorbent material before or after being inserted into the adsorbent cavity 220. In aspect, at least a portion of the space of the adsorbent cavity 220 is filled with the adsorbent filler 232, and at least a portion of the inner surface of the shell 204 within the adsorbent cavity 220 is covered by the adsorbent filler 232. The adsorbent filler 232 may be any suitable adsorbent material capable of adsorbing the gas located in the back cavity 216. For example, the adsorbent filler 232 may include the following combination FIG. 4A to FIG. 4B and FIG. 5A to FIG. 5B The acoustically active beads described above are configured to adsorb air molecules. The adsorbent material may be in the form of loose particles. More specifically, the adsorbent filler 232 may include unbound particles that are free to move within the adsorbent cavity 220, for example, the particles may be shaken during use of the device. Therefore, the permeable partition 222 may be used as a barrier to prevent the adsorbent filler 232 from shaking from the adsorbent cavity 220 into the rear cavity 218 behind the speaker driver 202.

[0033] Figure 2B Another aspect of an audio speaker for an electronic device is shown. In various aspects, the rear cavity 218 and the adsorption cavity 220 can have different relative orientations. For example, in Figure 2A In the illustrated aspect, the adsorption chamber 220 is located to the side of the rear chamber 218, that is, laterally offset from the central axis 210 from the rear chamber 218. Therefore, sound emitted rearward from the diaphragm 206 can be directly transmitted to the rear wall of the rear chamber 218, rather than directly to the permeable partition 222.

[0034] But in Figure 2BIn the illustrated aspect, the audio speaker 106 includes an axially arranged back cavity 216. For example, the adsorption cavity 220 can be located directly behind the back cavity 218, such that the central axis 210 can intersect the back cavity 218 behind the diaphragm 206 and the adsorption cavity 220 on the opposite side of the permeable partition 222. Therefore, the permeable partition 222 can span the back cavity 216 along a plane, so that the normal vector 250 out of the first side 224 and pointing to the back cavity 218 is oriented in a direction parallel to the central axis 210. For example, the back cavity 218 and the adsorption cavity 220 can each be flat and thin, and both are positioned front-to-back along the central axis 210. Therefore, sound emitted rearward by the diaphragm 206 can propagate directly through the back cavity 218 and the permeable partition 222 along the central axis 210 and into the adsorption cavity 220.

[0035] The permeable partition 222 can be oriented at any angle relative to the central axis 210. That is, while the first face can face in a direction orthogonal or parallel to the central axis 210, in the aspect, the permeable partition 222 is oriented at an oblique angle relative to the central axis 210. Therefore, within the scope of the present specification, the adsorption chamber 220 can be some combination of being located to the side of the adsorption chamber 220 or directly behind it. In any case, the rear chamber 218 and the adsorption chamber 220 can be adjacent to each other such that opposite sides of the permeable partition 222 define a portion of each chamber.

[0036] Figure 3 Aspects of an electronic device including a micro speaker are schematically shown. As described above, the electronic device 100 can be one of several types of portable or fixed devices or apparatuses having circuits suitable for specific functions. Therefore, the illustrated circuits are provided by way of example and not limitation. The electronic device 100 can include one or more processors 902 that execute instructions to implement the different functions and capabilities described above. The instructions executed by the one or more processors 902 of the electronic device 100 can be retrieved from a local memory 904, and these instructions can be in the form of an operating system program with a device driver, and one or more application programs running on top of the operating system to perform the different functions described above, such as making or dialing calls and / or music playback. For example, the processor 902 can directly or indirectly implement a control loop and provide a drive signal to the voice coil 212 of the audio speaker 106 to drive the diaphragm 206 to move and produce sound.

[0037] The audio speaker 106 having the above structure may include a back cavity 216 divided into two cavities by a sound-permeable barrier (e.g., a permeable partition 222), the two cavities being: a back cavity 218 located directly behind the speaker driver 202, and an adsorption cavity 220 adjacent to the back cavity 218 across the permeable partition 222. In addition, the adsorption cavity 220 may be directly filled with an adsorption material so that the back cavity 216 has an adsorption volume just defined between the system housing 204 and the sound-permeable barrier. The adsorption volume may reduce the overall spring stiffness of the back cavity 216 and reduce the natural resonance peak of the audio speaker 106. That is, the adsorption filler 232 may absorb and release randomly traveling air molecules when the pressure in the back cavity 216 fluctuates in response to the propagating sound. Therefore, the audio speaker 106 may have higher efficiency at lower frequencies compared to a speaker having a back cavity 216 without an adsorption material. Therefore, the overall output power of the audio speaker 106 may be improved. More specifically, the audio speaker output can be louder during dialing or music playback, especially in the low-frequency audio range. Thus, the audio speaker 106 having the above structure can produce a louder, richer sound in the bass range using the same form factor as a speaker back cavity without multiple cavities, or can produce equivalent sound in the bass range in a smaller form factor. In addition, because the adsorption chamber 220 is defined between the housing 204 and the permeable partition 222 (the two are sealed together), the form factor of the audio speaker 106 can be smaller than, for example, a speaker back cavity that holds a secondary container filled with adsorbent material, such as a mesh bag.

[0038] Back cavity configuration with expandable filler

[0039] If the back cavity is not completely and densely filled with acoustically active beads, the use of beads may result in different sound qualities. This is mainly due to undesired movement of the beads within the back cavity. For example, when changing the spatial orientation of the loudspeaker module, the sound quality may change because the beads occupy the lowest possible space within the cavity. However, it is preferred to have a constant sound quality regardless of the spatial orientation.

[0040] A simple way to fix the acoustically active beads is to glue them together. However, since the acoustically active beads include a highly porous structure required to improve the acoustic properties, it is not possible to glue them together without losing the acoustic properties. The pores of the beads will be at least partially blocked by the glue, since the glue will penetrate the pores and, when hardened, will hinder any gas from passing through these pores or from being stored in these pores. And, unfortunately, capillary forces favor the penetration of the glue into the pores, i.e., the glue tends to be more likely to block the pores of the beads than to fix the beads simply by gluing them together. Another way to fix the beads would be to completely fill the back cavity. But in the production process, small variations in the filling density are extremely difficult to control and almost impossible to avoid.

[0041] Through many experiments conducted by the inventors, the results show that adding a second material comprising an expandable filler to the bead assembly and the expansion of this material can prevent the bead assembly from moving. By the correct amount of volume expansion of such a material, the beads are compressed and / or squeezed together so that they are fixed. Therefore, the changes in sound quality caused by different spatial orientations of the speaker can be reduced or completely suppressed.

[0042] FIG. 4A to FIG. 4C Aspects of an expandable filler material including a plurality of expandable beads in an audio speaker back cavity 400 are shown. Figure 4A shows an expandable bead before expansion, and Figure 4B The expandable beads are shown after expansion. Figure 4C The expansion of a single expandable bead is shown.

[0043] The back cavity 400 is a three-dimensional space defined by a plurality of walls 402a-402d. In this case, at least one of the walls 402a, wall 402a, is porous to allow gas to flow into and out of the back cavity. In the illustrated aspect, the back cavity 400 is a hexahedron, but in other aspects, it may be some other type of regular or irregular polyhedron. In other aspects, the back cavity 400 need not be a polyhedron, but may be composed of a combination of curved surfaces, a combination of planes, or a combination of the two.

[0044] The back cavity 400 is partially filled with an expandable filler consisting of a plurality of expandable beads 404 and partially filled with an acoustic filler comprising a plurality of acoustically active beads 406. The acoustically active beads 406 are beads having adsorptive properties that allow the beads to adsorb or desorb gases driven by the driver portion of the speaker through the porous wall 402a to reach the back cavity 400. In the illustrated aspect, the expandable beads 404 and the acoustically active beads 406 have the same shape—both beads are spherical in this case, but in other aspects, the two types of beads need not have the same shape.

[0045] In one aspect, the average size of the plurality of expandable beads 404 is similar to the average size of the plurality of acoustically active beads 406, meaning that the sizes of the beads are within an order of magnitude of each other, and in another aspect, within 90%-110% of each other. The density of the expandable beads 404 is also similar to the density of the acoustically active beads 406, meaning that their densities are within 90%-110% of each other. When the expandable beads 404 and the acoustically active beads 406 are mixed within the back cavity 400 or before being inserted into the back cavity, it is desirable that the expandable beads are evenly distributed among the acoustically active beads, or vice versa. The similarity in size and density of the expandable beads 404 and the acoustically active beads 406 may be desirable to reduce or prevent the two types of beads from being separated when mixed; a larger difference in size or density may allow gravity or other inertial forces (such as those caused by vibration) to separate the two types of beads from each other. It is also advantageous to have expandable beads of similar size and density as the acoustically active beads, as existing methods for packing the beads can be used with no or only minor modifications.

[0046] For example, a mixture of two spheres having at least one order of magnitude different sizes will separate quickly upon vibration, and the smaller spheres will fall through the gaps between the larger spheres and collect in the bottom. However, in some aspects, expandable beads and acoustically active beads having different sizes and densities can be used, for example, if the mixing of the two types of beads is done directly before filling the speaker back cavity.

[0047] Figure 4B The expandable beads 404 are shown in their expanded state. As further explained below, the expandable beads 404 are formulated so that they permanently expand from a first size to a larger second size when an expansion trigger is applied to the beads. The expansion trigger can be heat, light, electromagnetic radiation such as ultraviolet (UV) radiation, an alternating magnetic field, or some other trigger. When the expandable beads 404 expand, they reduce the space filled by the acoustically active beads 406, thereby applying mechanical forces to the acoustically active beads, thereby substantially reducing or eliminating the movement or mobility of the acoustically active beads within the back cavity 400. In other words, when expanded, the expandable beads 404 partially or completely lock or fix the acoustically active beads 406 in place. In one aspect, when expanded, the expandable beads 404 may occupy between 0.5% and 20% of the back cavity, for example, more specifically, between 1% and 2% of the back cavity. The acoustically active beads occupy at least a portion of the remainder of the back cavity. Those skilled in the art will appreciate that the percentage of back cavity 400 occupied by expandable beads and acoustically active beads will not reach 100% of the back cavity due to the presence of void spaces between the beads.

[0048] Figure 4CThe expansion of a single expandable bead 404 is shown. Upon application of an expansion trigger, the bead 404 expands from a radius ra to a radius rb, thereby increasing its volume from a volume Va to a volume Vb. Depending on the formulation of the bead and the expansion coefficient defined by f = Vb / Va, where Vb is the volume after expansion and Va is the volume before expansion, the free volume within the back cavity is reduced. An assembly of multiple acoustically active beads is squeezed together to obtain a block in which all beads are mostly or completely immobilized. Generally speaking, the higher f, the higher the degree of immobilization.

[0049] Acoustically active beads 406 may be any of a variety of known formulations. In one aspect, they may have a formulation comprising a polymer binder and a zeolite, but other bead formulations are possible. Examples of adsorbent materials that may be used include zeolites, activated carbon, or metal organic frameworks (MOFs). Since expandable formulations do not contribute to increasing virtual volume, and zeolite beads can achieve the purpose of increasing virtual volume, there is an optimal percentage of the formulation in the acoustic beads, allowing reasonable fixation and satisfactory acoustic performance. It is advantageous to use an expandable formulation between 0.5% and 20% by mass, more advantageously to use an expandable formulation of 1% and 5% by mass, and most advantageously to use an expandable formulation of 1% and 2% by mass.

[0050] FIG. 5A to FIG. 5B Another aspect is shown where the expandable filler may be applied to the back cavity 500 as a layer or sheet including expandable portions that may be placed into the back cavity.

[0051] Similar to the back cavity 400, the back cavity 500 is a three-dimensional space defined by a plurality of walls 502a-502d. Each of the walls 502b-502d has an inner surface 503: the wall 502b has an inner surface 503b, the wall 502c has an inner surface 503c, and the wall 502d has an inner surface 503d. In this case, at least one of the walls 502a, the wall 502a is porous so as to allow gas to flow into and out of the back cavity. In the illustrated aspect, the back cavity 500 is a regular hexahedron, but in other aspects, it may be some other type of regular or irregular polyhedron. In other aspects, the back cavity 500 need not be a polyhedron, but may be composed of a combination of curved surfaces, a combination of planes, or a combination of the two.

[0052] The back cavity 500 is partially filled with an expandable filler comprising a plurality of expandable layers or sheets 504 deposited on an inner surface 503 of at least one wall 502. The back cavity 500 is also partially filled with an acoustic filler comprising a plurality of acoustically active beads 406. The acoustically active beads 406 are beads having adsorptive properties that allow the beads to adsorb or desorb gases driven by the driver portion of the speaker through the porous wall 502a and into the back cavity 500.

[0053] The illustrated aspect has layers 504 deposited on multiple interior surfaces: layer 504b is deposited on interior surface 503b, layer 504c is deposited on interior surface 503c, and layer 504d is deposited on interior surface 503d. Because wall 502a is porous, no layer 504 is deposited on its interior surface, as this would prevent gas from flowing into and out of back cavity 500. In other aspects, layers 504 can be positioned on more or fewer interior surfaces 503 than the number of interior surfaces shown, ranging from a single interior surface of the back cavity to every interior surface, except for the interior surface of the porous wall of the back cavity.

[0054] Figure 5B The expandable layer 504 is shown in its expanded state. As further explained below, the expandable layers 504 are formulated so that they permanently expand from a first dimension t to a larger second dimension T when an expansion trigger is applied: layer 504b expands from thickness tb to thickness Tb, layer 504c expands from thickness tc to thickness Tc, and so on. The expansion trigger can be heat, light, electromagnetic radiation such as ultraviolet (UV) radiation, an alternating magnetic field, or some other trigger. When the layers 504 expand, they reduce the volume filled by the acoustically active beads 406, thereby applying mechanical forces to the acoustically active beads, thereby substantially reducing or eliminating the movement or mobility of the acoustically active beads within the back cavity 500. In other words, when expanded, the layer 504 partially or completely locks or fixes the acoustically active beads 406 in place. In one aspect, when expanded, the expandable filler 404 can occupy between 0.5% and 20% of the back cavity, and more specifically, for example, the expandable filler can be between 1% and 2% of the back cavity. The acoustic filler occupies at least a portion of the remainder of the back cavity. Those skilled in the art will appreciate that the percentage of back cavity 500 occupied by expandable layer 504 and acoustically active beads 406 will not reach 100% of the back cavity due to the presence of void spaces between the acoustically active beads.

[0055] Expandable filler manufacturer

[0056] Figure 6 A method for preparing an expandable filler such as a back cavity of an audio speaker is shown. FIG. 4A to FIG. 4B and FIG. 5A to FIG. 5B Aspects of the process 600 of an expandable filler are shown. The blocks shown in dashed lines are optional. The process begins at block 602.

[0057] At block 604, an aqueous slurry of expandable polymer material (i.e., a semi-liquid mixture of fine particles suspended in a solvent, in this case water) is formed by combining commercially available expandable polymer microspheres, optionally a density modifier, a solvent, and a polymer binder. The binder may be a polyacrylic acid or a polyurethane sol; surprisingly, the use of a polymer binder such as an acrylic acid or a polyurethane sol produces mechanically stable beads that retain their geometric shape upon expansion.

[0058] At block 606, depending on whether the expandable filler is to be a slurry that can be used to coat the inner surface of the back cavity, such as FIG. 5A to FIG. 5B , or whether the expandable filler will be formed as expandable beads for use in the back cavity, as shown in FIG. 4A to FIG. 4B As shown in , two different process options are available. If the expandable material is to be a slurry, at box 608, a thickener or viscosity adjusting compound is added to the slurry to adjust the viscosity of the slurry or to produce a stable gel. A slurry having a viscosity similar to that of the glue used in the commercial process has the advantage that existing glue coating equipment can be used. In one embodiment, the viscosity adjusting compound may be fumed silica, but different viscosity adjusting compounds may be used in other aspects. At box 610, the resulting slurry is mechanically stirred until fully mixed. If the stirred mixture does not yet have the desired consistency, it is allowed to rest or otherwise processed to thicken it into a slurry. The process begins at box 611.

[0059] If the expandable filler is to be expandable beads, then at optional block 612, a density adjusting compound is added to the slurry to adjust the density of the expandable beads to be similar to the density of the acoustically active beads with which they will be mixed. The density of such beads can be increased by adding relatively high density compounds, such as finely dispersed metal oxides, to the slurry. Oxides that can be used include zinc oxide (ZnO), tin oxide (SnO2), titanium oxide (TiO2), bismuth oxide (Bi2O3), zirconium oxide (ZrO2), or hafnium oxide (HfO2), among others. The density of many oxides, particularly those listed above, is higher than that of typical polymers, so that the addition of these oxides increases the density of the final beads.

[0060] At frame 614, the slurry is mechanically agitated until fully mixed. At frame 616, the slurry is pressurized and forced through an oscillating nozzle to produce drops of the slurry. For example, air can be used to pressurize the slurry and push the slurry through an oscillating nozzle of suitable diameter, which is powered by an amplifier connected to a functional generator. At frame 618, the drops that emerge from the nozzle at frame 616 are frozen, for example, by falling through a cooling tower. For example, the drops fall in a cooling tower about 3 meters high and are continuously cooled to, for example, a top temperature of -20±5°C and a bottom temperature of -50±5°C by a mixture of nitrogen and air.

[0061] At box 620, the frozen drops are collected from the cooling tower and freeze-dried, for example, by being subjected to a vacuum at box 624 to sublime any residual water in the drops. For example, the frozen drops can be collected in a round-bottom flask that is precooled to about -20°C and subjected to a vacuum until the water (ice) is completely removed from the frozen drops by sublimation, thereby freeze-drying the frozen drops into beads. In addition to or in lieu of freeze drying at box 622, the frozen drops or freeze-dried beads can be collected and heated at box 624 to obtain the final beads. For example, the freeze-dried beads can be collected on a steel tray, heated to a suitable temperature in a forced convection air oven, maintained at that temperature for a certain amount of time, and then cooled.

[0062] At box 626, the beads are mechanically filtered or sieved to obtain beads of a similar size to the acoustically active beads to be used. The process begins at box 628. Additional details of specific aspects of process 600 are given in Examples 1-3 below.

[0063] Example 1

[0064] 100.0 g of acrylic emulsion, 56.0 g of deionized water, 34.0 g of fine zinc oxide, 2.00 g of 15% KOH solution and 33.0 g of F-48D expandable microspheres were placed in a 0.5 L beaker. The slurry was stirred for 1 hour and dripped into excess liquid nitrogen using an electronically controlled oscillating nozzle. The frozen drops were freeze dried and sieved to obtain a fraction with a pellet diameter of 0.355 mm to 0.400 mm. A smaller fraction of about 100 mg was separated from the batch and when heated to 115° C. for about 2 minutes, the beads expanded several times in volume without losing their round shape and integrity.

[0065] Example 2

[0066] 100.0 g of acrylic emulsion, 60.0 g of deionized water, 32.0 g of fine zinc oxide, 2.00 g of 15% KOH solution and 35.0 g of EML101 expandable microspheres were placed in a 0.5 L beaker. The slurry was stirred for 1 hour and dripped into excess liquid nitrogen using an electronically controlled oscillating nozzle. The frozen drops were freeze dried and sieved to obtain a fraction with a bead diameter of 0.355 mm to 0.400 mm. A smaller fraction of about 100 mg was separated from the batch and when heated to 115° C. for about 2 minutes, the beads expanded several times in volume without losing their round shape and integrity.

[0067] The beads obtained as described above were mixed with acoustically active beads in a ratio of 1:49 and the back cavity loudspeaker was filled with this mixture. On the one hand, the relative amount of expandable beads should be sufficient to fix the acoustic beads after expansion, on the other hand, since the expandable beads are a neutral material, they should not be so large as to significantly reduce the acoustic performance of the entire assembly. The loudspeaker was heated at 115°C for a few minutes and its horizontal and vertical acoustic performance was measured. The loudspeaker containing the expandable beads exhibited the same performance independently of its spatial orientation.

[0068] Example 3

[0069] In a beaker, 0.15 g of fumed silica (particle size < 7 nm) and 5.00 g of F-48D expandable microspheres were added to 5.00 g of acrylic emulsion. The components were carefully mixed using a spatula to obtain a thick film slurry. About 40 mg of this slurry was placed as a strip in the corner of the back cavity of the speaker and dried at 70°C for 1 hour. The back cavity of the speaker was filled with acoustic beads, sealed and heated at 115°C for a few minutes. The speaker with the expanded strip in the back cavity showed the same performance in vertical and horizontal positions.

[0070] Figure 7 700 by which an expandable filler material may be used in an audio speaker back cavity. The process begins at block 702. At block 704, the back cavity is filled with a slurry, depending on whether the application is to use the slurry to coat the inner surface of the back cavity, such as FIG. 5A to FIG. 5B , or whether expandable beads in the back cavity will be used, as shown in FIG. 4A to FIG. 4B As shown in , two different process options are available.

[0071] If the slurry is to be used to coat the interior surface of a back cavity, then at block 706, the slurry is deposited as an expandable layer or sheet on at least one interior surface of the back cavity (see FIG. 5A to FIG. 5B). The application of the slurry can be carried out by various methods, such as doctor blade, spray or printing. The use of such a slurry is advantageous because the location of the unexpanded and subsequently expanded material can be precisely determined, while in the mixture of expandable beads and acoustically active beads, the expansion occurs statistically throughout the mixture of acoustically active beads and expandable beads.

[0072] At box 708, the deposited expandable layers are allowed to dry on the surface on which they were deposited, and at box 710, the remaining portion of the back cavity is filled with acoustically active beads. The back cavity is then closed so that the acoustically active beads do not flow out. At box 712, an expansion trigger is applied to the back cavity to permanently expand the expandable layer, thereby shrinking the acoustically active beads to a smaller volume and substantially fixing them. The expansion trigger can be heat, but other triggers such as electromagnetic waves or alternating magnetic fields are also possible. The process starts at box 714.

[0073] If expandable beads are to be used in the back cavity, then at block 716, the expandable beads are mixed with the acoustically active beads in the desired ratio. At block 718, the bead mixture is inserted into the back cavity (see FIG. 4A to FIG. 4B ), and then close the back cavity so that the beads do not flow out. In other aspects of the process, the expandable beads can be inserted into the back cavity before or after the acoustically active beads are inserted. At block 720, an expansion trigger is applied to the back cavity to permanently expand the expandable beads, thereby shrinking the acoustically active beads to a smaller volume and substantially fixing them. The expansion trigger can be heat, but other triggers such as electromagnetic waves or alternating magnetic fields are also possible. The process starts at block 722.

[0074] result

[0075] FIG. 8A to FIG. 8D 800 for an audio speaker in a smartphone such as an iPhone. The representation of the back cavity 800 does not necessarily represent the exact shape of the back cavity, but rather illustrates three back cavity orientations for testing whether the fixed acoustically active beads are effective in maintaining uniform sound from the audio speaker.

[0076] The back cavity 800 is a hexahedron and has three pairs of surfaces: a pair of surfaces 1 having the largest area, a pair of surfaces 3 having the smallest area, and a pair of surfaces 2 having an area between surfaces 1 and 3 . FIG. 8B to FIG. 8D The three orientations used are shown. Figure 8B In , surface 3 is horizontal, while surfaces 1 and 2 extend vertically. Figure 8C In , surface 2 is horizontal, while surfaces 1 and 3 extend vertically. And in Fig.8D Surface 1 is horizontal, while surfaces 2 and 3 extend vertically.

[0077] Fig. 9 The speaker performance of a speaker whose back cavity does not include expandable filler (e.g., a micro speaker) is shown. The speaker back cavity made of transparent plastic is filled with acoustically active beads (but not very densely) so that the beads can move slightly therein during vibration - and is sealed. The acoustic performance is measured for various spatial orientations. In the vertical position ( Figure 8B ), after a period of time, less free space appears in the speaker back cavity because the bead collection becomes slightly denser when vibrated by sound waves. Therefore, the vertical ( Figure 8B ) and level ( Fig.8D ) orientation, the acoustic performance of the speaker is different.

[0078] Fig. 9 The electrical impedance plotted against frequency for a loudspeaker module filled with acoustically active beads at three different orientations is shown. Curve 1 was recorded with the module in Figure 8B orientation; Curve 2 is recorded, where the module is in Fig.8D and curve 3 was recorded with the same spatial alignment as used for curve 1, but with an opposite surface 3 on top. By changing the orientation of the loudspeaker, changes in the resonant frequency were recorded up to 74 Hz.

[0079] Fig.10 Shows the use of FIG. 4A to FIG. 4B The results for the expandable filler are shown. The graph shows the electrical impedance plotted against frequency for a loudspeaker module filled with a mixture of acoustically active beads and expandable beads at two different orientations.

[0080] The expandable beads from Example 1 above in an unexpanded state were mixed with acoustically active beads in a ratio between 1:4 and 1:200. The back cavity of the loudspeaker was filled with this mixture and sealed. The loudspeaker was heated for several minutes at a temperature sufficient to trigger the expansion of the beads, and its acoustic performance in the horizontal and vertical directions was measured. The expandable beads fixed the acoustically active bead collection and prevented the acoustically active beads from aggregating in a portion of the loudspeaker back cavity. The loudspeaker containing the expanded beads exhibited the same performance independent of its spatial orientation. Curve 1 was recorded with the module in Fig.8D orientation, while curve 2 is recorded where the module is in Figure 8B The curves are within the measurement error and are essentially the same in the low frequency region below 1000 Hz.

[0081] The above description of various aspects is not intended to be exhaustive or to limit the invention to the form described. Specific aspects and examples of the invention are described herein for illustrative purposes, but various modifications are possible. To assist the Patent Office and any reader of any patent issued in this application in interpreting the appended claims, applicants wish to note that they do not intend any of the appended claims or claim elements to invoke 35 U.S.C. §112(f) unless the words "means for..." or "step for..." are expressly used in a particular claim.

Claims

1. An audio speaker, comprising: a housing defining a back cavity behind a speaker driver, wherein the speaker driver is capable of converting an electrical audio signal into sound such that the sound can propagate through a gas in the back cavity; a permeable partition for dividing the back cavity into a back cavity defined between the speaker driver, the housing and the permeable partition, and a sorption cavity defined between the housing and the permeable partition, and wherein the permeable partition includes a plurality of apertures that place the back cavity in fluid communication with the sorption cavity to allow the gas to flow between the back cavity and the sorption cavity; an expandable polymer filler positioned in the sorption chamber such that it occupies a percentage of the volume of the sorption chamber, wherein the expandable polymer filler is capable of permanently expanding from a first size to a second size upon application of an expansion trigger; and an acoustic filler positioned in the adsorption chamber together with the expandable polymer filler to adsorb the gas, the acoustic filler comprising a plurality of acoustically active beads, and The expandable polymer filler includes a plurality of expandable polymer beads mixed with the acoustically active beads, and the expandable polymer beads retain their geometric shape after expansion.

2. The audio speaker of claim 1, wherein the expandable polymer filler comprises an expandable polymer layer positioned on at least one interior surface of the adsorption cavity.

3. The audio speaker of claim 1, wherein the density of the expandable beads is within 90%-110% of the density of the acoustically active beads.

4. The audio speaker of claim 1, wherein an average size of the plurality of expandable polymer beads is within an order of magnitude of an average size of the plurality of acoustically active beads.

5. The audio speaker of claim 1, wherein the expandable polymer filler occupies between 0.5% and 20% of the volume of the adsorption cavity.

6. The audio speaker of claim 1, wherein the expandable polymer filler occupies between 1% and 2% of the volume of the adsorption cavity.

7. The audio speaker of claim 1, wherein the expansion trigger is heat, light, or ultraviolet radiation.

8. A filler for occupying a volume, the filler comprising: an expandable polymer filler positioned in the volume such that it occupies a percentage of the volume, wherein the expandable polymer filler is capable of permanently expanding from a first size to a second size upon application of an expansion trigger; and an acoustic filler positioned in the volume with the expandable polymer filler such that the acoustic filler can adsorb gas flowing into the volume, the acoustic filler comprising a plurality of acoustically active beads, and The expandable polymer filler includes a plurality of expandable polymer beads mixed with the acoustically active beads, and the expandable polymer beads retain their geometric shape after expansion.

9. The filler of claim 8, wherein the expandable polymer filler includes an expandable coating positioned on at least one interior surface of the volume.

10. The filler of claim 8, wherein the density of the expandable polymer beads is within 90%-110% of the density of the acoustically active beads.

11. The filler of claim 8, wherein an average size of the plurality of expandable polymer beads is within an order of magnitude of an average size of the plurality of acoustically active beads.

12. The filler of claim 8, wherein the expandable polymer filler occupies between 0.5% and 20% of the volume.

13. The filler of claim 8, wherein the expandable polymer filler occupies between 1% and 2% of the volume.

14. The filler material of claim 8, wherein the expansion trigger is heat, light, or ultraviolet radiation.

15. A method for filling an audio speaker, comprising: inserting an expandable polymer filler into a back cavity of the audio speaker, wherein the expandable polymer filler occupies a percentage of the back cavity; inserting an acoustic filler into at least a portion of the back cavity not occupied by the expandable polymer filler so that the acoustic filler can adsorb gas flowing into the back cavity, the acoustic filler comprising a plurality of acoustically active beads; as well as applying an expansion trigger to the expandable polymer filler and the acoustic filler such that the expandable polymer filler permanently expands from a first size to a second size to reduce movement of acoustically active beads in the back cavity, and The expandable polymer filler includes a plurality of expandable polymer beads mixed with the acoustically active beads, and the expandable polymer beads retain their geometric shape after expansion.

16. The method of claim 15, wherein positioning the expandable polymer filler in a back cavity comprises applying an expandable polymer layer to at least one interior surface of the back cavity.

17. The method of claim 15, wherein the plurality of expandable polymer beads are formed by combining expandable polymer microspheres, a modifier, a solvent, and a polymer binder, and wherein positioning the expandable polymer filler in the back cavity comprises mixing the expandable polymer beads with acoustically active beads, and inserting the mixture of beads into the back cavity.

18. The method of claim 17, wherein the density of the expandable polymer beads is within 90%-110% of the density of the acoustically active beads.

19. The method of claim 17, wherein an average size of the plurality of expandable polymer beads is within an order of magnitude of an average size of the plurality of acoustically active beads.

20. The method of claim 15, wherein the expandable polymer filler occupies between 0.5% and 20% of the volume of the back cavity.

21. The method of claim 15, wherein the expandable polymer filler occupies between 1% and 2% of the volume of the back cavity.

22. The method of claim 15, wherein the expansion trigger is heat, light, or ultraviolet radiation.

23. An audio speaker comprising: a housing defining a back cavity behind a speaker driver, wherein the speaker driver is capable of converting an electrical audio signal into sound such that the sound can propagate through a gas in the back cavity; an expandable filler material comprising a plurality of expandable polymer beads or an expandable polymer layer positioned in the back cavity such that it occupies a percentage of the volume of the back cavity, wherein the expandable filler material is capable of permanently expanding from a first size to a second size upon application of an expansion trigger, and the expandable polymer beads retain their geometric shape after expansion; and An acoustic filler is positioned in the back cavity together with the expandable filler to adsorb the gas, the acoustic filler comprising a plurality of acoustically active beads, wherein the plurality of expandable polymer beads are mixed with the acoustically active beads.

24. The audio speaker of claim 23, wherein the expandable filler comprises the expandable polymer layer positioned on at least one interior surface of the back cavity.

25. The audio speaker of claim 23, wherein the density of the expandable polymer beads is within 90%-110% of the density of the acoustically active beads.

26. The audio speaker of Claim 23, wherein an average size of the plurality of expandable polymer beads is within an order of magnitude of an average size of the plurality of acoustically active beads.

27. The audio speaker of claim 23, wherein the expandable filler occupies between 0.5% and 20% of the volume of the back cavity.

28. The audio speaker of claim 23, wherein the expandable filler occupies between 1% and 2% of the volume of the back cavity.

29. The audio speaker of claim 23, wherein the expansion trigger is heat, light, or ultraviolet radiation.

30. An electronic device comprising: Audio speakers, including: a housing defining a back cavity behind a speaker driver, wherein the speaker driver is capable of converting an electrical audio signal into sound such that the sound can propagate through a gas in the back cavity, an expandable polymer filler positioned in the back cavity such that it occupies a percentage of the volume of the back cavity, wherein the expandable polymer filler is capable of permanently expanding from a first size to a second size upon application of an expansion trigger, and an acoustic filler positioned in the back cavity together with the expandable polymer filler to adsorb the gas, the acoustic filler comprising a plurality of acoustically active beads, and wherein the expandable polymer filler comprises a plurality of expandable polymer beads mixed with the acoustically active beads, and wherein the expandable polymer beads retain their geometric shape after expansion; and A processor is coupled to the audio speaker and to a memory having stored therein one or more applications including instructions that, when executed by the processor, transmit signals to the audio speaker for transduction into sound.

31. An electronic device according to claim 30, wherein the expandable polymer filler comprises an expandable polymer layer formed on at least one inner surface of the back cavity by combining a thickener, a solvent, a polymer binder, and expandable polymer microspheres to produce a slurry that coats at least one inner surface of the back cavity.

32. The electronic device of claim 30, wherein the plurality of expandable polymer beads are formed from expandable polymer microspheres.

33. The electronic device of claim 32, wherein the density of the expandable polymer beads is within 90%-110% of the density of the acoustically active beads.

34. The electronic device of claim 32, wherein an average size of the plurality of expandable polymer beads is within an order of magnitude of an average size of the plurality of acoustically active beads.

35. The electronic device of claim 30, wherein the expandable polymer filler occupies between 0.5% and 20% of the volume of the back cavity.

36. The electronic device of claim 30, wherein the expandable polymer filler occupies between 1% and 2% of the volume of the back cavity.

37. The electronic device of claim 30, wherein the expansion trigger is heat, light, or ultraviolet radiation.

38. The electronic device of claim 30, wherein the electronic device is a smart phone, a tablet computer, or a laptop computer.

39. The electronic device of claim 30, wherein the application comprises one or more of a phone application, a voicemail application, a sound playback application, an email application, an Internet browsing application, a scheduling application, and a photo application.

40. The electronic device of claim 30, further comprising: a microphone coupled to the processor; a radio frequency (RF) circuit coupled to the processor; as well as A display is coupled to the processor.

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