Adding foam to acoustic cavity of audio device

Abstract

The invention relates to adding foam to an acoustic cavity of an audio device. An apparatus of the subject technology includes a speaker that receives an audio signal and generates an acoustic output and an output port that provides the acoustic output to a user. The apparatus also includes a housing containing the speaker and a cavity formed between the speaker and the output port, and an acoustic damping medium disposed in the cavity and configured to cancel acoustic standing waves.

Description

Cross-reference to related applications

[0001] This application claims priority to International Application No. PCT / CN2024 / 126814, filed October 23, 2024, and U.S. Nonprovisional Application No. 19 / 228,578, filed June 4, 2025, the entire contents of which are incorporated herein by reference. Technical Field

[0002] This disclosure relates generally to audio systems, and more specifically to adding foam to the acoustic cavity of an audio device. Background Technology

[0003] Acoustic absorbing components (e.g., foam or fiber materials) are typically used in speaker enclosures to reduce standing waves and enclosure wall warping. These materials are often applied as linings or simple fillers. Speaker modules for mixed reality (MR) headsets must conform to the dimensions and / or shape specified in the industrial design (ID) and use the plastics specified in the product design (PD). This often means that the speaker enclosure is not ideal for sound reproduction in terms of internal cavity dimensions and plastic wall thickness. Therefore, excessive and / or undesirable distortion often occurs, especially at high volumes. Summary of the Invention

[0004] In some aspects, this subject matter disclosure relates to an apparatus of the subject matter technology, the apparatus including a loudspeaker that receives audio signals and generates sound wave output, and one or more output ports that provide the sound wave output to a user. The apparatus also includes a housing and an acoustic damping medium, the housing containing the loudspeaker and a cavity formed between the loudspeaker and the output ports, the acoustic damping medium being placed in the cavity and configured to reduce acoustic standing waves.

[0005] In some other aspects, this subject matter disclosure relates to an MR device including an audio unit that includes one or more output ports providing a user with sound wave output played by the speaker. The audio unit also includes a housing and foam configured to contain the speaker and provide a cavity between the speaker and the output ports, the foam being placed within the cavity to reduce acoustic standing waves.

[0006] In several other aspects, this subject matter disclosure relates to a method comprising: providing an audio unit including a speaker and a sound output port contained in a housing; and configuring the speaker to receive an audio signal and generate an audio output. The method further comprises: configuring the sound output port to provide a sound wave output to a user; and configuring the housing to form a cavity between the speaker and one or more sound output ports. The method further comprises placing an acoustic damping medium in the cavity, the acoustic damping medium being configured to reduce acoustic standing waves. Attached Figure Description

[0007] To facilitate the identification of any particular element or action in the discussion, the highest significant digit in the figure references refers to the figure number in which the element first appears.

[0008] Figure 1A and Figure 1B Schematic diagrams illustrating examples of audio units without acoustic foam and audio units containing acoustic foam are provided to illustrate some aspects of the art in this subject matter.

[0009] Figure 2 The following is a plot showing an example curve (plot) illustrating the relationship between the sound pressure level (SPL) (in dB) of the audio unit of an MR device and frequency, based on some aspects of the art in this subject matter.

[0010] Figure 3 A graph illustrating the relationship between total harmonic distortion (THD) and frequency of the audio unit of an MR device, based on some aspects of the art in this subject matter.

[0011] Figure 4 A graph illustrating the relationship between higher order harmonic distortion (HOHD) and frequency of the audio unit of an MR device, based on some aspects of the art in this subject matter, is provided.

[0012] Figure 5 A graph illustrating the relationship between intermodulation distortion (IMD) and frequency of the audio unit of an MR device, based on some aspects of the art in this subject matter.

[0013] Figure 6 A graph illustrating the relationship between perceptual rub and buzz (PRB) and frequency of an audio unit in an MR device, based on some aspects of the art in this subject matter, is provided.

[0014] Figure 7A , Figure 7B , Figure 7C and Figure 7D A graph illustrating the relationship between the first pass yield (FPY) of the audio unit of an MR device and its configuration, based on some aspects of the art in this subject matter.

[0015] Figure 8A , Figure 8B , Figure 8C and Figure 8D The diagram illustrates examples of audio units with different foam configurations, based on some aspects of the technology of this subject.

[0016] Figure 9 A flowchart illustrating an example of a method for providing acoustic foam for an audio unit, based on some aspects of the technology of this subject, is provided.

[0017] In one or more embodiments, not all components depicted in each figure may be required, and one or more embodiments may include additional components not shown in the figures. Variations may be made in the arrangement and type of the components without departing from the scope of this subject matter disclosure. Within the scope of this subject matter disclosure, additional components, different components, or fewer components may be utilized. Detailed Implementation

[0018] The detailed descriptions below depict various configurations of the subject matter and are not intended to represent the only configuration in which the subject matter can be practiced. The detailed descriptions include specific details to provide a thorough understanding of the subject matter. Therefore, dimensions regarding certain aspects may be provided as non-limiting examples. However, it will be apparent to those skilled in the art that the subject matter can be practiced without these specific details. In some instances, to avoid obscuring the concept of the subject matter, well-known structures and components are shown in block diagram form.

[0019] It should be understood that this disclosure includes examples of the subject matter technology, but does not limit the scope of the included provisions. Various aspects of the subject matter technology will now be disclosed based on specific, but not limiting, examples. The various embodiments described in this disclosure may be implemented in different ways and variations, and depending on the desired application or implementation.

[0020] Numerous specific details are set forth in the following detailed description to provide a thorough understanding of this disclosure. However, it will be apparent to those skilled in the art that embodiments of this disclosure can be practiced without some of these specific details. In other instances, well-known structures and techniques have not been shown in detail so as not to obscure this disclosure.

[0021] This subject matter discloses aspects aimed at addressing technical problems of audio distortion and acoustic vibration in audio devices, such as MR headsets. This subject matter addresses these problems by adding acoustic damping media, such as acoustic foam (hereinafter referred to as foam), to the acoustic cavity of the audio device by placing one or more foam components with specific acoustic properties within one or more internal cavities of the housing. For example, in the speaker module of an MR headset, acoustic standing waves are generated at certain frequencies where the sound wavelength has a slight correlation with the internal cavity size. This can lead to excessively high internal sound pressure levels, potentially resulting in undesirable non-uniformity in the pressure frequency response. Furthermore, an increase in noticeable nonlinear distortion is typically observed at these frequencies, such as increased high total harmonic distortion (THD), higher-order harmonic distortion (HOHD), and intermodulation distortion (IMD) measurements. Broadband distortion may also occur in these types of modules at frequencies where high-speed airflow passes through small internal cavities, speaker motor clearances, and outlet ports. These different distortion mechanisms can contribute to a deterioration in the auditory experience.

[0022] The module housing is typically made of thin-walled plastic or other materials, and the high internal pressure applied to the walls can cause them to bend, leading to distortion. These walls can also resonate at certain frequencies in response to pressure excitation, sometimes to extreme levels that exacerbate the problem.

[0023] This technique mitigates these effects by strategically placing one or more foam components with specific acoustic properties within one or more internal cavities of a housing. By doing so, some sound is absorbed by the foam, thus reducing the buildup of total sound pressure. Furthermore, when the foam is compressed between the walls of the housing, it also reduces vibrations in the plastic by acting as both a reinforcement and absorber. Both of these effects can smooth the frequency response and / or reduce distortion. Airflow noise at resonant frequencies can also be reduced by decreasing internal velocities.

[0024] In some embodiments, by molding the foam, the disclosed technique transmits sound waves between the speaker driver and the output port to improve frequency response without significantly reducing the module's minimal distortion output. In some embodiments, specific features may be included in the molded foam. For example, creating cutouts in the material with channels or recesses of specific dimensions (e.g., in the range of about 1 mm to 5 mm) can create a resonator that reduces pressure build-up at one or more frequencies. In some embodiments, some walls of the foam may be coated, heat-sealed in some way, or lined with other materials that reduce their acoustic absorption or even reflectivity. By doing so, the center frequency and bandwidth of the resonator can be tuned to reduce acoustic resonance at specific frequencies.

[0025] In some embodiments, by controlling the amount of foam compression between two or more walls of the housing, the present invention significantly reduces the vibration of the plastic walls while maintaining effective sound absorption properties. In some embodiments, the amount of compression can be controlled by the thickness of the foam element before the foam element is inserted into the cavity. In some embodiments, the thickness is selected based on the desired density of the foam under compression.

[0026] In some implementations, memory foam can be used in applications where it is compressed prior to module assembly so that it rests flat against one or more walls before the individual module housings are joined together. After assembly, the memory foam expands to the desired level of compression as it fills the internal cavities and presses against the opposing sidewalls. This foam mounting method makes it easier to properly align plastic components before they begin pressing against the opposing plastic walls. For example, in the case of ultrasonic welding of plastic components, this allows time to complete the welding before the foam contacts the surfaces to be welded, which could otherwise result in poor weld quality or extended welding cycles. Similarly, if plastic components are glued together, the adhesive's setting time can be achieved before the foam begins to press them.

[0027] Adding foam improves the listening experience by reducing distortion. This makes the product sound louder and has better low-frequency extension. Furthermore, by reducing variation and high distortion values, it increases yield and lowers overall cost.

[0028] This technology can be used in audio devices with acoustic cavities and ports, where internal standing waves or resonances can cause distortion, abnormal frequency response, and variations in both.

[0029] Now turn to the attached diagram. Figure 1A and Figure 1B Schematic diagrams illustrating examples of an audio unit 100A without acoustic foam and an audio unit 100B containing acoustic foam are provided to illustrate some aspects of the subject matter. The audio unit 100A includes a top 102 (lead) and a body with an internal structure shown in a three-dimensional (3D) view 110 and a top view 120. As shown in the 3D views, the audio unit 100A includes an interface module 112, a speaker module 114, a cavity 116, and an audio port 118. The speaker module 114 is connected to an audio amplifier via a voltage-carrying wire (not shown). The sound output generated by the speaker module 114 can be propagated through the cavity 116 to the audio port 118 (e.g., an outlet port) to reach the user's ear.

[0030] The problem with the audio unit 100A is that acoustic standing waves form at certain frequencies where the sound wavelength has a slight correlation with the size of the cavity 116. The formation of standing waves can lead to excessively high internal sound pressure levels, which may cause undesirable non-uniformity in the pressure frequency response. Furthermore, non-linear distortions such as THD, HOHD, and IMD may increase, resulting in a degraded listening experience.

[0031] Audio unit 100B includes a top 102 and a body similar to that of audio unit 100A, the internal structure of which is shown in 3D view 130 and top view 140. As shown in 3D view 130, audio unit 100B includes an acoustic damping medium (e.g., foam) 104 (hereinafter referred to as foam 104) located in a cavity 116, which mitigates the disadvantages of audio unit 100A, such as the formation of acoustic standing waves and nonlinear distortion, by placing foam 104 in the cavity 116 to prevent these disadvantages.

[0032] In some embodiments, the amount of compression of foam 104 is controlled to significantly reduce vibration of the plastic walls (e.g., top 102 and bottom walls) while maintaining effective sound absorption characteristics. In some embodiments, the amount of compression of foam 104 can be controlled by the thickness of foam 104 before it is inserted into cavity 116. In some embodiments, the thickness is selected based on the desired density of the foam under compression. In some embodiments, foam 104 may be memory foam, which is used to flatten against the walls before the individual module housing parts are assembled together. After assembly, the memory foam can expand to the desired degree of compression. Foam (or fibrous material) 104 may be low-density or high-density foam, open-cell or closed-cell, with different pore sizes, and may or may not have features such as slits, as described below, which have different effects on acoustic performance. In some embodiments, foam may also be used on top of speaker module 114.

[0033] Figure 2 Figure 200 illustrates example curves 210, 220, and 230 of the relationship between the SPL (in dB) and frequency of an audio unit in an MR device, according to some aspects of the art of this subject. The audio unit can be as discussed above. Figure 1A Audio unit 100A or Figure 1BOne of the audio units 100B. Curve 210 corresponds to audio unit 100A without foam. Curve 220 is associated with audio unit 100B, where foam 104 is foam type A, which may be low-density foam. Curve 230 corresponds to audio unit 100B, which has foam type B (e.g., high-density foam). It can be clearly seen from curves 210, 220, and 230 that type B foam achieves the lowest SPL at many frequencies. This indicates that the subject matter technology can control SPL by selecting different foams, and that the desired SPL can be achieved by adjusting the characteristics of foam 104 (e.g., foam material, size, composition, and / or density).

[0034] Figure 3 Figure 300 illustrates example curves 310, 320, and 330 showing the relationship between THD and frequency of the audio unit of an MR device, based on some aspects of the art of this subject. The audio unit can be as discussed above. Figure 1A Audio unit 100A or Figure 1B One of the audio units 100B. Curve 310 corresponds to audio unit 100A without foam. Curve 320 is associated with audio unit 100B, where foam 104 is foam type A (e.g., low-density foam). Curve 330 corresponds to audio unit 100B, which has foam type B (e.g., high-density foam). Curves 310, 320, and 330 show that type B foam achieves the lowest THD at many frequencies. Therefore, the present invention can control THD by selecting different foams, and the desired THD can be achieved by adjusting the characteristics of foam 104 (e.g., foam material, size, composition, and / or density).

[0035] Figure 4 Figure 400 illustrates, for some aspects of the art, the relationship between HOHD (10-15) (including the 10th to 15th harmonics) (in dB) and frequency of an audio unit in an MR device. The audio unit may be as discussed above. Figure 1A Audio unit 100A or Figure 1BOne of the audio units 100B. Curve 410 corresponds to audio unit 100A without foam. Curve 420 is associated with audio unit 100B, where foam 104 is foam type A (e.g., low-density foam). Curve 430 corresponds to audio unit 100B, which has foam type B (e.g., high-density foam). Curves 410, 420, and 430 indicate that type B foam achieves the lowest HOHD at higher frequencies (e.g., above approximately 200 Hz). Therefore, the subject matter technology can control HOHD by selecting different foams, and the desired HOHD can be achieved by adjusting the characteristics of foam 104 (e.g., foam material, size, composition, and / or density).

[0036] Figure 5 Figure 500 illustrates example curves 510, 520, and 530 showing the relationship between the IMD (in dB) and frequency of the audio unit of an MR device, based on some aspects of the art of this subject. The audio unit can be as discussed above. Figure 1A Audio unit 100A or Figure 1B One of the audio units 100B. Curve 510 corresponds to audio unit 100A without foam. Curve 520 is associated with audio unit 100B, where foam 104 is foam type A (e.g., low-density foam). Curve 530 corresponds to audio unit 100B, which has foam type B (e.g., high-density foam). Curves 510, 520, and 530 show that IMD can be reduced by using foam. At low frequencies, type B foam appears to be the best choice, while at high frequencies, any foam is better than no foam. Therefore, the subject matter technique can control IMD by selecting different foams, and the desired IMD at a specific frequency can be achieved by adjusting the characteristics of foam 104 (e.g., foam material, size, composition, and / or density).

[0037] Figure 6 Figure 600 illustrates example curves 610, 620, and 630 showing the relationship between PRB (Phon) and frequency for the audio unit of an MR device, according to some aspects of the subject matter. PRB is a measure of audible distortion in speakers and other audio devices. PRB is particularly useful because it focuses on whether the distortion is audible to the listener, making it more relevant to assessing the actual audio quality of the user experience. PRB is also less sensitive to transient background noise, making it reliable even in noisy environments.

[0038] The audio unit can be as discussed above. Figure 1A Audio unit 100A or Figure 1BOne of the audio units 100B. Curve 610 corresponds to audio unit 100A without foam. Curve 620 is associated with audio unit 100B, where foam 104 is foam type A (e.g., low-density foam). Curve 630 corresponds to audio unit 100B, which has foam type B (e.g., high-density foam). Curves 610, 620, and 630 show that type B foam achieves the lowest PRB at almost all frequencies. Therefore, the subject matter technique can control PRB by selecting different foams, and the desired PRB can be achieved by adjusting the characteristics of foam 104 (e.g., foam material, size, composition, and / or density).

[0039] Figure 7A , Figure 7B , Figure 7C and Figure 7D Graphs 700, 710, 720, and 730 illustrate example curves showing the relationship between the FPY and configuration of the audio unit of an MR device, according to some aspects of the art of this subject. Graph 700 includes curves 702 and 704, with curve 702 illustrating an audio unit with foam (e.g., Figure 1B The relationship between the FPY (in percentage) and configuration number of the audio unit 100B under a fixed TD is shown in curve 704, which illustrates the relationship between the FPY (in percentage) and configuration number of the audio unit without foam (e.g., Figure 1A The relationship between the FPY (in percentage) of the audio unit 100A under a fixed TD and the configuration number. The configuration number identifies various configurations associated with different manufacturers, manufacturing tools, and materials used. Curves 702 and 704 show that the use of foam can improve the FPY to some extent for some configurations.

[0040] Chart 710 includes curves 712 and 714. Curve 712 shows the relationship between the FPY (in percentage) of an audio unit with foam and its configuration number under a fixed PRB, while curve 714 shows the relationship between the FPY (in percentage) of an audio unit without foam and its configuration number under a fixed PRB. Curves 712 and 714 demonstrate that using foam can improve the FPY to some extent for only a few configurations.

[0041] Chart 720 includes curves 722 and 724. Curve 722 shows the relationship between the FPY (in percentage) of an audio unit with foam and its configuration number at a fixed third harmonic (TD) of 10. Curve 724 shows the relationship between the FPY (in percentage) of an audio unit without foam and its configuration number at TD10. Curves 722 and 724 demonstrate that using foam can improve the FPY to some extent for a limited number of configurations.

[0042] Chart 730 includes curves 732 and 734. Curve 732 shows the relationship between the FPY (in percentage) of an audio unit with foam and its configuration number at a fixed IMD, while curve 734 shows the relationship between the FPY (in percentage) of an audio unit without foam and its configuration number at a fixed IMD. Curves 732 and 734 demonstrate that using foam can improve the FPY for almost all configurations.

[0043] Charts 700, 710, 720, and 730 generally demonstrate that the use of foam makes FPY independent of the configuration number, which is the desired feature of the technique in this subject.

[0044] Figure 8A , Figure 8B , Figure 8C and Figure 8D Schematic diagrams illustrating examples of audio units 800A, 800B, 800C, and 800D with different foam configurations are shown to illustrate some aspects of the art in this subject matter. Except for the size of foam 804A, audio unit 800A is similar to... Figure 1B The audio unit 100B and audio unit 800A allow some space around the foam 804A to form an audio channel, which is used to allow the audio output from the speaker 814A to reach the audio port 818A.

[0045] Except for the configuration of foam 804B, audio unit 800B is similar to audio unit 800A. Foam 804B includes a special cutout 825B that can be used as a resonator (e.g., a Helmholtz resonator). When the size of the resonator is selected to be related to the wavelength of the acoustic standing waves inside the audio unit (e.g., tuned with the wavelength of the acoustic standing waves), the resonator can eliminate those acoustic standing waves.

[0046] Apart from the configuration of foam 804C, audio unit 800C is similar to audio unit 800A. Foam 804C consists of two parts that form a special cutout 825C, which provides a direct audio channel between speaker 814C and audio port 818C.

[0047] Apart from the configuration of the foam 804D, the audio unit 800D is similar to the audio unit 800C. The foam 804D has a special cutout 825D, which can be configured to affect the audio performance of the audio unit 800D.

[0048] Figure 9 A flowchart illustrating an example of a method 900 for providing acoustic foam for an audio unit, based on some aspects of the art of this subject, is provided. For illustrative purposes, see reference to [link to relevant documentation]. Figure 1A The components of the audio unit 100A and Figure 1BThe components of the audio unit 100B are illustrated in method 900. Method 900 includes process steps 910, 920, 930, 940, and 950.

[0049] In step 910, an audio unit (e.g., Figure 1A The audio unit 100A includes a speaker (e.g., a speaker housed within a housing) Figure 1A The speaker module 114) and the sound output port (e.g., Figure 1A The audio port 118 is the output port for generating sound waves.

[0050] In step 920, the speaker is configured to receive audio signals and generate sound waves.

[0051] In step 930, the sound output port is configured to provide audio output to the user.

[0052] In step 940, the housing is configured to form a cavity between the speaker and the sound output port (e.g., Figure 1A Cavity 116).

[0053] In step 950, the acoustic damping medium (e.g., Figure 1B An acoustic damping medium 104 is placed in the cavity and configured to eliminate acoustic standing waves.

[0054] One aspect of this subject matter relates to an apparatus that includes a loudspeaker for receiving audio signals and generating sound waves, and an output port for providing sound waves to a user. The apparatus also includes a housing and an acoustic damping medium, the housing containing the loudspeaker and a cavity formed between the loudspeaker and the output port, the acoustic damping medium being placed within the cavity and configured to eliminate acoustic standing waves.

[0055] In some implementations, the acoustic damping medium includes foam and is also configured to suppress vibrations of the cavity's sidewalls.

[0056] In one or more embodiments, the foam includes a compression memory foam configured to expand to a degree of compression sufficient to fill the cavity and push against the sidewalls of the cavity.

[0057] In some implementations, the acoustic damping medium includes foam, wherein the foam can be configured by changing foam properties, including material, shape, size, and density.

[0058] In one or more implementations, foam is configured to reduce distortion and improve user experience.

[0059] In some implementations, the foam is configured to improve the distortion of perceived abrasive and hum (PRB) measurements.

[0060] In one or more embodiments, the foam is configured to allow the speaker to play louder while reducing low-frequency extension.

[0061] In some implementations, the foam is configured to reduce HOHD and IMD values.

[0062] In one or more implementations, the foam is configured to improve production yield and reduce total production costs.

[0063] In some implementations, one or more walls of the foam are coated with a material that improves acoustic properties by reducing the acoustic absorption or reflection of one or more walls.

[0064] Another aspect of this subject matter relates to an MR device including an audio unit with an output port providing sound waves played by a speaker to a user. The audio unit also includes a housing and foam configured to contain a speaker and provide a cavity between the speaker and the output port, the foam being placed within the cavity to eliminate acoustic standing waves.

[0065] In some implementations, the audio unit is an attachable unit configured to use a universal serial bus (USB) interface.

[0066] In one or more embodiments, the foam can be configured by changing its foam properties, including material, shape, size, and density.

[0067] In some implementations, the foam is configured to allow the speaker to play louder with reduced distortion and improve the user experience.

[0068] In one or more embodiments, the foam is configured to improve distorted PRB measurements.

[0069] In some implementations, the foam is configured to reduce HOHD and IMD values.

[0070] In one or more embodiments, one or more walls of the foam are lined with a material that improves acoustic properties by reducing the acoustic absorption or reflectivity of one or more walls.

[0071] Another aspect of this subject matter relates to a method comprising: providing an audio unit including a speaker and a sound output port contained in a housing; and configuring the speaker to receive an audio signal and generate a sound output. The method further comprises configuring the sound output port to provide sound output to a user; and configuring the housing to form a cavity between the speaker and the sound output port. The method further comprises placing an acoustic damping medium in the cavity, the acoustic damping medium being configured to eliminate acoustic standing waves.

[0072] In one or more embodiments, the foam can be configured by changing foam properties, including material, shape, size, and density, to reduce HOHD and IMD values, and one or more walls of the foam can be coated or lined with a material that improves acoustic properties by reducing the acoustic absorption or reflection of one or more walls.

[0073] In some implementations, the term “exemplary” as used herein means “serving as an example, instance, or illustration.” Any embodiment described herein as “exemplary” is not necessarily to be construed as being more preferred or advantageous than other embodiments. Phrases such as one aspect, that aspect, another aspect, some aspects, one or more aspects, an embodiment, that embodiment, another embodiment, some embodiments, one or more embodiments, an embodiment, that embodiment, another embodiment, some embodiments, one or more embodiments, a configuration, that configuration, another configuration, some configurations, one or more configurations, subject matter, disclosure, this disclosure, other variations thereof, etc., are for convenience and do not imply that the disclosure associated with one or more such phrases is necessary for the subject matter, or that such disclosure applies to all configurations of the subject matter. The disclosure associated with one or more of these phrases may apply to all configurations or one or more configurations. The disclosure associated with one or more such phrases may provide one or more examples. Phrases such as one aspect or some aspects may refer to one or more aspects, and vice versa, and this also applies to other foregoing phrases.

[0074] Unless otherwise specified, elements referred to in the singular are not intended to mean "one and only one," but rather "one or more." Masculine pronouns (e.g., his) include feminine pronouns (e.g., her) and neuter pronouns (e.g., its), and vice versa. The term "some" refers to one or more. Underlined and / or italicized headings and subheadings are for convenience only and do not limit the subject matter or relate to the interpretation of the description of the subject matter. Relational terms such as "first" and "second" may be used to distinguish one entity or action from another without necessarily requiring or implying any actual such relationship or order between these entities or actions. All structural and functional equivalents of the elements of the various configurations described throughout this disclosure, known or hereafter known to those skilled in the art, are expressly incorporated herein by reference and are intended to be covered by the subject matter. Furthermore, nothing disclosed herein is intended to be offered to the public, whether or not such disclosure is expressly stated in the foregoing description.

[0075] While this specification contains numerous details, these details should not be construed as limiting the scope of the content, but rather as descriptions of particular embodiments of the subject matter. Certain features described in the context of individual embodiments may also be implemented in combination in a single embodiment. Conversely, various features described in the context of a single embodiment may also be implemented individually or in any suitable sub-combination in multiple embodiments. Furthermore, although features may be described above as functioning in certain combinations, and even initially described so, one or more features from the described combinations may be removed from that combination in some cases, and the described combinations may involve sub-combinations or variations thereof.

[0076] The subject matter of this specification has been described with respect to certain aspects, but other aspects may also be implemented and are within the scope of the accompanying clauses. For example, although the operations are described in a specific order in the accompanying drawings, this should not be construed as requiring these operations to be performed in the specific order or sequential order shown, or requiring all the operations shown to be performed to obtain the desired result. The actions described in the clauses may be performed in different orders and may still obtain the desired result. As an example, the processes depicted in the accompanying drawings do not necessarily require the specific order or sequential order shown to achieve the desired result. In some cases, multitasking and parallel processing may be advantageous. Furthermore, the separation of the various system components in the foregoing aspects should not be construed as requiring such separation in all aspects, and it should be understood that the described program components and systems can generally be integrated together in a single software product or packaged into multiple software products.

[0077] The title, background information, description of the accompanying drawings, abstract, and figures are incorporated herein by reference and are illustrative examples, not limiting descriptions. It is understood at the time of filing this document that they are not intended to limit the scope or meaning of the provisions. Furthermore, in the detailed description, illustrative examples can be seen, and various features are combined in various embodiments for the purpose of simplifying this disclosure. The disclosed methods should not be construed as reflecting an intention to require more features than are expressly listed in each clause. Rather, as reflected in the clauses, the subject matter of the invention lies in all features of fewer than those in a single disclosed configuration or operation. These clauses are incorporated herein by reference, each as a separate, separately described subject matter.

[0078] As used in this article, the phrase “at least one of” following a series of items and the terms “and” or “or” used to separate any items modify the entire list, not each member of the list (i.e., each item).

[0079] With regard to the terms “comprising”, “having”, etc., as used in the specification or claims, the term is intended to be inclusive in a manner similar to how the term “comprising” is interpreted when used as a transitional word in the claims.

[0080] Unless otherwise specified, elements referred to in the singular are not intended to mean "one and only one," but rather "one or more." All structural and functional equivalents of the elements of the various configurations described throughout this disclosure, known or hereafter known to those skilled in the art, are expressly incorporated herein by reference and are intended to be covered by the subject matter. Furthermore, nothing disclosed herein is intended to be offered to the public, whether or not such disclosure is expressly stated in the foregoing description.

[0081] While this specification contains numerous details, these details should not be construed as limiting the scope of the claims, but rather as descriptions of particular embodiments of the subject matter. Certain features described in the context of individual embodiments may also be implemented in combination in a single embodiment. Conversely, various features described in the context of a single embodiment may also be implemented individually or in any suitable sub-combination in multiple embodiments. Furthermore, although features may be described above as functioning in certain combinations, and even initially claimed in this way, one or more features from a claimed combination may, in some cases, be removed from that combination, and the claimed combination may involve sub-combinations or variations thereof.

Claims

1. An apparatus comprising: A loudspeaker configured to receive audio signals and generate sound wave output; An output port, configured to provide the acoustic wave output to a user; A housing, the housing including the speaker and a cavity formed between the speaker and the output port; as well as An acoustic damping medium is placed in the cavity and configured to eliminate acoustic standing waves.

2. The apparatus according to claim 1, wherein, The acoustic damping medium comprises foam and is further configured to suppress vibrations of the sidewalls of the cavity.

3. The apparatus according to claim 2, wherein, The foam includes compression memory foam configured to expand to a degree of compression sufficient to fill the cavity and press against the sidewalls of the cavity.

4. The apparatus according to claim 1, wherein, The acoustic damping medium includes foam, and the foam can be configured by changing foam properties, including material, shape, size, and density.

5. The apparatus according to claim 4, wherein, The foam is configured to reduce distortion and improve the user experience.

6. The apparatus according to claim 4, wherein, The foam is configured to improve the perceived abrasive and hum PRB measurements to improve distortion.

7. The apparatus according to claim 4, wherein, The foam is configured to allow the speaker to play louder while reducing low-frequency extension.

8. The apparatus according to claim 4, wherein, The foam is configured to reduce the High-Order Harmonic Distortion (HOHD) value and the Intermodulation Distortion (IMD) value.

9. The apparatus according to claim 4, wherein, The foam is configured to increase production yield and reduce total production costs.

10. The apparatus according to claim 4, wherein, One or more walls of the foam are coated with a material that improves acoustic properties by reducing the acoustic absorption or reflection of the one or more walls.

11. A mixed reality (MR) device, comprising: An audio unit, the audio unit comprising: An output port configured to provide an audio output played by a speaker to a user; A housing configured to include the speaker and provide a cavity between the speaker and the output port; and Foam, which is placed in the cavity and configured to eliminate acoustic standing waves.

12. The MR device according to claim 11, wherein, The audio unit is an attachable unit configured to use a Universal Serial Bus (USB) interface.

13. The MR device according to claim 11, wherein, The foam can be configured by changing its properties, including material, shape, size, and density.

14. The MR device according to claim 13, wherein, The foam is configured to allow the speaker to play louder with reduced distortion and improve the user experience.

15. The MR device according to claim 13, wherein, The foam is configured to improve distorted PRB measurements.

16. The MR device according to claim 11, wherein, The foam is configured to reduce HOHD and IMD values.

17. The MR device according to claim 11, wherein, One or more walls of the foam are lined with a material that improves acoustic properties by reducing the acoustic absorption or reflection of the one or more walls.

18. A method comprising: An audio unit is provided, the audio unit including a speaker and a sound output port contained in a housing; The speaker is configured to receive audio signals and generate sound wave output; Configure the sound output port to provide the sound wave output to the user; The housing is configured to form a cavity between the speaker and the sound output port; as well as An acoustic damping medium is placed in the cavity, and the acoustic damping medium is configured to eliminate or reduce acoustic standing waves.

19. The method of claim 18, wherein, The audio unit can be attached to an MR device via a USB interface, and The acoustic damping medium comprises foam and is also configured to suppress vibrations of the sidewalls of the cavity.

20. The method according to claim 19, wherein, The foam can be configured by changing its properties, including material, shape, size, and density. The foam is configured to reduce HOHD and IMD values, and One or more walls of the foam are coated or lined with a material that improves acoustic properties by reducing the acoustic absorption or reflection of the one or more walls.

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