Perforated compression chamber with acoustic lens effect for AVAS applications

Abstract

The invention relates to a perforated compression chamber with an acoustic lensing effect for AVAS applications. A compression chamber having two acoustic outlet paths includes an inner boundary surface formed by an outer surface of a diaphragm and an outer boundary surface formed by a perforated shutter body disposed opposite the diaphragm. The perforated shutter body includes at least one opening extending through its thickness forming a first acoustic exit path. A second acoustic outlet path is present around a peripheral edge of the compression chamber. Acoustic energy from the two outlet paths is combined to provide frequency selective increase and directional control of sound pressure levels within a specific frequency range. The design enables a single electrodynamic transducer to be effectively used for broadband acoustic vehicle alarm system applications and high sound pressure level horn applications by controlling acoustic impedance parameters including the thickness of the perforated shield body, the diameter of the perforated hole, and the total opening area.

Description

[0001] Cross-reference to related applications

[0002] This application claims the benefit and priority of U.S. Provisional Patent Application No. 63 / 684,805, filed August 19, 2024, entitled "Perforated Compression Chamber with Acoustic Lensing Effect for AVAS Application," which is incorporated herein by reference in its entirety. Technical Field

[0003] The embodiments relate to acoustic devices, specifically to compression chambers for loudspeakers used in applications requiring both wideband acoustic output and frequency-selective sound pressure level enhancement. The compression chamber utilizes dual acoustic exit paths to achieve controlled acoustic impedance across different frequency ranges. More specifically, the embodiments relate to acoustic devices suitable for acoustic vehicle alarm systems (AVAS) applications, where both warning sounds and horn functionality from a single transducer assembly are required. Background Technology

[0004] In some jurisdictions, hybrid and electric vehicles are already required to have an Acoustic Vehicle Alarm System (AVAS) to provide audible warnings to pedestrians. These systems require transducers capable of producing broadband sound at medium sound pressure levels. Additionally, vehicles are required to have a horn capable of producing high sound pressure levels at specific frequencies for signaling in emergency situations.

[0005] Traditional cone speakers can adequately produce the wideband sound required for AVAS applications. However, these same speakers are insufficient to meet the sound pressure level requirements for vehicle horn applications at the desired frequencies. The fundamental limitation lies in the acoustic impedance mismatch between the rigid speaker cone and the flexible ambient air. This mismatch hinders effective acoustic power transfer, especially at frequencies where maximum output is required for horn operation.

[0006] Existing technologies have addressed the challenges of acoustic coupling through various methods. Horn-loaded transducers utilize an expanded horn section to achieve impedance transformation between the driver and free space. Resonant cavity designs employ Helmholtz resonators to enhance output at specific frequencies by storing acoustic energy. Some implementations combine these methods with stacked horn and resonator configurations. While some devices attempt to accommodate both AVAS and horn operation simultaneously, the most common configuration uses separate transducer systems for both horn and AVAS functions. This leads to increased cost, space requirements, and complexity within the vehicle.

[0007] Various methods for implementing AVAS have been disclosed in the prior art. US Patent No. 10,482,687 teaches a diagnostic system for AVAS that uses sensors and a processor to detect system errors, but it does not address the acoustic performance limitations of the transducer itself. Japanese Patent No. 6,806,834 describes an AVAS system with multiple acoustic paths, including conduits and connecting paths between openings, which is a complex mechanical solution. Japanese Patent No. 5,499,911 discloses an alarm device with a shield that creates openings in a specific direction in a 180-degree orientation, focusing on directional control rather than improving acoustic impedance coupling.

[0008] Other prior art attempts focus on specialized diaphragm configurations. Chinese Patent No. 113196801 teaches loudspeakers with conical and flexural diaphragms mechanically coupled and driven by a single exciter, requiring complex mechanical connections. PCT Application No. PCT / EP2022 / 056129 teaches a specific volume ratio between the protective grille space and the loudspeaker mounting cavity for enhancing SPL in narrow frequency bands.

[0009] The challenge of combining AVAS and horn functionality (H-AVAS) in a single device lies in the conflicting requirements. AVAS operation needs to achieve a medium-level frequency response across a wide spectrum. Emergency alarm (i.e., "horn") operation demands maximum acoustic output at a specific frequency, typically achieved through acoustic resonance enhancement. Existing solutions require separate transducers for each function, increasing cost, weight, complexity, and installation time. Furthermore, existing technologies fail to provide a simple solution for achieving dual-mode operation through control of acoustic impedance in the region near the transducer. Summary of the Invention

[0010] We propose a novel acoustic device design that enables a single transducer to be effectively used for both wideband AVAS operation and high SPL horn operation. This design utilizes a perforated compression chamber that provides two distinct acoustic exit paths, whose combined acoustic impedance characteristics produce enhanced frequency selectivity while maintaining wideband capability.

[0011] The compression chamber is defined on one side by a vibrating diaphragm of an electric transducer and on the opposite side by a perforated shielding body. The perforated shielding body provides a first acoustic exit path through its thickness via uniformly sized and shaped openings. A second acoustic exit path exists around the outer edge of the compression chamber. These two paths combine to form an acoustic impedance that provides an increased sound pressure level in a specific frequency range while maintaining a suitable frequency response in other frequency ranges.

[0012] The parameters of the perforated shielding body (including thickness, perforation diameter, and total opening area) control the resistive and reactive components of the acoustic impedance passing through the perforated shielding body. Combined with the peripheral path impedance, these parameters allow for tuning of the frequency range, thereby enhancing the output from the compression chamber. Furthermore, the interaction of the two acoustic paths produces an acoustic lensing effect, which provides directional control of the radiated sound over a portion of its bandwidth.

[0013] Unlike existing designs that require complex internal geometry, multiple transducers, or multiple subsystems, this design achieves AVAS and horn functions by controlling acoustic impedance using simple geometric parameters and is easy to manufacture using conventional techniques. Attached Figure Description

[0014] For a more complete understanding of this disclosure, reference is now made to the following brief description, taken in conjunction with the accompanying drawings and detailed description, wherein similar reference numerals denote similar parts, in which:

[0015] Figure 1A This is an isometric view showing an embodiment of the main external features of the compression chamber and the sealed baffle-type enclosure.

[0016] Figure 1B This is an isometric view showing an embodiment of a perforated shielding body forming part of a compression chamber separate from this embodiment;

[0017] Figure 2 This is a cross-sectional view of a compression chamber assembly according to an embodiment of the present invention, showing the diaphragm, perforated shielding body, dual acoustic outlet paths, and perforation arrangement according to the embodiment;

[0018] Figure 3AIt is a simulation graph showing the relationship between the real components of acoustic impedance and frequency, comparing the performance of the embodiment with and without the perforated compression chamber.

[0019] Figure 3B It is a measurement graph showing the relationship between sound pressure and frequency, comparing the performance of the perforated compression chambers of multiple sample units in the embodiment;

[0020] Figure 4 It is a polar coordinate simulation diagram showing the directional pattern achieved through the acoustic lensing effect of the compression chamber;

[0021] Figure 5 This is an exploded view showing a sealing baffle-type closure attached behind the diaphragm of an electric transducer;

[0022] Figure 6A This is a top view of an alternative embodiment having a non-uniform circular perforation forming a first acoustic path outlet;

[0023] Figure 6B It is a dimetric view of an alternative embodiment having a non-uniform circular perforation forming the exit of the first acoustic path;

[0024] Figure 7A It is a top view of an alternative embodiment having a uniform non-circular perforation forming a first acoustic path outlet;

[0025] Figure 7B It is a biaxial view of an alternative embodiment having a uniform non-circular perforation forming a first acoustic path outlet;

[0026] Figure 8A It is a top view of an alternative embodiment having perforations of mixed size and shape forming the outlet of the first acoustic path;

[0027] Figure 8B It is a biaxial view of an alternative embodiment of a perforation having mixed sizes and shapes forming a first acoustic path outlet;

[0028] Figure 9A This is a top view of an alternative embodiment with adjustable perforations that obstruct some of the first acoustic path exits;

[0029] Figure 9B It is a biaxial projection of an alternative embodiment with adjustable perforations that block some of the first acoustic path exits;

[0030] Figure 10A This is a top view of an alternative embodiment, wherein the second acoustic outlet formed by the outer wall of the compression chamber extends beyond the periphery of the vibrating diaphragm;

[0031] Figure 10BThis is a biaxial view of an alternative embodiment, wherein the second acoustic outlet formed by the outer wall of the compression chamber extends beyond the periphery of the vibrating diaphragm;

[0032] Figure 11A This is a top view of an alternative embodiment, in which a convex dome-shaped vibrating diaphragm forms a boundary of the compression chamber opposite to the perforated shielding body;

[0033] Figure 11B This is a biaxial view of an alternative embodiment, in which a convex dome vibrating diaphragm forms a boundary of the compression chamber opposite to the perforated shielding body. Detailed Implementation

[0034] The following detailed description refers to the accompanying drawings, wherein similar reference numerals denote similar elements in several views. The embodiments described herein are provided by way of example only and are not intended to limit the scope of the invention.

[0035] The accompanying figures show a compression chamber assembly for a loudspeaker. This assembly is designed to provide wideband acoustic output and frequency-selective sound pressure level (SPL) enhancement, suitable for applications such as acoustic vehicle alarm systems (AVAS) and vehicle horn functions.

[0036] Specific reference Figure 1A , Figure 1B , Figure 2 and Figure 5 The acoustic transducer 100 is shown as being formed by a cabin 11, which, in the exemplary embodiment shown, is a generally cylindrical component having an outer wall extending around a central axis AA common to both the cabin 11 and the acoustic transducer 100. The cabin 11 also includes a substantially closed end 11a and an opposing open end 11b, both extending perpendicularly to the central axis AA. A basket 10 is disposed within the open end 11b of the cabin 11. The basket 10 supports a suspension 4, a voice coil 5, a first magnet 6, a top plate 7, a second magnet 8, and a yoke 9. These elements 4-9 are combined in a known manner to drive a diaphragm 3, which is disposed on the basket 10 and communicates with these elements 4-9. The diaphragm 3 is circular and arranged generally symmetrically around a central axis AA located at the center of the diaphragm and perpendicular to its outer surface. A gasket 2 is disposed around the diaphragm and serves to seal and isolate the basket 10 and the cabin 11 from the external environment. Finally, the perforated shielding body 1 is placed on the diaphragm 3.

[0037] Figure 2A cross-sectional view of the acoustic transducer 100 is shown, with particular emphasis on the compression chamber 20 defined within the transducer 100. The compression chamber 20 is defined by an inner boundary surface 22 formed by the outer surface of the diaphragm 3, and the outer boundary surface 24 formed by the inner surface of the perforated shielding body 1. In one exemplary embodiment, the perforated shielding body 1 has a substantially uniform thickness T and is spaced from the diaphragm 3 at a substantially uniform distance D. The thickness T of the perforated shielding body 1 is selected to optimize acoustic output and performance. For example, the thickness can range from about 1 mm to about 10 mm.

[0038] This invention provides at least two different acoustic exit paths for the acoustic energy generated by the diaphragm 3.

[0039] The first acoustic exit path 26 is formed by at least one opening 28 extending completely through the thickness T of the perforated shielding body 1. The first acoustic exit path 26 allows a portion of the acoustic energy generated by the diaphragm 3 within the compression chamber 20 to pass through the opening 28 to the outside of the acoustic transducer 100, propagating in a direction generally parallel to the axis AA. The opening 28 forming the first acoustic exit path 26 can be a uniform circular perforation, a non-uniform circular perforation, a uniform non-circular perforation, or a combination of sizes and shapes, such as... Figures 6A-8B As shown. The total opening area, size, and shape of opening 28 are selected to control the resistive and reactive components of the acoustic impedance of the first acoustic exit path 26. For example, the total opening area provided by opening 28 can be from about 1% to about 30% of the total surface area of ​​the perforated shielding body 1. In the case of a circular opening, it can include a diameter of about 1 mm to about 10 mm. In a preferred embodiment, for a uniform circular opening, the thickness T of the perforated shielding body is about 3 mm, the diameter of opening 28 is about 3.1 mm, and the total area of ​​the opening is about 3.2% of the surface area of ​​the perforated shielding body 1.

[0040] like Figure 1A-Figure 1B As shown, the opening 28 in the perforated shielding body 1 may include uniformly shaped circular perforations, each with the same diameter. It may have a single circular opening 28, or multiple circular openings 28 as shown, such as thirty uniformly shaped circular openings 28.

[0041] However, in other embodiments, the opening 28 in the perforated shielding body 1 may include non-uniform perforations. For example, Figure 6A and Figure 6B An embodiment is shown where opening 28 is a non-uniform circular perforation, which allows for customized impedance characteristics. That is, Figures 6A-6B The opening 28 has a circular shape with different diameters.

[0042] In another embodiment, the opening 28 in the perforated shielding body 1 may include uniform non-circular perforations. For example, Figure 7A and Figure 7B An opening 28 with a non-circular perforation (e.g., a slit or an ellipse) of uniform shape and size is shown. Non-circular perforations can be oriented in a specific direction to influence the directional characteristics of radiated sound. For example, radially or tangentially aligned elongated slits can be used to shape the polarity of a loudspeaker, enhancing directivity to customize the frequency response for the application.

[0043] In another embodiment, the opening 28 in the perforated shielding body 1 may include a perforation having a mixed shape. For example, Figure 8A and Figure 8B Openings 28 with mixed perforation sizes and shapes are depicted to enable adjustment of composite acoustic impedance. In the illustrated embodiment, openings 28 comprise a mixture of circular openings 28 with various diameters and elliptical openings 28 with a common length and width. In other embodiments, the length and width of the elliptical openings 28 can be varied as needed to achieve a desired acoustic effect. This approach supports composite acoustic impedance profiles (distributions), allowing designers to combine the advantages of non-uniform and non-circular perforations. The total opening area of ​​openings 28, as well as their distribution and geometry, can be optimized to achieve a desired balance between wideband output and frequency-selective enhancement. This embodiment is useful for applications requiring support for AVAS and speaker functions with independent acoustic characteristics.

[0044] Opening 28 may include any other geometric shape, such as triangle, square, rectangle, parallelogram, rhombus, trapezoid, pentagon, hexagon, heptagon, octagon, nonagon, or any regular or irregular polygon, or any non-geometric abstract shape. Various shapes and sizes may be mixed together, or they may be used in a uniform manner in terms of size and / or shape.

[0045] The spatial distribution of opening 28 can be uniform and regular, or varied, or a combination of both.

[0046] By strategically altering the size and arrangement of the openings 28, designers can enhance or attenuate specific frequency ranges, thus providing a customized response for unique AVAS or speaker requirements. For example, larger perforations can be located near the center of the perforation body to facilitate low-frequency transmission, while smaller perforations on the periphery can help shape high-frequency output.

[0047] The compression chamber 20 includes a peripheral edge 32, which is formed by a first peripheral edge 34 of the inner boundary surface 22 and a second peripheral edge 36 of the outer boundary surface 24. See, for example, [link to relevant documentation]. Figure 2 The outer edge 32 extends around the periphery of the compression chamber 20 and around the periphery of the acoustic transducer 100. The second acoustic exit path 30 extends from the compression chamber 20, passes through the outer edge 32, and reaches the exterior of the transducer 100. That is, the acoustic energy generated by the diaphragm 3 can propagate radially relative to the axis AA, along the second acoustic exit path 30, through the outer edge 32, and to the exterior of the transducer 100 in a direction approximately perpendicular to the axis AA. Figure 2 As shown, the first peripheral edge 34 and the second peripheral edge 36 are disposed close to each other and aligned along an axis parallel to axis AA. However, in other embodiments, such as Figure 10A and Figure 10B As shown, the second peripheral edge 36 of the outer boundary surface 24 extends beyond the maximum diameter of the diaphragm 3, thus exceeding the first peripheral edge 34 of the inner boundary surface 22. That is, in this variant, the first peripheral edge 34 and the second peripheral edge 36 are not aligned along an axis parallel to axis AA. This configuration increases the effective area of ​​the second acoustic exit path 30, which can be used to further control the directionality and acoustic impedance of the radiated sound. By extending the periphery, the designer can control the frequency range in which this embodiment exhibits the strongest directional control over its polar radiation behavior and lower the center frequency at which the sound is amplified by the perforated body to achieve speaker function.

[0048] The combined acoustic impedance of the first acoustic exit path 26 and the second acoustic exit path 30 varies with the geometric parameters of the perforated shielding body 1 (including its thickness T, the diameter and shape of the opening 28, and the total opening area). By adjusting these parameters, the frequency range of sound pressure level enhancement can be precisely adjusted. The interaction of the two acoustic exit paths 26 and 30 also produces an acoustic lensing effect, enabling directional control of the radiated sound along the central axis AA, such as... Figure 4 The polar plot is shown below. Here, the polar plot simulates the relationship between the normalized output of the idealized compression chamber 20 and the radiation angle.

[0049] So far, the total opening area of ​​the first acoustic exit path 26 has been fixed and is determined by the size and number of openings 28. However, in alternative embodiments, the total opening area of ​​the first acoustic exit path 26 is adjustable. For example, as... Figure 9A and Figure 9BAs shown, one or more louvers 38 or similar blocking elements can be positioned to selectively block a portion of a plurality of openings 28, thereby allowing real-time adjustment of acoustic impedance and output characteristics. In the illustrated embodiment, the louvers 38 includes a peripheral member 40 extending around its outer circumference and a central hub portion 42 centered relative to an axis AA. A plurality of radial members 44 extend from the central hub 42 to the peripheral member 40 in a direction substantially perpendicular to the axis AA. The peripheral member 40, the central hub 42, and the radial members 44 define an opening region 46. The louvers 38 can be rotatably fixed to the transducer 100 by a fixing element 48. Thus, the louvers 38 can rotate about the central axis AA, allowing the radial members 44 to move to a blocking position where some openings 28 are blocked, while other openings 28 are aligned with the opening region 46 and are not blocked. This feature enables dynamic switching between AVAS and horn modes, or adaptation to varying frequency requirements for horn operation under different operating environments.

[0050] Similar louver-like components can be used to adjust the total area of ​​the second acoustic exit path 30. That is, a louver-like component with one or more peripheral members can support multiple blocking members, thereby defining the opening space. This louver-like component can be an extension of the aforementioned louver-like component 38 and can be rotated and manipulated therewith, or it can be a separate element fixedly or movably mounted on the transducer 100. The louver-like component extends along the second acoustic exit path 30 and blocks certain portions of it to selectively reduce the total area of ​​the path 30. This louver-like component can be used independently or in combination with the aforementioned louver-like component 38.

[0051] The various louvered components described herein can be mechanically or electronically actuated to selectively block or open portions of the multiple openings 28 in the perforated shielding body 1. This adjustability allows the compression chamber assembly 20 to switch between different operating modes (e.g., wideband AVAS mode and high-output horn mode) or adapt to changing environmental or regulatory requirements. The ability to dynamically adjust the total opening area of ​​the first acoustic exit path 26 and / or the second acoustic exit path 30 provides significant flexibility and practicality.

[0052] In some embodiments, the diaphragm 3 may also form a partial boundary of the inflatable mechanical closure 50 (e.g., a sealing baffle) located behind the diaphragm 3, such as Figure 2As shown in one embodiment. The enclosure 50 provides an acoustic impedance load on the diaphragm 3 opposite the compression chamber 20, which can be adjusted to optimize the overall frequency response and efficiency of the system. The sealed baffle-type enclosure 50 can be implemented in various shapes and volumes to accommodate installation constraints and acoustic requirements of vehicles or other end-use environments.

[0053] like Figure 1A-Figure 2 and Figures 5-10B As shown, the diaphragm 3 has a concave or conical shape. That is, the central region of the diaphragm 3 is positioned closer to the closed end of the housing 11, while the outer edge of the diaphragm is closer to the open end of the housing 11. In this way, the outer region of the diaphragm 3 extends at an upward angle relative to the axis AA, as shown. Figure 2 As shown. Thus, when viewed in cross-section, the concave diaphragm 3 has a roughly batwing shape, as... Figure 2 As shown.

[0054] In an alternative embodiment, the diaphragm 3 may be convex or dome-shaped, such as Figure 11A and Figure 11B As shown in the example, the central region of the convex diaphragm 3 extends upward along axis AA toward the perforated shielding body 1, while the outer region of the convex diaphragm 3 extends in the opposite direction along axis AA.

[0055] The use of a convex or concave diaphragm 3 alters the modal behavior and radiation patterns of the loudspeaker, which can be used to achieve specific acoustic goals. Control of the diaphragm curvature interacts with the amount of available radiation area, modal behavior, and the performance of the electromechanical components driving the diaphragm. The compression chamber 20 accommodates both diaphragm geometries, further increasing the design versatility.

[0056] The different alternative embodiments described herein demonstrate the adaptability of the compression chamber assembly 20 to a variety of acoustic requirements. By changing the geometry and arrangement of the perforated shielding body 1, the construction of the acoustic outlet paths 26, 30, the shape of the diaphragm, and the use of the adjustable louvered member 38 or the sealing closure 50, the invention can be tailored to achieve optimal performance in AVAS and loudspeaker applications, as well as in other demanding acoustic environments such as emergency signaling.

[0057] In use, the electroacoustic transducer 100 drives the diaphragm 3 to vibrate and generate acoustic energy. This acoustic energy is radiated into the compression chamber 20, where it exits the transducer 100 via a first acoustic exit path 26, through the perforated shielding body 1, and via a second acoustic exit path 30 at the peripheral edge 32 of the compression chamber 20. The combined effect of these paths 26 and 30 results in an increased SPL within a specific frequency range and provides directional control of the radiated sound, which is required for AVAS and loudspeaker applications. For example, the SPL can be increased from approximately 1 kHz to approximately 3 kHz; directional control can be increased from approximately 1.5 kHz to approximately 3.5 kHz.

[0058] Figure 3A The effect of the present invention on acoustic impedance is illustrated. The lower curve, shown in blue, represents the impedance of a conventional loudspeaker transducer without the perforated shielding body described herein. The higher curve, shown in green, represents the impedance of the transducer 100 with the perforated shielding body 1. This configuration minimizes the impedance mismatch between the flexible air in the compression chamber 20 and the relatively rigid diaphragm 3. That is, increasing the real (i.e., resistive) component of the acoustic impedance near the diaphragm 3 improves acoustic coupling in the frequency range above 2 kHz, such as... Figure 3A As shown. Enhanced coupling means that more electrical energy sent to the transducer advantageously appears as an acoustic output.

[0059] Figure 3B The measured SPL versus frequency relationship for six samples of a loudspeaker acoustic transducer with a perforated shielding body as described herein is shown. It can be seen that the SPL is advantageously enhanced, peaking in the frequency range of 1000–3000 Hz.

[0060] As described and illustrated herein, the present invention provides a novel acoustic transducer having at least two acoustic exit paths, wherein at least one exit path can be adjusted to influence and control the resistive and reactive components of the acoustic impedance of the compression chamber. Specifically, the thickness of the perforated shielding body, the perforation diameter, and the total opening area provided by the perforated shielding body can be customized to control these impedance components and provide enhanced acoustic output and directivity control.

[0061] Various embodiments of the invention have been described herein with reference to the accompanying drawings. Alternative embodiments may be devised without departing from the scope of the invention. It should be noted that various connections and positional relationships (e.g., above, below, adjacent, etc.) between elements are listed in the description and drawings. Unless otherwise specified, these connections and / or positional relationships may be direct or indirect, and the invention is not intended to be limiting in this respect. Thus, coupling of entities may refer to direct or indirect coupling, and positional relationships between entities may be direct or indirect positional relationships.

[0062] The term “exemplary” herein means “as an example, instance, or illustration.” Any embodiment or design described herein as “exemplary” is not necessarily to be construed as being more preferred or advantageous than other embodiments or designs. The terms “at least one” and “one or more” are understood to include any integer greater than or equal to one, i.e., one, two, three, four, etc. The term “multiple” is understood to include any integer greater than or equal to two, i.e., two, three, four, five, etc. Terms such as “connected to” and “attached to” can include both indirect “connection” and direct “connection.”

[0063] The description of various embodiments of the invention is for illustrative purposes and is not intended to be exhaustive or limiting of the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein has been chosen to best explain the principles of the embodiments, their practical application, or to make technical improvements to techniques found in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A compression chamber for a loudspeaker, comprising: a. An inner boundary surface formed by the outer surface of a diaphragm, wherein the diaphragm is configured to vibrate and generate acoustic radiation when driven, and wherein the diaphragm is arranged to be substantially symmetrical about a central axis located at the center of the diaphragm and perpendicular to the outer diaphragm surface; b. An outer boundary surface disposed opposite to and offset from the diaphragm, wherein the outer boundary surface is formed by the inner surface of a shielding body having a substantially uniform thickness, and wherein the shielding body at least partially shields the acoustic radiation of the diaphragm. c. A first acoustic exit path is formed by at least one opening extending through the thickness of the shielding body, wherein the at least one opening acoustically connects the inner surface of the shielding body to the outer surface. as well as d. A second acoustic exit path, located at the outer edge of the compression chamber, and formed by the outer edge of the inner boundary surface and the outer edge of the relatively positioned outer boundary surface; e. The acoustic energy from the first acoustic exit path and the second acoustic exit path is combined to provide an increased sound pressure level within a specific frequency range and to provide directional control of radiated sound along the central axis within the specific frequency range.

2. The compression chamber according to claim 1, wherein the outer boundary surface of the compression chamber is spaced from the inner boundary surface of the compression chamber at a substantially uniform distance.

3. The compression chamber according to claim 1, wherein the second acoustic outlet is axially symmetrical about the central axis.

4. The compression chamber of claim 1, wherein the thickness of the shielding body is selected as at least one of the resistive and reactive components of the acoustic impedance of the first acoustic outlet path.

5. The compression chamber of claim 1, wherein the at least one opening comprises a uniform circular perforation, the diameter of which is selected as at least one of a resistive component and a reactive component of the acoustic impedance for controlling the first acoustic outlet path.

6. The compression chamber of claim 1, wherein the at least one opening comprises a non-uniform circular perforation, wherein the total opening area of ​​the non-uniform circular perforation controls at least one of the resistive and reactive components of the acoustic impedance of the first acoustic outlet path.

7. The compression chamber of claim 1, wherein the at least one opening comprises a uniform non-circular perforation, the size of which is selected to control at least one of a resistive component and a reactive component of the acoustic impedance of the first acoustic outlet path.

8. The compression chamber of claim 1, wherein the at least one opening comprises a non-uniform, non-circular perforation, wherein the total opening area of ​​the non-uniform, non-circular perforation controls at least one of the resistive and reactive components of the acoustic impedance of the first acoustic outlet path.

9. The compression chamber of claim 1, wherein the at least one opening comprises a perforation having a mixed size, shape, and spatial distribution, wherein at least one size distribution of the mixed size, shape, and spatial distribution of the perforation controls at least one of the resistive and reactive components of the acoustic impedance of the first acoustic outlet path.

10. The compression chamber of claim 1, wherein the total opening area of ​​at least one opening in the first acoustic path is adjustable by one or more louvered members positioned to selectively block a portion of the at least one opening.

11. The compression chamber of claim 1, wherein the periphery of the second acoustic outlet formed by the outer wall of the compression chamber extends beyond the maximum diameter of the diaphragm.

12. The compression chamber according to claim 1, wherein the diaphragm comprises a concave or convex surface of an electric transducer, and the electric transducer comprises one of a cone-shaped loudspeaker or a dome-shaped loudspeaker.

13. The compression chamber of claim 1, wherein the inner surface of the vibrating diaphragm forms a partial boundary of an inflatable mechanical closure that provides an acoustic impedance load on the diaphragm opposite the compression chamber.

14. The compression chamber of claim 1, wherein the opening of the shielding body comprises a plurality of concentric rings of openings, each ring having an opening of a different diameter.

15. The compression chamber of claim 1, wherein the opening of the shielding body comprises a plurality of elongated slits radially oriented relative to the central axis.

16. The compression chamber of claim 1, wherein the opening of the shielding body comprises a plurality of elongated slits tangentially oriented relative to the central axis.

17. The compression chamber of claim 1, wherein the opening of the shielding body comprises a mixture of multiple geometries, including circles, ellipses, triangles, squares, rectangles and polygons.

18. The compression chamber of claim 1, further comprising a louvered member configured to selectively block a portion of at least one opening of the perforated blocking body.

19. The compression chamber of claim 18, wherein the louvered member is driven electronically or mechanically in response to a control signal.

20. The compression chamber of claim 1, wherein the diaphragm defines a sealing baffle-type closure, the volume of which is selected to optimize acoustic impedance load for a predetermined frequency range.

21. The compression chamber of claim 18, wherein the second acoustic outlet path includes a louvered member configured to selectively block a portion of the peripheral edge.

22. The compression chamber according to claim 1, wherein the shielding body comprises a plurality of micro-openings with a diameter of less than 1 mm.

23. A loudspeaker comprising the compression chamber of claim 1.

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