A multi-stage pre-cavity helmholtz acoustic tuning structure, application and earphone
Patent Information
- Application Number
- CN202611226481.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-08-13
- Publication Date
- 2026-10-30
AI Technical Summary
[0002]耳机前腔容积直接影响低频谐振频率，现有单级前腔结构在耳机有限的外形尺寸下，难以获得更大的等效容积，若强行扩大前腔体积会显著增大耳机的整体尺寸，影响佩戴体验与产品外观设计
1.本发明通过设置至少两个具有不同声学参数的亥姆霍兹谐振单元，使前腔主管路形成至少两个局部谐振支路，能够在多个频率位置产生声阻抗调谐作用，通过多个局部谐振支路在频率轴上的分布，能够将单一窄带调谐作用扩展为多频段调谐作用。
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Figure CN123016964A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of acoustic technology, specifically to a multi-stage front cavity Helmholtz acoustic tuning structure, its application, and headphones. Background Technology
[0002] The volume of the headphone's front cavity directly affects the low-frequency resonant frequency. Existing single-stage front cavity structures, within the limited dimensions of headphones, struggle to achieve a larger effective volume. Forcibly increasing the front cavity volume would significantly increase the overall size of the headphones, impacting wearing comfort and product design. Simple parallel cavity designs can only optimize low-frequency performance to a certain extent by increasing the total volume, but cannot finely adjust the low-frequency response, easily leading to issues like abnormally high low-frequency bulges at single points. Furthermore, existing structures cannot effectively suppress low-frequency standing waves generated within the front cavity, or phase coupling deviations when multiple low-frequency units are combined, making it difficult to develop a modular low-frequency acoustic tuning solution with flexible parameter adjustments.
[0003] Among existing tuning technologies, most publicly disclosed ones employ single-stage Helmholtz resonant tuning structures. Single-stage Helmholtz structures have a narrow effective tuning bandwidth, easily resulting in single-point peaks, making it difficult to balance low-frequency quantity, depth, and transient response. Furthermore, the limited internal space of multi-driver headphones makes it difficult to implement traditional methods of simply increasing cavity volume to improve low-frequency extension. Additionally, for dual-dynamic coaxial or stacked structures, these are highly sensitive to the air load between the two diaphragms and the pressure distribution in the duct. Sudden changes in the front cavity impedance can lead to low-frequency phase shift, increased group delay, or transient divergence. Summary of the Invention
[0004] The purpose of this invention is to provide a multi-stage front cavity Helmholtz acoustic tuning structure, its application, and headphones, so as to expand the front cavity equivalent acoustic compliance, reduce the low frequency resonant frequency, smooth the low frequency response, and suppress single-point low frequency peaks.
[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: A multi-stage front cavity Helmholtz acoustic tuning structure includes: The front cavity main circuit has at least two Helmholtz resonant units, each Helmholtz resonant unit including a resonant cavity and a neck channel, one end of which is connected to the corresponding resonant cavity and the other end of which is connected to the front cavity main circuit. Wherein, at least two of the Helmholtz resonant units are different from each other in at least one of the following: resonant cavity volume, neck cross-sectional area, neck equivalent length, and damping configuration, so that the at least two Helmholtz resonant units have different resonant frequencies; At least two of the Helmholtz resonant units form a front cavity acoustic impedance tuning structure with at least two local resonant branches through the front cavity main circuit.
[0006] Optionally, some of the Helmholtz resonant units are connected to the front cavity main circuit in any of the following ways: parallel connection, series-parallel composite connection, hierarchical coupling connection, or ring array arrangement.
[0007] Optionally, several of the Helmholtz resonant units are distributed along the lateral, circumferential, or layered housing direction of the front cavity main circuit.
[0008] Optionally, the Helmholtz resonant unit is three parallel resonant units: a first resonant unit, a second resonant unit, and a third resonant unit. The resonant cavity volumes of the first resonant unit, the second resonant unit, and the third resonant unit decrease sequentially, and the equivalent lengths of the corresponding neck channels shorten sequentially. The resonant frequencies of the first resonant unit, the second resonant unit, and the third resonant unit increase sequentially.
[0009] Optionally, the first resonant unit, the second resonant unit, and the third resonant unit correspond to ultra-low frequency, low frequency, and mid-low frequency tuning, respectively. The first resonant unit includes a first resonant cavity and a first neck channel communicating with the first resonant cavity. The volume of the first resonant cavity is 17.84 mm³ ± 10%, the cross-sectional area of the first neck channel is 0.78 mm² ± 10%, and the equivalent length of the first neck channel is 3.8 mm ± 10%. The second resonant unit includes a second resonant cavity and a second neck channel communicating with the second resonant cavity. The volume of the second resonant cavity is 10.26 mm³ ± 10%, the cross-sectional area of the second neck channel is 0.78 mm² ± 10%, and the equivalent length of the second neck channel is 2.15 mm ± 10%. The third resonant unit includes a third resonant cavity and a third cervical channel communicating with the third resonant cavity. The volume of the third resonant cavity is 6.53 mm³ ± 10%, the cross-sectional area of the third cervical channel is 0.85 mm² ± 10%, and the equivalent length of the third cervical channel is 1.6 mm ± 10%.
[0010] Optionally, at least one of the Helmholtz resonant units has a folded neck or a labyrinthine neck, so that the neck has a folding extension path within the predetermined installation space; at least one of the resonant cavities is provided with at least one damping member selected from damping mesh, foam, microporous sheet or porous material. The damping component is used to adjust the acoustic loss of the corresponding Helmholtz resonant unit.
[0011] Optionally, it also includes a front cavity venting structure, on which at least three layers of layered acoustic structures are provided. The layered acoustic structures sequentially include a main circuit layer, at least one resonant cavity layer, and a neck passage layer. The neck passage layer includes a folded neck passage or a labyrinthine neck passage. Each layer of the layered acoustic structures is acoustically connected to the main circuit layer through micropores or slits.
[0012] Optionally, the layered acoustic structure has four layers, namely, a main circuit layer C1, a first resonant cavity layer C2, a second resonant cavity layer C3, and a neck layer C4 connected in series. Each layer of the layered acoustic structure has a different intrinsic resonant frequency, and the peak values of the single cavities are staggered from low frequency to high frequency in sequence. After being connected in series, they form a wideband TL envelope. The volume of C1 is 17.9 mm³ ± 10%, the volume of C2 is 25.1 mm³ ± 10%, the volume of C3 is 25.3 mm³ ± 10%, and the volume of C4 is 8.1 mm³ ± 10%. The cross-sectional areas of the micropores or slits in layers C1, C2, and C3 are 1.4 mm² ± 10%, 1.4 mm² ± 10%, and 1.4 mm² ± 10%, respectively, and the cross-sectional area of layer C4 (the neck layer) is 0.78 mm² ± 10%. The maximum energy value of each chamber in the layered acoustic structure varies with frequency: C1 dominant: 200-380Hz C2 dominant: 400-560Hz C3 dominant: 580-740Hz C4 dominant: 760-1200Hz.
[0013] An application of a multi-stage front-cavity Helmholtz acoustic tuning structure, as described above, is applied to a coaxial multi-moving-coil low-frequency transducer module; the coaxial multi-moving-coil low-frequency transducer module includes at least two moving-coil units; the coaxial multi-moving-coil low-frequency transducer module is a coaxial dual-moving-coil low-frequency transducer module, including an upper moving-coil unit, a lower moving-coil unit, and a transducer module support; The upper moving coil unit and the lower moving coil unit are stacked in the same direction along the axial direction of the transducer module bracket and are connected in parallel in phase. They are installed on the transducer module bracket and generate unidirectional sound pressure output under the same driving signal. The coaxial dual-moving coil low-frequency transducer module further includes at least one of a pressure relief pipe, a low-frequency sound pressure pipe, and an ultra-low-frequency sound pressure pipe, and the front cavity main circuit forms an acoustic connection with the coaxial dual-moving coil low-frequency transducer module.
[0014] An earphone that uses the multi-stage front cavity Helmholtz acoustic tuning structure as described above, or a structure used in an application of the multi-stage front cavity Helmholtz acoustic tuning structure as described above.
[0015] Compared with the prior art, the present invention has the following beneficial effects: 1. By setting at least two Helmholtz resonant units with different acoustic parameters, the front cavity main circuit forms at least two local resonant branches, which can generate acoustic impedance tuning at multiple frequency positions. Through the distribution of multiple local resonant branches on the frequency axis, the single narrowband tuning effect can be extended into a multi-band tuning effect.
[0016] 2. By using different resonant units for ultra-low frequency, low frequency and mid-low frequency tuning respectively, it is beneficial to improve the transition between adjacent frequency bands; by setting damping components in the resonant cavity, acoustic loss and resonant peak quality factor can be adjusted, reducing the problem of excessively sharp local resonant peaks. 3. By spatially integrating the main circuit layer, resonant cavity layer, and neck channel layer through a layered acoustic structure, the internal space utilization of the headphones can be improved. At the same time, by connecting C1 to C4 in series, the maximum acoustic energy of each chamber in the series-connected arrangement changes spatially with the frequency of the excitation sound wave in the frequency range of 200Hz to 1200Hz. Different frequency bands are dominated by four different chambers, which play an acoustic dominant role respectively. In addition, the design of three parallel Helmholtz resonant units in the main circuit of the front cavity expands the equivalent acoustic compliance of the front cavity, reduces the low-frequency resonant frequency, smooths the low-frequency response, and suppresses single-point low-frequency peaks.
[0017] 4. In a coaxial dual-moving-coil low-frequency transducer module with a pressure-relief coupling structure, two moving-coil units are stacked in the same direction, but connected with the same polarity, causing the two diaphragms to generate synergistic pressure changes around the inner cavity of the support and the rear-mounted sound-generating duct. The sound-generating duct is simultaneously subjected to the sound pressure generated by the upper and lower moving-coil units, thus forming pressure coupling, rather than the mechanical push-pull relationship between the two opposing diaphragms in a traditional push-pull structure. After multiple Helmholtz resonant units with different parameters are connected in parallel to the main circuit of the front cavity, the front cavity no longer exhibits a single volume load, but rather a distributed acoustic compliance, acoustic quality, and acoustic resistance network that varies with frequency. In the low-frequency range, some resonant units provide additional equivalent acoustic compliance, increasing the equivalent front cavity volume of the system and lowering the low-frequency resonant frequency; near the resonance, each branch selectively absorbs, releases, and compensates for the sound pressure of the main circuit, thereby smoothing the low-frequency response and controlling the low-frequency Q value. Attached Figure Description
[0018] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below.
[0019] Figure 1 This is a planar structural diagram of the multi-stage front cavity Helmholtz acoustic tuning of the present invention; Figure 2 This is a three-dimensional structural diagram of the multi-stage front cavity Helmholtz acoustic tuning of the present invention; Figures 3-4 This is a diagram of the multi-stage front cavity Helmholtz acoustic tuning structure + coaxial dual dynamic coil low-frequency transducer module of the present invention; Figure 5 This is a disassembled diagram of the multi-stage front cavity Helmholtz acoustic tuning structure + coaxial dual-dynamic low-frequency transducer mode of the present invention. Figure 6 This is a partial diagram of the internal structure of the multi-stage front cavity Helmholtz acoustic tuning structure + coaxial dual moving coil low-frequency transducer of the present invention. Figure 7 This is a comparison chart of the peak loss values of the present invention; Figure 8 This is a graph showing the maximum chamber energy as a function of frequency in this invention. Figure 9 This is a comparison diagram of the frequency response of the same earphone of the present invention with and without a multi-stage front cavity Helmholtz acoustic tuning structure.
[0020] In the picture: 1: First resonant cavity 2: Second resonant cavity 3: Third resonant cavity 4: Main road layer 5: First resonant cavity layer 6: Second resonant cavity layer 7: Cervical canal layer 8: Pressure relief pipe 9: Low-frequency sound pressure pipe 10: Ultra-low frequency sound pressure pipe 11: Anterior cavity main tube pathway 12: Upper dynamic coil unit 13: Transducer module bracket 14: Lower moving coil unit. Detailed Implementation
[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.
[0022] In the description of this invention, it should be noted that the terms "inner", "front", "rear", "left", "right", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the product of this invention is usually placed when in use. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.
[0023] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set" and "connection" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.
[0024] The relevant structures in the following embodiments are referenced. Figures 1-6 As shown, the relevant technical effects are referenced. Figures 7-9 As shown: Specific Implementation Example 1 This embodiment provides a multi-stage front cavity Helmholtz acoustic tuning structure, including a front cavity main circuit and at least two Helmholtz resonant units.
[0025] The front cavity main pipeline is used to transmit sound energy between the transducer output end and the headphone sound output end. The front cavity main pipeline can be a straight pipeline, a curved pipeline, a ring pipeline, a branch pipeline, or a combination pipeline formed by connecting multiple pipeline segments.
[0026] The Helmholtz resonant units can be connected to the front cavity main circuit in any of the following ways: parallel connection, series-parallel composite connection, layered coupling connection, or ring array arrangement. Furthermore, the Helmholtz resonant units can be distributed along the side, circumferential, or layered shell direction of the front cavity main circuit.
[0027] At least two resonant units differ in at least one of the following parameters: resonant cavity volume, neck cross-sectional area, neck equivalent length, and damping configuration. Through these parameter differentiation settings, each resonant unit has a different intrinsic resonant frequency.
[0028] The Helmholtz resonant unit includes a resonant cavity and a neck channel. In this embodiment, three resonant units are arranged in parallel, referred to as the first resonant unit, the second resonant unit, and the third resonant unit. Each resonant unit acoustically forms a local resonant branch.
[0029] One end of each neck channel is connected to the corresponding resonant cavity, and the other end is connected to the main front cavity circuit through a connector. Thus, the first resonant cavity 1, the second resonant cavity 2, and the third resonant cavity 3 form local acoustic branches through their respective neck channels and the main front cavity circuit.
[0030] The center frequency of a single resonant element can be approximately satisfied as follows: in, : Helmholtz resonant frequency; ( Speed of sound in air; ): Cross-sectional area of the cervical canal; ): Resonant cavity volume; ): Equivalent length of the cervical canal.
[0031] In this embodiment, the volumes of the first resonant cavity 1, the second resonant cavity 2, and the third resonant cavity 3 decrease sequentially, and the equivalent lengths of the first neck channel, the second neck channel, and the third neck channel shorten sequentially, causing the resonant frequencies of the first resonant unit, the second resonant unit, and the third resonant unit to increase sequentially. The first resonant unit is used for extremely low-frequency tuning, the second resonant unit is used for low-frequency tuning, and the third resonant unit is used for mid-to-low-frequency tuning. In terms of structural design… In this embodiment, calculations show that the first resonant unit includes a first resonant cavity and a first neck channel communicating with the first resonant cavity. The volume of the first resonant cavity is 17.84 mm³ ± 10% (± 10% is the allowable tolerance, the same below), the cross-sectional area of the first neck channel is 0.78 mm² ± 10%, and the equivalent length of the first neck channel is 3.8 mm ± 10%. The second resonant unit includes a second resonant cavity and a second neck channel communicating with the second resonant cavity. The volume of the second resonant cavity is 10.26 mm³ ± 10%, the cross-sectional area of the second neck channel is 0.78 mm² ± 10%, and the equivalent length of the second neck channel is 2.15 mm ± 10%. The third resonant unit includes a third resonant cavity and a third cervical channel communicating with the third resonant cavity. The volume of the third resonant cavity is 6.53 mm³ ± 10%, the cross-sectional area of the third cervical channel is 0.85 mm² ± 10%, and the equivalent length of the third cervical channel is 1.6 mm ± 10%.
[0032] The above design uses three Helmholtz resonant units with different parameters connected in parallel to the main front cavity circuit. The front cavity no longer behaves as a single volume load, but as a distributed acoustic compliance, acoustic quality, and acoustic resistance network that varies with frequency. In the low-frequency range, some resonant units provide additional equivalent acoustic compliance, increasing the equivalent front cavity volume of the system and lowering the low-frequency resonant frequency. Near the resonance, each branch selectively absorbs, releases, and compensates for the sound pressure of the main circuit, thereby smoothing the low-frequency response and controlling the low-frequency Q value.
[0033] In some embodiments, the neck of at least one of the Helmholtz resonant units is a folded neck or a labyrinthine neck; the neck has a folding extension path within a predetermined installation space, so as to obtain a predetermined actual or equivalent length of the neck without significantly increasing the external dimensions of the structure.
[0034] In some embodiments, at least one damping component selected from the following materials is provided in at least one resonant cavity: a damping mesh, foam, microporous sheet, or porous material; to adjust the acoustic loss of the corresponding Helmholtz resonant unit; to broaden the resonance peak and reduce the Q value, thereby avoiding low-frequency single-point peaks. Specific Implementation Example 2 In some embodiments, a front cavity venting structure is further included, on which at least three layers of layered acoustic structures are disposed. The layered acoustic structures sequentially include a main circuit layer 4, at least one resonant cavity layer, and a neck passage layer. The neck passage layer includes a folded neck passage or a labyrinthine neck passage. Each layer of the layered acoustic structures is acoustically connected to the main circuit layer 4 through micropores or slits. The layered acoustic structure can be independently applied to existing tuning structures. In this embodiment, it is based on the structure in specific embodiment 1, with the addition of this structure. The layered acoustic structure in this embodiment has four layers, namely, a main circuit layer 4 connected in series (C1), a first resonant cavity layer 5 (C2), a second resonant cavity layer 6 (C3), and a neck passage layer 7 (C4). Each layer of the layered acoustic structures has different intrinsic resonant frequencies to form different local resonance characteristics. The single cavity peak values are staggered sequentially from low frequency to high frequency, and after being connected in series, they form a wideband TL envelope.
[0036] In this embodiment, the calculated volume is as follows: C1 is 17.9 mm³ ± 10%, C2 is 25.1 mm³ ± 10%, C3 is 25.3 mm³ ± 10%, and C4 is 8.1 mm³ ± 10%. The cross-sectional areas of the micropores or slits in layers C1, C2, and C3 are 1.4 mm² ± 10%, 1.4 mm² ± 10%, and 1.4 mm² ± 10%, respectively, and the cross-sectional area of layer C4 (the neck layer) is 0.78 mm² ± 10%. In this embodiment, after being connected in series, the peak insertion loss of a single cavity is: C1: 360Hz, 28.97dB C2: 520Hz, 31.31dB C3: 700Hz, 57.65dB C4: 880Hz, 24.75dB Four-chamber series connection result: Peak: 700Hz, 59.37dB Insertion loss >= 6dB: 220-1120Hz Insertion loss >= 10dB: 300-360Hz, 440-1060Hz Insertion loss >= 15dB: 340-360Hz, 500-540Hz, 640-720Hz, 780-980Hz Insertion loss >= 20dB: 360Hz, 520-540Hz, 680-720Hz, 820-940Hz Maximum chamber energy shifts with frequency: C1 dominant: 200-380Hz C2 dominant: 400-560Hz C3 dominant: 580-740Hz C4 dominant: 760-1200Hz Rainbow capture judgment: The equivalent COMSOL result satisfies the three core criteria for rainbow-trapped acoustic metamaterials: There is a spatial gradient in the structure: the cavity / neck parameters of C1-C4 change step by step, forming different intrinsic resonance frequencies.
[0037] There is misaligned resonance in the spectrum: the peak values of the single cavity are staggered from low frequency to high frequency, and after being connected in series, they form a wideband TL envelope.
[0038] There is a frequency-position mapping in the field distribution: low-frequency energy is localized in the pre-stage cavity, and high-frequency energy gradually migrates to the post-stage cavity, exhibiting a rainbow trapping characteristic of C1->C2->C3->C4. Specific Implementation Example 3 An application of a multi-stage front-cavity Helmholtz acoustic tuning structure is disclosed, wherein the multi-stage front-cavity Helmholtz acoustic tuning structure is applied to a coaxial multi-moving-coil low-frequency transducer module; the coaxial multi-moving-coil low-frequency transducer module includes at least two moving-coil units.
[0040] Optionally, it can be applied to coaxial dual-moving-coil low-frequency transducer modules; The coaxial dual-moving-coil low-frequency transducer module includes an upper moving-coil unit 12, a lower moving-coil unit 14, and a transducer module bracket 13. The upper moving coil unit and the lower moving coil unit are stacked in the same direction along the axial direction of the transducer module bracket and are connected in parallel in phase. They are installed on the transducer module bracket and generate unidirectional sound pressure output under the same driving signal. In this embodiment, the coaxial dual-moving coil low-frequency transducer module is provided with a pressure relief coupling structure. The coaxial dual-moving coil low-frequency transducer module includes at least one of a pressure relief pipe 8, a low-frequency sound pressure pipe 9, and an ultra-low-frequency sound pressure pipe 10. The front cavity main circuit forms an acoustic connection with the coaxial dual-moving coil low-frequency transducer module.
[0041] As shown in the figure, in this embodiment, the pressure relief pipe is placed in the middle of the transducer module and connected to the internal cavity of the transducer module. It serves to relieve pressure in the front cavity of the upper moving coil unit and the rear cavity of the lower moving coil unit. The low-frequency sound pressure pipe is placed in front of the transducer module, and the ultra-low frequency sound pressure pipe is placed in front of the ultra-low frequency unit. The two sound pressures are combined into the front cavity main pipe circuit output after passing through their respective sound pressure pipes.
[0042] An earphone that uses the multi-stage front cavity Helmholtz acoustic tuning structure as described above, or a structure used in an application of the multi-stage front cavity Helmholtz acoustic tuning structure as described above.
Claims
1. A multi-stage front cavity Helmholtz acoustic tuning structure, characterized in that, include: The front cavity main circuit has at least two Helmholtz resonant units, each Helmholtz resonant unit including a resonant cavity and a neck channel, one end of which is connected to the corresponding resonant cavity and the other end of which is connected to the front cavity main circuit. Wherein, at least two of the Helmholtz resonant units are different from each other in at least one of the following: resonant cavity volume, neck cross-sectional area, neck equivalent length, and damping configuration, so that the at least two Helmholtz resonant units have different resonant frequencies; At least two of the Helmholtz resonant units form a front cavity acoustic impedance tuning structure with at least two local resonant branches through the front cavity main circuit.
2. The multi-stage front cavity Helmholtz acoustic tuning structure according to claim 1, characterized in that: Several of the Helmholtz resonant units are connected to the front cavity main circuit in any of the following ways: parallel connection, series-parallel composite connection, hierarchical coupling connection, or ring array arrangement.
3. The multi-stage front cavity Helmholtz acoustic tuning structure according to claim 1, characterized in that: Several of the Helmholtz resonant units are distributed along the side, circumferential or layered shell direction of the front cavity main circuit.
4. The multi-stage front cavity Helmholtz acoustic tuning structure according to claim 1, characterized in that: The Helmholtz resonant unit consists of three parallel-connected first resonant unit, second resonant unit, and third resonant unit; The resonant cavity volumes of the first resonant unit, the second resonant unit, and the third resonant unit decrease sequentially, and the equivalent lengths of the corresponding neck channels shorten sequentially. The resonant frequencies of the first resonant unit, the second resonant unit, and the third resonant unit increase sequentially.
5. The multi-stage front cavity Helmholtz acoustic tuning structure according to claim 4, characterized in that: The first resonant unit, the second resonant unit, and the third resonant unit correspond to ultra-low frequency, low frequency, and mid-low frequency tuning, respectively; The first resonant unit includes a first resonant cavity and a first neck channel communicating with the first resonant cavity. The volume of the first resonant cavity is 17.84 mm³ ± 10%, the cross-sectional area of the first neck channel is 0.78 mm² ± 10%, and the equivalent length of the first neck channel is 3.8 mm ± 10%. The second resonant unit includes a second resonant cavity and a second neck channel communicating with the second resonant cavity. The volume of the second resonant cavity is 10.26 mm³ ± 10%, the cross-sectional area of the second neck channel is 0.78 mm² ± 10%, and the equivalent length of the second neck channel is 2.15 mm ± 10%. The third resonant unit includes a third resonant cavity and a third cervical channel communicating with the third resonant cavity. The volume of the third resonant cavity is 6.53 mm³ ± 10%, the cross-sectional area of the third cervical channel is 0.85 mm² ± 10%, and the equivalent length of the third cervical channel is 1.6 mm ± 10%.
6. The multi-stage front cavity Helmholtz acoustic tuning structure according to claim 1, characterized in that: At least one of the Helmholtz resonant units has a folded neck or a labyrinthine neck, so that the neck has a folding extension path within a predetermined installation space; at least one of the resonant cavities is provided with at least one damping member selected from damping mesh, foam, microporous sheet or porous material. The damping component is used to adjust the acoustic loss of the corresponding Helmholtz resonant unit.
7. The multi-stage front cavity Helmholtz acoustic tuning structure according to claim 1, characterized in that: It also includes a front cavity venting structure, on which at least three layers of layered acoustic structures are provided. The layered acoustic structures sequentially include a main circuit layer, at least one resonant cavity layer, and a neck passage layer. The neck passage layer includes a folded neck passage or a labyrinthine neck passage. Each layer of the layered acoustic structures is acoustically connected to the main circuit layer through micropores or slits.
8. The multi-stage front cavity Helmholtz acoustic tuning structure according to claim 7, characterized in that: The layered acoustic structure consists of four layers: a main circuit layer C1, a first resonant cavity layer C2, a second resonant cavity layer C3, and a neck layer C4 connected in series. Each layer of the layered acoustic structure has a different intrinsic resonant frequency, and the peak values of the single cavities are staggered from low frequency to high frequency. After being connected in series, they form a wideband TL envelope. The volume of C1 is 17.9 mm³ ± 10%, the volume of C2 is 25.1 mm³ ± 10%, the volume of C3 is 25.3 mm³ ± 10%, and the volume of C4 is 8.1 mm³ ± 10%. The cross-sectional areas of the micropores or slits in layers C1, C2, and C3 are 1.4 mm² ± 10%, 1.4 mm² ± 10%, and 1.4 mm² ± 10%, respectively, and the cross-sectional area of layer C4 (the neck layer) is 0.78 mm² ± 10%. The maximum energy value of each chamber in the layered acoustic structure varies with frequency: C1 dominant: 200-380Hz C2 dominant: 400-560Hz C3 dominant: 580-740Hz C4 dominant: 760-1200Hz.
9. An application of a multi-stage front cavity Helmholtz acoustic tuning structure, characterized in that: The multi-stage front cavity Helmholtz acoustic tuning structure as described in any one of claims 1 to 8 is applied to a coaxial multi-moving coil low-frequency transducer module; the coaxial multi-moving coil low-frequency transducer module includes at least two moving coil units; the coaxial multi-moving coil low-frequency transducer module is a coaxial dual-moving coil low-frequency transducer module, including an upper moving coil unit, a lower moving coil unit, and a transducer module support. The upper moving coil unit and the lower moving coil unit are stacked in the same direction along the axial direction of the transducer module bracket and are connected in parallel in phase. They are installed on the transducer module bracket and generate unidirectional sound pressure output under the same driving signal. The coaxial dual-moving coil low-frequency transducer module further includes at least one of a pressure relief pipe, a low-frequency sound pressure pipe, and an ultra-low-frequency sound pressure pipe, and the front cavity main circuit forms an acoustic connection with the coaxial dual-moving coil low-frequency transducer module.
10. An earphone, characterized in that: The structure used in applications employing the multi-stage front cavity Helmholtz acoustic tuning structure as described in any one of claims 1 to 8, or the multi-stage front cavity Helmholtz acoustic tuning structure as described in claim 9.